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White fly

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White fly
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Bulletin - University of Florida Agricultural Experiment Station ; 67
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Gossard, H. A. (Harry Arthur), 1868-1925
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Florida Agricultural Experiment Station
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English

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Lake City ( flego )
City of Tallahassee ( flego )
Insects ( jstor )
Larvae ( jstor )
Groves ( jstor )

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FLORIDA AGRICULTURAL EXPERIMENT STATION


WHITE FLY.
(Aleyrodes citri.)


By H. A. GOSSARD.

The bulletins of this Station will be sent free to any address in Florida upon applieation to the Director of the Experiment Station, Lake City, Fla.

DeLand, Fla.:
E. 0. PAINTER & COMPANY 1903,


BULLETIN NO. 67.


JUNE, 1903.













BOARD OF TRUSTEES.


GEO. W. WILSON, President .Jacksonville. F. E. HARRIS, Vice-President .Ocala. J. D. CALLAWAY, Secretary . . Lake City. C. A. CARSON, Chairman Executive Committee, Kissimmee. J. R. PARROTT. Jacksonville. E. D. BEGGS. . Pensacola. L. HARRISON . . Lake City.



STATION STAFF.


T. H. TALIXFERRO , C. E., Ph. D . .Director. H. K. MILLER, M. S .Vice-Director and Chemist. H. A. GoSSARD, M. S .Entomologist. H. H. HUME, B. Agr., M. S.Botanist and Horticulturist. CHAS. F. DAWSON, M. D., D. V. S .Veterinarian.
*C. M, CONNER, B. S .Agriculturist. A. W, BLAIR, M. A. . Assistant Chemist. LUCIA MCCULLOCII, B. S., Asst. Biologist and Asst. Librarian. W. P. JERNIGAN. Auditor and Bookkeeper. A. L. GLAYTON. . Stenographer and Librarian. JOHN H. JEFFERIES. . Gardener in Horticultural Department. Louis DEGOTTRAU, Supt. Citrus Experiments at Boca Raton.

*Supt. Farmers' Institutes.













CONTENTS.



Introduction . . . . . . . . . . . . . . . 599
The Family Aleyroclidae . .6oo Origin and Distribution . . 6oo Description. . .604 Life History and Habits . .6o8 Methods of Dissemination . .613 Effect of Cold . . . . .614 Food Plants . . . .616 Character of Injury. Sooty Mold . .617 Natural Enemies . . .20 Fungous Diseases . . .621 .MIethods, of Introducing Fungous Diseases into Infested
Groves . . .624 HF-ow Far i\Iav the Fung-us be Trusted? .625 Sprays . . . . .629 Other Spray s than Resin Wash . 631 When to Spray and What to Use . . .634 How to Spray . . . .635 Scalding of Resin Wash Explained .641 Fumigation . . . .643 The Nursery SituatiIn . . . .65o Insects Sometimes Mfistaken for White Fly . 655 The Outlook . . . .657 Acknowledgements . . 659 Summary of Important Facts and Recommendations . 659 The Nearest Relatives of the White Fly (By Prof. T. D.
A. Cockrell) . . . .661



















The White Fly.




Aleyrodes citri Riley & Howard.

This insect first attracted the notice of entomologists in 1878, when it was observed in the orangery of the U. S. Dept. of Agriculture at Washington. Some observations were made upon its life history during that summer but no description of the insect xvas published -until 1885 when Mr. W. H. Ashmead furnished a mneagre description in the Florida Dispatch, Vol. XI, new series. The first adequate description was given by Riley & Howard in Insect Life, Vol. V, NO. 4, issued in April. 1893. The name which Mr. Ashmead had bestowed, rileyrodes citri, was retained by Riley & Howard, the insufficient description being discarded. The next important contribution to the literature of the insect wxas by Prof. H. J. Webber in an issue from the U. S. Division of Vegetable Physiology anid Pathology in 1897. Prof. Webber's pamphlet
-\,,as entitled Sootv MNold of the Orange and its Treatment; but it recognized sooty mold as a development resulting from white fly attack. Prof. Webber's recommendations pointed out the necessity for destroying the fly, it being the cause of the mold, and the article w as a very important one because it first emphasized the efficacy of resin spray against the insect and also described the twxo fungous diseases that constitute the greatest natural checks upon its multiplication.
The most extensive work with hiydrocyanic acid gas against the insect in the field was performed by the writer about two years ago, a summary of which was published in the annual report of the Experiment Station for the same year.








BULLETIN NO. 67.


The Family Aleyrodidae.

The family Aleyrodidae, to which the white fly belongs, contains a large number of species, most of which are of little economic importance, usually being kept in good subjection by minute hymenopterous parasites. Among the exceptions to the general statement of harmlessness is a European species, A. vaporarioruin, which has long been known as something of a pest in Europe; and in this country, relieved of its European parasites, it is all too fast getting the reputation of being a first-class pest in greenhouses and gardens. The white fly of the Melon Papaw (Carica papaya-) Aleyrodes variabilis is also a pest that is not to be despised when on papaw; but owing to the restricted cultivation of its host it will not attract great attention unless it should prove its ability to multiply on other and important crops. The orange white fly, Aleyrodes cirri, is the most destructive insect of the family. The family is characteristic of the tropics, but some species thrive out of doors in the northernmost parts of the United States. The immature
insects are very scale-like, being closely related to the Coccidae or family of scales. The most conspicuous character separating the two families is that both sexes of adult Aleyrodidae possess two pairs of wings and can fly, while only the males of the Coccidae are motile and are possessed of a single pair of wings.

Origin and Distribution.

The original home of the white fly is not definitely known. Some entomologists incline to the belief that it is a native of Florida, others think it an importation. I submit at the conclusion of the bulletin an interesting contribution from Prof. T. D. A. Cockerdll, who believes, from a comparative anatomical study of A. citri and many other species which he has collected from various parts of the world through many years, that our pest belongs to an Asiatic or Australasian group of white flies, and hence is not native. On the other hand, Prof. A. L.








THE WHITE FLY.


Quaintance, who has made a specialty of the family, believes it quite probable that the insect is native, giving as his chief reason for so thinking that he has found it on Vliurnum nudumn and occasionally on Qiiercits aquatica in primeval hammock many miles from an orange grove; the conditions under which he has found it on the former plant in dense hammocks particularly emphasize to his judgment the possibility of its being indigenous to Florida. An instance of orange infestation which, I think, might be considered as sustaining Prof. Quaintance's view is found in the Manatee river- section. The insect's first appearance in this district was in the Foster grove near Manatee. I am informed that not a bud or plant of any description was permitted to come upon this place from abroad for some years before the fly appeared. Did it migrate to the oranges from a native plant in the dense woonds surrounding the grove? Or, did some one of the tens of thousands of migrating birds f rom the tipper part of the State get some of the newly hatched insects entangled in its feathers and carry then to tfie Foster grove? Or again, m-ight the calculating eye of a conscienceless competitor f rom- tipper Florida have feared the rich promise held out to the settlers in the Manatee region by the vigorous grove of M\r. Foster and have chosen to equalize the race between the respective sections by a malicious infection before the stress of competition was felt? Or what is, perhaps, more probable, is there some mistake abotit the report that no plants were introduced from abroad? However these questions may he answered, I incline to the view that the white fly is an imported insect. It is very unusual for an insect as vulnerable to parasitic attack as white fly to multiply in suich excessive numbers. I have found A. floridensis on orange at Candler, but very sparsely, and the same insect has been sent to me from Arcadia. Such native species rarely become troublesome, it being well known that hymenopterous parasites usually keep them in subjection. The history and spread of Ale yrodes vaporarioron, a species known to have been imported, apparently exactly parallels that of A. citri. Few indeed are the insect enemies of the orange white fly; I have observed none







602 BULLETIN No. 67.

except lace-wing larvae and some mites and these scarcely deserve mention, they make so little impression on the insect. It may be possible to explain the spread of the fly as a native insect without its being accompanied by parasites by paralleling it with the Colorado potato beetle, a native insect originally feeding in restricted numbers upon a wild Solanaceous p-afift in Colorado and outstripping all of its enemies in a march to the Atlantic Seaboard as soon as the potato patches of the settlers furnished it with a suitable food plant outside of its original habitat; but if such were the case with white fly, would not some parasites ere this have made themselves known in some quarter of the infested teritory? While Mr. Marlatt of the U. S. Dept. of Agriculture was in China and Japan hunting for the home of San Jose scale he collected some species of Aleyrodes but A. citri was not among them. Mr. E. Ernest Green has not collected A. citri in Ceylon, nor has Mr. H. W. Peal of Calcutta found it in Bengal. Mr. H. Maxwell Le-Froy, of the Imperial Dept. of Agriculture of the West Indies, has not found it in the West Indies, though another species of Aleyrodes is a pest upon the orange in Antigua. Inportations of citrus plants have been made from time to time from China, Japan, and other parts of the East; and also thirty or forty years ago some large wholesale importations were made from Brazil, suggesting that it may have originated in the American tropics. Mr. Alexander Craw of the California State Board of Horticulttre writes that he has received the insect upon plants from Chili where it is a great orange pest.
The fly seems to have been first known in Florida throughout the region comprised in Volusia, Marion, Lake, Alachua, and Orange counties from which, I have little or no doubt, it was transferred to the Manatee country and to local centers along the northern border of the State. Following the severe freezes during the years from T895 to, i9OO the insect was so thoroughly exterminated in the northern part of its range by successive defoliations due to cold that it was believed to be extinct throughout the section, and for all practical purposes was so. However, during the past two seasons there have been








THE WHITE FLY. UVO

indications of a revival in local spots, some of these, when upon oranges, being so conspicuously adjacent to hammocks as to suggest that the insects emerged from them. The nurseries, which for some years have furnished a supply of clean stock, are now becoming threatened and, while with proper care on the part of the nurserymen. I believe clean stock can vet be supplied for several years to come, the time is already here when the buyer must depend upon the representations and reliability of the respective nurserymen to guide him and not upon the inspections of the Entomologist. Certificates of freedona from the pest. correct when issued, may become untrue before their expiration, a year after being given; hence I can assume no further responsibility toward restricting its spread by inspection work.,
In some of the southern counties it is found in a majoritV of the groves, but there is probably no county that does not possess many trees which are not vet infested. Manatee county is perhaps in the worst condition of any, at least 75 per cent. of the groves being infested. There are spots of infestation in Polk, Lee, Hillsboro, Marion, Putnam, Alachua, and Orange counties: it is also established at three or four points on the East Coast railroad in the counties of Duval, Volusia and Brevard; and in local spots in Baker, Columbia, Jefferson and Leon counties. It doubtless occurs at many places of which I have no record. I have no resources at my command to make a general inspection of the entire State, and correspondents sometimes seem disposed to conceal the fact that it is in their neighborhood. From information based upon its acknowledged distribution before the freeze of i895 and letters on file in my offce I conclude that a general and thorough State inspection would probably discover it in Lake, Osceola, DeSoto, Sumter and Pasco counties at least.
Outside of Florida the insect is recorded as either now being or having once been in Louisiana, Georgia, North Carolina, District of Columbia, and Texas. California newspaper reports sometime since indicated that some insect resembling Alevrodes citri was present in the neighborhood of Los Angeles,








BULLETIN No. 67.


but the horticultural officers of that state seem to be confident that it is not present, and it is probable that with the thorough methods of warfare there employed, coupled with climatic influences, the insect would not attract much notice. The orange districts of Louisiana are quite generally infested, the insect probably having been introduced at the time of the New Orleans exposition in 1895. The white fly is often mentioned in connection with greenhouse infestation but here there may easily be confusion of specific identities.

Description.

THE EGG.-Very minute, about 1-125 of an inch (0.211M) in length, being attached to the leaf by a slender stem or footstalk; about four times as long as thick, widest just beyond the middle towards the free end; color pale yellow, when first laid tinged with greenish, becoming darker as the embryo develops and some specimens becoming of a dark steel grey or blue. Surface smooth and shiny, often with clinging particles of white wax. Red eyes of embryo conspicuous through the shell as it approaches maturity.
LARVA.-Passes through four mnoults before reaching the puLpa stage. When first hatched the insect is about i-So of an inch in length (0.31-m), of a pale greenish yellow color with two darker yellow spots on the back of the abdomen. There are four conspicuously long bristles at the posterior part of thle body and six long ones on the anterior end with minute ones along the sides, each arising from a tubercle. Antennae, three or four jointed. Four eyes, dark reddish. Legs short, six in number. Mouth parts consist of a long, sucking tube. On the dorsal side of the last abdominal segment is a subovate, brown colored opening, the vasiform orifice. Appearance in second and third stage not markedly different {.rorn the first except in size and minute microscopical characters. in the fourth stage the length has increased to about 6-ioo of an inch (i.5mm), the width to 4-1OO of an inch (imni) and the conspicuous bristles have vanished; a pair of persistent minute








THE WHITE FLY. V

bristles is found on the anterior border, one on each side, and another pair, also minute, is disposed one on each side of the anal cleft. The insect is very flat and close pressed to the leaf; the dorsum or back is crossed by twelve transverse ridges indicating the segments. Arising from the prothoracic region on each side, extending obliquely outward and forward to the margin is a distinct ridge or fold, the breathing fold. The outline of the developing wings of the embryo can be distinctly seen from the first.
PUJPA.-To ordinary observation quite similar to the fourth larval stage but more plump and of thicker body; broadly oval. Measurements about as in fourth stage, slightly narrower. A broad, deep orange or coral-red spot on the back near anterior end of abdomen; eyes purplish; vasiform opening and ring brown; transverse ridges on abdomen shorter and less distinct than in last larval stage.
ADULT.-Female: Length slightly over 1-20 of an inch (1.411m) ; wing expanse about twice the body's length (2.8mm) ; color light orange yellow; the rostrum or beak is tipped with black; the wings are colorless when newly hatched, but within two or three hours become covered with a fine white wax, hence, the name "mealy-wing" sometimes given to the insect. The body also becomes covered with more or less of wax but its ground color is not wholly obscured. Tarsi two-jointed. The eyes, i-edclish-brown in color, are each divided into two parts by a curved ridge projecting from the cheek, the upper divisions being the smaller. Ovipositor short, retractile.
ADUL.-Male: The male resembles the female but is smaller with the head and abdomen having heavier tufts of adhering wax. The abdomen is more slender and has at its termination a pair of claspers slightly curved upwards.









bbti BULLETTN No. 6;7.















EXPLANATION OF PLATE I.


Aleyrodes citri.

Fig. i-Adult female ,with expanded wings, much enlarged.
Fig. 2.-Adult female, with wings folded over the body in normal roof-like position.
Fig. 3.-Egg and foot-stalk of same, greatly magnified.
Fig. 4.-Egg-shell, showing the split through which the larva emerged.
Fig. 5.-Tip of male abdomen, showing claspers.
Fig. 6.-Antenna, showing aninlated joints.
Fig. 7.-Fore margin of front wing.

INSECTS SOMETIMES MISTAKEN FOR .4. cirri.
Fig. 8.-Larva of Aleyrodes florideints greatly magnified.
Fig. io.-Greatly enlarged section of waxen fringe, surrounding A. floridensis.
Fig. i.-Outline of larva of Leaniuon hesperidunr.





- , ',r ,-



























07


PLATI 11.









THE WHITE FY.

















EXPLANATION OF PLATE II.

Alevrodrs citri.

Fig. i.-Larva, fitst stage, greatly magnified.
Fig. 2.-Larva, first stage, drawn to same scale as figures 3, 4, 5, 8, 9, and io.
Fig. 3.-Larva, second stage.
Fig. 4.-Larva, third stage.
Fig. 5.-Larva, fourth stage.
Fig. 6.-Margin of advanced larva, greatly enlarged.
Fig. 7.-Vasiform orifice of fourth larval stage, showing crenulated operculun with lingua in the center
Fig. 8.-Pupa, showing embryo and distribution of orange colored areas. Waxen tufts extending from the breathing tubes arc shown.
Fig. 9.-Adult, wvith folded wings, emerging from the pupa case.
Fig. io.-Empty pupa case, showing split through which the fly emerged.








BULLETIN No. 67.


Life History and Habits.
FIRST BROOD OF ADULTS.-The first brood of adults issue during March, April and early May. The date varies with the season and locality. Localities not over a quarter of a mile from each other may exhibit a variation of two or three weeks, and particular spots or plants in an infested area may furnish an anticipation of the general appearance of the brood by a long interval. Thus, sorne sheltered lemon bushes at Ellenton, Fla., were observed by the writer to have produced adults on the I ith of February, though for the neighborhood at large the bulk of the brood issued during March and April. At Tampa, thirty to forty miles north of the Manatee section, the spring brood of flies has in sonie seasons preceded their appearance about Braidentown and Manatee by two weeks. Mr. A. J. Pettigrew, a close observer at Manatee, says that he once observed a few hatch about the 28th of January, and that he has twice seen them appear in considerable numbers in February, but that March hatches the bulk of the brood, most of thern being on the Nving before April ist. At Lake City, last year, the few infested bushes about the town showed the first adults about the 14th of April and hatching continued until late May, most of thern appearing during the last half of April. There was several days difference in the dates of appearance upon the different bushes. The present year found some of the adults on the wing at Lake City March 12, and they were reported on the wing at Orlando and at Palmetto on the 6th of March. At Lake City only a few stragglers were observed after the middle of April. Speaking of the entire district in which the insect can exist from South Florida to Georgia, the bulk of the first brood may be said to appear during March and April, with the adults which have hibernated as half-grown larvae straggling along into May and June. Only in the northern section will they ever linger as late as June. The adults live from three or four days to three weeks, the average period being from four to seven days.
The adults love close-planted, sheltered groves into, which








THE WHITE FLY. 6W

the winds enter with difficulty. Consequently, the insect never becomes so numerous in well spaced, open groves on high pine land as in thick-planted, unpruned groves on hammock land surrounded by thick woods.
PAIRING AND EGG-LAYING.-The courtship of white fly, as observed with a pair in confinement, is quite curious. The male showed evidence of having detected the presence of the unimpregnated female at a distance of one-fourth of an inch or more, and approached her nervously, stopping at intervals, especially as the distance was lessened, and swinging his body about excitedly in a semi-circle, the head being used as a pivot, his wings in the meanwhile opening and closing spasmodically. While no movement was made by the female, several retreats were made and she was repeatedly approached from many directions before coition occurred. Upon the trees the males and females rest side by side and two maJes, one on either side, may often be seen giving their attentions to the same female.
Egg-laying begins within eighteen to thirty hours after the adults issue when the wx eather is warm, (sixtY-five to seventyfive degrees) but with damp, cool weather several days may elapse before they are deposited. Egg deposition occurs upon the under surface of the leaves, preferably upon new ones, especially those of water sprouts, but old leaves may also be well covered with them; they are usually scattered over the .1irface of the leaf without much order of arrangement but sometimes are laid in the arc of a circle. From four to ten eggs may be observed in such an arc and are so placed by the female using her beak as a pivot around which the body is swung during oviposition. The eggs are not as numerous, ordinarily, near the edge of the leaf as further inward. Each female deposits from seventeen to twenty-five eggs in breeding cages, the rate of laying doubtless being governed by temperature. \Vith the thermometer at 70 degrees to 76 degrees F. for several hours on each of two successive days the eggs were all laid within twenty-four hours after the first one was deposited and








610 ULLETIN No. 67.


the fem-ales under observation died soon after they stopped laying.
By mathematical computation a leaf from young orange, five inches long and two and one-half inches wide in the middle, collected at Myers, June 22, 1901, had upon it upwards Of 20,000 eggs. While so mnany eggs upon such a space is beyond the average, it is by no means rare, and I have sometimes seen the number exceeded.
Hatching occurs in from three to twenty days according to the weather. In the summer season when the temperature maintains itself at from 8o degrees to 95 degrees for several days together the eggs hatch in three or four days. Hatching throughout the summer is very regular, comparatively speaking, the range probably being from three to eight days, while in spring and fall with temperature ranging from 5o degrees to 70 degrees from two to three weeks i's required. The egg becomes of a metallic bluish-grey color as the embryo matures and splits longitudinally for a short distance down both sides at the distal end to give exit for the young larva.
LARVAL HISTORY AND HABITS.-The young larva is mile and1 crawls about over the leaves and twigs for several hours like a young scale before it attaches itself to the leaf. The first molt occurs in from seven to twenty-five days according to the temperature. In mioulting, the larva bends the abdomen upward at a right angle to the leaf surface and with slow, struggling movement alternately raises and lowers it, the body meanwhile shrinking from the interior of the skin, causing the dorsal ridge to become distinctly elevated. The skin now splits at the anterior end or beneath the head and by abdominal wriggling the insect gradually pushes it off. The cast skin is very thin and fragile and is blown away by the wind or drops to the ground, seldom remaining long upon the leaf. The periods between all the moults seem to be determined by tempjeratur5 and the fifth or puipal molt occurs in from twenty to thirty days after hatching during July and August hut requires from four to five months during the winter. Add from ten to thirty days as thie pupaT stage add the life cycle from egg to adult is


610








THE WHITE FLY. U11

seen to range from forty or fifty days to six months. When the insect is ready to emerge from the pupa shell, the skin splits in the form of a cross beginning at the head of the larva and extending along the middle of the back to the front of the abdomen where it bisects at right angles a transverse slit extending to the margin on either side. The thorax of the fly comes out first, followed by the head. The wings are much folded and colorless when first exposed; the insect at once elevates them into a vertical position to dry, and in about fifteen minutes they are expanded and lowered to a horizontal position; in ten minutes more they are in their normal roof-like position over the back; about two hours elapse before they lose their transparency and commence to whiten, and five or six hours pass before the typical powdery white appearance is reached.
The larvae attach themselves to the under sides of the leaves and are inconspicuous because of their transparency and greenish tinge. If the leaf be so doubled in the hand that air is admitted beneath the insect, it at once becomes readily seen and is translucent whitish green, spotted with orange. When infestation is so excessive that the larvae overlap each other, many of those that are beneath do not succeed in emerging, especially if the head of the larva is the part covered. So far as observed by the writer the larvae do not settle and feed elsewhere than upon the leaves. \hile some reliable observers report having found them attached to twigs and in buds. the most diligent search has never revealed to me a single specimen so located. Is it possible that the immature stages of one of the Lecaniums (possibly hesperidum) have been mistaken for white fly by the observers mentioned ?
Seen best from the ventral side of the larva but also visible through the transparent dorsal surface, along the median line and slightly forward of a line connecting the inner points of the breathing folds, is a pulsating organ connected with the circulation which beats from one hundred-twenty to one hundredfifty times per minute. Along the back of the abdomen the slow pulsations of the heart proper, a long muscular tube, can often be observed with a fairly good microscope. Absence of visible


Bul. 68-2








612 BULLETIN No. 67.

movement iiq1 these organs may not be interpreted as perfect proof of death but they often furnish positive proof when death has not occurred and'thus are a valuable means of observation to determine what has been the effect of insecticidal treatment.
SUMMER AND FALL BROOS.-During June and July the second brood of adults are on the wing in the southern part of the State, appearing about two weeks later in the latitude of Lake City. At the latter place last summer they commenced appearing about the first of Juily and were still abundant on the i2th of August. Fromn this time onward there was no date until the middle of November when every stage of white fly from egg to adult could not be found in the neighborhood; not always every stage up)on the same bush but persistent search was sure to find it within a half mile. September seemed to bring the greatest number of adults, which, with early October, may be regarded as the maturing time for the third brood. This year the second brood comm-enced hatching at Lake City, during the first week in June, and were reported to be hat ched and in full swarm at Micanopy at the same time. The second brood, like the first, seems to be a month earlier this year than last.
While three generations a year seems to be the rule, there is a tendency to continuous breeding as some adults were observed upon privet at Lake City on Christmas clay, and Prof. H. A. Morgan has likewise observed that it issues upon warm winter days in Louisiana. Four generations a year doubtless occur often, but not in sufficient numbers to obscure three well defined broods as the rule. Mr. Pettigrew sums up the history of the adult as follows for Manatee: "The spring brood is in sight from three to four weeks, then none are visible for three or four weeks; the second crop is in sight four to five weeks with one or two weeks following without any, after which the broods run together so there is only a thick and a thin streak. Sometimes the eggs for the winter brood of larvae are all deposited in October and at other times nearly all in Ngovemher."
All the eggs of the winter brood are hatched before Christ-









TEE WHITE FLY.

mas. By 2\1arch i st a t ew of the insects are pupae and there are none that have not reached the third stage. The rapid development of the belated larva ae during the warm days of March and April enable them) to issue as adults vxithin a month after the first flies of the brood appear, so the first brood is well defined each year. So meting like ten to fifteen per cent, of the winter brood die. before spring, at Lake City, from no very definite ca-ille.
Methods of Dissemination.
The insect is not a strong flyer but can go considerable distances with the wind, and infected neighborhoods often furnish unmistakable examples of the influence of prevailing winds in scattering it. The flies are often found in clouds upon weeds and herbage by roadsides and covered vehicles may collect some of them under such circumstances and transport them to considerable dlistances. Thev hav e also been observed upon windows in railway coaches, indicating that they can be carried long distances in this wvay.
I have stood beneath a tree upon which adults were plentiful and had them alight upon my clothing; I have then walked nearly a half mile against a stiff breeze and picked the flies from me by the dozen at the termination of my journey. They cling tenaciously to their support in a stiff wind but take flight quickly in quiet air.
When newly hatched they crawl about like young scales and may be caught in the hair of horses brushing against the trees, or in the feathers of birds and be thus transported from one grove to another.
During the months from July to December young larvae as well as adults are apt to he present in small numbers, at least, without intermission in an infested grove. Pickers, teams, ladders, baskets, etc., going from an infested grove to a clean one during this time can become the means of transporting the pest as well as when the spring brood is hatching and flying. TIfested nursery stock is most apt to carry the insect into new localities.








614 BULLETIN No. 67.

Effects of Cold.

The larvae can stand more cold than the orange. I have, in repeated instances, taken larvae from leaves that had fallen to the ground because of cold ranging from 22 degrees to 17 degrees above zero, ten days to two weeks after the cold occurred and found by microscopic examination that the pulse was beating regular and strong. If infested leaves drop in early w inter the larvae doubtless perish as they invariably die upon detached drying leaves in the laboratory i from nine to fourteen days, but with leaves dropped in February and lying upon moist earth it is conceivable that some of the insects i-ay mature and issue. It seems certain that white fly will eventually range as far north as the hardiest orange. It will also be able to perpetuate itself upon the more hardy of its food plants, despite freezes that kill oranges to the ground.
To determine the degree of sudden cold which the isects can survive, Mr.A. 0. Mann of the Lake City Ice Factory gave mne the freedom of his factory for experimental purposes and suink an empty can into the brine for mny -use. The tem perature of the brine ranged from io degrees to 2o degrees, and the thermomneters kept suspended in the cain recorded temperatures as showii in the table. Tw igs of orange and Cape jessamine, having upon them well matured pupae of the fly were used April 12th and T4th as follows:

ime int Can Tettperatutre readings int Result canti ten att initerls.it
Experimentt No. 1 . 30 mill. 14 degrees, 15 de, i5 tie A fexi en ired and isnued as adults the
next dac0.
Experiment No. 2 . 1 hir. 12 de., 14 de., 15 de., 1.5 tie., All killed.
12 de,., 14 de.

In the following experiments the pupae were prepared for the extreme temperatures by first being put in cold storage. 'The temperature in the cold storage room was from 48 degrees to 5o degrees. Pupae left in this temperature for 48 hours were apparently uninjured and adults continued to issue in the












THE WHITE FLY.


cold storage room: but if any significance at all can be attached to the cold storage preparation it weakens the resisting power of the insects at this date as shown in the following experiments :


Time Iin Cold
Storage


Experiment No.3 1 hr. 45 ruin. s0

Experiment No. 4 48 lirs. 30

Experiment No. 1 hr. 45 min, 1 h
Experiment No. 6 1 hr, 45 rini. 2 h
ExperinAent No. 7 48 I hs. 2 1


Time Temperature readin can rngs, by degrees,
in cans.

mil. 12, 14, 15.

mill. 25, 20, 20, 18.

r. 12. 14, 15, 12.
rs. 12, 14, 15. 1.5, 12, 10.
rs. 30 ruin. 20, 20, 14, 12, 10.


Result.


Two flies issued, remainder killed. Al1 killed. All killed. All killed. All killed.


It is quite probable that had the experiment been performed during the winter months with larvae that had become accustomed to cold there would have been a larger percentage of surviving insects. Temperatures as low as those used are never reached in South Florida and seldom last for more than a few minutes il North Florida: and when reached in a given district there are always sheltered spots in Which the mercury does not fall so low. At various points along the line of the Seaboard Air Line R. R. from Jacksonville to Tallahassee the mercury has at different times, during the past ten years, descended to 6 degrees and io degrees. The fly, after such freezes, has disappeared from sight for a time but has invariably reappeared showing its abilitv to withstand the most extreme cold that occurs in this latitude. However, it is apparent that a deciduous orange adapted to North Florida and Georgia would not suffer much from the fly.

Mr. A. j. Mitchell, Section Director of the Florida Weather Service furnishes the following records for lowest temperatures at three points near the northern boundary:


JACKS NVILLE


14 degrees, Feb. 8, 1895. 11 degree,, Dee. 29. 19 1. 10 degrees. Fe,. 12, 1899.


LAKE CITY


15 degrees, Feb. , 1895. 16 degrees, Feb 1s. 1900. C degree., Feb. I.,. 1S,99


TALLAHASSEE 11 degrees, Feb. 8, 1895. 12 degrees, De. 29, 1894.
-2 degrees. Feb. 13. 1899.


]
2








BULLETIN NO. 67.


About two years after the 1899 freeze the insect was again observed at Lake City. It was reported from Jacksonville at about the same time.
State Chemist R. E. Rose informs me that the insect is present in considerable numbers at Tallahassee, and my office records show that it was present there before 1895.

Food Plants.

White fly occurs upon all varieties of citrus. C. trifoliata is, of course, only infested during the summer months, being a deciduous variety. The deciduous character of some of the C. trifoliata hybrids will tend to retard the multiplication of the pest upon them. The kumquat is still less a favorite than the pomelo, and the latter, though often badly infested, is usually attacked only after the adjacent oranges are oN'erstecked. The adult flies as well as the larvae sap the leaves and their taste for certain varieties leads them to oviposit ,)n these when possible, going to less favored plants only as they are driven by necessity to do so. Besides citrus, the Chinaberry tree (MV4elia azederach) and Viburnum nudum the Cape jessamine (Gardenia florida), the Japan persimmon (Diospyros kaki), California privet (Ligustrum amurense), Golden privet (Ligustrum sp.) and Mock Orange (Prunus Caroliniana)are food plants. Various species of Ficus are said to be food plants; I have seen it on two species, F. altissinia, and on an unknown species introduced from Costa Rica.
The water oak (Quercus aquatic) is occasionally infested, according to Quaintance, and I have taken two or three larvae advanced to third and fourth stage on scrub palmetto. Their presence upon the latter plant is very rare having been observed but once, though opportunities have been plentiful.
Prickly ash (Xanthoxylum sp.) is reported as a food plant upon, ihat I consider to be reliable authority, but I have not personally seen the insect upon any one of the three species found in this State.








THE WHITE FLY.

Character of Injury. Sooty Mold.

The injury caused by white fly is not as threatening to the life of the tree as that caused by scale insects. The latter kill branches and sometimes entire trees with great rapidity when associated with other ailments, but their destruction by the former is comparatively slow. White fly certainly does often kill branches and sometimes trees, but rarely does a tree die from its attack alone. Footrot, dieback, and kindred troubles are the usual accompaniments of white fly when death occurs. As an illustration of the resisting powers of the orange to its attacks, the Foster grove may be cited, the one before mentioned as being the first case of infestation on the WVest Coast. This grove is referred to in some of the earliest literature of White fly (Insect Li fe) and has been infested for more than ten years; with the exception of a few trees, it is still living and looks as if it can keep up the struggle indefinitely. When seen by me about eighteen months ago the interior branches of most of the trees had a color, thrift and vigor not found in some groves wholly free from this insect. Except that the bearing capacity of the grove has been reduced, it mnay still be called one of the most valuable in the State. I w as told by parties acquainted with its recent history that it bears a good crop about once in three y 'ears followed by two comparative ely light crops. It -,vas hardly carrying more fruit than w ould pay for the cost of maintenance at the time of my inspection of it. Seedling groves are inclined to alternate heavy with light crops so one of the light crops is accounted for, but the other is doubtless due to the fly. I believe any practical grower will think me well within the hounds of truth in saying that, through a six-year period, the yield with white fly present will be from twenty-five to forty per cent. less than it would be with the insect absent. Manatee county alone produces 250,000 boxes of fruit per year and thirty per cent, increase would be 75,000 boxes which, valued at $.2.50 per box, would amount to $187,500. This is not far from the actual loss, as most of the groves in this county are infested. WVhen the loss








616 BULLETIN No. 67.

in other districts and the indirect losses due to impaired quality and diminished carrying power are added, the State must receive nearly a half million dollars less annually than she would if the insects were absent. The acid and sugar content of the fruit is much reduced, an orange from a white fly tree being comparatively tasteless and insipid.
The following table shows the results of a chemical analysis made at my, request by Profs. Miller and Blair of three tots of fruit picked the same day from adjoining Dancy tangierine groves, both of which were infested with white fly and had been given practically the same treatment as regards cultivation and fertilizing. Fifteen or twenty oranges were selected for eachl of three lots, representing as accurately as possible the average condition as to size and maturity on each of the three trees from which they were taken.
Sample No. I was from a tree that had been infested for several years and had been left to take care of itself.
SaMple NO. 2 was from a tree about forty feet from 'No. I, and was regularly and properly sprayed three or four times each year but stood in the row adjoining the unsprayed grove and the insects could not he prevented from developing upon it in numbers sufficient to cause more or less mold.
Sample No. 3 wkas from a tree about 8o feet from _No. Y, which was properly sprayed as w~as NO. 2, but with better results. A few larvae were present on the leaves, but, practi-, cally, white fly could be considered wholly absent.


Rledueing Sugar. Total Sugar Dextrose, Citric Acid, Per Cent. Per Cent. Pcr Cent.

Sample No. 1 2.18 6.71 A25
Sample No. 2 2.23 6 2 6 .394
Sample No. 3 2.58 7.91 .445


These samples were collected in February after they bad passed their best, but it is believed that they kept their relative quality.








THE WHITE FLY.


A liberal use of fertilizer tends to keep up the quality but the sooty mold upon the rind must be removed by hand-washing, by revolution in barrels filled with water and cross-cut sawdust or by suitable machinery provided with revolving brushes, and the consequent bruising of the rind invites quick decay which often occurs in transit.
The subtraction of so much sap from the tree by the insects, aided by the interference with assimilation caused by sooty mold, delays ripening of the fruit, varieties which ought to be at their prime by the first of December not being marketable before Christmas time and often not until three or four weeks thereafter.
The sooty mold is a black, saprophytic fungus, Mecliola Cainelliae (Call.) Sacc., that grows in the honey dew excreted by various insects. Among the Coccidae or scale insects which it follows, may be mentioned the various Lecaniums, the mealy bugs, the wax scales. Iccrya pitrchasi, and others. The plant lice, or various species of Aphis, are also followed by it as wel as all forms of Alevrodidae -xxhich multiply excessively. Any insect excreting honey dew in any quantity is certain to be accompanied by the mold. Sooty trees and plants, tl.erefore, are not always infested by-hite fly, though such an appearance upon any of the insect's food plaiits should receive an immediate investigation. The white fly larvae being located on the under sides of the leaves, the honey dew drops upon the upper surface of the leaves growing just below, so the black mold occurs chiefly upon the upper surface of the foliage and fruit. It forms a close, smothering, membranous covering that can sometimes be peeled back as if it were tissue paper. This membrane is composed of the netted mx celial threads of the fungus which reproduces by means of various reproductive bodies some of which are shown in cut No. I, from Prof. Humne's bulletin on Citrus Troubles. The wind is the chief agent in disseminating the reproductive bodies. The effect which a heavy coating of this fungus produces upon a tree differs only in degree from what would be produced by enclosing it in a black tent. The circulation of air through the tree and entrance








620 BULLETIN No. 67of light is not interfered with, but contact of air and light with the foliage is cut off on the upper surface and partially also from the lower surface. The sooty mold is one of the most aggravating factors of white fly damage, It disappears with the destruction of the fly.


enlarged). i. Mycelium or fungal with immature spores. (Drawing by


threads; 2- Conidia: Miss L. McCulloch.)


Natural Enemies.
The young of the lace-winged flies and a mite are the only insects that I have observed feeding upon the eggs or larvae. Lady-bugs possibly feed upon them to a slight degree but I have never observed them doing so. A correspondent at Kissimmee








THE WHITE FLY.

reports that a carnivorous ant is quite efficient as a destroyer of the larvae. I cannot say that any of these appreciably reduce the insect, even locally.
Through the kindness of Mr. Ehrhorn of California, some hymenopterous parasites upon another species of Aleyrodes were sent to me and enclosed on an infested tree beneath a cheese-cloth tent, but several weeks later a freeze dropped all the leaves from the tree and only a negative result could occur. Further experiments of a similar nature are desirable, but too much must not be hoped from them. The parasites of many
-other Alevrodidae in the State seem to have no taste for A. ,city-.

Fungous Diseases.

If insect enemies are ineffective, the same cannot be said of fungnus diseases. Three species of fungi are known to find their natural medium for growth in the white fly larvae, and two of them are sometimes wonderfully successful, in certain localities, in reducing the pest.
BRoWN FuNGsUs.-First in order of effectiveness must be named the brown fungus whose botanical position is thus far unknown n and indeterminable because its fruiting has never been observed. The fungus forms brown pustules of about the size and resembling in some degree the red scale, Aspidiotus fcus, differing from the scale, however, in always being on the under sides of the leaves.
The fungus attacks all stages of larvae and pupae, the vegetative threads penetrating all parts of the body cavity, bursting out as a fringe around the edges of the body, and then growing up over it, forming a compressed hemispherical brown wvart or pimple (stroma), one over each larva destroyed. The size of the stroma depends upon the size attained by the larva when the fungus reaches it. From the base of the stroma growing filaments or mycelial threads reach out sometimes to the distance of half an inch in every direction. By such growth other larvae are reached and thus the disease spreads rapidly








622 BULLETIN No. 67.

over the surface of the infested leaf. Fragments of this nmycelium are supposed to be transported by wind, birds or insects to other leaves, trees and groves where they start a new infection. The fungus does little or no damage to the leaf, never penetrating the tissues and only causing injury by smothering under many of the breathing pores. The appearance of a wYell matured case of brown fungus is well shown by the accompanying photograph (Plate 111, fig. 3.) taken hy Prof. Hume.
THE RED AscHERSONIA (A1schersonia aleyrodis Webber)
-This fungus is very conspicuous, form-ing more elevated pustules than the brown fungus, and which are of a ruby-red -or pink color. The pustule, when matured, consists of a ruiby-red center surrounded by a fringe of pinkish orange, sometimes approaching whitish. When immature the center consists of sev eral to many ruby-red cups developing in craters of pinkish white. The red cups fill out, project slightly beyond their craters, and finally coalesce to form a ruby-red cone surrounded by a light pink base-the matured form. The deep red material consists of the sporuiles of the fungus and the lighter encircling ring is its mycelial woof. The inycelial threads do not reach out so far as those of the brown fungus and dissemination is probably accomplished altogether by spores. The sportiles are gelatinous and adhere together so strongly in masses that the wind would seem unable to scatter them. The spores are loosened by the masses becoming wet, and heavy dews or light showers combined with a fluttering breeze so that drops of water are shaken from one leaf to another is probably one means of scattering them. If all the pustules were exposed to the full force of a heavy, driving raini, all the sportiles ,N ould probably be dislodged and carried to the ground, but it is conjecturedl that their position on the under surfaces of the leaves protects them from too rapid dispersion tinder such circumstances, and at the same time gives possible opportunity for spreading them. The young larvae move about freely for several hours upon the leaves on which they have hatched and occasionally pass to other leaves, and while thus traveling can become infected with the disease before settling permanently;








THE WHITE FLY. 623

however, it is safe to say that the insects that become infected in this manner are exceedingly few.
Ants are possibly important agents in distributing the spores. They visit the leaves for the purpose of feeding on the honey dew excreted by the white fly larvae and they could hardly pass over thoroughly infected leaves without entangling spores in their feet, especially if they were sticky with honey dew, and such spores would be readily transferred to the next larva visited. The first indication of larval infection is the appearance of translucent yellowish spots, usually near the edge of the larva, which becomes swollen and instead of throwing off its honey dew to the leaves beneath it, as is customary, allows it to accumulate over and around its body. The honey dew, being an excretory product, this early manifestation of the disease may be characterized as a violent diarrhoea. The hyphae or threads of the disease occupy a circle around the margin of the body, through which they eventually burst as a surrounding fringe. Death usually occurs before the hyphae appear through the ruptured margin. The threads, instead of reaching out over the leaf surface to any extent, grow into the larval body and over it, finally hiding it completely and forming the matured pustule as before described.
SPHAEROSTILBE COCCOPHILA Tul.-This fungus, well known as a parasite on scale insects, has been received from Orlando. growing upon Ai. citri. So far as can be judged at present its work upon white fly is comparatively insignificant, but under favorable conditions it might become a factor of considerable importance. The fungus appears, when matured, as stumpy, elongated, coral-reddish tufts around the body margin and on the dorsal surface, but rarely or never concealing the insect. The biology of this fungus is discussed by Prof. P. H. Rolfs in bulletin No. 41, of this Station.
BLACx FUNGUS OR SOOTY IIOLD.-I have received the sooty mold covering the under surfaces of the leaves and smothering many of the larvae, with the report that it was "a fungus destroying the fly." In some instances I have seen 40 per cent. to 5o per cent. of the larvae smothered to death by it; it







6L4 BULLETIN No. 67.

has no effect in killing the insect until infestation is excessive, and ceases to operate as a destroying agent when the larvae are sufficiently reduced in number to stop the flow of honey dew over the lower surface of the leaf.

Methods of Introducing these Fungouq Diseases into Infested Groves.

Until more is known of the developmental history of these diseases it will be wisest to approximate the conditions under which Nature spreads them as the surest way of getting them established where they do not at present exist. Introduction can, perhaps, be most satisfactorily accomplished by planting in the infested groves trees t1pon which the fungi are well established. The trees should be planted so that twigs of the infested ones interblend with those having -upon them the diseased larvae in order that the leaves of the two may thus be brought into contact. If the transplanted tree is small it may be planted in a tub and elevated to the proper height on a box, or the tub may be fastened in the fork of the tree which it is desired to infect. Even this method sometimes fails but it commonly succeeds. The time of transplanting is not important, the essential point being to get the tree to growing without dropping its leaves.
Pinning of fungous infested leaves with the fungous pustules in contact with the healthy larvae of uninfected leaves and thus leaving them; spraying with spores of the fungus and fragments of its mycelium suspended in water; hanging of cut infected branches among uninfected ones; inoculation by means of lightly pricking the larvae with a needle which has just been immersed in water containing an abundance of spores and fragments of mycelium; and placing the infected face of a leaf in contact with the larvae on an uninfected one and securing them in this position by means of a cheese-cloth band which binds in a moistened plaster of cotton or moss on each side of the leaf, have been tried by various experimenters, myself included, without marked success. However, an infection




























Fig. i.


Fig. 4.
Fig. 3.
PLATE 3. (PHOTOGRAPHS.)
Fig. i.-Larvae and pupae of White Fly on Orange. Fig. 2.-Red Fungus, 4.-cher.sonia aleyrodis Webber. Fig. 3.-Brown Fungus on Orange. Fig. 4.-Adult Flies and Eggs on Orange.











THE WHITE FLY.

is sometimes started by these methods. When the last is used the cotton or moss is moistened by pouring water upon it every two or three days and the bandages are removed in a week or ten days; care must be taken not to make the bandage so heavy that it will break off the leaf when the cotton is saturated with moisture.
How Far May the Fungus be Trusted to Destroy the Fly?
Different observers will give different answers to this question. Some intelligent growers, located near the coast in South Florida where conditions of heat and moisture are as favorable as they possibly can be for fungus growth and development, are sanguine in the belief that no spraying is necessary, while some of their neighbors are equally confident that the highest degree of profitable production can only be reached by diligent spraying or fumigation. Classed with neither the sprayers nor the non-sprayers is a numerous contingent that is confused between the claims and practices of the two schools, and therefore its representatives spray a little, then wait a year or two for the fungus to
develop, then spray a little more, then wait a-ain for the fungus to appear. This mixing of the practices
of the two schools fails to secure the benefits of either and groves that are improperly, intermittently or rarely sprayed would best be left wholly untouched if any fungus is present in them. I once thought there might be a middle road of practice between the two schools and that by observation of the natural agencies at work to destroy the insects it could be decided whether spraying was or was not necessary. While this may be true under some circumstances, careful observation for four years has convinced me that for th-, orange grower in Florida the truth lies at the two extremes of practice and not at all between them. I cannot too emphatically state my conviction that if one in this State is to trust his natural friends to destroy his insect enemies, he must carefully study the habits of these friends, introduce them, propagate them, disseminate them, and allow them to spread and multiply without hindrance by the application of caustic sprays which destroy friend and







BULLETIN No. 67.


foe alike. Fungi are easily destroyed by alkaline washes and soaps, whether the alkaline base is caustic potash, caustic soda, or lime; and in Florida with its long, hot, humid summers fungous diseases are commonly many times more effective than predaceous or parasitic insects. Where fumigation is practicable it has one distinct advantage over spraying in that it does not destroy fungous growths. The man who is not willing to leave the safe-keeping of his grove in Nature's hands should plan to spray regularly several times each year and the expenditure should be counted upon as an outlay just as necessary as is his fertilizer bill. I believe that seventy-five per cent. of the groves in this State, whether infested with white fly or not, if handled in this way, would slio\v an improvement as marked as a properly fertilized grove shows over an unfertilized or an improperly fertilized one. I repeat emphatically that while I have no word of condemnation for the man who with intelligence and skill directs Nature's agencies so that he secures results with most insects equal to the best, (and NN, e have some such in Florida), I believe that white fly is an insect that should be fought by everybody with insecticides from the day it is discovered in a grove. I admit that there is no spray that will kill white fly and not at the same time inflict injury to the trees upon which it is so often applied, but I am satisfied that the injury is far less than white fly causes, except during exceptional periods when fungous diseases are unusually active. Infested trees that are properly sprayed through many years and are correctly treated in other respects, I believe will live longer, yield better, and give much larger net profits than they will CIO if fungi alone are relied upon for protection.
The views of Mr. A. J. Pettigrew, being based upon many years of observation and the trial both of spraying and depending upon fungi, I think too valuable to omit. Mr. Pettigrew regularly sprays such of his groves as are planted on pine land in open fashion, that is where the distances between the trees are great enough to admit of the free circulation of air among them; but in case of close-planted trees on hammock soil and








THE WHITE FLY.

especially wx hen still closely surrounded by hammock woods, he depends wholly upon fungi.
Many of the attempts to introduce the fungi into the upper parts of the State have failed, and I have never seen the diseases doing effective work very far from the coast. In old orange days Prof. Webber records having seen the red Aschersonia in abundance at Gainesville and Panasoffkee. At present the districts in which the two important diseases are really successful are along the Manatee river and about Fort Myers. It is impossible to accurately judge at present what these fungi wNi- do in the upper and interior parts of the State.
For practice, I recommend that one hav ing an infested grove either spray it or fumigate it according to circumstances; that he persuade his neighbors to do likewise if possible: 3f the neighbors are obdurate and will not treat their trees, persuade there to introduce the fungi as the next best thing; if they will not do this it may be worth while to introduce the diseases for them and then work to create a State Entomological Department with sufficient resources at its command to enable it to supervise the introduction of such valuable fungi into ever neglected and infested grove in tle State.
Mr. A. J. Pettigrew, Manatee, Fla., has kindly given permission to refer to him as being prepared to supply for the trade, trees having upon the leaves both the red and the brown fungus in suitable condition for introduction into new localities. The frank honesty, which through many ),ears has characterized Mr. Pettigrew's dealings with the public and xx-hich now, in the interest of the public welfare, induces him to allow the use of his name in a way that most nurserymen would shun. deserves the appreciative consideration of our people. "f some citizen had not consented to do what Mr. Pettigrew has done I know of no regular source of supply of these diseases that could have been named, and I am not provided with the resources by which the work could be undertaken by my department. I feel sure that no one need fear to order defoliated, clean stock of Mr. Pettigrew, for his past record and present attitude is a certain guaranty that it will be furnished.


Bul, 67-3








BULLETIN No. 67.


Sprays.

As before noted three of the four pairs of spiracles or breathing pores of the larva are on the under surface of a V shaped fold or groove,witli the apex directed backwxard,which is readily observed at the anterior end of the body, approximating the separating line between Tae Eead and thorax; and indeed this fold was once supposed by entomologists to he the dividing line between head and thorax:- but as observed by Prof. Woodworth, it is wholly thoracic-in position and is a specialized apparatus for respiration.* Another or fourth pair of spiracles is on the under surface of an anal groove or fold. Since the larva is very closely pressed against the leaf and the only ingress -6air to the spiracles is through the grooves or breathing f(Ads mientioned, the efficacy of the resin sprays which close uip the outside aperttures of the breathing folds is readily understood. It is only necessary to obtain a ring of resinous wax around th-e body-ring of the larva, thus forming an hermetical seal, to suiff ocate it. If one or more of the four tube openiings are left unstopped while the others are closed the insect will probably survive just as a man with one lung will survive for a time; and if a rain comes to uncover the stopped tubes within teni or fifteen days, it will probably recover altogether, whereas, if all the tuibes are closed it will die in a few hours. The structure of the insect would seem to indicate that a fine and evenly distributed spray, would be most effective: but resin wash, going through a fine nozzle, froths a good daal, including so many air bubbles that a certain degree of coarseness of spray ,gives best satisfaction. A caustic property in the spray is also important in order that death may result before rains dissolve off the wash.
The formula in general use and which is most satisfactory, for regular work, cost and efficiency considered, is the one originally recommended by Prof. Webber, and is as follows:

*Canadian Entomologist, VOL 23, June i9off, P. 173.








THE \ILITE FLY.


I Resin, pulverized. . 2 lbs.
Caustic Soda, granulated, 98 per cent . 4 i-4 lbs.
F ish O il . . . . . 3 pts.
W ater for final bulk . i5o gals.
A somewhat cheaper formula is the following:
2 Resin, pulverized . .2o lbs.
Crude Caustic Soda, 78 per cent . 4 lbs.
F ish O il . . . . 2 1-2 ptS.
W ater for final bulk . ioo gals. to i -o gals.
Ordinary commercial resin, such as is bought by the barrel in Florida, is satisfactory, and the caustic soda is of the quality used in soap factories. The crude soda comes in drums of from 112 to'200 pounds each.
Another formula which has given good satisfaction to some growers because of the convenience of quickly obtaining the materials w ithout ordering them from a distance and of keeping the soda indefinitely without special precautions is as follows
3 Resin. pulverized .20 lbs.
Caustic Soda ( Star Ball Potash, pulverized) 7 lbs.
F ish O il . . . . 3 1-2 pts.
\Vater for final bulk . too gals.
Resin costs I 1-4 cents per pound. or if obtained direct from the naval stores farms i cent per pound or less. Caustic soda is quoted in Jacksonville at 8 cents per pound in ten-pound cans. 7 I -2 cents per pound in 25 -pound cans, 7 cents per pound in 5o-pound cans. This substance rapidly absorbs water from the air, becoming a very caustic liquid and is therefore best purchased in packages, the entire contents of which can be used at once after opening. If small quantities of spray are needed the smaller packages should be purchased. The crude caustic soda costs from 3 I-2 to 4 cents per pound in New York, f. o. b., and cannot be obtained in small packages. It becomes of an adamantine hardness after being exposed to the air for a few days and should be worked up at once after opening the drum. It is suitable for use where the grove is large and the








W6U BULLETIN No. 67.

spraying outfit, from preparing plant to number of nozzles at work, is of considerable magnitude. Star Ball Potash comes in cases of 48 pounds each, one-pound balls, at $3 per case or 6 1-4 cents per pound. It mnay be exposed to the air for any length of time without being injured as each ball is covered with a resinous jacket. It can be obtained from almost any large grocery. Fish oil costs about .50 cents per gallon. The mnaterials for ioo gallons of spray made by formula I will cost about 51t cents, by formula 2 about 6o cents, and by formula 3 about 90 cents. Formula I diluted to the same degree as the other two will cost about 76 cents per one hundred gallons.
As a smothering wash formula I is probably equal to 2 and 3, but its contact effects are less satisfactory. If the wash is to be used in summiner the dilution is about right, but for winter use better results are secured by diluting to 100 gallons instead of i5o. The materials for resin wash can be had from almost any wholesale dealer. Among the best known firms in Florida may be named E. 0. Painter & Co., Wilson & Toomier, and C. R. Tysen, all located, at Jacksonville.
The details of preparation are the same no matter which formula is tised. Procure a large iron kettle, a hog scalding vat is excellent, and another smaller kettle for hot -water. If a large kettle of from twenty five to forty gallons capacity is unavailable, a number of smaller ones can be used, the materials being divided between them as they are weighed out and measured. Heat in the large kettle thirteen or fourteen gallons of water, having previously placed the materials given in one of the formulae in the bottom. If the w ater is hot before the materials are put in, add the resin and fish oil first and then the soda in small lots to prevent a sudden boiling over. Boiling is be st continued for two or three hours over a hot but not too brisk fire. One hour's boiling or less will give a mixture which can be used but results will not be as satisfactory as when the wash is more thoroughly cooked. Whenever there is a tendency for the liquid to boil over, subsidenice will quickly occur if a pint or more of water from the water kettle, which is kept warm but not boiling, is added. Never add cold water while








THE WHITE FLY. t0o

the wash is cooking if you desire results that are certain. Increase the quantity of solution by gradual additions of warm water until a stock solution of thirty gallons is obtained. For use, this is to be diluted to one hundred-fifty gallons in case of formula i, to one hundred gallons with formula 2, and one hundred gallons with formula 3. The stock soluItion may be kept for a time and used as desired, but the wash is best used as fast as made. Any sediment or settling in the stock solution indicates that cooking was incomplete and must be repeated. \here a steam pump is possessed or a head of steam is available a set of barrels may be arranged with steam pipes leading through them and resin wash can be prepared rapidly and in quantity by boiling w ith steam. The stock solution should be strained before diluting it to remove any particles or trash that would clog the pump nozzle.

Other Sprays and Remcdies than Resin Wash.

KEROSE\E EM AULSION.-Kerosene used as an emulsion or in a ten per cent mechanical mixture with a kerowater pump is an efficient destroyer of the larvae and eggs of the fly, but is somew hat uncertain in its effects upon the tree. The emulsion, properly made, is much more reliable than the mechanical application, made with a kerowater pump. Bright, sunny days with a dry atmosphere should be chosen for making kerosene applications. If applied upon a cloudy, humid day that is followed by several days of cloudy weather, thus interfering with rapid evaporation of the oil, very serious injury to the trees is apt to follow. From ninety to ninety-five per cent of the larvae are killed by one thorough application. An occasional spraying with the emulsion may not be objectionable, but I do not recommend it for continuous use. Crude pretroleum should never be used upon citrus trees.
WItALE OIL SOAP.-Any good whale oil soap will be found useful in fighting white fly. Of the hard, or soda soaps, Leggett's Anchor Soap is probably not surpassed. The true potash soaps seem to give better results with the insects and trees, con-








632 BULLETIN NO. 67.

sidered together, than any of the insecticidal washes, when used continually for several seasons, as must be done in case of white fly. Good's Potash Whale Oil Soap No. 3 is well suited for such use and is safe as a summer application. Used at the rate of one pound to four gallons of water it will kill about sixty per cent of the grown larvae in March, and, when used at the rate of one pound to three gallons of water on half grown larvae in May or early June, from eighty-five to ninety-five per cent of them are killed. Though a very heavy rain fell within two hours after making an application at the latter strength in early June, not less than ninety per cent of the insects were dead two or three days afterwards. Leaves, having upon them pupae from which the adults were emerging and larvae in less advanced stages, when immersed for ten minutes in a solution of the soap, one pound to four gallons of water, have invariably had all the insects upon them killed unless they w ere peculiarly sheltered.
In laboratory experiments, Good's Tobacco Whale Oil Soap No. 6 (lid not seem more effective than did the No. 3 soap, but in the field one pound of it in five gallons of water seemed to give somewhat better results than one pound of the No. 3 soap in three gallons of water. Leggett's Whale Oil Soap Compound a true potash soap, used at the rate of one pound in three galIons of water, gave, in the field, about the same results as Good's No. 3, but in laboratory tests it seemed to be not so effective.
For summer use and for trees that have been weakened by the use of more severe sprays, the potash soaps are especially recommended.
Purchased by the half-barrel, Good's Potash Soap No. 3 costs 3 I-2 cents per pound; or, if used at the rate of one pound in three gallons of water, one hundred gallons of spray will cost $f.T7; if the dilution be one pound to four gallons of water, one hundred gallons of spray will cost .87 t-2 cents.
HAMMOND'S THRIP JUICE.-This preparation made by Benj. Hammond, Fish-kill-on-the-Hudson, N. Y., is apparently a very concentrated potash-tar soap which readily dissolves








THE WHITE FLY. V00

in warm water. In twenty gallon kegs, it costs $i.6o per gallon, and as the dilution recommended is one part of Thrip Juice to one thousand parts of water, one hundred gallons of spray will cost sixteen cents. Used at the dilution given restilts have not been satisfactory at all as compared -with those gotten with the use of potash whale oil soaps applied at the same time and under the same conditions. A few of the younger larvae were killed, hut nearly all of the well-grown cnes survived. It is possible that this insecticide, diluted about one part of Thrip Juice to eight hundred parts of water, will prove a valuable application to use about the middle of May or a little earlier when the larvae are all quite young.
MONTTGOMERY'S IxsECTICiDu--Apparently a potash-sodatar-resin preparation, with possibly other unknown ingredients, the whole quite resembling the ordinary resin wash. Since part, and possibly the largest part, of its base is true potash. the w ash is apt to be more stable than the ordinary soda wash and is therefore probably better suited for summer use than many preparations. The full effect of the wash is not apparent until several days have passed after spraying, but so far as tested, results have been quite as satisfactory as with any preparation used. The stock preparation is sold by Dr. L. Montgomery and Son, Micanopy, Fla., at $8.75 per barrel of 5o galions. For use, the stock preparation is diluted one part to seven or ten parts of water: one hundred gallons of spray, 'therefore, cost $2.5o at the former dilution and $1.75 at the latter.
ToBacco DECOCTION.-Tobacco infusions at all strengths are practically worthless, the effect on white fly larvae being little more marked than if rain water were used. The larvae may be immersed in such decoctions for several hours without being killed. Roseleaf Insecticide, a patented preparation of tobacco extract, gives results but little better than the ordinary decoction.
SULPHUR DusT.-Dusting the trees liberally with flowers of sulphur when the young are hatching has been found to be of no value at all.








BULLETIN NO. 67.


CAMPHOR BALLS.-Camphor balls enclosed in cheese cloth sacks and tied in the trees as repellants are worthless.
LIGHT TRaPs.-Trapping the adults with lights gives no results worth mentioning.
FIGHTING TIE ADULTS-Warfare of any sort directed against the adults is doomed to failure, since the females generally lay their eggs within twenty to forty-eight hours after hatching.

When to Spray and What to Use.
Spraying must be so timed that the greatest number of insects are destroyed, and another and even more important consideration is to avoid injury to the tree, bloom and fruit. Spraying cannot be done effectively while the insect is on the wing. There are three larval periods, the longest of which extends from late Nov ember until the first of March; another extends through May and June; another without well defined limits through late July, August, September and October. The winter larval period offers the best opportunity for satisfactory spraying. Two thorough applications of resin wash should be made during this period as a regular practice and, if a grove is badly infested, the first year that spraying is adopted three may be made with profit. The earlier the spraying is done the less will be the sapping of the trees by the larvae during the winter. The first spraying should be done in December, if possible, and the second in January. A third may be made in February.
Spraying should cease wx hen the blossoms commence opening, but may be continued until the buds ar swollen and ready to burst. A swollen bud in spring is not more liable to damage from a resin spray than it is during the winter. No spaying with resin wash should be done during April, May or early June. Some growers have dropped many thousands of collars worth of fruit by spraying in late May in Soath P lo,'da, and as it has been the experience of not a single grower but of a mnmber and of not a single season but of several, the conclusion must








THE WHITE FLY.


be stated with emphasis that spraying bearing trees with resin wash during the spring larval period is hazardous. Late May in South Florida corresponds to early June in the northern orange section. Spraying with resin wash at any time during June is questionable.
So far as present experience and reports indicate a potash halee oil soap may be used \-ith safety after the fruit has been set for two or three weeks. Where the flies are bad a soap spray may be used in late May or early June. This will diminish the June and July hatching of adults and therefore tend to hold down the numbers of the second brood of larvae which cause the smutting of the fruit. Either the resin wash or soap can be used in July, August and September without danger of dropping fruit, but some scarring and burning will be caused by the former. For summer use I am inclined to believe that a potash soap, used exclusively. will give best results. If a quart by measure of flowers of sulphur is dissolved by boiling with ten pounds of soap in twelve or fifteen gallons of water, the solution being diluted to thirty or forty gallons of liquid for use, a spray is obtained that is effective against the purple and six-spotted mites, the rust mite. scale insects and white fly. Three or four well made applications during the summer, about a month apart and timed to catch the white fly larvae, will keep the fruit free from rust, scale and sooty mold if winter treatment was properly made.

How to Spray.

A good force pump, capable of supplying two to four nozzles and of elevating the spray when required to a height of thirty-five or forty feet is a necessity. Among the hand pumps that can be recommended as filling such requirements may be named the "Friend" pump made by the "Friend" Manufacturing Co., Gasport, N. Y., and the Gould Sentinel Junior pump made by the Gould Manufacturing Co., Seneca Falls,N. Y. There are other good pumps than these, but as I have had practical experience with both of these machines as well as








U36 BULLETIN No. 67.

others I can pronounce then among the best. The latter is well known to our growers. The former is yet a stranger to them, but is something unusually good and deserves an introduction for high power work. If steam, gasoline engines or compressed air pumps-capable of supplying from six to twelve nozzles-are wanted, correspond with such firms as these: Gould Manufacturing Co., Seneca Falls, N. Y.; Friend Mann-


The "Friend" Pump. Gould's Sentinel Jr. Pump.

facturing Co., Gasport, N. Y.; Win. Stahl, Quincy, Ill.; Deming Co., Salem, 0.; The Pierce-Loop Sprayer Co., Northeast, Pa., or Field Force Pump Co.,, Lockport, N. Y.
The leads of hose should be long enough to carry the extension rods, well towards the tops of the trees. Ladders are sometimes used in reaching the tops of very tall trees. A high








THE WHIITE FLYS.

platform is sometimes erected on the spray wagon above the tank on W hich the operators stand to reach high tops, but as spraying for w b-ite fly must be from the inside of the tree outward instead of from the outside inward, such a platform is of little use unless the w agon is driven very close to the tree. Brass extension rods encased in bamboo are less unwieldy than the ordinary gas pipe extension rods and should be eight or ten feet long.
Nozzles that can he adjusted to throw either coarse or fine spray are to be preferred for applying resin wash or whale oil soap, and the spray shou-ld he put on as fine as it can be and at the same time carry well to the foliage. Resin wash when too fine behaves like fine soap bubbles, drifting in the air instead of going to the point at which the nozzle is directed. Nozzles of such types as the Nixon, Bordeaux, M1\cGoven,, Seneca, 'Masson, etc., are suited to this work. For applying any of the preparations of kerosene a finie N ermorel nozzle should be used.
A\ nozzle than can he adjusted to any angle so as to reach the under side of the leaN es from any, position, such as the Gould's Carnation or Erin,, is at times a convenience but is not so necessary as it may appear to he to one who has not learned that the underside of nearly every leaf upon a tree, as ordinarily grown, can be covered by using a straight rod nozzle. The underside of every leaf must be hit and well covered wvithi spray to kill the white flv larvae. The operator must not be afraid of the drip and should stand iveli under the tree and thrust his rod through the forks so the spray w ill be throw n w ith good force against the low er leaf surfaces. For high trees having thick foliage a powerful pump is necessary to drive the spray through to the top.
Some growers prune out all the interior growth from their trees so as to leave then hollow cones. Such trees are easily sprayed, bu-t other grow ers believe the resulting gain is more than offset by losses in other directions. An excessive grow th of water sprouts is often stimulated by too severe pruning, and these are specially attractive to the flies. A growth of water sprouts is the normal outcome of an effort by thle tree to remedy








BULLETIN No. 67.


an abnormal condition-that is, to balance a sufficient top growth against a root system that is overdeveloped. Insufficient drainage is a cause sometimes inducing excessive root growth, and hence indirectly influencing the development of water sprouts. Cutting all of them out, along with the interior fruit twigs, encourages a Dew and more numerous growth of them. Where it is possible to do it train them to grow outward in the foliage zone and allow them to harden and become ordinary normal wood as soon as they will. When they are in the heart of the tree and numerous it is necessary to cut them out as w eli as dead twigs before spraying is commenced.
Trees upon tall trunks are readily developed into the hollow cone. I believe the foliage zone of such trees should be deep, and if spraying seems difficult effort should be directed toward obtaining a pumrp of higher power rather than to diminish the depth of the foliage by pruning. If low branched, sqjuatty trees are more difficult to spray, they are much easier to fumigate than high-topped ones, hut can also be sprayed successfully.
With low trees an adjustable or elbowed nozzle for throwing the spray upward is almost a necessity. The operator will often find it best to thrust his rod through to the side of the tree opposite from where he is standing, tu hIttn
the under surfaces of the leaves on that side. With low-topped trees having dense foliage most of the work must be done by this method. Somne of the leaves, especially at the top, are best reached from a position outside and away from the tree. A clever operator will quickly learn by experience how most conveniently to send the spray where it is needed. The quantity of spray used should he liberal. One thorough spraying is cheaper than two that are half done. Trees from 1-9 to 20 feet high will r-equire from 8 to I 5 gallons of spray; f rom 20 to 3o feet high from 15 to 25 or 30 gallons of spray. Use more than these quantities rather than less.
The following extracts are taken from letters bearing variotis dates, written by well known orange growers whose large








THE WHITE FLY. --experience with resin and soap washes gives deserved weight to their opinions:
"I have used resin wash against white fly for eleven years with perfect success. My long experience with its use has made me very familiar with its effects on trees and fruit at whatever season of the year applied. Several years ago I lost many miiidreds of boxes of fruit by using it in May. I used it again last May, the weather conditions being identical with what they were when I previously lost fruit, namely, very hot aid dry. I think the resin draws the heat and scalds the oranges. An experiment in which I diluted Professor \Vebber's stock solution of wash to I8o gallons instead of 15o gave tihe same results. vWe Yost last May ,ooo boxes of oranges worth from $2,500 to $3,ooo had they matured. William Palmer, Sam Harris and L. C. Randall all used the wash at the same time with Le same results. I am positive that the wash \\-ill take the fruit off every time in the -May period.
"I have kept the white fli under conlrai ever since I commenced spraying. The only trec> that ever became black with smut were near neighboring groves that were never sprayed at all,or else not thoroughly. The fly has not yet reached some parts of my grove. (Mr. Kirkhuff's grove contains about 2,300 trees.) I have sometimes thought the resin spray has some effect in hardening the bark. I thoroughly soak the entire tree. I find, when so applied twice, it takes off about one-third of the foliage and causes ripe fruit to drop badly. I have sprayed in August and September when the weather was dry and had good results in keeping down the sooty mold on tree and fruit. Nearly all the larvae Were killed.
"I commenced by spraying once in January, once in May and once in August. After discovering the danger of spraying in May I gave one application in winter, one in August and another in September. I now spray in winter making two very thorough applications. I believe that I do not have fifty trees out of 2,300 that have any smut on them. I may be obliged to wash a few boxes of oranges."-W. I. Kirkhuff, Braidentown, Fla.








BULLETIN No. 67.


"I was well pleasedl with the results of spraying for white fly last season. My tauigierine grove was comparatively free from fly, so much so that I shipped all the fruit without washing any of it and it was 90 per cent.'fancy bright.' Only about 200 boxes out of 3,500 from the Bank of Kingwood Grove were touched by the fly and these not badly. By being careful to keep all the water sprouts from the trees and spraying well withh resin, fish oil and Star Ball Potash) once or twice in, January or February we have kept the fly out of our groves for the past tw o years. Mr. Nichols was well enough pleased with his last year's spraying to spray again this year.
"I have never sprayed wxithi resin wash in the spring, June being the earliest date I have tried. I have never had any fruit to fall from the use of the wash, hut have had a small percentage of the fruit to burn where it was most exposed to the sun-perhaps from 2 to 5 per cent. of it; from the entire grove, 2 per cent. would probably cover the amount of burnt fruit."-C. P. Fuller, Ellenton, Fla.
"Il beg to say that after making experiments with varying strengths of the Good soap. I have found iS pounds to .50 gallons of water just right. I would not hesitate to spray at any time with this soap, and have actually sprayed the bloom to kill thrips, apparently without injuring the crop of fruit. It is a safe preparation to use, and I have found it will rid the trees of scale, and I feel sure it will be effective against the white fly.
"I have long contended against the use of resin wash and have had, in the past, bad results on young fruit from its use." E. P. Porclier, Cocoa, Fla.
"I have no very definite idea as to the effect of spraying very young fruit with Good's whale oil soap, as I have always avoided spraying trees when fruit was passing through the dropping stage. By the time that the fruit is the size of mnarbles most of the weak ones have dropped off, and from this time on I have used Good's potash soap without seeing any bad results from it, but I have burned spats on oranges two-thirds grown with soap of my own make when used at a strength








THE WHITE FLY. "k

of one pound to four gallons of w ater; but this soap was much stronger than Good's. having less than one-half of the water in it that Good's has.
"I have never noticed any direct injury to trees from one application of resin wash, but when applied as often as three times inside of three or four months it certainly does injure a tree to such an extent that it will 1 take an entire season for it to recover."-C. WV. Butler, St. Petersburg, Fla.
Mr. Porcher and iMr. Butler have not had experience in spraying for White fly, but their knowledge of the comparative effects of the resin w ashes and potash soaps upon treeF, and fruit can be depended upon as valuable.


Scalding Action of Resin Wash Explained.

Sodium resinate, formed by boiling together sodium hydroxide and resin, is a salt composed of a strong base and a weak acid; in the presence of moisture it easily separates again into sodium hydroxide and the original acid. Chemical separation is especially apt to occur if cooking the wvash was incomplete or hurried. The following, therefore, is the probable explanation for the scalding and falling of the fruit:
The hiermetical seal or covering of resin on the young fruit preverits evaporation, thus confining, within, the moisture necessary to cause the dissociation of the chemical elements constituting the inside of the resin jacket; and these being held by the outside layer of resin in contact with the young and tender fruit pulp for an indefinite time cause scalding and burning, culminating in the dropping of the oranges. It is also possible that there is some accumulation of heat inside the resin shelf. Anyone wxho has wxorn a pair of rubber boots for a short time in the sunshine on a hot summer dlay knows that his feet scald. The explanation is found in the fact that evaporation is prevented, and rubber also possessing a great capacity for absorbing heat, an accumulation of it occurs inside the boot., By a somewhat different principle glass enclosures accumulate








BULLETIN No. 67.


heat withinthe phenomenon of plants burning in a closed greenhouse in hot sunshine being a familiar one. According to the results obtained by Mr. W. W. Coblentz of Cornell University, resin is not highly diathernious like glass, but possesses a moderate transmitting power for heat. I think it not improbable that the accumulation of heat inside the resin shell is sufficient to stimulate the chemical activities which, but for its presence, would inflict less injurious effects. As the fruit increases in size it becomes of tougher character and, relatively, so small a portion of the pulp is burned that scalding occurs only in spots, not involving enough of the flesh to cause falling. It is also conceivable that, to a smaller extent, drops of the wash accumulating on the undersides of the fruit, harden into more or less persistent concavo-convex lenses, with sufficient curvature to focus such of the sun's rays as strike them to centers inside the shell, thus furnishing an excess of heat in a local spot, possibly not enough iA itself to cause burning but sufficient to encourage unusual chemical activity in any free sodium hydroxide near such a point. No matter which is the primary agent in causing the falling, whether chemical or physical, it is associated with hot, dry weather and direct sunshine, heat being an important factor in causing it. Besides the original accumulation of wash in drops on the lower part of the fruit, the dews and light rains will regularly carry more of it to the same spot and at the same time stimulate chemical disintegration, thus subjecting such spots to the action of sodiurn hydroxide for a continuous and indefinite period. In like manner some of the fruit may be so located that the drip from dew or light rain from above falls constantly on the same spot, causing a scalded place on the tipper surface or side.
The relatively large calyx cup receives and holds considerable quantities of the spray and this in breaking tip into sodium hydroxide and resinous acid would scald the tender stem of the fruit, inducing shriveling and falling. It is probable that i-nost of the dropping is caused by injury to the stem.








THE WHITE FLY.L0

Fumigation.

Fumigation w ith hydrocyanic acid gas is recognized in nearly every progressive citrus producing country in the world as one of the most effective methods for destroying orange pests. A process that has been found so valuable in every other part of the world is certain to eventually come into favor in Florida. The conditions that exist in our State set some limitations upon its range of usefulness and I think it should not be "boomed" into disfavor. but a gradually increasing number of growers can adopt it each year with profit. The Florida growers bav e had little experience in fumigating trees and think the method intricate and mysterious. Familiarity xvith such work removes such misconceptions and it is discovered that a fumigation outfit is not more mysterious or difficult of mastery to an orange growver than is a spray pump with its accompaniments to a - ocer. It is well-nigh necessary, however, to secure the help) of an experienced fuimigator when beginning such work.
Since it will be necessary. at a later time, to publish directions for fumigating in the field I will burden as little as possible the already full pages of this bulletin with the details of such work, giving only a resume of the results reached two years ago while working in conjunction with Prof. C. AV. Woodworth of the California Experiment Station. Upon Prof. XWnndw orth's arrival in Florida. our first work vas to visit the MlcFarland Tent Factory, then located! at Tituisvilie, and look to the selection and treatment of cloth, patterns of tents, etc. Six ounce drilling, treated with paraffine, a sort of cloth used by the compaivN in the manufacture of tents for protection against cold, was tested, but seemed to allow too much escape of gas. Several patterns of tent, sheet, hoop and bell were made ready, using either eight ounce duck or six ounce drilling, some of our largest bell tents for trees thirty feet in height and twenty-fiv e feet in diameter being made from the latter material. TI practice, the drillug proved quite satisfactory for the smaller tents, but wvas too easily torn for heavy work. Subsequent tly,








644 BULLETIN No. 67.

the people of Candler, Florida, have used a light, six-cent muslin quite satisfactorily, but I am inclined to recommrrend heavier cloth. The cloth for the Station tents was milidewproofed at the factory, and when on the ground where it was to he used, was painted w ith linseed oil, into which enough lamnp-black wxas stirred to giv e body and color to the preparation. We experienced some trouble with burning of cloth; in fact, foumnd it impossible to paint a large bell tent without serious damage, necessitating extensive patching, unless the derrick upon w hich it wxas swung was in perfect working order and repair, so as to avoid the risk of leaving a fold in the canvas for even a short time while drying out. The weight of oiled tents is also a great objection to then. Cactus Juice. whlichl is sometimes used in California, is not available in Florida inufi dient quantities for tent treatment and some new application must be found. Fortunately a preparation, known to sailors in tropical waters has come to my attention and, except that. it renders cloth somewhat objectionable for handling, has thus far giv en g-oocd satisfaction. MAr. Arthur W~eaver, who, superintended the fumigating of M_%r. A. G. Liles' grove, -used the preparation and reported it lighter, cheaper, and in all respects siniuenior to oil w ith which hie had had equal experience. It se~ins not to burn cloth and to be mildew-proof. Cloth so treated and in use upon boats in tropical waters is reported to last for five or six years. The following is the formula as developed and employed by -Mr. Weaver: Five pounds white lead, fifteen pounds of laundry soap, chipped, tenl pounds of lamp-black, two gallons of boiled linseed oil, six gallons of water. Heat to boiling two vessels of w ater, having three gallons in each. In one dissolve the soap and keep the other hot. Thoroughly pulverize the lamp-black by stirring and mixing well with one-half gallon of vinegar. Now add the lamp-black to the linseed oil, stir, and pour into the soap solution. Akdd the white lead, mix the w,,hole thoroughly, using all the water, and apply to cloth with brush, keeping the paint hot enough to just show steaming while being used. If the first coating is not sufficient, reverse the tent and give an application to the opposite side.








THE WHITE FLY.


For trees not oN-er twelve feet high I found hoop tents most satisfactory: above that to tw entv feet in height I think sheet tents will prove best; above twenty feet the bell or sheet wNi- be most satisfactory. As one result of the work a new pattern of derrick was devised for swinging large bell tents, which seems more flexible to vaning requirements than the California patterns; or perhaps I should designate tents handled after this plan as box tents, for they are swung in pairs with the derricks upon the same general principle as ta-e box 'eot; i. e., the type ,f box I nt described in Bulletin 122 of the California Station, the derrick taking the place of a lifter. The idea that a bell tent might be swung like a box tent was (lue to Prof. \Voodworth. who mentioned it upon the day of his departure, and the practical working out of the idea was achieved by the writer's combination of ideas derived from various sources; -Mr. Arthur Weaver's suggestions were especially helpful.
Our derrick consists of a main mast of spruce pine about thirty-five feet high for trees thirty feet in height, and stands between the rows to be treated. To each side of it is attached a gaft twenty-two feet long, also of spruce pine. The foot of the gaft clasps the mast with arms of oak, being raised and lowered with double blocks and pulleys exactly after the manner of a ship gaft. The top of the gaft is double blocked and pulleyed to the top of the mast, so by means of its top and bottom attachments the gaft can be raised to any height, its top many feet above the top of the mast if necessary, or it can be lowered to reach the ground. Since it can take any angle of direction also, it may be quickly adjusted to trees of any height and of variable distances apart. The top of the bell is attached by pulley near the end of the gaft. Three trail poles of hickory, each about ten feet in length, are fastened to one side of the lower border of the tent, their ends being securely lashed to each other with rope, so when they pull against each other the rope and not the cloth will catch the strain. The cloth is caught up and bagged slightly at these points of union of the trail poles as additional protection against








BULLETIN NO. 67.


tearing. The center of each of these trail poles is connected with the top of the gaft by pulley, and thus the border of the tent to which they are attached may be elevated to any height, the opposite border swinging free, within reach, near the ground. A trail rope is attached to each of the trail poles. All pulley ropes belonging to the apparatus are secured to cleats on the inast.
In operation, when the main inast, on rollers or wheels, has been placed in position, the height of the tree to be fumigated and its distance from the mast are noted, and the foot of the gaft is raised or lowered to the point of greatest advantage as learned from experience. A similar adjustment is made of the top of the gaft. The top of the tent is next drawn fully up and then the three trail poles; the hanging free edge near the ground and as mt-ich of the border as possible is now brought into position, and the top of the gaft lowered some if necessary. Slack is now given to the trail poles and a man at each trail rope so pulls the pole to which his line is attached that the whole tent drops into position over the tree. The lower border of the tent must be extra strong to avoid tearing; it is best bound with rope. To remove the tent from the tree the procedure is almost exactly reversed. With inen trained to work together, the tent may be lowered over a tree in seven or eight minutes and removed in about five. Since the operation of removing the tent from one tree raises it almost in position to drop it upon the next, the time required for changing will not be the sum of eight and five minutes, but the last five minutes is divided between the two trees, removing from the one and at the same time getting almost in position to lower upon another by a quick adjustment.
-of the angle of the gaft, it requiring less than eight minutes to cover a tree from this position. The apparatus requires four
-men, one of whom may be the fumigator if he has his mate -1als weighed out beforehand. A gang of four can operate about four tents or two derricks, if the rows are not more than twentyfive or thirty feet apart. This gives forty minutes time to the tree and allows ten minutes for shifting of the tent. In order








THE WHITE FLY. tI

to realize this expeditiousness in practice all apparatus must be in perfect working order and repair and the men trained to handling it. The results secured in my practice satisfied me that this would be a reasonable estimate, for it was done often enough in this time wiith our then imperfected apparatus to justify such a conclusion. Full specifications and illustrations of the derrick at work will he published later on in bulletin form.
Some determinations suggested by Prof. Woodworth and made by Prof. Miller, of the Chemical Department, are o interest and importance. He found that one ounce of sulphuric acid and one ounce of water, mixed and cold, when added to one ounce of potassium cyanide, yielded 428.4 cuhic inches of gas; that one ounce of sulphuric acid and one ounce of water, mixed and added immediately, while warm, to one ounce of potassium cyanide, yielded 467.9 cuhic inches of gas, greater hy a little more than nine per cent. than with a cold mixture of water and acid. Mixing the acid and water, therefore, only as used, means a saving of six or seven cents per tree on large trees requiring two pounds of cyanide. He further determined that a greater proportion of acid did not materially alter the results, and that ammonia seems not to be. formed immediately after the reaction, under laboratory concitions.
A number of experiments were made with citrus twigs, orange, lemon, pomelo, etc., infested with white fly, to determine the susceptibility of the insect to the gas, dose of chemicals to use, length of time necessary and most favorable temperature for treatment, influence of moisture being present upon the leaves when fumiglated, etc.
It ivas found that the insect in its larval and pupal stages is very readily killed by a much lighter dose of gas than is commonly used against the black scale in California: in fact, our field practice with tents demonstrated that we could reduce it about one-half; that the time should he ahout forty minutes; the variation in temperature ordinarily encountered in Florida seems to he a neglectable factor; moisture did not seem to interfere greatly with the efficiency of the work, unless the








BULLETIN NO. 67.


leaves were almost dripping, when it became a factor of much disturbance, though not so great as we had thought probable.
Trees were fumigated in the field in warm sunshine, at all hours of the day, in cloudy weather and at night. We observed but little injury to trees or foliage if fumigated at night, during cloudy weather, early in the morning or late in the evening. Trees fumigated after 9 a. m. and before 4 P. M. in sunshine were invariably somewhat injured, some of the younger limbs dying back and all of the leaves usually shedding. The fallen leaves were all replaced by new growth in a few weeks and no permanent injury done, but the crop upon such trees was noticeably reduced. The dropping of leaves from a tree in Florida has comparatively little significance, the trees, instead of dying, as they sometimes do in California, putting on new foliage and going along as if nothing special had happened. However, the burning of limbs and injury to bloom is another matter, and, therefore, midday fumigation can hardly be practiced. While some defoliation occurred with trees fumigated at other times than midday, ev en after night, it was not strikingly noticeable, nor was damage to limbs or crop of sufficient amount to be detected after a few months. Some of this work was done as late as February 18, when the blossoms were beginning to open, some of them being well expanded. The bloom seemed unaffected by the treatment unless the work was done with the sun at high meridian.
The white fly seemed practically exterminated upon the treated trees. In examining hundreds of leaves from dozens of trees about ten days after they were fumigated, and covering thousands of insects, I was able to find but a single living specimen. If a grove was segregated from all others, I have no doubt that one fumigation would render it so nearly clean that it would need no additional attention for two or three years. The great hindrance to its becoming a practicable remedy is that but few groves are so isolated that the fly will not come to them from neighboring groves, and since the insect seeks young and tender growth for egg-laying purposes, there is perhaps, some tendency for it to go to trees that have been fumi-








THE WHITE FLY.


gated and are therefore putting out new growth. Under ordinary circumstances, the insect is not a great traveler, though Winged, and \vill often take a whole season, extending over three full broods to spread over a ten-acre grove: its progress will be marked bv the trees showing sooty mold.
Special observations were made to determine the effect of the gas upon lady-bugs. On the afternoon of January 22, seventv-two lady-bugs, almost all Chilocorus bivnhicros, which had fallen to the ground under fumigation treatment, were placed in a shallow tin box and left until January 23 : at 9:30 a. m. of the latter date seventh beetles were in the box, a few of them active: at 4 P. m. sixty-six remained in the box, about a dozen of them showing signs of activity. At 8:45 a. m. January 24, sixty-tw o lady-bugs were in the box, and sixty at 12 :4o p. m. ; the sixty never exhibited signs of animation, all being observed to be dead several days afterward. January 24, by i p. m. another lot of one hundred-seventy-one fallen bugs, nearly all of the same species as before, was collected and kept in the same manner as the first ones. January 25 at 4:30 p. I., one hundred-sixty of these were dead, sixteen out of the lot having recovered. In the first lot, sixteen per cent. of the wholh revived, in the second lot about nine per cent.
Since fumigation does not destroy fungous growths many growers vill prefer giving it a trial before using a caustic spray.
No matter what style of tent is used, when it is in position a few shovels-ful of earth are thrown on the bottom to holcl It in place and render it gas-tight around the base. The generating vessel is set under it, as near to the tree trunk as possible, and the water is poured in, then the acid; the dose of cyanide, wrapped in paper, is next dropped into the vessel and the operator, carrying the edge of the tent with him on his back, quickly steps away, holding his breath and letting the tent fall into position as he does so. A shovel-ful of earth is then thrown upon that part of the tent border just dropped and everything is left undisturbed for forty minutes.
The following table shows the amounts of chemicals used for different sized trees by the Horticutural Commissioners of









BULLETIN NO. 67.


Riverside County, California. These amounts are intended for the destruction of scale insects and can be reduced fifty per cent. or more in quantity if it is not specially desired to kill other insects than white fly:

Height of Diameter of Cyanide C. P. Sulphuric Acid,
Tree. Tree. Water. (98 per cent). (66 per cent).

Feet. Feet. Ounces. Ounces. Ounces.

6 4 2 1 1
8 6 3 11, I1%
10 8 5 2 '/ 2',
12 14 11 .5 5 Y
16 16 17 8 9
20 16-20 226 10 12
20-24 18-22 20 14 16
24-30 2028s 24 16 28
20236 215-0 5224 28

The cost of fumigating trees, labor included and not considering the cost nor wear of the tents, is about equal to the cost of giving the same trees three sprayings with resin wash. Low, squatty trees, such as are grown on C. trif oliata stocks, with their branches hanging to the ground, are of the shape that should be sought when it is intended to fumigate them regularly.
The precautions to be observed in handling the chemicals are given In the succeeding section on nursery fumigation work.

The Nursery Situation.

No provision is made by the State for the inspection of nurseries, hence there is no way of officially determining their exact status throughout the State. My knowledge of their condition must necessarily come through chance channels and the information 1 receive is often too unreliable to warrant any public statement regarding it. The reputation of the respective nurserymen for reliability of statement, care in handling their goods and the general condition of the neighborhood in which they are located are the only guides that can be depended upon in choosing from whom to purchase. The safest practice for all





PLATE IV.

FUMIGATING WITH HOOP TENTS AT CANDLER, FLA.











THE WHITE FLY.

parties, customers and nurserymen alike, will be to handle, in the future, only stock that has been defoliated and cut back. I believe that citrus stock prepared in this way is safer from white fly than is inspected and fumigated peach stock from scale, when shipped from a San Jose scale neighborhood. When fumigation with hydrocyanic acid gas is added I regard the protection as perfect. Fumigation should always be practiced during the spring and summer months and is best never omitted. If stock is shipped during spring or summer, every vestige of leaf should be carefully cut aw ay so as to make certain that no1 unhatched eggs remain, since these are not readily destroyed by fumigation. Fumigation is undoubtedly effective in destroying the adults and larvae. Dipping and even soaking infested leaves for considerable periods of time in tobacco decoction, Rose-leaf Insecticide, Good's Potash Whale Oil Soap NO. 3, Good's Potash Tobacco Soap No. 6, Leggett's Whale Oil Soap Compound and resin wash have been tried, but Nvithiout satisfactory results. The odor accompanying most of these washes is objectionable and even when the leaves are left immersed in them for considerable periods of time, protected larvae escape injury; thus a leaf with a blister or cavity produced by scale or red spider w hich was netted over with a spider's web and threads of the sooty mold was submerged for ten minutes in a solution of Good's soap NO. 3, one pound to two gallons of water, wxithut killing the larvae sheltered beneath the web as shown by an examination made 72 hours later.
To determine the dose of potassium cyanide (KCN-\) necessary to give the correct amount of gas to kill the white fly larvae in an air-tight fumnigatoriuim, I commenced by using one gramme of KCN to 15 cubic feet of space for thirty minutes time. An examination made three days later revealed that about 47 per cent. of the larvae bad been killed. One gramme of KCN used for I 1, 9 and 7 I -2 cubic feet, respectively, for the same length of time showed constantly decreasing percentages of living larvae. One grarnme of KCN to 6 1-2 cubic feet of space allowed but one larva out of many that were examined








Daz BULLETIN No. 67.

to comne through alive. One gramnme to 6 cubic feet seemed to kill everything but to make the dose more certain one gramme to 5 3-4 cubic feet was adopted as the standard dose and has been repeatedly tried. alw ays giving the uniform result of killing all larvae and adults. This dose requires about 17 grammes; or 3-5 of an ounce of KCN for every i00 cubic feet of space, or i~o grammues, that is about 8 ounces, Avoir., for every i,ooo cubic feet of space.
The following experiment was made to determine the effect of fumigation on the true eggs. A potted lemon bush, entirely free from white fly, was confined under a cheese-cloth cover and several hundred adult flies were captured and liberated inside the cover. At the end of 48 hours the leaves were covered with thousands of eggs, several hundred of them occurring on each of several leaves. The bush was then fumigated for thirty minutes with the standard dose, or one gramme of KCN to each 5 3-4 cubic feet of space enclosed. The bush was then kept in an unused recitation room, into which no adult fly could possibly enter by accident. After three weeks it was found that about 5 per cent. of the eggs had hatched and the larvae had set upon the leaves. As there could be no possible error as to each egg having been subjected to the gas it is evident that a stronger dose is necessary to kill them. H-ad the plant been left in full sunshine it is probable that a yet larger percentage of the eggs would have hatched. The bush wvas severely burned by the gas and it appears that the v et undetermined (lose which is necessary to make certain the killing of the egg, is equally certain to damage citrus plants. During the period of heaviest nursery shipments from December is to the ist of March, there are no unhatchedl eggs, hence no danger exists because of them during this period. Since the eggs are never laid elsewhere than upon the leaves, defoliation and cutting back of the terminal growth removes all possibility of danger from unkilled eg-gs at all times.
No citrus leaves from an infested nursery should be allowed to get into, the moss used in packing. Such leaves could hardly be a source of danger except when harboring well








THE WHITE FLY. -1.

grown larvae or pupae but, as before mentioned, both larvae and pupae will live for several days upon detached, drying leaves in the laboratory : and if they were packed in damp moss it is very probable that nearly matured ones xvould issue as adults even as long as three weeks or a month after they were packed.
This spring two lots of trees, six in each, infested with
-white fly larvae, were fumigated with the standard dose of KCN and set upon the Station grounds without being defoliated: most of the leaves fell as a result of the fumigation but a few adhered carrying the dead larvae. No white fly developed on these nor was there any injury to the stock apparent, due to the fumigation. Another dozen similar trees, not fumigated and planted out at the same time, held a fraction of their leaves, the white fl appearing upon them at the regular time.
Mv fumigating box has never been packed full of stock With the foliage remaining upon it and it may be doubted if the dose I use is sufficient to kill all larvae under such circumstances : but I think there can be no doubt that in case it were filled as full as possible of defoliated stock all chance larvae present would be killed.
The accompanying photograph shows a fumigating bo-of similar pattern to the one in use on the Station grounds. It consists of an inside and an outside box, with an intervening space of six inches filled with sand. The outside box needs no floor but the inside one should be floored to prevent partial absorption of the gas by the moist, earthen floor. The lid which is hinged and lifted by means of double blocks and pulleys is made of two thicknesses of wainscot or flooring with a laver of raw-hide building paper between. Two good coats of lead and oil paint should be applied to the cover inside and out. An air-tight joint is secured between the cover and the box by running around the under side of the cover, Which overlaps -ti edges of the inside box, a pine strip, 2 inches in depth, which thus dips dovn into the sand. It is best to have a small door about I foot square in the bottom of the box, on one side and as








654 BULLETIN No. 67near the center as possible. This door furnishes safe means for introducing the chemicals; its edges should fit against a cushion of felt or burlap; it is tightly pressed against the cushion by some form of sliding wedge driven into place by a smart rap with a hand mallet. If a slatted platform is constructed six or eight inches from the floor to support the plants, the gas being generated below it, diffusion will be comparatively uniform anl results with both trees and insects more satisfactory than can be otherwise secured. A tight box-hood should cover tae upper half of the generating box which is a foot in each of its three dimensions, the lower half of it being left open, thus forcing the gas out beneath the slatted floor.
The following dimensions will give a box of 99 cubic feet capacity (practically ioo cubic feet) which will be one of the most convenient sizes. Length of the inside box, I I feet; width, 3 feet; height, 3 feet. Length of outside box, 12 feet; width, 4 feet; eighth, 3 feet.
To charge the box with gas, fill it -with the trees to be fumigated and close down the lid; if the sand is not sufficient in quantity, fill in enough to make a tight joint certain. Now through the trap door introduce into the generating box the generating vessel, which should be of earthenware, China or glass-a glass fruit jar will do; with a glass graduate, measure out in liquid ounces a number of ounces of sulphuric acid (H2SO4) greater by half than was used of ounces of cyanide, or in this case, add to 3-5 ounce equal .6 ounce, 1-2 of itself, or .3 and 9-io liquid ounces is obtained as the correct amount of acid. Of water, use 1-2 more liquid ounces than of acid; in this case, 9-io plus 1-2 of itself equals .9 plus .45 equals 1-35 or 1 1-3 ounces (nearly). First pour the water in the generator, next the acid. The cyanide should be weighed out beforehand and kept, each dose wrapped in paper, in an air-tight receptacle. The dose, paper and all (use, as little paper in wrapping as possible) is dropped into the water and acid, the door being immediately closed and wedged into place. After remaining closed for 30 minutes the upper lid is raised. The residue in the generator consists of sulphate of potash, sulphuric acid and


































OPEN.


CLOSED.


PLATE V.

FUMIGATING IMX.












THE WHITE FLY,


water; should it come in contact with the skin or clothing, -11 will corrode and is best buried in the ground when the generating vessel is emptied. It should never be forgotten that cyanide of potassium is a niost deadly poison and that a very minute particle of it introduced into the moutfl will1 cause immediate death. It is best to use forceps in handling it; never allow it to touch cuts or open sores on the hands. It should be kept away from children and uninformed persons. The gas is the deadliest known, and while no fatalities have ever attended its use as an insecticide, such have occurred in chemical aboratories, and the greatest caution should be observed in working with it. For fuller information concerning fumigating appliances and methods of procedure, the reader is referred* to Prof. W. G. Johnson's Fumigation Methods, published by the Orange Judd Co., New York.

Insects Sometimes Mistaken for White Fly.

Lecanium hesperiduni Linn.-The immature stages of this insect are perhaps more easily, or, at least, are more frequently mistaken for white Bly than any other species. The flat, oval scale upon the leaf so nearly similates the larva of white fly that the ordinary observer is quite excusable in being deceived at first sight. H owever, the Lecanium is more elongated than Alevrodes citri and, relative ely, it broadens much more distinctly towards the posterior extremity. The length when full grown is more than twice that of the mature white fly larva, the width being not quite double that of the latter. The body is distinctly notched inward at the posterior end, a formation differing from that in case of white fly. The young are found on the stems and tender branches of various plants (a position never occupied by white fly larvae so far as I have been able to discover) as well as upon the leaves. When upon the leaves, the young tend to range themselves beside the mid-ribs and principal veins, a habit which again disagrees with that of A. citri. The scale is commonly spoken of as the turtle-back or soft scale. The dorsal skin may be called yellowish or red-








BULLETIN NO. 67.


dish brown, inclining to dark, in some specimens almost to a shining black toward the center. This insect agrees with white fly in causing an excessive growth of sooty mold upon its host plants. (Plate I, fig. I I.).
Nearly related species of Lecanium, such as L. oleae (Oleander is one of its common food plants) are found on various plants, being always followed by sooty mold.
Aleyrodes floridensis Quaintance.-The Guava white fly is found sparsely upon orange. It is a smaller insect than A. citri and the larva is surrounded by a fringe of glassy, waxen rods, conspicuous enough when once noticed, but not readily observed unless looked -or. The insect does no damage to orange. It has been collected from many parts of the State upon guava, which it infests seriously, and several years ago Prof. J. H. Comstock collected it at Arcadia, Fla., on "alligator pear."* A few weeks ago it was sent to me from Arcadia by Mr. E. A. Thomas, taken Trorn orange trees that had been planted out, according to his statement, for one year. There can be no reasonable doubt that the insect went to his trees from guavas or "alligator pears" in the neighborhood. (Plate I., fig.
8.).
Ceroplastes fioridenisis, the white wax scale, often causes patches of gallberry bushes to become very black with sooty mold, the appearance frequentTy be-ing ascribed to the presence of white fly.
Aphis and many other insects which secrete honey dew and hence are followed by sooty mold have been supposed at one time or another to be white fly.
The papaw white fly, Aleyrodes variabilis, has been received once or twice under the supposition that it was the orange white fly. Several species of Aleyrodes may be readily mistaken for it.


*Billetin-U. S. Dept. Agr. Division of Entomology, Technical series No. 8, (19oo) p. 27.









THE WHITE FLY.


The Outlook.

As already indicated, the insect is known to be established in fourteen different counties in the State. I have reasons for thinking that it occurs in several other counties than these, but no resources are at my disposal to make a thorough inspection of the State and determine authoritatively its exact distribution. I feel sure that Nvithmn two years more every neighborhood that wvas infested before the freeze will discover that it is still infested. \Vhere the insect has become well established by three or four year's of breeding it is well nigh or quite impossible to exterminate it. It is seldom discovered until four or five years have elapsed after its introduction, that is~not until measures of extermination are very apt to prove futile. At the time of discovery it will appear to-he confined to a small area, in most cases from a few bushes or trees to a quarter of an acre, but in reality it is sparsely scattered ov er a territory having a radius ol from a quarter to a half mile from the center of infection. I have proved this too many, -times to be deceived; yet many groves and yards in a town may be infested for several years Without the insect's finding its way in to groves not more than a mile or txvo from town.
With the habits of the insect well known and its distribution once authoritatively established, its spread ox-er the State could be greatly retarded hut not finally prevented. Fifteen or txventy years may yet remain before the insect xWill have found its way into, every neighborhood in'fd da, but this it 'will certainly do in time. This certainty of eventually getting it should cause no indifference, discouragement or carelessness on the part of any neighborhood or individual; rather ought it to determine everyone to postpone the evil day as long as possible. Five, ten or fifteen years of immunity from the fly, with consequent bright, early maturing fruit of high quality, xv-hen competition xvith other parts of the Wvorld will be close and a large part of Florida handicapped because of the insect, is a reward well worth the price of a diligent and persistent lookout to obtain. Special caution should be observed to receive no improperly pre-








BULLETIN NO. 67.


pared nursery shipments from any suspicious quarter; and when the insect appears in any neighborhood the preceding section of this bulletin upon methods of dissemination should be carefully studied and the suggestions there given to restrict its spread should be put into practice at once.
Will the orange business be ruined by the insect? No, certainly not; granting that teri years from now the State will receive three-fourths of a inillion or even a million dollars less per annuin than it would receive if the insect were absent, Florida oranges can still be grown at a profit as has been proved by numerous growers through many years of trial. If groves in the heart of the present white fly districts are quoted at prices but little if any lower than if they were located outside of them, they will continue to be paying holdings there and elsewhere, notwithstanding the presence of the fly. No insect of this nature has ever withstood the skill of mail in the end, destroying a great industry, and white fly is not so difficult to control as many believe. Natural enemies, restoring
Nature's balance, will appear in time, and until then the various means of control already known will be employed by an increasing number of growers. Legislation could be helpful in certain ways, chiefly in increasing the resources of the Entomological Department for experimental work and thus enabling it to introduce the important diseases of the insect into such sections as do not at present have them. The establishment of quarantine regulations would be of questionable utility unless an appropriation of sufficient magnitude were made to maintain a large force of inspectors, and the exercise of all possible vigilance on their part would still be less effective than the simple observance by every purchaser of the recommendations embodied in this publication. So far as the grove problem is concerned, as previously observed, the sentiment of our people is sharply divided regarding wise insecticidal practice, and, until it can be united, the enforcement of prescribed methods of treatment by State officials could only be a source of friction and irritation. Those who believe that treatment of all infested groves should be enforced by law should become home mission-








THE WHITE FLY.


aries for the next few years, satisfying the majority of their neighbors that such treatment pay ,-a task which I believe can be readily wrought by two or three seasons of practical demonstration with spray pump or fumigating tent.
The ultimate distribution of the fly will be over all the Gulf States northward to an isothermal line running somewhere through northern Georgia and wvestward; California is very likely included in the infested territory now, but it is in the moist gulf regions that the uiepreciations of the insect are to be feared. Citrus fruits will be profitably produced, notwithstanding its presence, wherever climatic conditions are suitable.

Acknowledgments.

In the prosecution of this investigation I have freely consulted the writings of Riley & Howard, Webber, Morgan,. Woodworth. Ouaintance and others. Valuable information and suggestions hav e been given me from time to time by Mr. A. J. Pettigrew, Prof. H. H. Hume, Prof. C. WV. Woodlworth, Mr. F. D. Waite, and others too numerous to mei3tion. The drawings for plates I and 2 were made by Miss L. McCulloch, tinder mny supervision. The drawings for plate 6 were made by Prof. Cockerell. The negatives for plates 4 and 5 were taken by me and the prints were made by Prof. Hume. The first three figures of plate 3 are wholly the work of Prof. Hume,, while Fig. 4 of the same plate is credited to Prof. H. G. DorseySummary of Important Facts and Recommendations.

I. White fly, an insect of unknown origin, is probably our worst orange pest where it now occurs. It is known to be established in 14 counties in Florida and probably exists in a nuiher of others.
2. There are three annual broods of the insect of which the first two broods of adults, one occuring in March, April and May and the second in June. Jjuly and August. respectively, are well defined and distinct; the third brood occurs in greatest








660 BULLETIN NO. 67numbers in September and October, its time limits being poorly defined. The insect shows a tendency to continuous breeding during the last half of the year.
3. The eggs are laid only upon the leaves and the young are motile for a few hours after hatching. When wandering ceases, the larvae fasten themselves to the under surfaces of the leaves and imbibe the sap, at the same time covering the upper surfaces of the leaves vertically beneath them with a coating of honey dew in which a smothering, black, sooty mold develops.
4. The fruit is delayed several weeks in ripening and its sugar and acid content is much reduced; it becomes covered with black mold, necessitating hand or machine washing to prepare it for market, and its carrying qualities are often much injured by such preparation. The annual loss inflicted on the State amounts to hardly less than a quarter of a million dollars and will increase unless the insect is fought.
5. The insect is scattered by nursery shipments, by wind currents, by being carried in covered vehicles, in railway coaches, etc. The inotile young may become entangled in the feathers of birds and adult flies are undoubtedly occasionally carried by the same means.
6. White fly has few insect enemies, but two fungous diseases are very efficient in suppressing it under favorable conditions. In close planted groves, surrounded by hammock woods near the coast, these diseases are depended upon wholly by some growers in South Florida to control the insect. It does not become so numerous in open planted groves upon high pine land.
7. Spraying against the white fly is not often abandoned .by growers who have once tried it. The most favorable time for spraying is during the winter larval period. At least two thorough sprayings should be made during the winter. Summer spraying is sometimes useful but the materials should- be carefully chosen.
8. Resin wash is a very satisfactory spray for winter use but should not be used while the fruit is young. Apotashwhale








THE WHITE FLY. U

oil soap spray may be safely used, at proper strength, any time except when the trees are in bloom. Kerosene emulsion, caustic soda solutions of sulphur and salt, Thrip juice and Montgomery's insecticide are all useful to a certain extent and will be sometimes chosen according to the personal preferences of the grower. There seems to be a general and well founded opinion that a good potash whale oil soap is less apt to cause injury to the tree than most insecticides.
9. Fumigation of infested groves is effective and sometimes useful, but at present can only be recommended for use in particular instances.
io. Infested nursery stock is rendered wholly safe by being defoliated, cut back and properly fumigated.
I I. The insect will eventually spread over the entire citrus belt but its march can be greatly retarded by care in purchasing and by vigorous repressiv-e measures where it is already establishedl.

THE NEAREST RELATIVES OF WHITE FLY.

In response to an inquiry addressed to Prof. T. D. A. Cockerell, formerly connected with the New Mexico Experiment Station and at an earlier time Stationed in Jamaica with the Imperial Department of Agriculture for the West Indes, he kindly offered to make the comparative study here given of A. citri and its allied forms, thinking such a study might throw some light on its origin. The recognized standnig of Prof. Cockerell as a comparative anatomist and the large amount of information in his possession relating to this family of insects gives instant interest, to anything written by him on such a question. Whether or not his conclusions ever prove to have been correct, since they direct the attention of entomological workers in other parts of the world to the subject, thereby making possible the discovery of the insect's original home, the thanks of Florida are due him for his effort.








662 BULLETIN No. 67.




THE WHITE FLY.
(Aleyrodes citri) AND ITS ALLIES.
BY T. D. A. COCKERELL.

The genus Aleyrodes (often spelled Aleurodes) was first distinguished and named by Latreille in his "Histoire Naturelle des Crustaces et Insectes," Vol. XII. p. 347. In ihis work published in 1804, there is given a description of the genus, the type of which is the Tinea proletella of Linnaeus. This species, which lives in Europe on leaves of Chelidonium majus, was made the subject of an excellent memoir by Reaumur (Mem. Ins., Vol. II, pp. 302-317, Pl. XXV, figs. 1-7), and consequently was quite well known at the time of Latreille's publication, though it had been erroneously placed among the Lepidoptera.
A close ally of this A. proletella is A. brassicae, Walker, 1852, which occurs on cabbage. This is said to be hard to distinguish from proletella in the adult, but the larva (pupa?) is long, while that of proletella is round-oval. In 1868 Signoret published a revision of the then-known Aleyrodidae, describing seven as new. Most of the species were European., but two were known from Chili, two from the United States, and one from Mauritius. In 1896 Maskell (Trans. New Zealand Institute, XXVIII.) gave a list of all the Aleyrodidae known at that time, numbering 66. Of these, 22 were described as new.

Character.

The adult Aleyrodidae are small, four-winged insects, very similar to one another, except for the fact that some have the wings variously spotted and banded. The pupae, however, present very strong distinctive characters, and are largely used in classification. These pupae are small, oval objects attached to







THE WHITE FLY. 663

leaves, usually to the lower surfaces, and in general resemble the smaller kinds of scale-insects. Under a compound microscope one is able to see certain characters which greatly assist in the identification of Aleyrodid pupae. On the back toward the hind end, is an orifice of a more or less triangular or rounded shape, known as the vasiform oriice. In this is seen a lid-like structure, the opercilun, and a more or less tongue-like object, called the lingua. The margins of the pupae are also variously sculptured, and offer good characters.
With a lens, one notices the color, shape and convexity of the pupa, and the character of the waxy secretion, if any. This secretion covers the whole pupa, but more often it forms a fringe around the sides.

Divisions of the Aleyrodidae.

At present, only two genera are recognized in the family. Aleyrodes, Latreille, includes the great majority of the species, these having the main vein of the wings not bifurcated towards the end. In 1892 Douglas separated the genus Aleurodicus which contains those species having the main vein of the wings bifurcated. This is a perfect valid distinction, but care must be taken not to mistake a fold which often occurs in the wings of Alevrodes for a branch vein. It has not been considered that Aleurodicus can be distinguished from Aleyrodes by the pupa, but I believe it has sufficient characters in this stage also. These are found in the short, broad operculum, combined with a very large lingua, which has two or four bristles at its end. The pupa also has large submarginal orifices, especially in the abdominal region, and the margin is likely to exhibit bristles at rather distant intervals.
Having regard to these characters, I believe that the following, hitherto referred to Alevrodes, may be safely transferred to Aleurodicus.
(I.) Aleurodicus altissimus (Aleurodes altissiMa, Qpaintance, tom. cit p. 2o.)
(2.) Aleurodicus perseae (Aleurodes perseae, Quaintance, tom. cit., p. 32.)








BULLETIN NO. 67.


(3.) Aleurodicus holmesii (Aleurodes holmesii, Maskell, tom. cit., p. 435.)
All the species of A leurodicus belong to the warmer parts of America (North and South), except A. holmesii, which is from Fiji. I suspect that the latter was introduced into Fiji from South America, along with the guava (Psidium) on which it lives.
Although Aleyrodes, after excluding Aleurodicus, includes a great many diverse types, it has not yet been subdivided. An examination of the vasiform orifice, lingua and operculum brings out the following facts:
(1.) There is a group, apparently exclusively American, in which the orifice is rather elongated, and the lingua is long and narrow, and usually strongly crenulated. This includes such forms as A. erigerontis, A. nicotianae, A. vittata, A. variabilis, A. pergandei A. litchi and A. ruborum.
(2.) A small American group, allied to this, has the lingua enlarged distally, with a distinct terminal joint. This includes A. pergandei A. /ltchi and A. ruborum.
(3.) A third American group, found principally on the oak, has the pupa very dense, quite black, with the orifice elongated. The margin of the pupa is peculiar, and there is a white waxen fringe. A. melanops (figs. 2, 3, 4) and A. perileuca (fig. 5) are examples.*
(4.) There is a group of the Old World, from India to New Zealand, in which the orifice is usually short, sometimes broader than long, and the lingua is much abbreviated. Examples are A. cotesii (India), A. croseata (Australia), A. eugeniae (India), A. aurantii (India), A. fodiens (New Zealand) and A. piperis (Ceylon).

Aleyrodes perileuca, n. SP.-Pupa perfectly black, 1250 micromillimeters long, of the usual oval shape, with a very narrow regular fringe of straight white waxen ribbons, about ioo micromillimeters long. A sharp, elevated, submarginal keel; dorsum strongly longitudinally keeled, the abdominal portion with transverse ridges making the segments. The dorsal keel in the thoracic region is sharp, but in the abdominal region it is broad and rounded, with its surface irregularly tesselate, and is crossed by six transverse narrow antero-posteiorly corrugated bands. Vasiform orifice shovel-shaped. Marginal area with very








THE WHITE FLY.

Other groups are suggested by various species, but do not seem to be so clearly defined. Curiously, A. fioccosa and A. stellata, from Jamaica, seem to be related to the Australian series of A. stypheliae, A. nigra, A. limbata, A. hirsuta and A. banksiae.

Aleyrodes Citri.

The white fly, or citrus mealy-wing, was described in detail, with excellent figures, in Insect Life, Vol. V, (1893) pp. 219-226. Unfortunately, however, the detailed characters of the pupa were not given in such a manner as to permit adequate comparison with other species. Prof. H. A. Gossard has kindly supplied me with abundant material on leaves of Cape jessamine (Gardenia) from Florida, and I am able to give diagrams of the pupa (fig. 7) and of the vasiform orifice (fig. 6). It will be seen that the vasiform orifice is broader than long, and the lingua is short and broad. These characters are not those of the typical American groups, but agree well with the Asiatic group, No. 4 above.
On examining the other characters of the pupa, we find three deep furrows (fig. 7, a,a,a, and A,), one on each side, and one at the caudal end. At the distal end of each furrow is a somewhat star-shaped opening. Such structures as these I find described only in two species, namely, A. eugeniae, Maskell, tom. cit., p. 430, and A. aurantii (eugeniae var. aurantii, Masaurantii (which appears to be a valid species) occurs abundantly on leaves of orange in the northwest Himalayas.

numerous regular radiating furrows, the areas between them minutely punctured. Margin very regularly crenulate. No dorsal section wha'tever. The conical black larval skin was found in one example on the back of the pupa, but ordinarily it falls away.
Hab. Solitary on the upper side of leaves of live oak; Cuero, Texas, June 2, 1898. (C. H. T. Townsend); La Jolla, San Diego Co., California, Aug. 19Ol, (Cockerell).
Aleyrodes nelanops, n. sp.-Pupa black, similar in structure to A. perileuca, but larger (about I i-2mm. long), broad-oval, with the white fringe much longer and curled over, so as to be strongly convex above.
Hab. Solitary on the upper side of leaves of oak (Quercus), at Alpine Tavern, Mt. Lowe, California, Aug. 19Ol. (Cockerell.)








VOU THE WHITE FLY.

The Original Home of Aleyrodes Citri.

I believe that Aleyrodes citri is a native of China or some neighboring country for the following reasons:
(I.) It's affinities seem to be wholly with an Asiatic and Australasian group, and particularly with a species found on orange in the Himalayas.
(2.) Orange trees have been brought to Florida from China, and the Aleyrodes would be very easily carried with them.
(3.) Florida has had, at least as long as the Aleyrodes, two scale-insects of the orange, which are almost certainly Asiatic and very likely Chinese. These are Parlatoria pergandei and Mytilaspis gloveri. These were probably brought over at the same time as the Aleyrodes.
(4.) A. citri occurs also on the Cape jessamine (Gardenia fiorida), which is a native of China.
(5.) A. citri multiplies excessively in Florida, indicative that it is probably not American. The American species of Aleyrodes are not commonly harmful. In Arizona I found an Aleyrodes of a native type living upon the oranges but it was not doing any harm or multiplying excessively. This insect (described in Science Gossip, May 1900, p. 366,) appears to be only a variety of Aleyrodes mor, Quaintance. It may be called A. mori var Arizonensis.
[In the article just cited, owing to an editorial blunder two paragraphs are run together, making nonsense, page 367, first col., line 14, dele "They are," and begin a new paragraph.]


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PLATE VI.




Full Text

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BULLETIN NO. 67. JUNE, 1903. FLORIDA AGRICULTURAL EXPERIMENT ST A TION WHITE FLY. By H. A. GOSSARD. Th e bulletins of this Statio n will b e sen t free to any address in Florid a up on applica ti o n to th e Director of th e Ex periment St1ttlon, Lake City , Fla. De Land, Fla.: E . 0. PAINTER & COMPANY 1903.

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BOARD OF TRUSTEES. GEO. W. WILSON, President ... ... . . . .. ...... Jacksonville. F. E. HARRIS, Vice-President ..................... Ocala. J. D. CALLA w AY, Secretary . .... ... .. .... . .... Lake City. C. A. CARSON, Chairman Executive Committee, Ki _ ssimmee. J. R. PARROTT ... .. ....................... Jacksonville. E. D. BEGGS. . . . . . . . . . . . . . . . . . . . . . . . . . .. ... Pensacola. L. HARRISON. . . . . . . . . . . . . . . . . . . .. .. .. .. . .. Lake City. STATION STAFF. T. H. TALI AFE RRO. C. E., Ph. D ........... ... .. Director. H. K. MILLER, M. S .. . .. .. . . . .. Vice-Director and Chemist. H. A. Gos sAR D, M. S .................... . Entomologist. H. H. Hu ME, B. Agr., M. S ..... Botanist and Horticulturist. CHAS. F. D AWS ON , M. D., D. V. S .... . ...... Veterinarian. *C. M, CoNNE R, B. S ....... . ............. Agriculturist. A. 'vV. BLAIR, M. A .... ........... .. .. Assistant Chemist. LucIA McCULLOCH, B. S., Asst. Biologist and Asst. Librarian. W. P. JERNIGAN .......... . ..... Auditor and Bookkeeper. A. L. GLA YTO>T . . . . . . . . . . . . . . Stenographer and Librarian. JOHN H. JEFFERIES .. Gardener in Horticultural Department. Lours DEGOTTRAU , Supt. Citrus Experiments at Boca Raton. *Supt. Farmers' Institutes.

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CONTENTS. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 The Family Aleyrodidae . . . . . . . . . . . . . . . . . . . ..... 600 Origin and Distribution . . . . . . . . . . . . . . . . . . . . . . . . 600 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604 Life History and Habits . . . . . . . . . . . . . . . . . . . . . . . . 608 Methods of Dissemination . . . . . . . . . . . . . . . . . . . . . . 613 Effect of Cold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 Food Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616 Character of Injury. Sooty l\fold . . . . . . 617 Natural Enemies .............................. 620 Fungous Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 l lV[ethods of Introducing Fungous Diseases into Infested Grayes ................................... 624 How Far i\fay the Fungus be Trusted? ............... 625 Sprays ...................................... 628 Other Sprays than Resin \Vash, ..................... 63 I \Vhen to Spray and \Vhat to Use, .................. 634 How to Spray ................................ 635 Scalding of Resin \Vash Explained, .... . .............. 641 Fumigation, . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 643 The Nursery Situati~n .......................... 650 Insects Sometimes Mistaken for White Fly, .......... 655 The Outlook, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657 Acknowledgements, . . . . . . . . . . . . . . . . . . ............ 659 Summary of Important Facts and Recommendations ... 659 The Nearest Relatives of the white Fly (By Prof. T. D. A. Cockrell) . . . . . . . . . . . . . . . . . . . ... i. . . . . . . . 661

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The White Fly. Aleyrodes citri Riley & Howard. This insect first attracted the notice of entomologists in 1878, when it was observed in the orangery of the U. S. Dept. of Agriculture at Washington. Some observations were made upon its life history during that summer but no descrip tion of the insect was published until 1885 when Mr. W. H. Ashmead furnished a meagre description in the Florida Dis patch, Vol. XI, new series. The first adequate description was given by Riley & Howard in Insect Life, Vol. V, No. 4, issued in April, 1893. The name which Mr. Ashmead had bestowed, Aleyrodes citri, ,vas retained by Riley & Howard, the insufficient description being discarded. The next impor tant contribution to the literature of the insect was by Prof. H. J. \Vebber in an issue from the U. S. Division of Vegetable Physiology and Pathology in 1897. Prof. \Vebber's pamphlet was entitled Sooty :Mold of the Orange and its Treatment; but it recog11ized sooty mold as a development resulting from white fly attack. Prof. Webber's recommendations pointed out the necessity for destroying the fly, it being the cause of the mold, and the article was a very important one because it first emphasized the efficacy of resin spray against the insect and also described the two fungous diseases that constitute the greatest natural checks upon its nrnltiplication. The most extensive work with hyclrocyanic acid gas against the insect in the field was performed by the writer about two years ago, a summary of which was published in the annual report of the Experiment Station for the same year.

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600 BULLETIN NO. 67. The Family Aleyrodidae. The family Aleyrodidae, to which the white fly belongs, contains a large number of species, most of which are of little economic importance, usually being kept in good subjection by minute hymenopterous parasites. Among the exceptions to the general statement of harmlessness is a European species, A. vaporariorimi, which has long been known as some thing of a pest in Europe; and in this country, relieved of its European parasites, it is all too fast getting the reputation of being a first-class pest in greenhouses and gardens. The white fly of the Melon Papaw ( C arica papaya) A leyrodes variabilis is also a pest that is not to be despised wl1en on papaw; but owing to the restricted cultivation of its host it will not attract great attention unless it should prove its ability to multiply on other ~nd important crops . The orange white fly, Aleyrodcs citri, is the most destructive insect of the family. The family is charac teristic of the tropics, but some species thrive out of doors in the northernmost parts of the United States. The immature insects are very scale-like, being "closely related to the Coc cidae or family of scales . The most conspicuous character sepa rating the two families is that both sexes of adult Aleyrodidae possess two pairs of wings and can fly, while only the males of the Cocciclae are motile and are possessed of a single pair of wmgs. Origin and Distribution. The original home of the white fly is not definitely known. Some entomologists incline to the belief that it is a native of Florida, others think it an importation. I submit at the conclu sion of the bulletin an interesting contribution from Prof. T. D. A. Cockerell, who believes, from a comparative anatomical study of A. citri and many other species which he has collected from various parts of the world through many years, that our pest belongs to an Asiatic or Australasian group of white flies, and hence is not native. On the other hand, Prof. A. L.

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THE WHITE FLY. 601 Quaintance, who has made a specialty of the family, believes it quite probable that the insect is native, giving as his chiet reason for so thinking that he has found it on Viburnum nudum and occasionally on Quercus aquatica in primeval hammock many miles from an orange grove; the conditions under which he has found it on the former plant in dense hammocks particu larly emphasize to his judgment the possibility of its oeing indig enous to Florida. An instance of orange infestation which, I think, might be considered as sustaining Prof. Quain tance's view is found in the Manatee river-section. The insect's first appearance in this district was in the Foster grove near Manatee. I am informed that not a bud or plant of any descrip tion was permitted to come upon this place from abroad for some years before the fly appeared. Did it migrate to the oranges from a native plant in the dense ,voods surrounding the grove? Or, did some one of the tens of thousands of migrat ing birds from the upper part of the State get some of the newly hatched insects entangled in its feathers and carry them to tfie Foster grove? Or again, might the calculating eye of a con scienceless competitor from upper Florida have feared the rich promise held out to the settlers in the Manatee region by the vigorous grove of J\fr. Foster and have chosen to equalize the race between the respective sections by a malicious infection before the stress of competition was felt? Or what is, perhaps, more probable, is there some mistake about the report that no plants were introduced from abroad? However these ques tions may be answered, I incline to the view that the white fly is an imported insect. It is very unusual for an insect as vul nerable to parasitic attack as w hit e fly to multiply in such excessive numbers. I have found A. floridensis on orange at Candler, but very sparsely, and the same insect has been sent to me from Arcadia. Such native species rarely become trouble some, it being well known that hymenopterous parasites usually keep them in subjection. The history and spread of Aleyrodes vaporariorum, a species known to have been imported, appar ently exactly parallels that of A. citri. Fe" indeed are the insect enemies of the orange white fly; I have observed none

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602 BULLETIN NO. 67. except lace-wing larvae and some mites and these scarcely deserve mention, they make so little impression on the insect. It may be possible to explain the spread of the fly as a native insect without its being accompanied by parasites by paralleling it with the Colorado potato beetle, a native insect original1y feeding in restricted numbers upon a wild Solanaceous pfant in Colorado and outstripping all of its enemies in a march to the Atlantic Seaboard as soon as the potato patches of the settlers furnished it with a suitable food plant outside of its original habitat; but if such were the case with white fly, would not some parasites ere this have made themselves known in some quarter of the infested teritory? While Mr. Marlatt of the U. S. Dept. of Agriculture was in China and Japan hunting for the home of San Jose scale he collected some species of Aleyrocles but A. citri was not among them. Mr. E. Ernest Green has not collected A. citri in Ceylon, nor has Mr.. H. vV. Peal of Calcutta found it in Bengal. Mr. H. Maxwell Le-Froy, of the Imperial Dept. of Agriculture of the West Indies, has not found it in the vVest Indies, though another species of Aley rodes is a pest upon the orange in Antigua. Importations of citrus plants have been made from time to time from China, Japan, and other parts of the East; and also thirty or forty years ago some large wholesale importati o ns were made from Brazil, s uggesting that it may have originated in the American tropics. Mr. Alexander Craw of the California State Board of Horticult\ire writes that he has received the insect upon plants from Chili where it is a great orange pest. The fly seems to have been first known in Florida through out the region comprised in Volusia, Marion, Lake, Alachua, and Orange counties from which, I have little or no doubt, it was transferred to the Manatee country and to local centers along the northern border of the State. Following the severe freezes during the years from 1895 to 1900 the insect was so thoroughly exterminated in the northern part of its range by successive defoliations clue to cold that it was believed to be extinct throughout the section, and for all practical purposes was so. However, during the past two seasons there have been

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THE WHITE FLY. 603 indications of a revival in local spots, some of these, when upon oranges , being so conspicuously adjacent to hammocks as to suggest that the insects emerged from them. The nurseries, which for some years hav e furnished a supply of dean stock, are now becoming threatened and, while with pr o per care on the part of the nurseryme n, I belie v e clean stock can y e t be supplied for several y ear s t o come, the time is already here when th e buyer must depend upon the representations and reliability of the respective nur s erymen to guide him and not upon the inspections of the Entomologist. Certificate s of free dom from the pe s t, correct wh e n issued, m ay become untrue before their e x piration , a year after being given; hence I can assume no further responsibilit y toward restricting it s spread by in s pe c tion work. _ In s o me o f th e southern counties it is found in a maj o rity of the gro v e s. but there is probably no county that does not possess m a n y tree s ,vhi c h ar e n ot yet i nfe s ted . J\!Ianatee county is perhaps in the worst conditi o n of any, at least 75 per c ent. of the grO\es bein g infe sted . There are spots o f infestation in Po lk, Le e, Hillsboro, lviarion , Putnam, Alachua, and Oran g e co un t i es: it is also established at three or four p o ints on th e E as t Co ast railr o ad in the counties of Duval, Volusia an d B re va rd: a nd i n l oc al spots in Baker, Columbia, J e ffer s on a nd Leon co untie s. It clonbtless o ccur s at man y pl ac es o f which I ha ve no rec o rd. I ha ve n o resources at my co mm a nd to make a general in s pection of th e entire S tate , and c o rrespondents so m eti me s se e m di s po se d t o con c eal the fact that it is in their neighborhood. F ro m informati o n b as ed upon its ackno,declged distribution b efo r e t h e freezeof 1895 an d letters o n file in my offi c e I c o nclu d e th a t a general a nd tho ro ugh St a te in s pe ctio n would probabl y cli scon r it in Lake. Osceola, De So to , Sumter and Pasco cou n tie s at least. Out s ide of Fl o rid a th e in sec t i s re co rded a s either now being or h a vin g once been in L o uisi a na, G eorgia, North Caro lina, District of C o lumbia. and Te xas . California newspaper report s so metime si nc e indicate d th a t some insect re sem bling A leyrodes citri ,va s pre se nt in the nei g hb o rhood of Los Angeles,

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604 BULLETIN NO. 67. but the horticultural officers of that state seem to be confident that it is not present, and it is probable that with the thorough methods of warfare there employed, coupled with climatic influences, the insect would not attract much notice. The orange districts of Louisiana are quite generally infested, the insect probably having been introduced at the time of the New Orleans exposition in 1895. The white fly is often mentioned in connection with greenhouse infestation but here there may easily be confusion of specific identities. Description. !HE EGG.-V ery minute, about I-I 2 5 of art inch ( 0.2mm) in length, being attached to the leaf by a slender stem or foot stalk; about four times as long as thick, widest just beyond the middle towards the free end; color pale . yellow, when first laid tinged with greenish, becoming darker as the embryo develops and some specimens becoming of a dark steel grey or blue. Surface smooth and shiny, often with clinging par ticles of white wax. Red eyes of embryo conspicuous through the shell as it approaches m a turity. LARVA.-Passes through four moults before reaching the pupa stage. When first hatched the insect is about r-80 of ;,1.ll inch in length ( o. 3mm), of a pale greenish yellow color with two darker yellow spots on the back of the abdomen. There are four conspicuously long b _ ristles at the posterior part of the body and six long ones on the anterior encl vvith rninute ones along the sides, each arising from a tubercle. Antennae, three or four jointed. Four eyes, dark reddish. Legs short, six in number. Mouth parts consist of a long, sucking tube. On the dorsal side of the last abdominal segment is a snbovate, brown colored opening, the vasiform orifice. Appearance in second and third stage not markedly different from the first except in size and minute microscopical characters. In the fourth stage the length has increased to about 6mo of an inch ( r. 5mm), the width to 4-100 of an inch ( 1mm) and the con spicuous bristles have vanished; a pair of persistent minute

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THE WHITE FLY. 605 bristles is found on the anterior border, one on each side, and another pair, also minute, is disposed one on each side of the anal cleft. The insect is very flat and close pressed to the leaf; the dorsum or back is crossed by twelve transverse ridges indicating the segments. Arising from the prothoracic region on each side, extending obliquely outward and forward to the margin is a distinct ridge or fold, the breathing fold. The out line of the developing wings of the embryo can be distinctly seen froth the first. PuPA.-To ordinary observation quite similar to the fourth l a rval stage but more plump and of thicker body; broadly oval. Measurements about as in fourth stage, slightly narrower. A broad, deep orange or coral-red spot on the back near anterior end of abdomen; eyes purplish; vasiform opening and ring brown: transverse ridges on abdomen shorter and less distinct than in la s t lar va l stage. AnULT.-Female: Length slightly over 1-20 of an inch ( 1.4111111) ; wing expanse about twice the body's length (2.8mm); color light orange yellow; the rostrum or beak is tipped with black; the wings are colorless when newly hatched, but within two or three hours become covered with a fine white wax. hence, the name "mealy-wing" sometimes given to the in sect. The body also becomes covered with more or less of wax but its ground color is not wholly obscured. Tarsi two-jointed. The eyes. reddish-brown in color, are each divided into two parts by a curved ridge projecting from the cheek, the upper divisions being the smaller. Ovipositor short, retractile. ADULT.-Male: The male resembles the female but is smaller with the head and abdomen having heavier tufts of adhering wax. The abdomen is more slender and has at its termination a pair of claspers slightly curved upwards.

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606 BULLETfN KO . 6;-. EXPLANATION OF PLATE I. Aleyrodes citri. Fig. 1-Adult iemal e ,with e xpanded win g s. much enlarged. Fi g . 2. A dult i c m a le, with wing s folded over the body in normal roof-like posi , tion. . ged. Fig . 3 . -Egg and f oo ts talk of same, gr ea tly m a gnified. Fi g . 4. -E gg s h e ]l. s howin g th e s plit througl1 which the larva emerFig. 5 . -Tip of mal e abdom e n, showing claspers. Fig. 6.-Ant e nn a , showing annulated joint s . Fig. 7 . ----'F o re margin of front wing. INSECTS SOM E TIM E S MISTAK E N FOR A. citri. Fig. 8--Larva of Aleyrodes fl,oride11sis gr e atly magnified. Fi g . 10. Gr e atl y enl2.r g ed s ection of waxen fringe, surrounding A_. fioriclensis. Fig. I r.-Outline of larva of Le c a niwn hesperLdum.

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/ ';< _ ,. :co> > :r __ , ./ .. ::-. 9 \ \ ~ ~ i.. ---. . +-= --.. --------J O PU\TE J. ,; ' . , ., ./5~ \ ! \ }

PAGE 16

<\, •" \ \ ' \ r Q .'1. ~ , iB ~ij; "-:'! ... 8 --' ---:::::==::... .\ -----' \~-~ P l , 1 \TE TI .

PAGE 17

THE WHITE FLY. 607 EXPLANATION OF PLATE II. Ale}wodcs citri. Fig. r.-Larva, fitst s,tage, greatly magnified. Fig. 2.-Larva, first stage, drawn to same scale as figures 3, 4, 5, 8, 9, and 10. Fig. 3.-Larva, second stage, Fig. 4.-Larva, third stage. Fig. 5.-Larva, fourth stag e . Fig. 6,-Margin of advanced larva, greatly enlarged. Fig. 7.-Vasiform orifice oi iourth lanal stage, showing crenulated operculum with lingua in the center Fig. 8.-Pupa, s howing embryo and distribution of orange colored areas. \Vaxen tuf , t s extt'nding irom the breathin g tubes are shown. Fig. 9.-AduJt , with folded wing s, emerging from the pupa case. Fig. 10.-Empty pupa case, showing split through which the fly emerged.

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608 BULLETIN NO. 67. Life History and Habits. FrnsT BRoon OF ADULTS.-The first brood of adults issue during March, April and early May. The date varies with the season and locality. Localities not over a quarter of a mile from each other may exhibit a variation of two or three weeks, and particular spots or plants in an infested area may furnish an anticipation of the general appearance of the brood by a long interval. Thus, some sheltered lemon bushes at Ellenton, Fla., were observed by the writer to have produced adults on the I Ith of February, though for the neighborhood at large the bulk of the brood issued during March arn;l April. At Tampa, thirty to forty miles north of the Manatee section, the spring brood of flies has in some seasons preceded their appear ance about Braidentown and Manatee by two weeks. Mr. A. J. Pettigrew, a close observer at Manatee, says that he once observed a few hatch about the 28th of January, and that he has twice seen them appear in considerable numbers in February, but that March hatches the bulk of the brood, most of them being on the wing before April 1st. At Lake City, last year, the few infested bushes about the town showed the first adults about the 14th of April and hatching continued until late May, most of them appearing during the last half of April. There was several clays difference in the dates of appe a rance upon the different bushes. The present year found some of the adults on the wing at Lake City March 12, and they were reported on the wing at Orlando and at Palmetto on the 6th of March. At Lake City only a few stragglers were observed after the middle of April. Speaking of the entire district in which the insect can exist from South Florida to Georgia, the bulk of the first brood may be said to appear during March and April, with the adults which have hibernated as half-grown larvae straggling along into May and June. Only in the northern section will they ever linger as late as June. The adults live from three or four days to three weeks, the average period being from four to seven days. The adults love close-planted, sheltered groves into which

PAGE 19

THE WHITE FLY. 609 the winds enter with difficulty. Consequently, the insect never becomes so numerous in well spaced, open groves on high pine land as in thick-planted, unpruned groves on hamm oc k land surrounded by thick woods. PAIRING AND EGG-LAYING.-The courtship of white fly , as ob se rved with a pair in confinement, is quite curious. The male s howed evidence of h a Ying detected the presence of the unimpregnated fem a le at a distance of one-fourth of a n inch or m o re, a nd approached her nervously, stopping at intervals, especially as the distance was le sse ned, and swinging his body about excitedly in a semi-circle, the head being L1sed as a piv0t, his wings in the me a nwhile opening and dosing spasmodically. vVhile no movement wa s made by the female, several retreats were made and she was repea ted ly approached from m any directi o ns before c o ition occur red . Upon th e trees the m ales and females rest side by side and two males, one on either side, may often be see n giving their attentions to the same femal e. Eg g-laying be gins within eighteen to thirty h o urs after foe a d ult s issue when the weather is warm, ( s ixt_ v five to seventy five degrees) but with cl amp, cool weather several days may el a pse before they are deposited. Egg deposition occL:rs upon the under surface of the l ea ves, prefer ab ly t1pon 11ew ones, especially those of water sprouts, but o ld le a , , es may a 1s o be well c ov ered witfi them ; they are usually sc attered over t,1e :. mface of the leaf without much order of arrangement but s01net1mes are laid in the arc of a circle. From four to ten egg;; may be observed in such an arc and are so placed by the female using her beak as a pivot around which the body is swung during oviposition. The eggs are not as numerous, ordinarily, near the edge of the leaf as further inward. Each female deposits from seventeen to twent y -five eggs in breeding cages, the rate of laying doubtless being governed by temperature. \Vith the thermometer at 70 degrees t o 76 degree s F. for several hours on each of two successive clays the eggs were all laid within twenty-four hours after the fir s t one was deposited and

PAGE 20

610 BULLETIN NO. 67. the females under observation died soon after they stopped lay mg. By mathematical computation a leaf from young orange, five inches long and two and one-half inches wide in the mid dle, collected at Myers, June 22, I901, had upon it upwards of 20,000 eggs. While so many eggs upon such a space is beyond the average, it is by no means rare, and I have some times seen the number exceeded. Hatching occurs in from three to twenty days according to the weather. In the summer season when the temperature maintains itself at from 80 degrees to 95 degrees for several days together the eggs hatch in three or four days. Hatching throughout the summer is very regular, comparatively speak ing, the range probably being from three to eight days, while in spring and fall with temperature ranging from 50 degrees to 70 degrees from two to tnree weeks fa required. The egg becomes of a metallic bluish-grey color as the embryo matures and splits longitudinally for a short distance clown both side1; at the distal encl to give exit for the young larva. LARVAL HrsTORY AND HABITs.-The young larva is motile and crawls about over the leaves and twigs for several hours like a young scale before it attaches itself to the leaf. The first molt occurs in from seven to twenty-five days according to the temperature. In moulting, the larva bends the abdomen upward at a right angle to the leaf surface and with slow, struggling movement alternately raises and lowers it, the body meanwhile shrinking from the interior of the skin, causing the dorsal ridge to become distinctly elevated. The skin now splits at the anterior encl or beneath the head and by abdominal wriggling the insect gradually pushes it off. The cast skin is very thin and fragile and is blown away by the wind or drops to the ground, seldom remaining long upon the leaf. The periods between all the moults seem to be determined by temper ature and the fifth or pupal molt occurs in from twenty to thirty days after hatching during July and August but requires from four to five months during the winter. Add from ten to thirty days as tlie pupaT stage ana the life cycle from egg to adult is

PAGE 21

THE WHITE FLY. 611 seen to range from forty or fifty days to six months. vVhen the insect is ready to emerge from the pupa shell, the skin splits in the form of a cross beginning at the head of the larva and extending along the middle of the back to the front of the abdo men ,Yhere it bisects at right angles a transverse slit extending to the margin on either side. The thorax of the fly comes out first, follo\\ecl by the head. The ,Yings are much folded and colorless when first exposed; the insect at once ele,-ates them into a yertical position to dry, and in about fifteen minutes t~ey are expanded and lowered to a horizontal position; in teri min utes more they are in their normal roof-like position over the back; about two hours elapse before they lose their transparency and commence to whiten, and fiye or six hours pass before the typical powdery white appearance is reached. The lanae attach themselves to the under sides of the leaYes and are inconspicuous because of their transparency and greenish tinge. If the leaf be so doubled in the hand that air is admitted beneath the insect, it at once becomes readily seen and is translucent whitish green, spotted with orange. vVhen infestation is so excessi,e that the larvae merlap each other, many of those that are beneath do not succeed in emerging, especially if the head of the larva is the part covered. So far as obserncl by the ,niter the lanae clo not settle and feed else where than upon the leaws. \Vhile some reliable obseryers report ha,ing found them attached to t\yigs and in buds, the most diligent search has never revealed to me a single specimen so located. Is it possible that the immature stages of one of the Lecaniums (possibly hesperidum) have been mistaken for white fly by the observers mentioned? Seen best from the ventral side of the larva but also visible through the transparent dorsal surface, along the median line and slightly forward of a line connecting the inner points of tfie breathing folds, is a pulsating organ connected witl1 the circu lation which beats from one fiundred-twentv to one hundred fifty times per minute. Along tne back of th~ abdomen the slow pulsations of the heart proper, a long muscular tube, can often be observed with a fairly good microscope. Absence of visible Bui. 68-2

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612 BULLETIN NO. 67. movement i11J. these organs may not 6e interpreted as perfect pro o f of death but they often furnish positive proof when death ha s not occurred an cf' thus are a valuable means of observation to determine what has been the effect of insecticidal treat ment. SUMMER AND FALL BRooos.-During June and July the second brood o f adults are on the wing in the southern part of th e State, appe aring about two weeks later in the latitude of Lak. e City. At the latter place last summer they commenced appearing abo ut the first of Jul y and were still abundant on the 12th of August. From this time onward there was no date until the middle of November when every stage of white fly from egg to adult could not be found in th~ neighborhood; not alw ays e very stage upon the same bush but persistent search wa s sure to find it within a half mi]e. September seemed to bring the greatest number of ad ults, which, with early October, m ay be regarded as the maturing time for the third brood. This year the second brood commenced hatching at Lake City, during the first week in June , and were reported to be hatched and in full swarm at Micanopy at the same time. The second brood, like the first, seems to be a month earlier this year than last. while three generations a year seems to be the rule, there is a tenden cy to continuous breeding as some adults were observed upon privet at Lake City on Christmas day, and Prof. H. A. Morgan has likewise observed that it issues upon warm winter days in Louisiana. Four generations a year doubtless occur often, but not in sufficient numbers to obscure three well denned broods as the rule. Mr. Pettigrew sums up the history of the adult as follow.; for Manatee: "The spring brood is Ill sight from three to four weeks, then none are visible for three or four weeks ; the second crop is in sight four to five weeks with one or two weeks following without any, after which the broods run together so there is only a thick and a thin s treak. Sometimes the eggs for the winter orood of larvae are all deposited in October and at other times nearly all in N'ovem ber." All the eggs of the winter brood are hatched before Christ

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THE WHITE FLY. 618 mas. By 11Iarch I st a fe,Y of the insects are pupae and there are none that Eave not reached the third stage. The rapid develop ment ot the belated lan e during the warm clays of March and April enable them to issue as adults within a month after the first flies of th e brood appear, so the first brood is well defined each year. Something like ten to fifteen per cent. of the winter brood die. before s pring. at Lake Ci ty, from no very definite cause. Methods of Dissemination. The insect is not a strong flyer but can go considerable distances with the wind, and infected neighborhooos often fur nish unmistakable examples of the influence of prevailing winds in scattering it. The flies are often found in clouds upon weeds and herbage by roadsides and covered vehicles may collect some of them under such circumstances and transport them to con side rabl e distances. They ha ,e also been observed upion window s in railway coaches, indicating that they can be carried long distances in this way. I have stood beneath a tree upon which adults were plenti ful and had them alight upon my clothing; I have then walked nearly a half mile against a stiff breeze and picked the flies from me by the dozen at the termination of my. journey. They cling tenaciously to the i r support in a stiff wind but take flight quickly in quiet air. when newl y hatched they crawl about like young scales and may be caught in the hair of horses brushing against the trees, or in the feathers of birds and be thus transported from one grove to an o ther. During the months from July to December young larvae as well as adults are apt to be present in small numbers, at least, without intermission in an infested grove. Pickers, teams, ladders, baskets , etc., going from an infe s ted grove to a cfean one during this time can become the means of transp o rting the pest as well as when the spring brood is hatching and flying. Infested nursery stock is most apt to carry the insect into new localities.

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614 BULLETIN NO. 67. Effects of Cold. The larvae can stand more cold than the or,mge. I have, in repeated instances, taken larvae from leaves that had IaTlen to the ground because of cold ranging from 22 degrees to I 7 degrees above zero, ten days to two weeks after the cold occurred and found by microscopic examination that the pulse was beating regular and strong. If infested leaves drop in early winter the larvae cloufitless perish as they invariably die upon detached drying leaves in the laboratory in from nine to fourteen days, but with leaves dropped in February ana lying upon moist earth it is conceivable that some of the insects may mature and issue. It seems certain tf-iat white fly will eventually range as far north as the hardiest orange. It will also be able to perpetuate itself upon the more hardy of its food plants, despite freezes that kill oranges to the ground. To determine the degree of sudden cold which the insects can survive, Mr.A. 0. Mann of the Lake City Ice Factory gave me the freedom of his factory for expenmental purposes and sunk an empty can into the brine for my use. The temperature of the brine ranged from IO degrees to 20 degrees, and the ther mometers kept suspended in the can recorded temperatures as shown in the table. Twigs of orange and Cape jessamine, hav ing upon them well matured pupae of the fly were used April 12th and 14th as follows: Tim.c in Can Experiment No. 1. ...... 30 min. Experiment No. 2.. 1 hr. Tem1wratnre r~•n.dings jn 1 1 Result cnn tn.l;;:L•n at 1nt.L'l'\'als. 1J. dpgrees, 15 de, 15 de. .(t frnr snrviY-ed and 1ssuerl as adults the I next day. 12 ck., H de., 15 de., lii de., All killed. 12
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THE WHITE FLY. 615 cold storage room: but if any significance at a ll can be attached to the cold s torage p re parat i on it weakens the resi s ting power of the in sec ts at this elate as s ho,Yn in the fo ll owing experi rne nts : Tim e in Co l d Tinw I T empcmturc read, :::ronige i n Cilll ing s , l.,y degrees, Re s ul t. in eu ns. , Exp cr imentXo. 3 1 hr. 45 ruin. 30 min. j 12 , H , 15. Two flies jssued, remaind e r killed. Exp er iment X o . 4 48 hrs . 30 min. ~ 5 1 20, 20, 18 . All kill ed. Exp erime nt Xo. : ) 1 hr. 45 ruin , 1 hr. n 14, 15 , 12. All killed. Exp erime nt X o . 6 1 hr , 45 m in . :.! hrs . 1 > H , 1,, , 15 , 1 2, 10. A ll kill ed. Exp e riment :X o. i -18 h r~. 2 hrs. 30 min . 20 , ~o. H, 12, 10. All kill ed . It is quite probable that had the experiment been per formed during th e "-inter months \Yith lan -a e that h a d bec o me accu s tomed to cold ther e " o ul d haYe been a larg e r percentage of s tir\Tl'ln g insects. Tem per at ures as low as th os e used are neYer reached in S o uth Flo rid a a nd seldom last for more than a fe\\ minutes in .\" ort h Florida: and when reac h ed in a given distri c t th ere are a l\yay s sh elt ered sp ots in whi ch the m ercu ry do es not fa ll so l o,,. _-\t Yarious points along the line of the Seab oa rd Air Line R. R. from Jacks o nville to Tallahassee the mercmy has at different tim es . during the pa st ten years, cle scencl ecl t o 6 degrees an d IO degrees. The fl y, after s uch fr eezes. h as di sa ppeared fro m sight for a tim e bu t has invari a bly reappeared s hO\ving i ts ab ilit y to with s tand the m ost extreme cold that occ urs in this latitude . HO\nver, it is apparent tha t a clecicluous oran ge acl ap tecl to :: , forth Fl orid a and Ge o rgia w ou l d not s uffer much fro m the fly. :.\Ir. A. J. :.\Iitchell. Se ctio n Di rect o r of the Florid a \ \ ' eat her Sen-ice furnishes the following reco rd s fo r l ow est tem pera ture s at three points near the n ort hern boundary: JACKSO N VILI,E 14 d eg ree s, F eb . 8. 1 89,,. 1 ! d eg ree ~ . D ec. '29. 1 8 9 1. 10 degrf•cs. F1:.•l . 1. 1:\ 18 ~19. LAKE C ITY 15 ckg reeN, Feb . 8, l~ \l5. 16 ckg rees . Fd, 1 s. rnoo . T .H,LAHASREE 11 cle gre es , Feb. 8 , 1895. I:.! degrees, DeP. ~9 . 1894. :2 ,kgrf'C'S. F e b. rn . .1S99.

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616 BULLETIN NO. 67. About two years after the 1899 freeze the insect was again observed at Lake City. It was reported from Jacksonville at about the same time . State Chemist R. E. Rose informs me that the insect is present in considerable numbers at Tallahassee, and my office records show that it was present there before 1895. Food Plants. White fly occurs upon all varieties of citrus. C. trif oliata is, of c o urse, only infested during the summer months, being a deciduous v ariety. The deciduou s c haracter c.,{ so me of the C. trifoliata hybrids will tend to retard the nmltipli cat i o n of the pest upon them. The kumquat is still less a favorite than the pomelo, and the latter, though .Jften l x1d ly infested , is usua11y attacked o nly after the adjacent oranges are onr stc,cke d. The adult flies as well as the larvae sap the lea ves and their taste for certain varieties lead s them to oviposit n the se when possi ble, going to less favored plants only as they are driven by necessity to do so. Besides citrus, the Chinaben-y tree ( NI elia azederach) and Viburnum nudu111 the Cape jessamine ( Gar denia florida) , the Jap a n persimmon ( Diospyr os lwki) , Cali fornia privet (Ligustrum amurense), Golden privet (Ligus trum sp.) and Mock Orange (Prunus Carolinian a)a re food plants. Various species of Ficus are said to be food plants; I have seen it on two species, F. altissi111a _ , and on a n unknown species introduced from Costa Rica . The water oak ( Quercus aqitatica) i s occasionally infested , according to Quaintance, and I have taken two or three larvae advanced to third and fourth stage o n scrub palmetto. Their presence upon the latter plant is very rare having been observed but once, though opp o rtunities have been plentiful. Prickly ash (Xanthoxylum sp.) is reported as a food plant upon, , hat I consider to be reliable authority, but I have not per sonally seen the insect upon any one of the three species found in this State.

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THE WHITE FLY . 617 .. Character oflnjury. Sooty Mold. The injury caused by white fly is not as threatening to the life of the tree as that caused by s _ cale insects. The latter kill branches and sometimes entire trees with great rapidity when associated with other ailments, but their destruction by the former is comparatively slow. White fly certainly does often kill branches and sometimes trees, but rarely does a tree die from its attack alone. Footrot, dieback, and kindred troubles are the usual accompaniments of white fly when death occurs. As an illustration of the resisting powers of the orange to its attacks, the Foster grove may be cited, the one before men tioned as being the first case of infestation on the \Vest Coast. This grove is referred to in some of the earliest literature of white fly (Insect Life) and has been infested for more than ten years; with the exception of a few trees, it is still living and looks as if it can keep up the struggle indefinitely. \\'hen seen by me about eighteen months ago the interior branches of most of the trees had a color, thrift and vigor not found in some groves wholly free from this insect. Except that the bearing capacity of the gro\e has been reduced, it may still be called one of the most valuable in the State. I \\'as told by parties acquainted with its recent history that it bears a good crop about once in three years foflo,Yed by two comparatively light crops. It was hardly carrying more fruit than would pay for the cost of maintenance at the time of my inspection of it. Seedling groves are inclined to alternate heavy with light crops so one of the light crops is accounted for, but the other is doubtless due to the fly. I believe any practical grower will think me well within the bounds of trnth in saying that, through a six-year period, the yield with white fly present will be from twenty-five to forty per cent. less than it would be with the insect absent. lvlanatee county alone produces 250,000 boxes of fruit per year and thirty per cent. increase would be 75,000 boxes which, valued at $2.50 per box, would amount to $187,500. This is not far from the actual loss, as most of the groves in this county are infested. \Vhen the loss

PAGE 28

618 BULLETIN NO. 67. in other districts and the indirect losses due to impaired quality and dimini s hed carrying power are added, the State must receive nearly a half million dollars less annually than she would if the insects were absent. The acid and sugar content of the fruit is much reduced , an orange from a white fly tree being comparatively ta s tele ss and in si pid. Th e fo ll ow ing table shows the re s ults of a chemical analy sis m ad e at m y. requ es t by Profs. Miller and Blair o f three fots of fruit picked the sa me day from adjoining Dancy tangierine grove s, both of which we re infested with white fly a nd had been given practic a ll y the same treatment as regards cultivation and fertilizing. Fifteen o r t we nty oranges were selected for eac& o f three l o t s, repre sen tin g as accurately as pos sib le the average conditi on as to size and maturity on each of the three trees from which they were taken. Sample No. I was from a tree that had been infe s ted for several y ears and h ad been l eft to take ca re of itself. Sample No . 2 was from a tree abo ut forty feet from No . r, and wa s r eg ularl y and properly sprayed thr ee or four times each year but stood in the row a dj o ining the un s pra y ed grove and the insects could n ot be prevented from developing up o n it in numbers sufficient t o cause more o r less mold . Sample No . 3 was from a tr ee abo ut 80 feet fr o m No. r, which was properly sprayed as was No. 2, but with better re s ult s. A few larvae were p r ese nt on the leaves , but, practica !l y, wh it e fly could be considered who lly absent. Snmpl e N o . 1 S, unpl e No . 2 Sa mpl e N o. ;l R e, l n e in g Sngn r . T o t 1t l f; u ga r D e xtro s e , P e r Ce nt. P e r Ce nt . 2 . l S li . 71 0 ::!fi 7 . 9 1 C itr ic A c id , P e r C e nt . . 425 .3 94 .445 These sa mples were co llected in February after they had passed their best, but it i s believed that they kept their rel a t iv e qual it y .

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THE WHITE FLY. 619 A liberal use of fertilizer tends to keep up the quality but the soo ty mold upon the rind must 6e remo ved by hand-wash ing, by revoluti o n in barrels filled with water and cross-cut sawdust or by suitable machinery provided with revolving brushes, and the consequent bruising of the rind invites quick decay whicfi orten occurs in transit. The s ubtraction of so mu c h sap from the tree by the insects, aided by the i nt erference ,Yith assimilation caused by sooty mold, delays ripening of the fruit, nrieties which ought to be at their prim e by the first of December not being mar ke table before Christmas time and often not until three or four week'> thereafter. The sooty mold is a black. saprophytic fungu s, J,f eliol a Ca111elliae (Call.) Sacc., th at gro ws in the honey dew excreted by var ious insects. A.mong the Coccidae or scale inse cts w hich it follmvs, m ay be mentioned the ya riou s Lecaniums, the 1 nealy bug s, the wax sca les. J ccrya p11rchasi, and ot her s . T h e plant fi ce, or various s pecies of .-1.phis, are also fo1lowecl by i1 ,:.s weil as all forms of Aleyrodiclae "hich mul tiply excessively. Any insect excretin g honey clew in any quantity is cert ai n to be accompan ied by the mold. Sooty trees and plants. tl--crefore, are not always infested by iYhite fl: , tho u g h s uch an appear ance upon any of the in sec t 's food pb 11 t:s hould r<.'ce i "e an immediate in ves ti ga tion. The \Y hite fly laryae bein g l oca ted on the under sides of the le aves, the honey clew drops upon the upper surface of the lea ves grow ing ju st below, so the black mold occurs chiefly up o n the upper surface of the foliage and fruit. It form s a close. smothering, membranou s covering that can so metim es be peeled back as if it were tissue pap e r. This membrane is composed of the netted mycelial thre ads of the fungus which reproduces by means of vario us rep roduct ive bodies so me of \\hich are s h o m1 in cut No. I , from Pro f. Hume's bulletin o n Citru s Troubles. The wind is the chief age nt in disseminating the rep roductive bodie s. The effect which a heavy coating of this fungus produces upon a tree diff ers only jn degree from what would be produced by enclosing it in a black tent. The circulation of air throu gh the tree and entrance

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620 BULLETIN NO. 67. of light is not interfered with, but contact of air and light with the foliage is cut off on the upper surface and partially also from the lower surface. The sooty mold is one of the most aggravating factors of white fly damage. It disappears with the destruction of the fly. Cut 1-Sooty mold (greatly e nlarg ed), I. Mycelium or fungal threads; 2. Conidia: 3. Pycnidia with immature spores . (Drawing by Miss L. McCulloch.) Natural Enemies. The young of the lace-winged flies and a mite are the only insects that I have observed feeding upon the eggs or larvae. Lady-bugs possibly feed upon them to a slight degree but I have never observed them doing so. A correspondent at Kissimmee l t_ !

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THE WHITE FLY. 621 repo r ts that a carnivorous ant is quite efficient as a destroyer of th e larne. I cannot say that any of these ap preciably reduce the insect, eYe n l oca lly. Throu g h the kindness of 1fr. Ehrh o rn of California, some hymenopter o us par as ites upon another species of Aleyrodes were se nt t o me a nd enclosed on an inf e sted tree beneath a cheese cloth tent. but se,eral wee ks later a freeze dropped all the l eayes fr o m the tree and o nly a neg at ive result could occur. Further ex per iments of a si mil ar nature are desirable, but too much mnst not be hoped from them. The parasites of many o ther _ \ ]ey rodi cla e in the State see m to have no taste for A . .citri. Fungous Diseases. If in sec t enemie s are ineffectiYe, the sa me cann o t b e s aid of fungous diseas es . Thr ee species of fungi are kn ow n to fine! their n a tur a l medium or growth in the white fly l a r v ae , a nd two of them are so metime s wonderfully successful, in certain locali tie s. in reducing th e pest. BROWK F i:_ xGcs. -Fir st in or der of effectiveness mu s t be nam ed the brown fungus who se botanical position is thus far unkn mv n and ind e terminable beca use its fruiting has never been o bser\'ecl. The fungus form s brown pu s tules of about the size an d r ese mblin g in som e d egr ee the reel sc ale, As pidiotus ficu s, differing from the scale, however , in always being on the und er s ides of the leaves. The fungus attacks a ll stages of larvae and pupae , the veg etative thread s penetrating all parts of the body cavity, burst ing o ut as a frin ge around the edges of the body, and then gro,, ing up over it , forming a compressed hemispherical brown wart or pim ple ( stroma), one over each lar va destroyed. The size of the stroma depends upon the size attained by the larva when the fungus reaches it. From the base of the stroma grmving fil ame nts o r mycelial threads reach o ut sometimes to the distance of half an inch in every direction. By such growth other l a rvae are reached and thus the disease spreads rapidly

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622 BULLETIN NO. 67. over the surface of the infested leaf. Fragments of this myce lium are supposed to be transported by wind, birds or insects to other leaves, trees and groves where they start a new infec tion. The fungus does little or no damage to the leaf, never penetrating the tissues and only causing injury by smothering under many of the breathing pores. The appearance of a well matured case of brown fungus is well shown by the accompa nying photograph ( Plate III, fig. 3.) taken by Prof. Hurne. THE RED AscHERSONIA (,-1.scherson-ia aleyrodis vVebber) -This fungus is very conspicuous, forming more elevated pus tules than the brown fungus, and which are of a ruby-red or pink color. The pustule, when matured, consists of a ruby-red center surrounded by a fringe of pinkish orange, sometimes approaching whitish. vVhen immature the center consist~ of several to many ruby-red cups developing in craters of pinkish white. The red cups fill out, project slightly beyond their cra ters, and finally coalesce to form a ruby-reel cone surrounclecl by a light pink base-the matured form. The deep red nuterial consists of the sporules of the fungus and the lighter encircling ring is its mycelial ,voof. The mycelial threads do not reach out so far as those of the brown fungus and dissemination is probably accomplished altogether by spores. The sporules are gelatinous and adhere together so strongly in masses that the wind would seem unable to scatter them. The spores are loos ened by the masses becoming wet, and heavy clews or light showers combined with a fluttering breeze so that drops of water are shaken from one leaf to another is probably one means of scattering them. If all the pustules were exposed to the foll force of a heavy, driving rain. all the sporules wonld probably be dislodged and carried to the ground, but it is con jectured that their position on the under surfaces of the leaves protects them from too rapid dispersion under such circum stances, and at the same time gives possible opportunity for spreading them. The young larvae move about freely for several hours upon the leaves on which they have hatched and occasionally pass to other leaves, and while thus traveling can become infected with the disease before settling permanently;

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THE WHITE FLY. 623 howeHr, it is safe to say that the insects that become infected in this manner are exceedingly few. Ants are possibly important agents in distributing the spores. They visit the le av es for the purpose of feeding on the honey dew excreted by the ,Yhite fly larvae and they could h a rdly pass over th oro ughly infected leaves without entangling spores in their feet, especi a lly if they were sticky with honey dew, an d such sp o res 1Yould b~ readily transferred to the next l ana v i s ited . The fir s t indicati o n of lan a l infection is the appearance of translucent yellm , s h spots, u s ually near the edge of the larva, \Yhich becomes s,, o llen and instead of thrmY ing off its honey ty mold covering the under surfaces of the leaves and smothering many of the larvae, with the report that i.t was "a fungus destroying the fly." In some instances I have seen 40 per cent. to 50 per cent. of the larvae smothered to death by it; it

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624 BULLETIN NO. 67. has no effect in killing the insect until infestation is excessive, and ceases to operate as a destroying agent when the larvae are sufficiently reduced in number to stop the flow of honey dew over the lower surface of the leaf. Me,hods of Introducing these Fungoui: Diseases into Infested Groves. Until more is known of the developmental history of these diseases it will be wisest to approximate the conditions under which Nature spreads them as the surest way of getting them established where they do not at present exist. Intrnduction can, perhaps, be most satisfactorily accomplished by planting in the infested groves trees tjpon which the fungi are well estab lished. The trees should be planted so that twigs of the infested ones interblend with those having upon them the diseased larvae in order that the leaves of the two may thus be brought into contact. If the transplanted tree is small it may be planted in a tub and elevated to the proper height on a box, or the tub may be fastened in the fork of the tree which it is desired to infect. Even this method sometimes fails but it com monly suceeeds. The time of transplanting is not important, the essential point being to get the tree to growing without dropping its leaves. Pinning of fungous infested leaves with the fungous pus tules in contact with the healthy larvae of uninfected leaves and thus leaving them ; spraying with spores of the fungus and fragments of its mycelium suspended in water; hanging of cut infected bran:hes among uninfected ones; inoculation by means of lightly pricking the larvae with a needle which has just been immersed in water containing an abundance of spores and fragments of mycelium ; and placing the infected face of a leaf in contact with the larvae on an uninfected one and securing them in this position by means of a cheese-cloth band which binds in a moistened plaster of cotton or moss on each side of the leaf, have been tried by various experimenters, my self included, without marked success. However, an infection

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Fig . I . Fig . 3. PLATE 3 . (PHOTOG H . .-\PH:3 . ) Fig. 1. L a r vae and pupae o f \ it e Fly o n Ora n ge . Fig. 2 . -Red Fungus, A sc h e r on i a aleyrndis Webber. Fig . 3 . Brown Fungu s o n Orange. Fig. 4. Adu l t Fli es and Eggs o n Ora n ge. F i g . 2. F i g. 4.

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THE WHITE FLY. 625 is sometimes started by these methods. \Vhen the last is used the cotton o r moss is m o istened by pouring water up o n it every two or three da ys a nd the bandages are rem ov ed in a ,veek or ten days; care must be tak e n not to make the bandage so heavy that it will break off the le a f when the c o tton is satur a ted with moisture. How Far May the Fungus be Trusted to Destroy the Fly? Different observers will give diff ere nt a n sw er s to this question. Some intelligent growers , located ne a r the coast in South Fl or ida where conditions of heat and m o isture are as favorable as they p ossi bly can be fo r fungus gro wth a nd devel o pment , are sa nguine in the belief th a t no sp rayin g is neces sa ry , while so me of their neighbor s are eq ually confident that the highest degree o f profitable production can only be reached b y diligent spraying or fumi ga ti o n. Classed w ith neither the sp ray er s nor the nons prayers is a numerous c o ntin gent that is confu se d between the cl ai ms and practices o f the two sc h oo l s, and therefore its repre se nt at iw s s pray a little, then \vait a year or two for the fungus to develop, the n spray a little m orn , then wait aga in for the fungu s to ap pear. This mi x ing of th e pr ac tices of the t\v o sc ho o l s fails to secure th e ben efits of e ither a nd gro v es that are improp e rl y, int e rmitt e ntl y or r a r e ly sprayed would best be left wholly untouched i f any fungus is present in them. I once thou g ht there mi g ht be a middl e road of practice between the two schools and that b y observation of the natural agencies a t work to destroy the insects it could be decided whether s pra y ing was or wa s not necessar y. this may be trne undff some circumst a nces, careful observation for four years has convin c ed me that for th; oran g e grower in Florida the truth lies at the two extreme s of practice and not at all between them. I cannot too emphatically state my con viction that if one in this State is to trust his natural friend~ to destroy his insect enemies , he must carefully study the habit s of these friends, introduce them, propagate them, disseminate them , and allow them to spread and multiply without hindrance by the application of caustic sprays \'rhich destroy friend and

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626 BULLETIN NO. 67. foe alike. Fungi are easily destroyed by alkaline washes and soaps, whether the alkaline base is caustic potash, caustic soda, or lime; and in Florida with its long, hot, humid summers fungous diseases are commonly many times more effective than preclaceous or parasitic insects. where fumigation is practica ble it has one distinct advantage over spraying in that it does not destroy fungous growths. The man who is not willing to leave the safe-keeping of his grove in Na tu re's hands should plan to spray regularly several times each year and the expendi ture should be counted upon as an outlay just as necessary as is his fertilizer bill. I believe that seventy-five per cent. of the groves in this State, whether infested with white fly or not, if hanclled in this way, would show an improvement as marked as a properly fertilized grove shows over an unfertilized or an improperly fertilized one. I repeat emphatically that while I h a ve no word of condemn a ti o n for the man who with intelli gence and skill directs Nature's agencies so that he s e ~ ures results with most insects equal to the best ( and we have some such in Florida), I believe that white fly is an insect that should be fought b y everybody with in s ecticides from the day it is discovered in a grove. I admit that there is no spray that will kill white fly and not at the same time inflict injury to the trees upon which it is so often applied, but I am satisfied that the injury is far less than white fly causes, except dnring exceptional periods when fungous diseases are unusually active. Infested trees that are properly sprayed through many years and are correctly treated in other respects, I believe will live longer, yield better, and give much larger net profits than they will do if fungi alone are relied upon for protection. The views of Mr. A. J. Pettigrew, being based upon many years of observation and the trial both of spraying and depend ing upon fungi, I think too valuable to omit. Mr. Pettigrew regularly sprays such of his groves as are planted on pine land in open fashion , that is where the distances behveen the trees are great enough to admit of the free circulation of air among them; but in case of close-planted trees on hammock soil and

PAGE 39

THE WHITE FLY. 627 especially \\hen s till closely s urrounded by h am mock ,, o ods, he depend s wh o ll y u po n fun g i . : Many of the a ttempts to introduce the fungi int o the upper parts of the State h a ve failed, and I h av e ne, r seen the diseases doing effective w or k very far fr o m the c oast. In old orange days Prof. \Vebber rec o rd s havin g see n th e red Aschersonia in abundance at Gaines,ille and Pan asoff kee. A t pre se nt the dis tricts in ,, hich the t\YO im po rtant d i sea ses a re really s uccessful are al ong the ?vlanatee riYer a nd about Fort :-Iyers. It is impo s s i ble to acc urately judge at present "hat th ese fungi will d o in the upp er and int e rior part s of the Sta te. F or p ractic e , I rec om mend that one h avi ng an i nfested grove either s pr ay it or fumi ga te it acco rdin g to circumstances ; that he persuade his neigh bo rs to do like"iYi se if po ssib le; if the neighb o rs are obdurate and will n o t treat th e ir tree s. persuade them t o introduce the fun g i as the next best thing ; if they will n ot do this it m ay be ,yorth whil e to introdu ce the di se ases for them and then w or k to c re a te a Sta te Ent o mologic a l Depart ment with sufficient res ources at it s command to enable it t o supervi s e t fie intr od ucti on of s uch va luable fun g i into eYery n eg lect ed a nd in fest ed g rove in t11 e S tate. Mr. A . J. Pettigrew, 1Ianate e, Fla., h as kindly giYe n p er mission t o refer t o him as bein g prep ared to s uppl y fo r the trade, tr ees having upon the leave s both th e r eel and the brown fungus in suitable co nditi on for int rod uction into new l oc alitie s . The frank hon esty . \\hich thro u gh many years ha s cha racter i z ed l\fr. P ettigr ew's de a lin gs ,yith the publi c and " hi c h n ow. in the interest of the publi c \Yelfare, induces him to all ow the u se of his n a me in a \\ay that m ost nurserymen ou l d shun. deser v e s the appre c iatiY e co n s iderati o n of o nr people. If some citizen h ad not conse nte d to do ,,hat Mr. Pettig re" h as d one I h."11ow of no re g ular source of s u pp ly of these dis eas es that could ha ve been named, and I a m not provided with the re so urce s b y which the w o rk co uld be undert a k e n by m y depart ment. I feel sure that no o ne ne ed fear to o rder defoliated. clean stock ofMr. Petti g re,Y. for his past r eco rd and present attitude is a certain guaranty that it will be furni s hed. Bnl. 67 3

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628 BULLETIN NO. 67. Sprays. As before noted t hree of the four pairs of spiracles or 0reathing p o res of the l a rva are on the under surface of a shaped fo ld o r groove,with the apex directed back wa rcl,which is readily observed at the anterior end of the body, approximati11g the s eparating line bet w een Tiie fiead and thorax; and indeed this fold was once supp osed by entom o l ogis ts to b e the dividing line between head and th o rax; J;mt as o bserved by Fro. Wood worth, it i s wholly thoracic-in position and is a speciali z ed appa ratus for re s piration.* Ano ther or fourth pair of sp iracles is o n the under s urface of an a nal gro ove or fold . Since the lar va is very closely piessed agains t the leaf and the only ingress o1 air to the sp iracles is through the g-roovee. or br ea thing fokls mentioned , the efficacy of the resin sp rays wfi.ich close up the outside ap e rtures of the breathing folds is readily understood. It is only nece ss ary to o btain a ring of resfnou s wax around . the b o d y -rin g o f the l a rv a, thus forming an hermetic a l seal, to suffocate it. If one or m o re of the four tube op en in g s are left unstopped while the others are closed the insect will probably survive just as a man with o ne lung will survive for a time; and if a ram comes to un cove r the stopped tubes within ter.i or fifteen clay s, it will prob a bly rec ov er altogether, whereas, if all the th1b es are closed it will die in a few hours. The structure of the insect would ~eem to indicate that a fine and evenly distributed spray would be most effective; but resin wash, going thr o u g h a fine n ozz le, froths a good deal, including so many air bubbles that a certain degree of coarseness of spray gives best satisfaction. A caustic property in the spray is also important in order that death may result before rains dis solve off the wash. The formula in gen eral us and which is most satisfactory, for regul a r work, cost and efficiency considered, is the o ne orig inally recommended by Prof. Webber , and is as follows: *Can adia n Entomologist, Vol. 23, June 190!, p. If3.

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THE \\'HITE FLY. r Resin, pulnrizecl .. . .. ... . . ........... 2u lbs. Caust ic S o da. granulated, 98 per cent. ... 4 1-4 lbs. Fish Oil . . ..... . .. ... . . . ............. 3 pts. \\'ater for final bulk ................. 150 gals . . \ som e,vh at cheaper fo rmul a is the following: 2 Resin, pulverized. . . . . . . . . . . . . . . . . ... . 20 lbs. Crude Caustic Soda, 78 per cent .... . ...... 4 lbs. Fis h Oil .......................... 2 1-2 pts. \Yater for final bulk ........ 100 gals. to 150 g::1ls. Ordinary com merci al resin, such as is bought by the barrel in Florida, is satisfactory, an d the caustic soda is of the quality used in soap factories . The crude so da comes in drums o f from I I 2 to pounds e ac h. _ \nother form ula which ha s g i-ven good sati sfac tion to so me gro,ye rs because of the con venie nce of quickly ob taining the n.1 ateriats ,vithout order ing them from a di sta n ce and of keeping the suda indefinitely ,vith o ut special precautions is as fol!o,, s: 3 Resin. pnlnrizecl. . .. . .......... . . .... 20 lbs. Ca ustic Soda ( Star Ball Potash. pulnrized) 7 lb s. F i sh Oil ... .. .................. .. . 3 1 -2 pts . \\ " ate r for fina l bulk .. .......... . . ... roo gals . Re s in costs I 1-4 cents per pound, or if obtained d irec t from the naval stor es farms I cent per pound or le ss. Caustic soda is quoted in J acksom i lle at 8 cents per pound in t en-pound cans. 7 1 2 cents pe r pound in 25 -p o und cans. 7 cents per pound in 50pou ncl cans. This subs tanc e rap idly abso rbs \\ate r from the air. becoming a Yery caustic l iqu id and is ther efo re best purchased in packages. the en tire co ntent s of \Yhich can be u sed at once after opening. If sma ll quanti tie s of spray are needed the sm a ller pack ages sh ou lcl be pmchased. The crude caustic soda c o sts fr om 3 1-2 to 4 cen ts per pound in New York, f. o. b., and cannot b obtai ned in small packages. It becomes of an adamantine hardness after being exp ose d to the air for a few days and sho uld be worked up at once after open ing the drum. It is s u itab le for use here the grove is l a rg e and the

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630 BULLETIN NO. 67. spraying outfit, from preparing plant to number of nozzles at work, is of considerable magnitude. Star Ball Potash comes in cases of 48 pounds each, one-pound balls, at $3 per case or 6 1-4 cents per pound. It may be exposed to the air for any length of time without being injured as each ball is covered with a resinous jacket. It can be obtained from almost any large grocery. Fish oil costs about 50 cents per gallon. The mate rials for mo gallons of spray made by formula r will cost about SI cents, by formula 2 about 60 cents, and by formula 3 about 90 cents. Fcrmula r diluted to the same degr~e as the other two will cost about 76 cents per one hundred gallons. As a smothering wash formula r is probably equal to 2 and 3, but its contact effects are less satisfactory. If the wash is to be used in summer the dilution is about right, but for winter use better results are secured by diluting to mo gallons instead of I 50. The materials for resin wash can be had from almost any wholesale dealer. Among the best known firms in Florida may be named E. 0. Painter & Co., \i'lilson & Toomer, and C. R. Tysen, all located at Jacksonville. The details of preparation are the same no matter which formula is used. Procure a large iron kettle, a hog scalding vat is excellent, and another sma1!er kettle for hot water. If a large kettle of from twenty-five to forty gallons capacity is unavailable, a number of smaller ones can be used, the materials being divided between them as they are weighed out and measured. Heat in the large kettle thirteen or fourteen gallons of water, having previously placed the materials given in one of the formulae in the bottom. If the water is hot before the materials are put in, add the resin and fish oil first and then the soda in small lots to prevent a sudden boiling over. Boiling is best continued for two or three hours over a hot but not too brisk fire. One hour's boiling or less will give a mixture which can be used but results will not be as satisfactory as when the wash is more thoroughly cooked. Whenever there is a ten dency for the liquid to boil over, subsidence will quickly occur if a pint or more of water from the water kettle, ,vhich is kept warm but n(l)t boiling, is added. Never add cold water while

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THE WHITE FLY. 631 the wash is cooking if you desire results that are certain. Increase the quantity of solution by gradual additions of warm water until a stock so lution of thirty gallons is obtained. For use. thi s is to be diluted to one lmnclrecl-fifty gallons in case of formula I, t o one hundred gallons with formula 2, and one hnnclrecl gallons ,,ith formula 3. The stock softttion may be kept for a time and u sed as desired, but the wash is best used as fast as made. . -\ny sediment or settling in the stock solution indicates that cooking was incomplete and must be repeated. \\!here a s team pump is possessed or a head of steam is availa ble a set of barrels may be arranged with steam pipes leading through them and resin ,nsh can be prepared rapidly and in quantity by boiling with stea m. The stock solution s hould be strained before diluting it to remove any particles or trash that would clog the pump n nule. Other Sprays and Remc:dies than Resin Wash. KEROSEXE. E;1n;LSION.-Kerosene used as an emulsion or in a ten per cent mechanical mixture with a kero,Yater pump i s an efficient destroyer of the l a rvae and eggs of the fly, but is some what uncertain in its effects upon the tree. The emulsion, properl y made. i s much m ore reliable than the mechanical appli cation. made ,,ith a kerO\rnter pump. Bright, sunny clays with a dry a tmosph e r e should be chosen for making, ker ose ne appli cations. If applied upon a cloudy, humid clay that is followed by several days of cloudy weather, thus interfering with rapid evaporation of the oil, very serious injury to the trees is apt to follow. From ninety to ninety-five per cent of the larvae are killed by one thorough application . An occasional s praying with the emulsion may not he objectionable. but I do n o t recom mend it for continuous use. Crude pretroleum shoulci never be used up o n citrus trees . \VII ALE OIL So.w.-An_v good whale oil soap will be found useful in fighting white fly. Of the hard, or soda soaps, Leg gett's Anchor Soap is probably not surpassed. The true potash soaps seem to give better results with the insects and trees , con

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632 BULLETIN NO. 67. sidered together, than any of the insecticidal washes, when used continually for several seasons, as must be done in case of white fly. Good's Potash Whale Oil Soap No. 3 is well suited for such use and is safe as a summer application. Used at the rate of one pound to four gallons of water it will kill about sixty per cent of the grown larvae in March, and, ,vhen used at the rate of one pound to three gallons of water on half grown larvae in May or early June, from eighty-five to ninety-five per cent of them are killed. Though a very heavy rain fell within two hours after making an application at the latter strength in early June, not less than ninety per cent of the insects were dead two or three clays afterwards. Leaves, having upon them pupae from which the adults were emerging and larvae in less ad vanced stages, when immersed for ten minutes in a solution of the soap. one pound to four gallons of ,vater. have invariably had all the insects upon them killed unless they were peculi arly sheltered. In laboratory experiments, Good's Tobacco \Vhale Oil Soap No. 6 did not seem more effective than did the No. 3 soap, but in the field one pound of it in five gallons of water seemed to give somewhat better results than one pound of the No. 3 soap in three gallons of water. Leggett's vVhale Oil Soap Compound a true potash soap, used at the rate of one pound in three gal lons of water, gave. in the field, about the same results as Good's No. 3, but in laboratory tests it seemed to be not so effective. For summmer use and for trees that have been weakened by the use of more severe sprays. the potash soaps are especially recommended. Purchased by the half-barrel, Good's Potash Soap No. 3 costs 3 1-2 cents per pound: or. if used at the rate of one pound in three gallons of water, one hundred gallons of sprav will cost $ r. I 7 : if the dilution be one pound to four gallons of water, one hundred gallons of spray will cost .87 r-2 cents. HAMMOND'S THRIP JurCE.-This preparation made by Benj. Hammond. Fish-kill-on-the-Hudson. N. Y., is apparent ly a very concentrated potash-tar soap which readily dissolves

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THE WHITE FLY. 633 in ,rnrm water. In twenty gallon kegs, it costs $r.6o per gal lon, and as the dilution recommended is one part of Thrip Juice to one thousand parts o f water, one hunclrecl gallons of spray will co s t sixteen cents. Used at the dilution given re sult s have not been sa tisfact ory at all as compared ,vith those gotten with the use of potash whale oil soaps ap plied a t the same time a nd under the sa me c onditio ns. A few of the young er larvae were killed, but nearly all of the ,vell-gro,vn o nes sur vived. It is possible th a t this insecticide, d iluted a bout one part of Thrip Juice to eight hundred parts of water. will prove a valuable a pplication to use abou t the middle of :May or a little earlier when the lanae are all quite young. Mo::--rTGO:\rnRv's IxsECTICIDE-Apparently a potash-sod a tar resin preparation, "ith po ss ibly other unkn ow n in g redient s. the wh o le quite resembling the ordinary resin wash. Since part, and possibly the largest part, of its ba s e is true potash. the w ash is apt to be more stable than the ordinary so d a wash and is therefore probably better su ited for s ummer us e th an m a ny preparations. The full effect of the s h is not apparent u nti l snera l days ha, e passed afte r sprayi ng. but so far as te s ted, results ha ,e be e n quite as sati s fact o ry as \\'ith a n y pr ep aration used. The st oc k preparation is so ld by Dr. L. ~Iont gomery and S o n, :-Iicanopy. Fla .. at $8 .73 per barrel of 30 gal ~on s . Fo r u se, the stock prepar at i on i s diluted one part to se\' e n or ten parts of ,Y a ter . : on e hunclrecl gallons o f sp r ay . :th e refore. cost $2.50 at the fo rm er dil ut io n and $1.73 at the latter. TOBACCO DECOCTIOK.-Tobacco infusions at all s trengths dr e pr ac ti ca lly \Yorthless, the effect on wh ite fly lanae being little more marked than if rain water w e re u sed. The lan ae m ay be immersed in such decoctions for se veral hours without being killed. Roseleaf Insecticide, a patented preparation of tob a cc o extract . , gives results but little better than the ordinary decoction. SULPHUR DusT.-Dusting the trees liberally with flowers of sulphur when the young are hatching has been found to be of no value at all.

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634 BULLETIN NO. 67. C AMPHOR BALL S.-Ca mphor ball s enclosed in cheese cl o th sac ks and tied in the trees as repellant s are worthless. L IGHT TRAPS.-Trapping the ad ult s with lights gives no results worth menti oni n g. F IGHTIN G THE ADULTS.-\Varfare of any sor t directed against the adul ts is d oo med to failure, si nce th e fema les gen erally l ay their egg s with in twent y t o forty-eight hour s after hatchin g. When to Spray and What to Use. Spraying must be so timed that the greatest number o f insects are de s tro yed , and anoth e r a nd even m o re important considerati on is to avoid injury t o the tree, bl oom and fruit. Sprayin g cannot be clone effectively while the insect is on the wing. There are thr ee l a rval peri ods , the l o n gest of which extends from late November until the first of JVIa r c h ; an o ther extend s th ro ugh May a nd June; another without welt defined limit s through late Jul y, A ugust, September and October. The winter l arva l period offers the best oppo rtunity for sa tisfactory spraying. Two tho ro u g h applications o f resin wash should be made during thi s peri o d as a regul a r practice and , i f a grove is badly infe s ted, the fir s t yea r that spraying is adop ted three may b e m ade with profit. The earlier the spraying is done the less will be the sappin g of the tr ees b y the larv ae during the winter. The first spraying should be clone in December, if p oss ible , and the second in Januar y . A third m ay be made in February. Spraying s h o uld cease w hen the blossoms comm en ce o pen ing, but may be continued until the bud,; are swull e n and ready to burst. A sw ollen bud in spring is not more liabl e to damage from a resin s pray th a n it is durin g the winte1. No s p rayi ng with resin wash should be clone during April , May o r early June. Some growers h ave dropped many th o ns a ncl s of dollars worth of fruit by spr aying in late l\ifay in Soltth l J o
PAGE 47

THE WHITE FLY. 635 be stated with emphasis thaLspraying bearing trees with resin wash during the spring larval period is hazardous. Late May in South Florida corresponds to early June in the northern orange section. Spraying with resin wash at any time during June is questionable. So far as present experience and reports indicate a potash \vhale oil soap may be u se d with safety after the fruit has been set for t\\'O or three weeks. vVhere the flies are bad a soap spray may be used in late :\fay or early June. This will dimin ish the June and July h a tching of adults and therefore tend to h o ld clown the numbers of the second brood of larvae which cau s e the smi.1tting of the fruit. Either the resin wash or soap can be used in July, August and September without clanger of dr op ping fruit, but some s carring and burning will be caused by the former. For summer use I am inclined to believe that a pot a s h soap, used exclusiYely. \Yill give best re s ult s. If a quart by measure of flower s of sulphur is dissolved by boiling with ten pounds of soap in t\Yelve or fifteen gallons of water , the solution being diluted to thirty or forty gallons of liquid for use, a spray is obtained that is effectiYe against the purple and six-spotted mites, the rust mite. scale insects and white fly. Three or four well made applications during the summer. about a month apart and timed to catch the white fly larrne, ,vill keep the fruit free from ru s t , sc a le ancl sooty mold if "inter treatment was pr o perly made. How to Spray. A good force pump, capable of supplying two to four nozzles and of ele va ting the spray when required to a height of thirty-foe or forty feet is a necessity. Among the hand pumps that can be recommended as filling su c h requirements may be named the "Friend" pump made by the "Friend" 11anu facturin g Co . , Gasport , N. Y., and the Gould Sentinel Junior pump made by the Gould Manufacturing Co., Seneca Falls,N. Y. There are other good pumps than these, but as I have had practical experience with both of these machines as well as

PAGE 48

636 BULLETIN NO, 67, _ others I can pronounce them am o ng the best. The latter is well known to our growers. The former is yet a stranger to them, but is something unusually good and deserves an introduction for high power work. If steam, gasoline engines or com pressed :air pumps-capable of supplying from six to twelve nozzles-are wanted, correspond with such firms as these: Gould Manufacturing Co . , Seneca Falls, N. Y.; Friend MarniThe "Friend'' Pump. Gould ' s Seutinel Jr. Pump. facturing Co., Gasport, N. Y.; Wm. Stahl, Quincy, Ill.; Dem i ng Co. , Salem, 0.; The Pierce-Loop Sprayer Co., Nortfieast, Pa. , o r Field Force Pump Co ., . Lockport, N . Y. . The leads of hose should be lol}g enough to carry the extension rods, well towards the tops of the tree s . Ladders a1'.e sometimes used in reaching the tops of very tall trees. A high

PAGE 49

THE WHITE FLY . 037 .., pl a tform is sometimes er ected on the spray wagon above the tank on "hich the operators s tand to reach high tops , but as spraying for white fly must be from the inside of the tree out ward ins t ead o f fr o m the outside imvard , such a platform is of littl e u se unless th e wagon is driven very close to the tree. Brass extension rod s en ca sed in bamb o o are less unwie @y th a n th e ordinary ga s pipe e xte n s i o n rods and sho uld be eight or ten feet l ong . Nozzles that can be adju s ted to throw either coarse or fine sp ra y are t o be pre fe rre d for applying re si n wash or whale oil s o ap, an d the sp ray s hould be put on as fine as it can b e and at the same time carry well t o the foliage. Resin wash when too fi ne b eh av es lik e fine s oa p bubbles, drifting in the air instead o f going t o the p oint at which the n ozz le is direct e d. Nozz le s of such t y pes as the Nixon , B o rdeaux, l\!IcGowen. Se n eca, l\fasson, etc .. are suited t o th is w or k. For applying any o f th e pr e p arat i o n s of ke rosene a fine Verrn o rel n oz zle s h o uld be u s ed. A. no zz le than ca n be a dj ust e d t o any a n g le s o as to re ac h the under s ide o f the I eaws fr o m any p os iti on, s u c h as the Go ul d's C a rnation or Erin, i s at ti me s a c o nvenien ce but is not so ne cessary a s it may appear to be to o ne who ha s not learned th a t th e und e r s ide of nearly ev er y leaf up on a tree, as ordinarily grown. can be cov e red by u s ing a straight r od nozzle. The under s ide o f e ve r y l ea f must be hi t and w e ll co v ered with spray t o kill the \\ hit e fl:, l a rv ae . The op er a tor must not be afraid of the dr ip and sh o uld s tan d ,y ell under the tree and thrust hi s rod th ro u g h the forks so th e s pr ay wi ll be th row n with good force a ga in st th e lm n r leaf s ur face s. For hi gh trees havin g thi c k foliage a powerful pump i s n ecessary to dri v e the spray throu g h t o the t o p. Some g rmver s prune out all the interior growth fr o m their tr ees so as to l e ave them h ollow con es . Such tree s are easily sprayed, but other growers belie v e the r esu lti ng gain is m or e tl'l a n o ffset by l os se s in o ther directions. A n exc e ssiv e g ro w th of wat e r sprout s is of ten s timulat ed b y too s ev e re pruni ng . and the s e a re s pecially at tr act i, e to the fli es . A growth of water sprout s is the n o rm a l outcome of a n effort by the tr ee to remedy

PAGE 50

638 BULLETIN NO. 67. an abnormal condition-that is, to balance a sufficient top growth against a root system that is overdeveloped. Insufficient drainage is a cause sometimes inducing excessive root gro.vth, and hence indirectly influencing the development of water sprouts. Cutting all of them out, along with the int~rior fruit twigs, encourages a new and more numerous growth of them. vVhere it is p o ssible to do it train them to grow outward in the foliage zone and allow them to harden and become ordinary normal wood as soon as they will. vVhen they are in the heart of the tree and numerous it is necessary to cut them out as well as dead twigs before spraying is commenced. Trees upon tall trunks are readily developed into the hollow cone. . I believe the foliage zone of such trees should be deep, and if spraying seems difficult effort should be directed toward obtaining a pump of higher povver rather than to dimin ish tl1e depth of the foliage by pruning. If low branched, squatty trees are more difficult to si)ra y , they are much easier to fumigate than high-topped ones, but can also be sprayed successfully. With low trees an adjustable or elbowed nozzle for throw ing the spr a y upward is almost a necessity. The operator will often find it best to thrust his rod through to the side of the tree opposite from where he is standing, thus hitting the under surfaces of the leaves on that side. With low-topped trees having dense foliage most of the work must be done by this method. Some of the leaves , especially at the top, are best reached from a position outside and away from the tree. A clever operator will quickly learn by experience how most conveniently to send the spray where it is needed. The quan tity of spray used should be liberal. One thorough spraying is cheaper than two that are half done. Trees from 12 to 20 feet high will i~equire from 8 to I 5 gallons of spray; from 20 to 30 feet high from 15 to 25 or 30 gallons of spray. Use more than these quantities rather than less. The following extracts are taken from letters bearing vari ous elates, written by well known orange growers whose large

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THE WHITE FLY. 639 experience with resin and soa p 1Yashes gives deserved weight to their opinions : "I have used resin wash against white fly for eleYen years with perfect success. J\Iy long experience with its use has made me very familiar with its effects on trees and fruit at whatever season ot tfie year applied. Several years ago I lost m a ny 111111dreds of boxes of fruit by u s ing it in :M ay. I used it dgain last May, the ,veather conditions being identical with \\"Lat they were when I previously lost fruit , namely, very hot an
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G.JO BULLETIN NO. 67. "I was well pleased with the re su lts of spraying for white fly l as t season. My tangier ine grov e was comparatively free from fly, so much so that I shipped all the fruit with~ut washing any of it ancl it was 90 per cent.'fancy bright.' Only about 200 boxes out of 3,500 from the Ba nk of Kingwood Grove were t o uched by the fly and the se not badly. By being careful to keep all the water sprouts from the trees and spraying well (with resin, fish oil and Star Ba ll Pota s h) once o r t wice in J a nuar y o r Februar y we h ave kept the fly out of our groves for the past t wo yea r s. ~fr. N i c h o l s was we ll enough plea sed with hi s l as t year's s pra y ing to spray agai n this year. ''I have never sprayed wi th re s in wash i n th e sp ring, June being the earliest elate I have tried. I have never ha d any fruit to fa ll from the use of the wash, but have.: bad a small per ce nt age of the fruit to burn w h e re it was most expo5ed to the su n-perh a ps from 2 t o 5 per Cnt. of it; from the entire grove, 2 per cent. would probably cover the amount of burnt fruit."-C. P. Ful1r, Ellenton, Fla. " I beg to say that after making experiments with va rying stre n gt h s of the Good soap, I ha ve found 18 p ou n ds t o ;;o ga ll o n s of water ju s t ri gh t . I wo uld not hesitat e t o spray at any time wit h this soap, and h av e actually sprayed th e bloom t o kill thrips, apparently without injuring the crop of fruit. It is a safe preparation to u se, and I have found it will rid the trees of scale_. and I feel s ure it will be effective a ga in st the white fly. "I h av e long contended against the use of resin wash and h av e had, in the past , bad result s on young fruit fr o m it s u se." E. P. Porcher, Cocoa, Fla. " I have n o very definite idea as to the effect of spraying v ery yo ung fruit with Good's w hale oil soap, as I have a lwa ys avoided spraying trees when fruit was passing through the dropping stage. By the time that the fruit is the size of mar bles most of the weak ones h av e dropped off, and from thi s time on I have used Good's p o t as h s oa p without seeing any bad re su lts from it, but I have burned spats on oranges two-thirds gro-wn with soap of my own make when used at a strength

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THE WHITE FLY. 641 of one pound to four gallons of water.; but this soap was much stronger than Good's, having less than one-half of the water in it that Good's has. "I have never noticed any direct injury to trees from one application of resin ,vash, but when applied as often as three times inside of three or four months it certainly does injure a tree to such an extent that it will take an entire season for it to rec ov er."-C. \V. Butler, St . Petersburg, Fla. Mr. Porcher and n.fr. Butler have not had experience in spraying for white fly, but their knowledge of the comparative effects of the resin washes and pota s h soaps upon treeii and fruit can be depended up o n as '>'aluable. Scalding Action of Resin Wash Explained. Sodium resinate, formed by boiling together sodium hydroxide and resin , is a ~alt composed of a strong base and a weak acid; in the pre'.ience of moisture it easily s
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642 BULLETIN NO. 67. I heat within,the phenomenon of plants burning in a closed green house in hot sunshine being a familiar one. According to the results obtained by Mr. W. Vv. Coblentz of Cornell University, resin is not highly diathermous like glass, but possesses a moderate transmitting power for heat. I think it not improb able that the accumulation of heat inside the resin shell is suffi cient to stimulate the chemical activities which, but for its presence, would inflict less injurious effects. As the fruit increases in size it becomes of tougher character and, rela tively, so small a portion of the pulp is burned that scalding occurs only in spots, not involving enough of the flesh to cause falling. It is also conceivable that, to a smaller extent, drops of the wash accumulating on the undersides of the-fruit, harden into more or less persistent concavo-convex lenses. with suffi cient curvature to focus such of the sun's rays as strike them to centers inside the shell, thus furnishing an excess of heat in a local spot, possibly not enough in itself to cause burning but sufficient to encourage unusual chemical activity in any free sodium hydroxide near such a point. No matter which is the primary agent in causing the falling, whether chemical or physical, it is associated with hot, dry weather and direct sun shine, heat being an important factor in causing it. Besides the original accumulation of wash in drops on the lower part of the fruit, the dews and light rains will regularly carry more of it to the same spot and at the same time stimulate chemical disintegration, thus subjecting such spots to the action of sodium hydroxide for a continuous and indefinite period. In like manner some of the fruit may be so located that the drip from dew or light rain from above falls constantly on the same spot, causing a scalded place on the upper surface or side. The relatively large calyx cup receives and holds consider able quantities of the spray and this in breaking up into sodium hydroxide and resinous acid would scald the tender stem of the fruit, inducing shriveling and falling. It is probable that most of the dropping is caused by injury to the stem.

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THE WHITE FLY. 643 Fumigation. Fumigation with hydrocyanic acid gas is recognized in nearly every progre ssive citrus producing co untry in the world as one of the mo s t effectiYe methods for de s troying orange pe s ts. A pr oc es s th a t has been found so valuable in every other part of the world i s certain to eventually come int o favor in Fl o ri da . The conditions that exist in our State set some limita tions upon its range of usefulness and I think it s hould not be "boomed" in to disfavor. but a gradually increasing number of growers can adopt it each year with profit. The Florida grow e rs have had little experience in fumigating trees and think the meth od intr icate and my s teri ous. Familiarity with such , vo rk remo,es such mi sco nceptions and it is discovered th at a fumi ga ti on o utfit is n ot more mysterious o r difficult of m as tery to a n o range grower than is a sp ray pump with its accompanim en t s to a g ro ce r. It is well-nigh necessary, h ow ever, to s ecure the help of an experiencec. fumig-ator when be g inning such work. Since it will Se neces sa ry. at a later time, to publish direc tions for fumig a ting in the field I will burden as little a s possi ble the already full pages o f this bulletin with the details of si 1ch work, giving only a re s ume o f the results reached two years ago while working in conjunction with Prof. C. vV . W o odworth of the California E xperiment Station. Upon Prof. vVood~ w o rth 's arrival in Florida. our first work was to visit the Mc F ar land Tent Factory , then l o c a te c i at Titusvilie , and l oo k to the selection and treatment of cloth, patterns of tents , etc. Six ounce drilling. treated with paraffine, a sort of cloth u s ed by the c o mpauy in the manufacture of tent s for protection against cold, was te s ted, but seemed to allow too mu c h escape of gas. Several patterns of ten;: , s heet , hoop and bell were made ready , using either eight ounce cluck or six ounce drilling, some of our largest bell tents for trees thirty feet in heigfit and twenty-five feet in d iame ter being made from the latter material. Iii practice, the drillng proved quite satisfactory for the smaller tents , but was t oo eas ily torn for heavy wofr. Subseq11e:tly,

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644 BULLETIN NO. 67. the people of Candler, Florida, have used a light, six-cent muslin quite satisfactorily, but I am inclined to recommend heavier cloth. The cloth for the Station tents was miidew proofed at the factory. nnd when on the ground where it was to be used, was painted with linseed oil, into which enough lamp-black vvas stirred to give body and color to the prepara tion. 'vV e experienced some trouble with burning of cloth; in fact. found it impossible to paint a large bell tent without serious damage, necessitating extensive patching, unless the derrick upon which it was swung was in perfect working order and repair, so as to avoid the risk of leaving a fold in the canvas for even a short time while drying out. The weight of oiled tents is also a great objection to them. Cactus juice ,vhieh is sometimes used in California, is not available in Florida i,1 c,1ffi cient quantities for tent treatment and some new application must be found. Fortunately a preparation, known to sailors in tropical waters has come to my attention and, except ti)a~ it renders cloth somewhat objectionable for handling, l1as thus far given good satisfaction. Mr. Arthur Weaver, who superin tended the fumigating of Mr. A.G. Liles' grove, used the prep aration and reported it lighter , cheaper, and in all respects $Upe rior to oil with which he had had equal experience. It se._ms not to burn cloth and to be mildew-proof. Cloth so treated ,1ncl in use upon boats in tropical waters is reported to last for fi v e or six years. The following is the formula as developed and employed by :\Ir. \Veaver: Five pounds white lead , fifteen pounds of laundry soap, chipped, ten pounds of lamp-black, two gallons of boiled linseed oil, six gallons of water. Heat to boiling two vessels of water, having three gallons in each. In one dissolve the soap and keep the other hot. Thoroughly pul verize the lamp-black by stirring and mixing well with one-half gallon of vinegar. Now add the lamp-black to the linseed oil, stir, and pour into the soap solution. Adel the white lead, mix the whole thoroughly. using all the water, and apply to cloth with brush, keeping the paint hot enough to just show steaming while being used. If the first coating is not sufficient, reverse the tent and give an application to the opposite side.

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THE WHITE FLY. 645 For trees not over t,Yeh e feet high I found hoop ten ts mo st satisfactory: aboYe that t o t,Yenty feet in height I think sheet tents "ill proye best: abO\e twenty feet the bell or sheet will be most satisfactory. A.s one result of the work a new pattern of derrick was de\ised for swing ing large bell tent s. ,,hich seems mor e flexible to Yarying requirements than the Ca lifornia pattern s; o r perhaps I should designate tents handled after thi s plan as box tent s , for they are s wung in pairs with the derricks UI:JOn the same general principle as t:1e bnx 'tl't; i. e., the type er box nt ::lescribecl 111 Bulle tin 122 of the Ca li fornia Station, the derrick taking the place of a lifter. The idea th a t a bell tent might be swung like a box tent ,yas due t o Prof. \Vo oc hYorth , ,Yh o menti one d it u po n the clay of his departure, and the practical w orki ng out of the ide a was a chie, ed by the writer"s combinati on of ideas cleri,;ecl from Yarious sources; Mr. ~ --\rthur \Veayer s s ug gesti o ns \Y e re esp eci ally helpful. Our derrick co nsi sts o f a main mast of sp ru ce pine abo ut thirty-fiye fee t high for tree~ thirty feet in height. a nd stands betw ee n the rmn t o be treated. To each side of it is att ac hed a gaft t\yenty-t\\o feet l o ng. a l so of s pruc e pine. The foo t of the ga ft clasp s the mast ,,;ith arms of oa k. being raised and lowered with double bl ocks and pull eys exactly af ter the manner of a ship gaft. The top of the gaft is double blocked and pulleyed to the top of the m as t, so by means of it s top and bottom attachments the gaft can be raised t o any height. its t op many feet abo,;e the top of the mast if necessary, or it ca n be Jmyerecl to reach the ground. Since it can take any angle of direction also . i t may be qui ck ly adjusted to tr ees o f any height ancl of nriable di sta nces apart. The t o p of the bell i s attached by pulley near the encl o f the gaft. T hre e trail pole s of hickory, ea ch abo ut ten feet in length. are fast ene d to one side of the lower borcler of the tent. their ends being securely l ashe d t o each ot her with rope. so when they pull again s t ea c h oth e r the rope and not the cl ot h "ill catch the strain. The cloth is caught up and bagged s ligh tly at the s e points of union of the trail poles as additional protection against

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646 BULLETIN NO. 67. tearing. The center of each of these trail poles is connected with the top of the gaft by pulley, and thus the border of the tent to which they are attached may be elevated to any height, the opposite border swinging free, within reach, near the ground. A trail rope is attached to each of the trail poles. All pulley ropes belonging to the apparatus are secured to cleats on the mast. In operation, when the main mast, on rollers or wheels, has been placed in position, the height of the tree to be fumi gated and its distance from the mast are noted, and the foot of the gaft is raised or lowered to the point of greatest advant age as learned from experience. A similar adjustment is made of the top of the gaft. The top of the tent is next drawn fully up and then the three trail poles; the hanging free edge near the ground arid as much of the border as pos sible is now brought into position, and the top of the gaft lowered some if necessary. Slack is now given to the trail poles and a m a n at each trail rope so pulls the pole to which his line is attached that the whole tent drops into position over the tree. The lower border of the tent must be extra strong to avoid tearing; it is best bound with rope. To remove the tent from the tree the procedure is almost exactly reversed. With men trained to work together, the tent may be lowered over a tree in seven or eight minutes and removed in about five. Since the operation of removing the tent from one tree raises it almost in position to drop it upon the next, the time required for changing will not be the sum of eight and five minutes, but the last five minutes is divided between the two trees, removing from the one and at the same time getting almost in position to lower upon another by a quick adjustment of the angle of the g a ft , it req1.1iring less than eight minutes to cover a tree from this positi o n. The apparatus requires four men, one of whom may be the fumigator if he has his matetials weighed out beforehand. A gang of four can operate about four tents or two derricks, if the rows are not more than twenty five or thirty feet apart. This gives forty minutes time to the tree and allows ten minutes for shifting of the tent. In order

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THE WHITE FLY . 647 to realize this expeditiousness in practice all apparatus must be in perfect working order and repair and the men trained to handling it. The results secured in my practice satisfied me that this would be a reasonable estimate, for it was done often enough in this time with our then imperfected apparatus to justify such a conclusion. Full specifications and illustrations of the derrick at work will be published later on in bulletin form. Some determinations suggested by Prof. Woodworth and made by Prof. :i\Iiller, of the Chemical Department, are oi interest and imp o rtance. He found that one ounce of sul phuric acid and one ounce of water, mixed and cold, when added to one ounce of potassium cyanide, yielded 428-4 cubic inches of gas; that one ounce of sulphuric acid and one ounce of water, mixed and added immediately, while warm, to one ounce of potassium cyanide , yielded 467.9 cubic inches of gas, greater by a little more than nine per cent. than with a cold mixture of water and acid. Mixing the acid and water, there fore, only as used, means a saving of six or seven cents per tree on large trees requiring two pounds of cyanide. He fur ther determined that a greater proportion of acid did not mate rially alter the results . . and that ammonia seems not to be. formed immediately after the reaction, under laboratory condi tions. A number of experiments were made with citrus twigs, orange, lemon, pomelo, etc., infested with white fly, to deter m i ne the susceptibility of the insect to the gas, close of cnem icals to use, length of time necessary and most favorable tem perature for treatment. influence of moisture being present upon the leaves when fumigated, etc. It ,ms found that the insect in its larval and pupal stages is very readily killed by a much lighter dose of gas than is comm o nly u se d against the black scale in California: in fact, our field practice with tents demonstrated that we could reduce it about one-half; that the time should be about forty minutes ; the variation in temperature ordinarily encountered in Florida seems to be a neglectable factor; moisture did not seem to interfere greatly \\ith -the efficiency of the work, unless the

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BULLETIN NO. 67. leaves were almost dripping, when it became a factor of much -disturbance, though not so great as we had thought probable. Trees were fumigated in the field in warm sunshine, at all hours of the day, in cloudy weather and at night. We observed but little injury to trees or foliage if fumigated at night, during cloudy weather, early in the morning or late in the evening. Trees fumigated after 9 a. 111. and before 4 p. 111. in sunshine were invariably somewhat injured, some of the younger limbs dying back and all of the leaves usually shedding. The fallen leaves were all replaced by new growth in a few weeks and no permanent in jury done, but the crop upon such trees was notice ably reduced. The dropping of leaves from a tree in Florida has comparatively little significance, the trees, instead of dying, as they sometimes do in California, putting on new foliage and going along as if nothing special had happened. However, the burning of limbs and injury to bloom i s another matter, and, therefore. midday fumigati o n can hardly be practiced. \Vhile some defoliation occurred with trees fumigated at other times than midday. even after night, it vvas not strikingly noticeable, nor was damage to limbs or crop of sufficient amount to be detected after a few month s . Some of this work was done as late as February 18, when the blossoms were beginning to open, some of them being well expanded. The bloom seemed unaf fected by the treatment unle s s the work was done with the sun at high meridian. The white fly seemed practically exterminated upon the treated trees. In examining hundreds of leaves from dozens of trees about ten days after they were fumigated, and covering thousands of insects, I was able to find but a single living speci men. If a grove was segregated from all others .. I have no doubt that one fumigation would render it so nearly clean that it would need no aclclitional attention for two or three years. The great hindrance to its becoming a practicable remedy is that but fev v grove s are so isolated that the fly will not come to them from neighboring zroves, and since the in s ect seeks young and tender growth fo r egg-l a ying purposes, there is, per haps, some tenclenc y for it to go to tree s that have been fumi

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THE \VHITE FLY. gated and are therefore putting o ut ne,, gro,,th. Vnder ordi nary circumstances , the inse ct is n ot a great tra v eler, though wing ed, a nd \Yill of ten take a ,,-h o le s ea so n . extending over three full broods to sprea d o, er a ten-acre g-r o,e : its progress will be marked by the trees s hmYing sooty mold . Special obsenations \Yere made t o determine the effect of the gas upon lad y-b u gs. On the a ftern oo n of January 22, seventy-two lady-bugs. almo s t all Chilo c orns bh;ulncrns, \Yhich h ad fallen to the gro und under fumigation treatment, ,, ere pl aced in a s hallmY tin b ox and l e ft until January 23: at 9 :30 a. m . of the latter elate sewnty beetles \Hre in the box, a fe,Y of them actin: a t 4 p. 111 . sixty-six remained in the box _ . ab o ut a dozen o f them s hmYin g sigi1s of actiYity. _-\t 8 :45 a. 111. Janu ary 24, s ixty-t,,o lady-bugs ,, er e in the box _ . and s ixty at 12 AO p. m.; the sixty never exhibited signs o f animation, all being obs erved to be dead seyeral d ay s afternard. January 24-, by r p. m. another lot o f o ne hunclrecl-se,enty-one fallen bugs, ne a rly all of the same s pecies as before, w as collected and kept in th e s ame manner as the fir:e-t ones. Janu a ry 25 a t 4 : 30 p . m .. one hundred-sixty o f the s e ,nr e dead. sixteen out o f the lot ha Y ing recovered. In the first lot, sixteen per cent. of the ,Yliole revived. in the second l o t a bout nine per cent. Since fumigati o n doe s n o t destroy fungous gro\\ths many gtmyers ,,ill prefer gi, ing it a trial before u s in g a caustic spray. Xo matt e r what stde o f tent is used, when it is in p os ition a few shonls-ful of ea;th are thro,vn on the b otto m to bola it in place a nd r ender it gas-tight around the base. The generating vessel is set under it, as near to the tree trunk a s p oss ible , and the water i s poure d in. then the acid; the close of cyanide, wr a pped in paper. i s ne x t dropped into the vessel and the o pera tor. carrying the edge of the tent with him on his back, quickly steps a ,Ya) ' . h o lding hi s br ea th and lettin g the tent fall into p os tion as he does so . A s hovel-fol of ea rth is then thro,Yn up o n that part of th e tent border just dropped and everything is left undisturbed for forty minutes. The following table shows the amounts of chemicals used for different sized tree s b y the Horticutural Commissioners of

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650 BULLETIN NO. 67. Riverside Co unty , California. These amount s are intended for the destruction of scale insects and can be reduced fifty per cent. or m o re in quantity if it is not specially desired to kill other insects than white fly: ~--------------H e i ght of Di amete r of Cy anid e C . P. Su lphuri c A cid , Tr ee. Tr ee. , vate r . (98 p e r ce n t). (66 per ce nt) . F eet . Feet. Oun ces. Oune es. Ounces. 6 4 2 1 1 8 6 3 1 l 10 8 5 2 2 12 H 11 .', 5 Hi 16 17 8 I 9 20 1 6 -20 . , 22 10 12 20 24 1 8 22 3 0 H 16 24 -30 2028 3,1 l l> 1 8 30 3ti t530 5 :! 24 28 -------------------The cost of fumig a ting trees, labor included and not con sidering the co s t nor wear of the tents , is about equal to the cost of giving th e s ame trees three sprayings with resin wash. Low, squatty trees, such as are grown on C. trifoliata stocks, with their branches hanging to the ground, are of the shape that should be sought when it is intended to fumigate them regu larly. The precautions t o be observed in handling the chemicals are given in the succeeding section on nursery fumigation work. Tht Nursery Situation. No provision i s made by the State for the inspection of nurseries, hence there i s no way of officially determining their exact status throughout the State. My knowledge of their con dition must necessarily come through chance channels and the information I receive is of ten too unreliable to warrant any public statement regarding it. The reputation of the respective nurserymen for reliability of statement, care in handling their goods and the general c o ndition of the neighborhood in which they are loc a ted are the only guides th a t can bedepended upon in choosing from whom to purcha se . The safest practice for all

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PLATE I V . FUM I GATING WITH HOOP TENTS AT CANDLER . FLA.

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THE WHITE FLY. 651 parties, customers and nurserymen alike, will be to handle, in the future, only stock that has been defoliated and cut back. I believe that citrus stock prepared in this way is safer from white fly than is inspected and fumigated peach stock from sca le, when shipped from a San Jose scale neighborhood. When fumigation with hydrocyanic acid gas is added I regard the pro tection as perfect. Fumigation s hould always be practiced dur ing the spring and s ummer months and is best never omitted. If stock is shipped during spring or summer, every vestige of leaf should be carefully cut away so as to make certain that no unhatched eggs remain, since these are not readily de s troyed by fumigation. Fumigation is undoubtedly effective in destroying the a dults and lan,ae. nipping and even soaking infested leave s for con siderab le periods of time in tol>acco decoction, Rose-leaf Insecticide, Good's Potash wh a le Oil Soap No. 3, Go o d's Potash Tobacco Soap No. 6, Leggett's \Vhale Oil Soap Compound and resin ,rnsh have been tried, but \Yith out satisfactory results. Th e odor accompanying most of these washes is objectionable and even when the leaves are left immersed in them for considerable periods of time, protected larvae escape injury; thus a leaf with a blister or cavity pro duced by scale or red spider which was netted over witn a spider's web and threads of the sooty mold was submerged for ten minute s in a solution of Good's soap No. 3, one pound to two gallons of water, without killing the l a rvae sheltered beneath the web as shO\vn by an examination made 72 hours later . To determine the dose of potassium cyanide (KC~) nec essary to g ive the correct amount of gas to kill the white fly larvae in an air-tight fumigatorium, I commenced by using one gramme of KCN to I 5 cubic feet ot space for thirty minutes time. An examination made three days later revealed that about 47 per cent. of the larvae had been killed. One gramme of KCN us e d for I I, 9 a nd 7 1-2 cubic feet, respectively, for the same l e ngth of time showed constantly decreasing percent ages of living larvae. One gramme of KCN to 6 1-2 cubic feet of space allowed but one larva out of many that were examined

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652 BULLETIN NO. 67. to come through alive. One gramme to 6 cubic feet seemed to kill everything but to make the dose more certain one gramme to 5 3-4 cubic feet was adopted as the standard dose and has been repeatedly tried, always giving the unifon~ result of kill ing all larvae and adults. This dose requires about 17 grammes or 3-5 of an ounce of KCN for every mo cubic feet of space, or 170 grammes, that is about 8 ounces, Avoir., for every 1,000 cubic feet of space. The following experiment was made to determine the effect of fumigation on the true eggs. A potted lemon bush, entirely free from white fly, was confined under a cheese-cloth cover and several hundred adult flies were captured and liberated inside the cover. At the end of 48 hours the leaves were covered with thousands of eggs, several hundred of them occurring on each of several leaves. The bush was then fumigated for thirty min utes with the standard dose, or one gramme of KCN to each 5 3-4 cubic feet of space enclosed. The bush was then kept in an unused recitation room, into which no adult fly could pos sibly enter by accident. After three weeks it was found that about 5 per cent. of the eggs had hatched and the larvae had set upon the leaves. As there could be no possible error as to each egg having been subjected to the gas it is evident that a stronger close is necessary to kill them. Had the plant been left in full sunshine it is probable that a yet larger percentage of the eggs would have hatched. The bush was severely burned by the gas and it appears that the yet undetermined close which is necessary to make certain the killing of the egg, is equally certain to damage citrus plants. During the period of heaviest nursery shipments from December 15 to the 1st of March, there are no unhatched eggs, hence no clanger exists because of them during this period. Since the eggs are never laid elsewhere than upon the leaves, defoliation and cutting back of the terminal growth removes all possibility of danger from unkilled eggs at all times. No citrus leaves from an infested nursery should be allmvecl to get into the moss used in packing. Such leaves could hardly be a source of danger except when harboring well

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THE WHITE FLY. 653 grown larvae or pupae but, as before mentioned, both laffae and pupae will live for several days upon detached, drying leaves in the laboratory: and if they were packed in clamp moss it is very probable that nearly matured ones would issue as adults even as long as three weeks or a month after they \vere packed. This spring t\vo lots of trees, six in each, infested with white fly larvae. \Wre fumigated ,vith the standard close of KCN and set upon the Station grounds \Yithout being defoli ated: most of the leaves fell as a result of the fumigation but a few adhered carrying the dead larvae. X o \vhite fly developed on these nor \vas there any injury to the stock appa rent. clue to the fumigation. Another dozen similar trees, not fumigated and planted out at the same time. held a fraction of their leaves. the white fly appearing upon them at the regular time. l\Iy fumigating box has nenr been packed full of stock with the foliage remaining upon it and it may be doubted if the close I use is sufficient to kill all laffae under such circum stances: but I ~hink there can be no doubt that in case it were filled as full as possible of defoliated stock all chance lanae present \voukl be killed. The accompanying photograph sho,vs a fumigating box of similar pattern to the one in use on the Station grounds. It consists of an inside and an outside box, with an intervening space of six inches filled with sand. The outside box needs no floor but the inside one should be floored to prevent partial absorption of the gas by the moist, earthen floor. The lid which is hinged and lifted by means of double blocks and pulleys is made of t\vo thicknesses of ,vainscot or flooring ,vitb a layer of raw-hide building paper between. Two good coats of lead and oil paint should be applied to the cover inside and out. An air-tight joint is secured between the cover and the box by running around the under side of the cover, which overlaps lhe edges of the inside box, a pine strip, 2 inches in depth, which thus clips clown into the sand. It is best to have a small door about r foot square in the bottom of the box, on one side and as

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BULLETIN NO. 67. near the center as possible. This door furnishes safe means for introducing the chemicals; its edges should fit against a cushion of felt or burlap; it is tightly pressed against the cushion by some form of sliding wedge driven into place by a smart rap with a hand mallet. If a slatted platform is constructed six or eight inches from the floor to support the plants, the gas being generated below it, diffusion will be comparatively uniform ana results with both trees and inse c ts more satisfactory than can be otherwise secured. A tight box-hood should cover tne upper half of the generating box which is a foot in each of its three dimensions, the lower half of it being left open, thus forcing the gas out beneath the slatted floor. The following dimensions will give a box of 99 cubic feet capacity (practically mo cubic feet) which will be one of the most convenient sizes. Length of the inside box, l l feet; width, 3 feet; height, 3 feet. Length of outside box, 12 feet; width, 4 feet; heighth, 3 feet. To charge the box w ith gas, fill it with the trees to be fumigated and close down the lid; if the sand is not sufficient in quantity, fill in enough to make a tight joint certain. Now through the trap door in troduce into the generating box the generating vessel, which shou ld be of earthenware, Cnina or glass-a glass fruit jar will do; with a glass graduate, measure out in liquid ounces a number of ounces of sulphuric acid (H2SO4) greater by half than was used of ounces of cyanide, or in this case, add to 3-5 ounce equal .6 ounce, 1-2 of itself, or .3 and 9-10 liquid ounces is obtained as the correct amount of acid. Of water, use 1-2 more liquid ounces than of acid; in . this case, 9-IO plus 1-2 of itself equals .9 plus .45 equals 1.35 or l 1-3 ounces (nearly). First pour the water in the generator, next the acid. The cyanide should be weighed out beforehand and kept, each dose wrapped in paper, in an air-tight receptacle. The close, paper and all ( use as little paper in wrapptng as possible) is dropped into the water and acid, the door being immediately closed and wedged into place. After remaining closed for 30 minutes the upper lid is raised. The residue in the generator consists of sulphate of potash, sulphuric acid and

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OPEN. CLOSED. PL AT E V. Fl MIGATINC BOX .

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THE WHITE FLY. 655 water; should it come in contact with the skin or clothing, il will corrode and is best buried in the ground when the generat ing vessel is emptied. It should never be forgotten that cyanide of potassium is a 1nost deadly poison and that a very minute particle of it introduced into the moutn will cause 1mmediate death. It is best to use forceps in handling it; never allow it to touch cuts or open sores on the hands. It should be kept away from children and uninformed persons. The gas is the deadliest known, and while no fatalities have ever attended its use as an insecticide, such have occurred in chemical Tabora tories, and the greatest caution should be observed in working with it. For fuller information concerning fumigating appli ances and methods of procedure, tfie reader is referred to Prof. W. G. Johnson's Fumigation Methods, published by the Orange Judd Co., New York. Insects Sometimes Mistaken for White Fly. Lecanium Jzesperidum Linn.-The immature stages of this insect are perhaps more easily, or, at least, are more frequently mistaken for wmte fly tFian any other species. The flat, oval scale upon the leaf so nearly similates the larva of white fly that the ordinary ooserver is quite excusable in being deceived at first sight. Howe,er, tFie Lecanium is more elongated than Aleyrodes citri and, relatively, it broadens much more distinctly towards the posterior extremity. The length when full grown is more than twice that of the mature white fly larva, the width being not quite double that of the latter. The body is distinctly notched inward at the posterior encl, a formation differing from that in case of white fly. The young are found on the stems and tender branches of various plants -( a position never occupied by white fly larvae so far as I have been able to discover) as well as upon the leaves. When upon the leaves, the young tend to range themselves beside the mid-ribs and principal veins, a habit whicn again disagrees with that of A. citri. The scale is commonly spoken of as the turtle-back or soft scale. The dorsal skin may be called yellowish or red

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656 BULLETIN NO. 67. dish brown, inclining to darl<, in some specimens almost to a shining black toward the center. This insect agrees with white fly in causing an excessive growth of sooty mold upon its host plants. ( Plate I, fig. Ir.). Nearly related species of Lecanium, such as L. oleae ( Ole ander is one of its common food plants) are found on various plants, being always followed by sooty mold. Aleyrudcs -fioridens1s Quaintance.-The Guava white fly is found sparsely upon orange. It is a smaller insect than A. citri and the larva is surrounded by a fringe of glassy, waxen rods, conspicuous enough when once noticed, but not readily observed unless lookeci 1or. The insect does no damage to orange. It has been collected from many parts of the State upon guava, wfuch it infests seriously, and several years ago Prof. J. H. Comstock collected it at Arcadia, Fla., on "alligator pear."* A few weeks ago it was sent to me from Arcadia by Mr. E. A. Thomas, taRen from orange trees that had been planted out, according to his statement, for one year. There can be no re aso nable doubt tfiat the insect went to his trees from guavas or "alligat o r pears" ir, the neighborhood. ( P!ate I, fig. 8.). Ceroplastes -fioridensis, the white wax scale, often causes patche s or gallberry bushes to become very black with sooty mold, the appearance frequentTy 'oeing ascribed to the presence of white fly. Aphis and many other insects which secrete honey dew and hence are followed by sooty mold have been supposed at one time or another to be white fly. The papaw white fly, Aleyroaes variabilis, has been recei ve d once or twice unaer the supposition that it was the orange white fly. Several species of Aleyrodes may be readily mistaken for it. *Bulletin u . S. D e pt. Ag-r. Di v i s ion of Entomology, Technical ,eries No. 8, (1900) p. 27.

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THE WHITE FLY. 637 The OutlookAs already indicated, the insect is known to be established in fourteen different counties in the State. I have reasons for thinking that it occurs in several other counties than these, but no re so urces are at my disposal to make a thorough inspection of the State a nd determine authoritatively its exact distribution. I feel sure that within t\vo years more every neighborhood that was infested before the freeze will discover that it is still infested. \Vhere the insect has become well e s tablished by three or four year's of breeding it is well nigh or quite impossible to exterminate it. It is seldom discovered until four or five years have elapsed after its introduction, that is,not until measures of extermination are very apt to prove futile. At the time of discovery it will appear to be confined to a small area, in most cases from a few bushes or trees to a quarter of an acre, but in reality it is sparsely scattered over a territory having a radius ot from a quarter to a half mile from the center of infection. I have proved tliis too many times to be deceived; yet many groves and yards in a town may be infested for several years without the insect's finding its way into groves not more than a mile or two from town. \\Tith the habit s of the insect ,vell known and its distribu tion once authoritatively established, its spread over the State could be greatly retarded but not finally prevented. Fifteen or twenty years may yet remain 6etore the insect will have found its way 111to every neighborhoocfinFfonda, out this it will cer tainly do in time. This certainty of eventually getting it should cause no indiHerence, discouragement or carelessness on the part of any neighborhood or individual; rather ought it to deter mine everyone to postpone the evil clay as long as possible. Five, ten or fifteen years of immunity from the fly, with consequent bright , early maturing fruit of high quality. when competition with other parts of the world ,vill be close and a large part of Florida handicapped because of the insect, is a reward well worth the price of a diligent and persistent lookout to obtain. Special caution should be observed to receive no improperly pre

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658 BULLETIN NO. 67. pared nursery shipments from any suspicious quarter; and when the insect appears in any neighborhood the preceding section of this bulletin upon methods of dissemination should be carefully studied and the suggestions there given to restrict its spread should 6e put into practice at once. vvill the orange business be ruined by the insect? No, certainly not; granting that ten years from now the State will receive three-fourths of a million or even a million dollars less per annum than it would receive if the insect were absent, Florida oranges can still be grown at a profit as has been proved by numerous growers through many years of trial. If groves in the heart of the present white fly districts are quoted at prices but little if any lower than if they were located outside of them, they will continue to be paying holdings there and elsewhere, notwithstanding the presence of the fly. No insect of this nature has ever withstood the skill of man in the encl, destroying a great industry, and white fly is not so difficult to control as many believe. Natural enemies, restoring Nature's balance, will appear in time, and until then the vari ous means of control already known will be employed by an increasing number of growers. Legislation could be helpful in certain ways, chiefly in increasing the resources of the Entomo logical Department for experimental work and thus enabling it to introduce the important diseases of the insect into such sec tions as do not at present have them. The establishment of quarantine regulations would be of questionable utility unless an appropriation of sufficient magnitude were made to maintain a large force of inspectors, and the exercise of all possible vigi lance on their part ' would still be less effective than the simple observance by every purchaser of the recommendations em bodied in this pubication. So far as the grove problem is concerned, as previously observed, the sentiment of our peo ple is sharply divided regarding wise insecticidal practice, and, until it can be united, the enforcement of prescribed methods of treatment by State officials could only be a source of friction and irritation. Those who believe that treatment of all infested groves should be enforced by law should become home mission

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THE WHITE FLY. aries for the next few years , satisfying the majority of their neighbors that such treatment pays,-a task which I believe can be readily wrought by t,rn or three seasons of practical demon stration with spray pump or fumigating tent. The ultimate distribution of the fly will be over all the Gulf States northward to an isothermal line running somewhere through northern Georgia and westward; California is very likely included i~ the infested territory now, but it is in the moist gulf regions that the uepreuations of the insect are to be feared. Citrus fruits ,Yill be profitably produced, notwith standing its presence, wherenr climatic conditions are suitable. Acknowledgments. In the prosecution of this investigation I have freely con sulted the writings of Riley & Howard, Webber, Morgan,. Woodworth. Quaintance and others. Valuable information and suggestions haYe been given me from time to time by Mr. A. J. Pettigrew, Prof. H. H. Hume, Prof. C. W. \iVooclworth, Mr. F. D. \Vaite, and others too numerous to meqtion. The drawings for plates I and 2 were made by Miss L. McCulloch, under my supervision. The drawings for plate 6 were made by Prof. Cockerell. The negatives for plates 4 and 5 were taken by me and the prints were made by Prof. Hume. The first three figures of plate 3 are wholly the work of Prof. Hume,. while Fig. 4 of the same plate is credited t o Prof. H. G. Dorsey. Summary of Important Facts and Recommendations. I. White fly, an insect of unknown origin, is probably our worst orange pest where it now occurs. It is known to be estab lished in 14 counties in Florida and probably exists in a num ber of others. 2. There are three annual broods of the insect of which the first two broods of adults _ . one occuring in March, April and May and the second in June. July and August. respectively, are well defined and distinct; the third brood occurs in greatest

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660 BULLETIN NO. 67. numbers in September and October, its time limits being poorly defined. The insect shows a tendency to continuous breeding during the last half of the year. 3. The eggs are laid only upon the leaves and the young are motile for a few hours after hatching. When wandering ceases, the larvae fasten themselves to the under surfaces of the leaves and imbibe the sap, at the same time covering the upper surfaces of the leaves vertically beneath them with a coating of honey dew in which a smothering, black, sooty mold
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THE WHITE FLY. 661 oil soap spray may be safely used, at proper strength, any time except when the trees are in bloom. Kerosene emulsion, caus tic soda solutions of sulphur and salt, Thrip Juice and Mont gomery's insecticide are all useful to a certain extent and will be sometimes chosen according to the personal preferences of the grower. There seems to be a general and well founded opinion that a good potash whale oil soap is less apt to cause injury to the tree than most insecticides. 9. Fumigation of infested groves is effective and some times useful , but at present can only be recommended for use in particular instances. IO. Infested nursery stock is rendered wholly safe by being defoliated, cut back and properly fumigated. r I. The insect will eventually spread over the entire citrus belt but its march can be greatly retarded by care in purchasing and by vigorous repressiYe measures where it is already estab lished. THE NEAREST RELATIVES OF WHITE FLY. In response to an inquiry addressed to Prof. T. D . A. Cockerell, formerly connected with the New Mexico Experi ment Station and at an earlier time Stationed in Jamaica with the Imperial Department of Agriculture for the West Indes, he kindly offered to make the comparative study here given of A. ctri and its allied forms, thinking such a study might throw some light on its origin. The recognized standng of Prof. Cockerell as a comparative anatomist and the large amount of information in his possession relating to this family of insects gives instant interest to anything written by him on such a question. Whether or n o t his conclusions ever prove to have been correct, since they direct the attention of entomol ogical workers in other parts of the world to the subject, thereby making possible the discovery of the insect's original home, the thanks of Florida are clue him for his effort.

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662 BULLETIN NO. 67. THE WHITE FLY. (Aleyrodes citri) AND ITS ALLIES. BY T. D. A. COCKERELL. The genus Aleyrodes ( often spelled Aleurodes) was first distinguished and named by Latreille in his "Histoire Naturelle des Crustaces et Insectes," Vol. XII. p. 347. In this work pub lished in 1804, there is given~ description of the genus, the type of which is the Tinea proletella of Linnaeus. This species, which lives in Europe on leaves of Chelidonium majus, was made the subject of an excellent memoir by Reaumur (Mem. Ins .. Vol. II, pp. 302-317, Pl. XXV, figs. 1-7), and conse quently was quite well known at the time of Latreille's publica tion, though it had been erroneously placed among the Lepidoptera. A close ally of this A. proletella is A. brassicae, Walker, 1852, which occurs on cabbage. This is said to be hard to dis tinguish from prol e tella in the adult, but the larva (pupa?) is long, while that of proletella is round-oval. In 1868 Signoret published a revision of the then-known Aleyrodidae, describing seven as new. Most of the species were European, but two were known from Chili, two from the United States, and one from Mauritius. In 1896 Maskell (Trans. New Zealand Insti tute, XXVIII.) gave a list of all the Aleyrodidae known at that time, numbering 66. Of these, 22 were described as new. Character. The adult Aleyrodidae are small, four-winged insects, very similar to one another , except for the fact that some have the wings variously spotted and banded. The pupae, however, pre sent very strong distinctive characters, and are largely used in classification. These pupae are small, oval objects attached to

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THE WHITE FLY. 663 leaves , usually to the lower surfaces, and in general resemble the smaller kinds of scale-insects. Under a compound micro scope one is able to see certain characters which greatly assist in the identification of . ..\leyrodid pupae. On the back toward the hind end, is an orifice of a more or less triangular or rounded shape, known as the vasiform orifice. In this is seen a lid-like structure, the operculunz, and a more or less tongue-like object, called the lingua. The margins of the pupae are also variously sculptured, and offer good characters. With a lens, one notices the color, shape and convexity of the pupa, and the character of the waxy secretion, if any. This secretion coYers the whole pupa, but more often it forms a fringe around the sides. Divisions of the Aleyrodidae. At present, o nly two genera are recogmzed in the family. Al e yrodes , Latreille, includes the great majorit y of the species, these having the main vein of the wings not bifurcated towards the end. In 1892 Douglas separated the genus Aleitrodicus which contains those species having the main vein of the wings bifurcated. This is a perfecty valid distinction, but care must be taken not to mistake a fold which often occurs in the wings of Aleyrodes for a branch vein. It has not been considered that Aleurodicus can be distinguished from Aleyrodes by the pupa, but I believe it has sufficient characters in this stage also. These are found in the short, broad operculum, combined with a very large lingua, which has two or four bristles at its end. The pupa also has large submarginal orifices, especially in the abdominal region, and the margin is likely to exhibit bristles at rather distant intervals . Having regard to these characters , I believe that the fol lowing, hitherto referred to Ale_vrodes , may be safely trans ferred to Aleurodicus. (I.) Alettrodicus altissimtts (Aleitrodes altissima, Qpain tance, tom. cit p. 20.) (2.) Aleurodicus perseae (Aleurodes perseae, Quaintance, tom. cit., p. 32.)

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664 BULLETIN NO. 67. ( 3.) Aleurodicus holmesii ( Aleurodes holmesii, Maskell, tom. cit., p. 435.) All the species of A leurodicus belong to the warmer parts of America (North and South), except A. holmesii, which is from Fiji. I suspect that the latter was introduced into Fiji from South America, along with the guava (Psidium) on which it lives . Although Aleyrodes, after excluding Aleurodicus, includes a great many diverse types, it h as not yet been subdivided. An examination of the vasiform orifice, lingua and operculum brings out the following facts : ( r.) There is a group, apparently exclusively American, in which the orifice is rather elongated, and the lingua is long and narrow, and usually strongly crenulated. This includes such forms as A. erigerontis, A. nicotianae, A. vittata, A. variabilis, A. p erga ndei A. fitchi and A. ruborum. ( 2.) A s mall American group, allied to this, has the lingua enlarged distally, with a distinct terminal joint. This includes A. pergandei A. fitchi a nd A. ruborum. (3.) A third American group, found principally on the oak, has the pupa very dense, quite black, with the orifice elon gated. The margin of the pupa is peculiar, and there is a white waxen fringe. A. melanops (figs. 2, 3 , 4) and A. perileiica (fig. S) are examples.* ( 4.) There is a group of the Old World, from India to New Zealand , in which the orifice is usually short , sometimes broader than l o ng, and the lingua is much abbreviated. Exam ples are A. cotesii (India), A. croseata (Australia), A. euge niae (India), A. aurantii (India), A. fodiens (New Zealand) and A. piperis (Ceylon). Aleyrodes perileuca. n. sp.-Pupa perfectly black, 1250 micromil limet ers long . of the u sua l oval shape, wi'th a very narrow regular fringe o f straight white waxen ribbons, about 100 micromillimeters Jong. A s h arp, elevated, submarginal keel; dorsum strongly JongLtudinally keeled, the abdominal portion with transverse ridges m ak ing the seg ments, The dors a l keel in the thor acic region is sharp, bu t in the ab domin a l region it is broad and rounded, with it s surface irregularly tes selate, a nd is crosse d by six tran sve rse narrow antero-posteiorly corru gated bands. Vasiform orifice shovel-shaped. Marginal area with very

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THE WHITE FLY. 665 Other groups are suggested by various species, but do not seem to be so clearly defined. Curiously, A. floccosa and A. stellata, from Jamaica, seem to be related to the Australian series of A. stypheliae, A. nigra, A. limbata, A. hirsuta and A. banksiae. Aleyrodes Citri. The white fly, or citrus mealy-v,ing, was described in detail, with excellent figures, in Insect Life, Vol. V, (1893) pp. 219-226. Unfortunately, however, the detailed characters of the pupa were not given in such a manner as to permit ade quate comparison with other species. Prof. H. A. Gossard has kindly supplied me with abundant material on leaves of Cape jessamine (Gardenia) from Florida, and I am able to give dia grams of the pupa (fig. i) and of the vasiform orifice (fig. 6). It will be seen that the vasiform orifice is broader than long, and the lingua is short and broad . These characters are not those of the typical American groups, but agree well with the Asiatic group , No . 4 above. On examining the other characters of the pupa, we find three deep furrows ( fig. 7, a,a , a, and A,), one on each side, and one at the caudal end. At the distal end of each furrow is a somewhat star-shaped opening. Such structures as these I find described only in two species, namely, A. eugenae, Maskell, tom. cit., p. 430 , and A. aurantii (eug en iae var. aurantii, Mas aurantii ( which appears to be a valid species) occurs abun dantly on leaves of orange in the northwest Himala y as. numerous re gu lar r ad iatin g furr o ws, the are a s b e tween them minutely punc'tured. Margin very r eg ularly cr e nulate . No dorsal section wha.t ever. The conical black larval skin w as found in one example on the ba c k of the pu pa, but ordinarily it falls away. Hab. Solitary on the upper side of leaves of live oak; Cuero, Texas, June 2, 1898. ( C.H. T. Townsend); La Jolla, San Diego Co., Cal if o rnia. Aug. r901, (C o cker e ll). AleiJrodes melanops, n. sp.-Pupa black, s imilar in structure to A . perileuca , but larger (about I 1-2mm. long), broad-oval, with the white fringe much l o nger and curled over, so as to b e strongly convex above . Hab. Solitary on the upper side of. leaves of o ak (Quercus), at Alpine Tavern, Mt. Lowe, California, Aug. r9or. (Cockerell.)

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666 THE WHITE FLY. The Original Home of Aleyrodes Citri. I believe that Aleyrodes citri is a native of China or some neighboring country for the following reasons : (I.) It's <;1,ffinities seem to be wholly with an Asiatic and Australasian group, and particularly with a species found on orange in the Himalayas. (2.) Orange trees have been brought to Florida from China, and the Aleyrodes would be very easily carried with them. ( 3.) Florida has had, at least as long as the Aleyrodes, two scale-insects of the orange, which are almost certainly Asiatic and very likely Chinese. These are Parlatoria pergan~ dei and M ytilaspis gloveri. These were probably brought over at the same time as the Aleyrodes. (4.) A. citri occurs also on the Cape jessamine (Gardenia florida), which is a native of China. (5.) A. citri multiplies excessively in Florida, indica6ve that it is probably not American. The American species of Aleyrodes are not commonly harmful. In Arizona I found an Aleyrodes of a native type living upon the oranges but it was not doing any harm or multiplying excessively. This insect ( described in Science Gossip, May 1900, p. 366,) appears to be only a variety of Aleyrodes rnori, Quaintance. It may be called A. mori var Arizonensis. [In the article just cited, owing to an editorial blunder two paragraphs are run together, making nonsense, page 367, first col., line 14, dele "They are," and begin a new paragraph.]

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