Citation
Whitefly conditions in 1906

Material Information

Title:
Whitefly conditions in 1906
Series Title:
Bulletin - University of Florida Agricultural Experiment Station ; 88
Creator:
Berger, E. W.
Publisher:
University of Florida Agricultural Experiment Station
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Lake City ( flego )
Fungi ( jstor )
Insects ( jstor )
Fungicides ( jstor )

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
The University of Florida George A. Smathers Libraries respect the intellectual property rights of others and do not claim any copyright interest in this item. This item may be protected by copyright but is made available here under a claim of fair use (17 U.S.C. §107) for non-profit research and educational purposes. Users of this work have responsibility for determining copyright status prior to reusing, publishing or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder. The Smathers Libraries would like to learn more about this item and invite individuals or organizations to contact Digital Services (UFDC@uflib.ufl.edu) with any additional information they can provide.

Downloads

This item has the following downloads:


Full Text


BULLETIN NO. 88


Florida
Agricultural Experiment Station


Whitefly Conditions


in 1906


The Use of the Fungi






7,7


Bv E. W. BER(;ER, Ph.D.
The Blleins )I this Station will be sent Iret to anv address in Florida upon appikii it,, ib. i.getir
,tt the Exierimi nt Station. (,ainesville. Fla.


E ). Painter Printing Co., Deland, Fta.


?1j1U,




















BOARD OF CONTROL.


N. P. BRYAN, Chairman . . Jacksonville, Fla. P. K. YQNGE. Pensacola. Fla. A. L. BROWN . . . .Eustis, Fla. T. B. KING . . Arcadia, Fla. J. C. BAISDE-N. . Live Oak, Fla.



STATION STAFF.

P. H. ROLFS, M.S . . Director. A. N7. BLAIR, A.M. . . Chemist. JOHN M. SCOTT, B.S. . .Animal Industry. E. H SELLARDS, M.A., Ph.D .Geologist CHARLES F. DAWSON, M.D., D.V.S., Jacksonville, Consulting Veterinarian. E. W\. BERGER, Ph.D . . Assistant Entomnologist. H. S. FAWCETT, B.S .Assistant Plant Pathologist. R. Y. WINTERS, B.S .Assistant in Botany. K. H. GTRAHAM . Auditor and Bookkeeper. R. D. .XLGEE . Stenographer. M. CREWS . . . Farm Foreman. F. M. STEARNS. . Gardener.












CONTENTS.
Page.
Im portant Facts . . . . . . . . . . . . . . . . . . . . . . 51
Introductory. . 53 The Fungi . . . 54 Conditions favorable for the Fungi. 5 The Red Aschersonia . 56 Inti oduicing this Fungus. . . . . ; Summary for the Red Aschersonia .5. 9 By SoDraying on Spores of the Ftungus . 6o By Pinning on Leaves. 63 The Yellow Aschersonia . . 64 The Brown Fungus.064 Scale and Whitefly .6_s Trimming Trrees. 66
Spraying and Fumigation . . . . . . . .66 Copperas . 68 Sooty Mold. . 69 The Snail . 69 Life History of the Whitefly . .70 Food Plants . . 71
Quarantine. . 73 Nursery Stock. . . .73 Vehicles and Private Roads. . .74 Picking Implements. . . 74 Plants to be Condemned . .75 Plates . . .76 Appendixes i. Where to Obtain Ftungus.82
2. The Fungi in Florida .82 3. Spraying Apparatus . 82 4. The Weather at Leesburg . 83 5. After Freeze Suggestions . 84 Acknowledgments. .86

PLATES.

Plate I. Whitefly egg and Adult .77 Plate 1I. Larvae and Pupa .79 Plate II1. Fungi and Whitefly on leaf .8








WhIteily Conditions in 1906.


IMPORTANT FACTS.

i. The fungi parasitic on the whitefly larvae and pupae can be started in whitefly-infested trees by spraying the spares suspended in water, by pinning on leaves having pustules of the fungi upon them, or by planting infested trees. The writer's success by the first two methods during the past summer was 98 per cent.
2. There are three of these fungi-the Red Aschersonia, the Yellow Aschersonia and the Brown Fungus. The spores of the latter have not been discovered, hence this fungus can probably not be successfully introduced by spraying. Dried fungus pustules have been kept for a month and found efficient for starting the fungi. They probably will retain their vitality much longer.
3. All these fungi will apparently thrive in any part of Florida. The Red Aschersonia was observed to thrive well as far north as Lake City during the past summer, while the Brown Fungus was also successfully introduced.
4. A humid atmosphere in a grove is important f or the thriving of the fungi. Suggestions for aids in accomplishing this are given in the test. Considerable warmth also appears to be necessary.
5. It appears from our present state of information that the best time for starting the fungi in whitefly-infested trees will be the months of May, June, July and August. March and April may also be good months. In general, periods of rain and summer temperature are considered favorable.
6. To insure the efficiency of the fungi, repeated "plantings" should be made to get a good start. Keep the fungi abreast of the whitefly, instead of tandem, or at its heels, which is the general situation 'at present.
7. Trees of all kinds along roadways should be trimmed high to avoid the distribution of the whitefly by carriages brushing against the branches.
8. Not every tree, bush or weed in the hammock is a food plant of the whitefly. The number of authentic food plants can probably be counted on the fingers of two hands.
g. The Cape jessamine, Chinaberry, Umbrella Tree, Prickly Ash,








Biill'tilt No. 88.


Privet, Trifoliate Orange, Mock Orange (Cherry Laurel), and all useless and neglected citrus stock should be condemned and destroyed. These should be cut down and BURNED AT ONCE.
io. The'greatest injury done by the whitefly is during its several larval and pupal stages while it lives in a wingless state attached to the under surface of the leaves.
ii. Where it is desired to spray or fumigate for the whitefly, the best time for doing this is during the months of December, January and February; or better, after the fruit is picked and the danger from frost is past. All of the eggs are probably hatched by December. The eggs are not easily killed either by spraying or fumigating.
12. There appears to be no good evidence to show that copperas is of any value for reducing the whitefly, to say nothing of extermination.
13. Snails in groves should be encouraged by providing mulch (coarse and fine mixed) under the trees, and burlaps in several of the narrower crotches.
14. Snails do not destroy whitefly, except incidentally some eggs and a few larvae, but feed upon the sooty mold, other fungi and lichens. They keep the tree clean when in sufficient numbers. They appear to avoid the fungi parasitic upon citrus tree insects.
15. The picking implements and the clothing of pickers should be disinfected by one of the several methods described in the text, before being transferred to a noninfested grove.
16. See the Summary for the Red Aschersonia, which probably holds good for all the fungi.













Whitefly Conditions in 1906-The

Use of the Fungi.



INTRODUCTORY.
The whitefly is on the increase and spreading to citrus growing sections of the State hitherto not infested. No doubt the mild winter of 19o5 to 19o6 favored its spread and increase in the more northerly sections of the State. Citrus trees that were generally quite defoliated during more severe winters retained some of their leaves and of course the whitefly larvae with them. This gave it an uncommonly good start last Spring. Railroad trains, carriages and -other less understood means of dissemination are spreading it to all parts of the State.
The situation is urgent. and some excitement prevails in orange growing sections that have recently become infested. Some have "Hit the line hard" when thev found the fly present last fall and winter, with very gratifying results, going even to the extent of cutting down infested trees, such as umbrella, Chinaberry, and others. Such means are rather drastic but are a certain remedy where the situation justifies it. Others have made strenuous efforts, doing everything in their power to keep the pest down. but found their efforts mainly ineffective because of the indifference of their neighbors. There appears to be the expectation on the part ,of some that a panacea will be discovered, which will do away with the whitefly on short notice. This is something to be hoped for, and possible, but not very probable. It is of no use to wait: fighting insects is much like fighting weeds in a garden, one must be ready to cut them down with the ,means at hand whenever they raise their heads.
The main purpose of this bulletin is to urge growers to do something and not to wait, and especially to urge the introduction of the fungi. While many new facts and demonstrations are introduced, much of necessity follows in the nature








Bulletin No. 88.


of suggestions which only future experience can prove necessary or erroneous. It would be well if growers generally followed out some of the suggestions made by the Station, if only on a small scale, for by so doing they will be of great aid to the Station Staff. The writer believes that future work upon the whitefly will consist, not so much in the discovery of new remedies and enemies, though this is desirable, but in a better understanding of how to use the remedies at hand.

THE FUNGI.

Plate III, Figs. 2 and 3.

Broadly speaking, the fungi belong to the lowest order of plants known, and are devoid of the green coloring matter (chlorophyll) so characteristic of the higher plants. Mushrooms, toadstools, mildews and the several molds are familiar examples of fungi. The majority of fungi generally propagate themselves by minute microscopic bodies called spores. These are produced in countless millions and chiefly relied upon when we desire to propagate, or start, fungi. These spores take the place of seeds produced by the higher plants, but structurally they are not seeds.
There are three fungi at present known to be parasitic upon the whitefly larvae and pupae. These are the Red Aschersonia (Aschersonia aleyrodes), the Yellow Aschersonia (Aschersonia flavo-citri a) and the Brown Fungus. Each occurs on the under surface of citrus leaves and transforms (kills) the larvae and pupae of the whitefly living there into pustules having the color characteristic of each fungus named, except that the young pustules of the Red Aschersonia are pink and only develop the scarlet red fruit bodies as they become mature. There is another fungus that occasionally destroys a few whitefly larvae, namely 'the Red Scale Fungus (Sphaerostible coccophila), but this occurs only rarely upon the whitefly and will not be further discussed in this paper. None of these are known to attack either the eggs or the adult whitefly.
It appears to be the observation of some that the Brown Fungus works more rapidly than the Red Aschersonia. On the other hand, the observation of others is quite the reverse, that the Red Aschersonia spreads more rapidly and is more efficient. This last is also the writer's personal observation to







Whitefly Conditions in 1906.


date. The Yellow Aschersonia appears to be quite the equivalent of the Red so far as present observations indicate.

CONDITIONS FAVORABLE FOR THE FUNGI.

All fungi thrive best in the presence of an abundance of moisture, and observations show that the Red and Yellow Aschersonias and the Brown Fungus work best in destroying the whitefly where the ground is sufficiently moist; or where the surrounding conditions are such as to retain the moisture in and about the trees and the ground. Plenty of dense vegetation (trees, shrubs, tall grass etc.) about and in the grove, will do this to a great extent. The trees and shrubs should be arranged in the nature of windbreaks, while the grass and beggredshould be permitted to grow tall and rank at the proper season as a cov er crop. It appears also, that where the fungi thrive best, there is frequently some decaying rubbish such as wxeeds, grass, etc., in the nature of mulch near or about the trees, which helps to conserve the mtoisture. That it is not such a difficult matter to reproduce these conditions, in some degree at least, will be admitted. It is easy to mulch a groe, and still easier to grow tall cover crops. Windbreaks can, of course, be planted. Ani occasional wetting in dry weather of both the trees and soil, where convenient, will add to the efficiency of the above provisions. Where 'groves are irrigated the problem is simple. Even a slight daily wetting of the trees and ground would no doubt be very favorable for the thriving of the fungi. Such a sprinkling outfit would have its other uses. To say nothing of its v alue for irrigation, it wo0u11( above all be effective e in reducing the red spider and favor the active ities of the snail wherever present, besides being- a possible protection against frost. But these problems are beyond the scope of this paper.
The conditions above set forth appear t, be those very generally exis~ting- in groves on hammnock land, and this no doubt accounts for the fact that the fungi thrive there so much better than on high pine land. If then, the growver can succeed in approximating these conditions in groves on pinxe land, by a liberal mulching and wetting when possible and the growing of tall cover crops and windbreaks, he will succeed in helping the fungi a long way toward the destruction of the whitefly. The main object is to produce a moist atmos-






Biillctii No. 88.


phere in the grove, and the mulch aids in this respect not only by conserving the moisture, but by actually adding a certain amount of water produced by the decay of the mulch.
The question of a temperature sufficiently high to meet the requirements of the fungi is also important. But the control of this is wholly beyond any means possessed by the grower. Careful observations covering the months of the dry season from some time in September, 19o6, until January, 1907, indicate that the fungi have spread but little during this period. These months have been very dry this season, there occurring only oie or two slight rains at Lake City, and in many other parts of Florida. The temperature, furthermore, probably averaged something like 70 degrees F. The fact, however, that heavy dews were quite frequent during these months, points to a high temperature as an important factor for the growth of these fungi. Efforts to start the Red and Yellow Aschersonia during the months of September, October and November have so far been only partially successful.
Summing up the conditions favorable for the growth and starting of the fungi, it is clear that abundant moisture together with a Florida summer temperature are important.

THE RED ASCHERSONIA.

Plate III, Fig. 2.
The Red Aschersonia, otherwise known as the Red Fungus of the Whitefly, has been known to occur in Florida since 1892. (See appendix 2.) It was observed to be doing good work then, and is doing good work now. It is at present reducing the whitefly in a yard near Lake City. On July 8th it was found on this place (Agnes Jones') and August 6th 47.2 per cent. (counting all larvae, purpae, and empty pupae cases) were infected and killed by the fungus. This is the count upon eighteen leaves that were brought to the laboratory. Not counting the empty cases upon the leaves the per cent. of infection w as 59.9 per cent. This shows that over one half of all the living larvae and pupae upon the leaves brought to the laboratory had been killed by the fungus and the work is still going on. Dr. Herbert J. Webber wrote, for Gainesville (about 1895) : "On many leaves it was difficult to find a living larvae or pupa of the mealy wing [whitefli] and in such







hitottly Conditioi 19o6.


cases the leaves were thickly dotted over with the pustules of Aschersonia." The destructive freeezs during the winter of 1894 to 1895 killed all the citrus trees to the ground, but left unharmed a number of species of host plants upon which the insect survived the winter. From these plants the new citrus sprouts w ere again infested the following spring and summer.
The large tjuantity of fine fruit shipped from the Manatee section and the large acreage of new groves being set out, indicate that any reports od the citrus industry being ruined in that section by the whitefly, are not well founded. Many of the most successful growers of this section depend upon the fungi to keep their trees clear from the whitefly, while others are abandoning spraying and are going to permit the fungi to take their course. Summing up all the facts and observations, it is difficult to understand w vhy a more general effort has 11t been imade t) spread this useful ren edy. It is admitted that in some groves the conditions are not as favorable for the gro,.wth of the fungi as in others, but extensive observations indicate that \\-here conditions are naturally unfavorable, they can be greatly improved, so that the fungi w ill thrive better.
INTRODUCING THIS FUNGUS.
The chief drawback to introducing the fungi has been the supposed difficulty of starting ("planting") then in whiteflyinfested trees. The matter appears to be much more simple than was heretofore supposed. At Lake City the writer succeede(i (June 2oth and August 8tl) in introducting the Red Aschersonia into four out of five trees by pinning leaves, with an abundance of fungus pustules, upon them, to the leaves of the trees. In two instances the fungus started in another part of the tree some distance from the pinned leaves, but as io other infected trees could be found within one-half mile of these, it is considered safe to assume that the fungus started from the infected leaves placed there. In two of the successful instances the leaves with the fungus pustules upon them zcrc dry and had been picked about a month before being pinned into the trees, showing that the spores of the fun'us retained their vitality for at least a month and no doubt longer. It was also found that the fungus had started in three different trees at Leesburg, into which Judge J. B. Gains had pinned so rue leaves.







Bulletin No. 88.


No Red Aschersonja had hitherto been observed at Leesburg, Since writing the first part of this paragraph, the writer has found the fungus started in each of thirty-seven trees into which he had pinned leaves of the Red Asehersonia six weeks previously (August 15th) at Lees'burg. In all, forty-two tr ees had been treated in this manner, but five of them were not examined for lack of time. In many of these trees the fungus had made good headway, and in one instance judge Gaines reported that it had started at the end of two weeks from the time of infection. W. H. Maxwell of Titusville, also reports that he has observed the Yellow Aschersonia to start in two weeks after plantingn" (pinning leaves) the same in trees infested with xvhitefly.
The writer has also succeeded in starting the Red Aschersonia by spraying a mixture of spores and water on the under surfaces of the leaves in trees infested with whitefly. This method of application was successful in starting an infection in two out of three citrus trees, sprayed at Lake City (July Io). In each case (leaves pinned or spores sprayed) the fungus was observed to have started in three to four weeks from the time of application of the spores or leaves. Eight trees were also sprayed at Leesburg at the same time (August 15th) that the fungus was started there by pinning on leaves, and examination six weeks later, showed that the fungus had started in each tree.
These experiments are a complete demonstration that this fungus can readily be started either by pinning on leaves or by spraying on spores, there being only one failure in fiftytwo trials made during the months of June, July and August, i~o6.
Hitherto, planting into a grove small trees with fungus-infested whitefly larvae upon them has been considered the only sure way of introducing it. This method is good and sure, where the trees can be kept from dropping their leaves, hut is rather impracticable on a large scale. The infected trees should be planted so that their branches and leaves extend among the leaves of the tree to be infected. If necessary, the infected trees may be planted in tubs and raised on platforms or otherwise elevated.
One serious objection is raised in regard to the efficacy of the fungus, namely, that when it has practically killed off the whitefly and the fly starts to infest the grove anew, it takes the fungus so long to start that the fly has done considerable







Whitefly Conditions in 19o6.


damage before the fungus gets it under control. The situation appears to be about as follows. During one year the fungus cleans up the fly; the second year the grove is generally clean, also the fruit; the third year the fly reinfests the grove, and the trees and fruit are again black with sooty mold; then the fungus does its work again; etc. Now, in view of the fact, that the fungus can be introduced by pinning on leaves or by spraying on spores, the f tingits should be started at the same time that the whitcdy larvae are first observed, and while the progress and injury of the fly may not be wholly offset, yet I believe a great deal can be done in this way to lessen the injury. It is purely a question of helping nature (the fungus) along by guiding her at the critical moment. This is an important point. A grower should not wait for the fungus to start of its own accord but should start it himself as soon as he discovers the presence of the whitefly, and this should be done whether the fungus has previously been present or not. The fungus should be introduced and handled with the same rational consideration with which spraying or fumigation is carried on. Because the fungus is a natural remedy and will of itself (generally) spread and reduce the whitefly is no reason why rational means for artificially spreading the same should not be used.
The problem of getting sufficient fungus many involve some difficulty, but a number of nurserymen advertise citrus stock having the fungus upon it for sale, and these no doubt will be glad to furnish leaves at reasonable prices. (See Appendix.)
SUMMARY FOR THE RED ASCHERSONIA.
i. Get it into your whitefly infested trees at almost any price,
2. By sprayingon the spores,
3. By pinning on leaves,
4. By planting trees with fungus upon them,
5. Mulch the trees and where convenient keep the mulch damp by an occasional wetting.
6. Spray the trees often with water in dry weather, where convenient,
7. Permit the cover crop to grow tall in the grove and let it remain there as long as possible,
8. Plant windbreaks.
9. Spray again with fungus spores and oftener, if necessary, in order to get a good start of fungus.






Bulletin No. 88.


BY SPRAYING ON SPORES OF THE FUNGUS.

Jf it is decided to introduce the fungus by means of spraying oil spores, care should be taken to spray against the under surface of the leaves. Future experiments may show that this precaution is not necessary but we are not likely to go very far astray by adopting it for the present. Forty well developed pustules having the bright red spots upon them are stifficient for a pint of water. Two well infected leaves may be taken as representing the forty pustules but one leaf will frequently have the required number and often more. A pint of the solution, I believe, should be sufficient for a tree of ordinary size where a very fine spray is used. From this it will be seen that spraying is the most economical in so far as infecting material required is concerned. Three thousand leaves will about fill a bushel measure. Two leaves per tree to make the spray, gives us fifteen hundred trees that can be treated with this number of leaves. Where an abundance of leaves are available the spraying -solution may be made stronger; it cannot be made too strong. After having poured the water over the leaves and stirred the sairie about for a few minutes, fifteen to thirty minutes should be allowed for the spores to become dissolved out of the red spots an the pustules of the fungus . Then the mass should be stirred again, thoroughly, in order to wash out all the spores possible. Do not permit the solution to settle but strain the liquid at once through a piece of cheesecloth or fine wire sieve. An atomizer spray is to be preferred because it does not require so much liquid to spray the tree. At all events, a nozzle that produces a very fine spray should be used. The above estimate of one pint of liquid per tree was based upon an atomizer spray. If on the other hand, no atornizer is available, a spraying machine may be employed. The spraying solution should under no conditions be permitted to stand in a copper or brass tank, for the amount of copper that would go into the solution might be fatal to the spores, as these are very sensitive to copper. If a spraying machine made wholly or in part of copper or brass, must be used, the same should be thoroughly cleaned before using, and then the work should be done as expeditiously as possible. If it is necessary to use the copper or brass reservoir connected with the spray pump, or spraying machine this should be partially filled with the solution, enough only being put in, to spray three







White fly Conditions in 1906.


or four trees. Spray the solution on the under surface of all the infested leaves giving special attention to the heavy infected new growth. If it happens that only a limited amount of the spraying solution is available it may he diluted with water. Thoroughly spraying all the trees with a weaker solution is considered preferable to spraying half the trees, or only part of each tree, with a stronger solution.
It goes without saying, that it would be futile to introduce fungus into a tree not infested with whitefly. The fungi in question, so far as known, can thrive only upon the whitefly, so that there would be nothing for them to live upon in a non-infested tree. It will also be well to wait before introducing fungus into a tree until the whitefly larvae can be abundantly found under a considerable number of leaves. To spray every tree in a grove regardless of the individual requirements of each tree would frquently lead to waste of material and labor. The writer's plan of campaign would be as follows: Stait the fungus in all the trees in which the xvhitefiy larvae can be readily found. Later, say in three or four weeks, inspect the grove and spray all the trees not previously sprayed and which now show the presence of xvhitefly. In another three or four weeks inspect again and spray. Each tree should be considered individually and treated accordingly. Any trees not shoxving a good start of fungus in three to six weeks should be sprayed again, wholly or in part. This kind of procedure should he continued from year to year. and the prediction is made that in a comparatively few years, when the citrus growing sections of the State have in this manner been thoroughly saturated with the fungi, there will he no xvhitefly problem.
I have stated above that the fungi in question can thrive only upon the whitefly larvae and puipae and this is probably true in nature. In the laboratory, however, Professor H. S. Fawcett has been successful in growing the Yellow and Red Aschersonias and to produce spores, upon several of the media generally used for such work. There is. but little doubt that the Brown Fungus can be cultivated on the same media. This opens up the possibility of producing spores of the fungi in the laboratory for use upon trees. But as an abundance can generally be obtained from infected groves it is not likely that we shall very soon he compelled to depend upon artificial means for a supply. The fact, however, that a fungus can be







Bulletin No. 88.


cultivated artificially gives the scientific investigator greater opportunity for careful and varied experiments and observations that may eventually lead to broad scientific principles of practical value.
It is considered important, especially on the drier soil, to mnulch the grove or trees treated, and the more liberal the mulching the better. As already stated, this not only has the effect of permitting the ground moisture to evaporate slowly and during a longer period of time, thus increasing the humidity of the grove, but also some water is actually formed during the process of the decay of the mulch, and this too adds to the humidity or dampness of the atmosphere. An occasional wetting of the mulch in dry weather is also recommended, or the trees can be sprinkled, as previously suggested. Reference to the usefulness of tall cover crops and windbreaks has already been made and also to the fact that the conditions herein set forth very closely approximate those existing in many groves on hammock land. The mulch, may furthermore, serve other purposes, such as harboring insects that aid in the distribution of the spores of the fungus throughout the tree, or as a possible medium for the development of other stages of the fungus.
I wish to state again that if the first attempt at introducing the fungus fails to produce a good start in a grove, or in individual trees of a grove, a second attempt should he made and a third one if necessary. This kind of spraying is much cheaper (and I believe spraying on the spores is preferable to pinning on the leaves: but both methods can be used,) than spraying with insecticides, and is perfectly harmless to the trees. This point, furthermore, should not be lost sight of, that the increase of the fungus in a tree (other things being equal) is in the same proportion that we succeed in starting it in that tree. Thus, if we succeed in starting ioo pustules of fungus in one tree and 300 in another, it will be evident that the spread of the fungus in the last tree will he three times as rapid as in the first one, and hence the importance of making as good a start of fungus as possible by repeated sprayings.
Attention should also be directed to the fact, that for subsequent sprayings, fungus from the trees previously treated may be used, provided it is suffciently developed. This will be evident as the pustules increase in size and become a bright scarlet red in the Red Aschersonia or a bright yellow in the Yellow Ascbersonia.







Whitefly Conditions in 19o6.


When is the best time for doing this work? Future experiments will give us more information. The months of June, July and August, as the experiments previously indicated show, are favorable months. Ordinary periods of cold and dry weather generally have only the effect of retarding the growth of fungi. We know that neither ordinary cold nor drying kills the fungi parasitic upon the whitefly. Note the fact already stated that leaves with fungus, and dried for a month, were as efficient as fresh leaves for starting the Red Aschersonia and the Brown Fungus.
The months of September (last half), October, November and December (19o6) were found unfavorable, probably because of drought and cooler weather. No experiments in starting the fungi have been tried during January, February, March and April, yet it is hardly to be expected that these will be exceptionally favorable. May being generally quite warm and immediately preceding the rainy season is believed to be a good month, and any one beginning work with the fungi at this time will hardly go far wrong. Prospective warm summer weather and rains may be taken as a guide for starting the work, and since the spores are to be mainly sprayed on the under surfaces of the leaves there is little dan-er that they will be washed off during heavy rains.
BY PINNING ON LEAVES.
To introduce the ftigus by pinning on leaves I would suggest that from one to a dozen or more well infected leaves be pinned to a tree. The number will be determined by the amount available. As Leesburg 12 leaves per tree were used. Each infected leaf should be pinned to the under surface of the leaf on the tree, with its under surface down, that having been its position before it was removed from the tree and is in closest keeping with nature. The infected leaves might be pinned with the infected (or under) side against the under side of the leaves on the tree, and I have obtained good results in this way, but for the sake of keeping close to nature I advise the other way for the present.
Each infested leaf should be pinned as high tip in the tree as is convenient, that is, at least as high as a man can reach. To pin it higher is desirable. It should, furthermore, be so placed that the drip from it, when it rains, will drop onto a cluster, or Ee Teral clusters, of leaves beneath it. Use two pins







Bulletin No. 88.


for each leaf. 1 hav e observed that the fungus sometimes starts onl the leaves beneath the pinned leaf rather than at the leaf to which the infected leaf was pinned. It is well to pin a small piece of paper on the tipper surface of the leaves to which the infected leaves are pinned as a mark. This will greatly facilitate later inspections.
THE YELLOW ASCHERSONIA.

This fungus, known at present to occur at WVinter Park, Orlando and Ai\Jis is very much like the Red Aschersonia, but the pustules are of a rich yellow color. It appears to spread rapidly: ninety per cent. of the larvae on some leaves examined in the laboratory being infected. It should be treated exactly like the Red Aschersonia, as the conditions under which it thrives seem to be the same, and each produces spores in abundance.
THE BROWN FUNGUS.

Plate III. Fi'g. 3.

What has been said for the Aschersonias applies (with one probable exception) also to the Brown Fungus. The spores of the Brown Fungus have not been discovered, and this fact makes it uncertain whether it can be successfully introdutced by spraying. This leaves two methods available for introducing the Brown Fungus: ( i) to pin leaves having whitefly larvae infected with the fungtms upon them onto the leaves of the tree into which it is to be introduced; . 2,) to plant ,,mall trees, having the fungus upon them, into the grove as lprevionsly explained for the Red Aschersonia.
Since writing the above paragraph I have been agreeably surprised to find that the Brown Fungus has started in four of the eight trees sprayed at Leesburg (Auigust i~th 'o6) with spores of the Red Aschersonia and previously noted in this paper. Some Brown Fungus was scattered over the leaves with the Red Aschersonia, used in preparing the mixture of spores and water for this spraying, and this clearly indicates that the Brown Fungus can be started by spraying. Inspection of these trees September 29th, 19o6, di~d not reveal any of the Brown Fungus, but at a later inspection (December 2 1St, 19o6) leaves having an abundance of this fungus upon them were found in four of the trees. Further experiments







TWhitefly Conditions in 19o6.


will be necessary to determine whether the method of starting the Brown Fungus by spraying can be made practical. However, in preparing a mixture of spores and water of the Red or Yellow Aschersonias for spraying, it will not be amiss to mix in any leaves at hand having Brown Fungus upon them. It may be well, however, to thoroughly triturate the pustules of this fungus to insure getting an abundance of small particles of it into the mixture. As already stated we are not certain that we have discovered the spores of this fungus, and it may have started in tte trees at Leesburg from small particles that were in the mixture sprayed into the trees.
I do not think that the infection could have come from another source since inspection of neighboring trees that had not been sprayed showed no signs of it.
It has been suggested that the Brown Fungus probably spreads more rapidly in cool weather that the Aschersonias, and this observation at Leesburg seems to be corroborative of this suggestion. Further observations will determnie this point.
That this fungus can be introduced by planting small trees having the Brown Fungus upon their leaves was first demonstrated by Dr. H. J. Webber and this method has since been successfully employed by many individuals throughout the State. It will be preferable, however, to use the method of pinning on leaves as it is easier and more practicable. The writer has something like seven instances on record where he succeeded in starting this fungus by pinning on leaves. Dr. H. J. Webber, also notes an instance where this fungus was started by this means (Bull. 13, U. S. Dept. Agri., Div. Veg. Phvs. and Path.).
SCALE AND WHITEFLY.

The question is sometimes asked, "If I depend upon the fungus to keep down the whitefly, what shall I do to keep down the scale? If I spray for the scale then I will kill the fungus." There are several fungi that are very effective in reducing the scale, and it may be desirable to introduce some of these. These fungi are the Red Headed Scale Fungus (Sphaerostilbe coccophila. See Bulletin 41), the Gray Headed Scale Fungus (Ophionectra coccicola), and the Black Scale Fungus (Myrangimn Duryii), and material can be obtained without much difficulty in many parts of the State. The best







Bulletin No. 88.


present known method for introducing them is to tie leaves and twigs having some of these fungi upon them into the scale-infested trees.
If the case requires immediate and drastic measures a thorough spraying of the tree with some good spray should be effective in reducing both scale and fly. Then, when the fly again shows signs of increasing in the tree one of the whitefly fungi should be introduced as previously directed.

TRIMMING TREES.

Trees infested with the whitefly and located where vehicles and persons pass, should be trimmed sufficiently high to give free passage; so that the flies cannot be brushed off and in that manner carried about the country. There is no doubt that this is one of the chief means by which the fly is carried from place to place, and it would require but very little effort along this line to reduce this source of infection. Everybody owning infested trees should become awake to the situation and do their part. In towns the city officials could compel the proper trimming of trees, while Boards of Trade could warn people, and instruct them in the desirability of keeping their premises in proper condition. I desire here to commend the Leesburg Board of Trade for their efforts in getting inforrnation and their foresight in issuing a circular to interest the people.
The railroad trains carry the fly farther than perhaps any other agent, and something could be done to lessen this means of distribution if railroad officials as well as people along the line would see to the proper trimming and destruction of infested trees and bushes on and near the right of way. This suggestion is important and should receive attention.

SPRAYING AND FUMIGATION.

For more complete directions in regard to spraying with contact insecticides, I shall refer the reader to the following bulletins: Press Bulletins 4 and 56 treat of the whitefly and methods of repression, and are both available for distribution. Bulletin 67 is the standard bulletin on the whitefly and is ,out of print but thousands of copies have been distributed throughout the State; Bulletin 76 is on Insecticides and Fungi-







Whitefly Conditions in 19o6.


cides, and is full of valuable information on spraying and fumigation in general.
judicious spraying with insecticides should be effective in reducing the ravages of the whitefly provided a grower can persuade his neighbors to spray at the same time. Co-operation is absolutely necessary for effective spraying.
December, January and February are the best months to spray for the whitefly as it is then in one or the other of its several larval stages or pupae tinder the leaves, and is more readily killed in these stages. It is practically useless to spray for the adults since the females lay their eggs when they are from iS to .1o hours old, so that the g-rower would have to spray every day during the swarming periods to insure killing them before they laid their eggs. The eggs are not readily killed either by spraying or fumigation. Spraying to be effective should, furthermore, be drastically thorough, and one such spraying M 7uinter after the fruit is picked and danger from frost is past will be worth more than several less thorough applications. To postpone spraying until danger of frost is past may save much labor and spraying material, since, should the leaves be dropped by freezing but little if any spraying would be necessary. In case of a freeze sufficiently severe to cause many leaves to drop, these should be plowed under or burned to insure against the possibility of any nearly mature whitefly front completing their development. It will thus be evident that a freeze may be a blessing to a whitefly infected grove.
Summer spraying may be practiced when conditions require it. The difficulty with spraying lies not so much in getting an insecticide that will kill the insect as in applying it so that all or a very large percent. -vill be killed. Any of the contact insecticides (including whaleoil soap) generally used for destroying insects on citrus trees, will be found useful. However, all kinds of spraying with emulsions and other chemical compounds generally in use, appear to be more or less injurious to orange trees. Of these, whaleoil soap is probably the least injurious. Before spraying, all excessive foliage should be removed from the trees by a thorough trimming. Spraying with insecticides is, also, more or less harmful to the Fungi, so that having decided to use the Fungi, spraying should be discontinued.
Fumigation has not been sufficiently tested in this State to







Bulletin No. 88.


warrant its being " 'boomed' into disfavor," as Professor H. A. Gossard has aptly put it.
COPPERAS.
Much has recently been said and written in regard to the use of copperas for killing the whitefly. Examination by competent persons of groves treated with copperas indicates that the latter is not efficient for reducing the whitefly, to say nothing of extermination. In one instance (Orlando) it was reported that an application of copperas had killed the whitefly, but examination showed the trees treated to be just as full of larvae and pupae as the trees not treated.
The following is taken from the Florida Farmer and Fruit Grower of August 31st, 19o6.

"ROYAL PALM NURSERIES, REASONER BROS.,
Oneco, Fla., August 22, 19o6.
Editor Farm and Fruit-Grower:
* * * I will again state, however, that I think it simply impossible to kill or drive away the whiteflies by any such mild measure as spreading copperas under the trees. I have evidence that it will not affect them at all! In Bradentown two of the best known citizens used copperas liberally on the soil, giving several applications through the year; 2 to 4 pounds per tree on from IOO to 200 trees each were used by them about six years ago and no effect whatever was notived on the flies which continued as thick as ever for some years thereafter. Now that the natural fungoid enemies of the flies are present, the groves look very well and are carrying a fair crop of fruit.
The fungus (two species) keeps groves generally clean in the infected localities of this, Manatee county, where the flies have been known about fiften years. Parts of the county have never had the flies present at all, and if we have normally wet summers the flies can never get bad again wherever the fungus has been introduced. It remains the only known successful "cure" for whiteflies."
(Signed). E. N. REASONER.







WI hitefy Conditions in 19o6.


SOOTY MOLD.
This mold (a species of meliola) of a sooty black, as its name implies, is found wherever whitefly or other insects, that excrete a sweet solution (honeydew) occur. As this sweet secretion (also relished by ants )nearly always collects on the upper surfaces of leaves, it follows that the mold, which thrives in this secretion, also occurs on the upper surface. Other insects that are accompanied by the sooty mold are: mealy bugs, plant lice (aphids), soft scale (Lecaniums), wax scales, cottony cushion scale, and others, so that sooty mold visible upon a tree is not necessarily a sure sign of whitefly. This fungus does not ordinarily become visible until after the trees have been infested by the whitefly for some months.

THE SNAIL.
There appear to be several species of snails that will feed upon the sooty mold accompanying the whitefly. Besides the Manatee Snail (Rulimnulus Dorm ani), another species brought from Miami by Professor Rolfs and spoken of by us as the Miami Snail, is also a good feeder upon the sooty mold and may become of considerable value. Their usefulness consists mainly in the fact that they will clean the sooty mold from all parts of a tree and the fruit. They do not feed upon the whitefly larvae as sometimes reported. That they will swallow and destroy some larvae and eggs is a fact but this is only incidental, the larave and eggs being swept off the leaves with the mold. This is, however, not of frequent occurrence since the snails seldom feed on the under surface of the leaves where the eggs and larvae are found, except when food is getting scarce. To those who have or suspect the presence of snails in their trees, the following may be recommended: Keep a liberal amount of mulch, coarse and fine mixed, around the base of the trees and hang pieces of burlap into several of the arrowest crotches -f each tree. The purpose of the above is to provide moisture-conserving places in and about the trees in which the snails can lay their eggs and conceal themselves. The above directions are iinpnrtant.







Bulletin No. 88.


LIFE HISTORY OF THE WHITEFLY.

Plates I, II and III.

The name whitefly is a misnomer, the insect in question not being a fly at all but a member of the Hemptera, the order to which the plantlice and scale insects belong. Flies have only two wings, but the whitefly has four, which fact at once separates it from the Diptera, or flies proper.
There are three well defined broods of the whitefly, with an interval of several days to several weeks between each brood, when few or none are seen on the wing. The first brood generally appears sometime during March, April or May, the second during June, July or August, although this summer it appeared as two quite distinct divisions at Lake City, and the third during September and October. Variations that occur are due to variations in the seasons and the locality. No doubt many people supposed that they had exterminated the whitefly by means of some treatment (copperas) when one or another of the several broods disappeared from the wing.
Larvae (the young stages) and pupae (the transf ormation stage) of the whitefly can, however, always be found on the under surfaces of the leaves, and seldom elsewhere. The larvae are scale-like (Plate III, Fig. i.) and closely appressed against the leaf. They vary in size from the very young, just visible to the unaided eye, to the fully matured larvae which measure about one-sixteenth of an inch in length.
The larvae are white and translucent with a tinge of yellow, and almost invisible upon the leaf. By holding a leaf underr surface up) at the ends, with the thumb and forefinger of each hand and then rubbing lengthwise along the leaf with one of the unused fingers, the larvae will appear as flattened whitish scales. The pupa (Plate II, Fig 8) (plural pupae) is the trans form ati on stage from the larva (plural larvae) to the adult, winged fly. The pupae are readily visible as yellowish white, plump, oval bodies with a dark reddish spot on the back. From the pupa. emerges the adult winged fly. The little white cases, with a T-shaped split on the back, and found on the under surface of a leaf, are the empty pupa cases from which the adults have emerged (Plate IT, Fig io). The eggs (Plate 1, Fgs. 3, 4) are just visible to the unaided eye as a fine dust upon the under surface of the leaves. An ordinary hand







Whitefly Conditions in 1906.


lens (magnifying glass) wvill show then as little egg-shaped bodies much resembling grains of wheat. There are, therefore. four stages in the life history of the whitefly: The egg visible as a fine particle of dust; the larva, a flattened scale; the pupa. plump and readily visible; and the adult winged insect. All of these stages are nearly always confined to the under surface of the leaves. (Plates 1, 11, 111.).
The following facts are a summary from Professor H. A. Gossard's Bulletin 67. Twventy thousand eggs have been estimated on a large orange leaf. From observations made in the laboratory, egg laying begins when the female is from eighteen to thirty hours old, and from seventeen to twenty-five eggs are deposited. These eggs are generally all laid within twenty-four hours after the first egg has been laid. Her length of life has been estimated at from three days in warm weather to three weeks in cool weather, and the complete length of life cycle from egg to adult is from forty or fifty days in summer to six months in winter.
It will thus he evident that in order to spray successfully for the adult fly it is necessary to spray practically every day to catch the females before they lay their eggs; an impossible task when a man has more than a few trees.

FOOD PLANTS.

There appear-s to be a great deal of misapprehension in regard to the number of food plants of the whitefly. Every tree, bush, or weed in the hammock is not a food plant, as many suppose. The definitely known number of food plants is a relatively small one. I cannot do better, perhaps, than to quote verbatim the page on Food Plants from Professor Gossard's Bulletin 67.
"White fliy 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 hybirds will tend to retard the multiplication of the pest upon then. 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 ovestocked. The adult flies as well as the larvae sap the leaves, and their taste for certain varieties leads them to oviposit on these when possible, going to less favored plants only as they are driven by







Bulletin No. 88.


necessity to do so. Besides citrus, the Chinaberry tree (Melia Azederach), Viburnum nudum, the Cape jessamine (Gardenia florida), the Japan persimmon (Diospyros kaki), California privet (Ligustruin Aiurense), 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. altissiua, and on an unknown species introduced from Costa Rica.
The water oak (Quercus aquatica) is ocsasionally 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 what 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."
To this list but few if any additions can be made at this time. The Umbrella tree, a variety of the Chinaberry, becomes as much infested as the latter. During the past summer the Prickly ash (Fagara Clava-Herculis) has been observed to be an undoubted food plant and several badly infested trees were found at Lake City. A similar observation was made at Leesburg. Specimens of whitefly were also found upon the wild persimmon. (Diospyros Virginiana) along a roadside south of Orlando. The umbrella tree and the wild persimmon, seem thus to be about the only additions that we can make at this writing.
That a definite knowledge of the food plants of the whitefly is important in devising means for its control will be evident to all, and all persons interested should send samples of any infested (or supposedly infested) plants, not in the above list, to the Experiment Station at once upon their discovery, so that we can make our knowledge as complete as possible. Were we to count all plants upon which a few larvae may occasionally mature, the number of food plants would be increased to two or three times the number listed; but the majority of these would represent plants that become slightly infested only when in close proximity to some tree that is badly infested. Thus Dr. Webber states (verbally to the writer) that larvae will occasionally mature upon magnolia under such conditions.
It appears that plants, in their food relations to the white-







TUhitefly Condlitions iM 1906.


fly may be divided into three classes: ( i) Food plants proper,
(2) Partial food plaits (those not gener-ally infested or but little infested) and (3~) Plants inimune. The majority of plants listed above belong to the first class, and all but six-are of Oriental origin, which furthermore, suggests that the fly is of Oriental origin. These six native plants, Viburnum nudu Milock Orange (Cherry Laurel,) Water Oak, Scrub Palmetto, Prickly Ash. and WVild Persimmon become only slightly infested (Prickly Ash excepted) and belong to class two.

QUARANTINE.

In localities where the 'whiteflv is not present. or where the amount present is very small and the chances for its elimination by a vig-orous application of drastic methods are favorable, quarantining should be effective to a great degree, at least in putting off the evil day, and thus be the means of saving thousands of dollars. This could he, and in fact has been, made effective in several different ways: by keeping out suspicious nursery stock; closing uip private roads and gates and keeping out vehicles coming from infested districts; keeping out pickers' implements when coming from infested districts, or compelling their disinfection at some safe point.

NURSERY STOCK.

In buying nursery stock the buyer can well afford to travel to any part of Florida to determine for himself the condition of the stock he desires to buy, provided the section in which he desires to plant the trees is free from the whitefly. If the section is already infested this is not so important. On the other hand, the present status of our knowledge indicates that it would be perfectly safe to buy nursery stock from any infested district provided the same be cut back, defoliated, and as a special precaution, fumigated with hydrocyanic acid gas. \Vhile eggs are frequently laid upon the tender wood of growing shoots, yet no larvae have ever been known to become mature there, and whenever this wood is cut back and the rest defoliated, and the tree fumigated as a special precaution, reasonable safety can be assured, especially during December, January and February, when absolute safety can be
uraned Duin these months all the eggs have hatched







Bulletin No. 88.


and proper fumigation can be depended upon to kill any stray larvae or pupae that might be attached to the bark.

VEHICLES AND PRIVATE ROADS.

Private roads should simply be closed to all vehicles, at least to any whose previous whereabouts are uncertain. This has been done in many places and no doubt has saved growers thousands of dollars by delaying infection, even if it was not effective in keeping out the whitefly permanently.

PICKING IMPLEMENTS.
The picking implements used by pickers, coming from an infested district have been excluded, from at least one section, (the Subpeninsula) of Florida, and this no doubt was one of several important factors that aided in keeping this section practically free from the whitefly for many years. On the other hand, a thorough disinfection of the implements, including ladders, sacks, etc., as well as the outer clothing of the pickers should be effective in reducing the chances of infection from this source to nothing. It has been suggested that where picking of citrus fruits is let by contract a clause requiring disinfection of the implements and clothing should be included. It is the writer's opinion that this is a very valuable suggestion. Ladders could be best disinfected by painting or spraying them with kerosene or kerosene emulsion, whaleoil soap, linseed oil, or by slowly passing them through the flames of a fire when the other means are not at hand. For disinfecting the picking bags, clothing, etc., nothing, perhaps, would be simpler than placing these in an air tight barrel or box, pouring a liberal quantity of gasolene over them, and closing the barrel or box tightly for several hours. If carbon bisulphide is at hand this can be used instead of the gasoline, and a treatment of an hour is sufficient. Three ounces (about one-fifth of a pint) of carbon bisulphide will be sufficient for a case the size of a barrel. If gasoline is used the dose should be several times as large. Finally, if a fumigating box is at hand, such as is used for fumigating nursery stock with hydrocyanic acid gas, the implements etc., can be fumigated in this, using the normal dose of the gas for forty minutes. The picking bags, etc., should be arranged loosely and with spaces between them to







Whitefly Conditions in 19o6.


insure a perfect circulation of the vapor or gas used, whether in barrel, box, or fumigating box.

PLANTS TO BE CONDEMNED.
The following plants should be condemned by every citrus grower and by all people in any community where citrus growing is an industry. These plants are: the Cape jessamine, the Chinaberry, the Umbrella Tree, the Prickly Ash, Golden Privet, California Privet, the Trifoliate Orange (Citrus trifoliata) and any useless and abandoned citrus of all kinds. The Mock Orange (or Cherry Laurel) should be included in this list whenever it is observed to become badly infested. These plants are generally of little value and can well be spared and replaced by others not subject to attack by whitefly. Including the trifoliate orange in this list does not preclude its being used as a foundation stock in nurseries. Of course anyone having only one or two of these trees may overcome the danger of their becoming a source of infection by spraying them to the extent of defoliation, or they can be defoliated by trimming; but in either case the work must be done thoroughly, every leaf must come off, and as a special precaution the tree should be sprayed besides, to insure the killing of any larvae that might be on the buds and elsewhere. Such an operation, however, might have to be repeated each year, and possibly oftener, so that cutting down and burning such trees and shrubs is the better plan. Do not cut them dozun and then let them remain about the premises so that the fly can continue to develop, but burn them at once!
It may seem akin to vandalism to be expected to sacrifice some of our garden and orchard pets, but all successful warfare consists in some degree at least in reducing the number of the enemies' strongholds. One Cape jessamine and two or three umbrella trees in a certain yard in New Smyrna seem to be responsible for the spreading of the whitefly in that place. In looking over this ground one is soon impressed with the fact that these trees were the focus of infection.















EXPLANATION OF PLATE I.*


Aleyrodes Citri.
Fig. I.-Adult female with expanded wings nuch enlarged.
Fig. 2 Adult female with wings folded over the body in normal roof-like position.
Fig. 3-Egg and footstalk of same, greatly magnified.
Fi. 4.-Eggshell, showing the split through which the larva emerged.
Fig. 5.-Tip of male abdomen, showing claspers.
Fig. 6.-Antenna, showing annulated joints.
Nig. 7.-Fore margin of front wing.
INSECTS SOMETIMES MISTAKEN FOR A. CITRI.
Fig. 8.-Larva of Aleyrodes floridensis greatly magnified.
Fig. io.-Greatly enlarged section of waxen fringe surrounding A. floridensis
Fig. ij.-Outline of Lecai mi hcspcridtm. (A soft scale).


*All plates are the same as in Bulletin 67. By Prof. H A Gossard.





fu



















EXPLANATION OF PLATE II,

Aleyrodes Citri.
Fig. i.-Larva, first 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 operculum with lingua in the center.
Fig. 8.-Pupa, showing embryo and distribution ot orange colored areas, waxen tufts extending from the breathing tubes are shoxn.
Fig. 9.-Adult with folded wings, emerging from the pupa case.
Fig. io.-Empty pupa case, showing split through which the fly emerged.





PLATE 11.
























EXPLANATION OF PLATE III.

From Photographs.
Fig. I.-Larvae and Pupa of Whitefly on Orange. Fig. 2.-Red Fungus, Aschersonia Aleyrodes, Webber. Fig. 3.-Brown Fungus on Orange. Fig. 4.-Adult Flies and Eggs on Orange.





r


Fil .


Fig.


Fit' .,. 2.


Fi"


1-1 LAT F I If.







Bulletin No. 88.


APPENDIXES.


I. WHERE TO OBTAIN FUNGUS.
The following persons living in Florida have consented to furnish leaves having fungus-infected whitefly larvae and pupae upon them at fifty cents per one hundred leaves.
A. J. Pettigrew. Manatee, (Red and Brown),
A. F. Wyman, Bradentown, (Red and Brown),
F. D. Waite, Palmetto. (Red and Brown),
C. A. Boone, Orlando, (Red, Yellow and Brown),
C. B. Thornton, Orlando, (Yellow and Red).
Larger quantities can no doubt be obtained at reduced rates.
2. THE FUNGI IN FLORIDA.
The following data have been taken from Bulletin No. 13, U. S. Dept. Agr., Div. Veg. Phys. a'nd Pathology, by Dr. H. J. Webber. Red Aschersonia first observed: Panasoffkee, 1892; Crescent City, August 1893; Bartow, January 1894; Citra, December 1894*; Myers, June 1895*; Gainesville, Manatee, I893-I897*. (Years with stars may be too great by one or several years).
Brown Fungus first observed: Manatee, March 1896. Yellow Aschersonia first recognized as distinct from the Red Aschersonia by Professor P. H. Rolfs on specimens sent from Winter Park by J. F. Adams, September, 19o6.

3. SPRAYING APPARATUS.
For those who expect to give the fungi a thorough trial it will be desirable to have a special outfit for spraying the mixture of fungus spores and water. Having a special outfit and using it only for the fungi, there will be no risks of poisoning the spores by small traces of any chemicals that may remain in an old outfit, especially one used for spraying fungicides. The writer has found the Lowell Fountain Compressed Air Sprayer, made by the Lowell Specialty Company of Lowell







White fly Conditions in 19o6.


Michigan, a very desirable machine. The tank holds three gallons and is furnished with nozzles giving three sprays of diffrent degrees of fineness, and a solid spray. The finest spray makes a mist and this is the one to use for spraying the fungus spores. It should be ordered with about ten feet of extension pipe for spraying in the tops of trees. It is made of brass or galvanized steel. The latter metal should be ordered for spraying the fungi. E. 0. Painter & Company, Jacksonville, are the agents. Cost complete about six dollars.
The "Auto" Compressed Air Sprayer sold by Peter Henderson &Company, New York, appears also to be a desirable machine. It can be obtained, made from galvanized steel, for $6.oo, extension pipe extra. Order with nozzle capable of producing spray as fine as mist.

4. THE WEATHER AT LEESBURG.

The following is an abstract from notes kindly kept for the writer by Mr. H. S. Budd, of Leesburg, during the period of the observations at that place noted in the text. These observations were begun August 15th and terminated December 22nd, 19o6. Unless otherwise mentioned, the weather was fair during this period.
August: 17th, some rain; 19th, light shower; 23rd, 5>2 hrs, rain; 24th, cloudy; 25th, heavy rain one hour, then steady; 26th, cloudy all day with frequent rains; 27th, cloudy all day, some rain; 28th, heavy showers and rain all day; 30th, rain and thunderstorm ; 3 1st, fine but rain after dark.
September: Ad partly cloudy and heavy storm; 8th, fine but one half hour rain at 7 P. in.; 9th, heavy storm p. in.; ioth, little rain; i8th, rain; 23d, light rain for one hour; 24th, rain; 25th, rain; 26th, rain; 27th, light rain.
October: ist, rain and thunderstorm; 2nd, rain; 5th, rain; 8th, little rain; 9th, slight rain; i5th, some rain; 16th, fine and cloudy; 17th, wet; i8th, rain, 19th, cloudy; 20th, mostly cloudy; 21st, rain; 22nd, cloudy; 23d, drizzle; 24th, dull; 28th, colder; 29th, colder.
December: Drought broken night of 19th; 19th and 20th cloudy with light rains.








!k 1IhCtili Vo. 88.


APPENDIX 4.
THE WEATHER AT LEESBURG.
The following notes have been inserted for the purpose of showing the contrast between the weather conditions as they existed during the months of June, July, August and part of September, when the Fungi started readily and spread rapidly, and the conditions during September, October, November and December. when this was not the case. There being no Weather Bureau Station at Leesburg, Mr. H. S. Budd kindly kept a record of the rainy days for me. but as I have since been able to get a complete record taken at Orange Home, only about eight miles from Leesburg, I have decided to let the latter record represent the conditions at Leesburg, but giving also Mr. fludd's record.
It will be observed from the table that during the months most fax,,rable for the Fungi, the mean temperature was above So and the precipitation (rain) very abundant; that during the less favorable (or unfavorable) nionths the temperature either dropped considerably below So or the amount of precipitation became strikingly less, or both. No experiments in starting the Fungi have been tried during January, February, March, April or May. but judged bv the conditions represented in the table, the first four months were very likely unfavorable. On the other hand, the Fungi would probably have done well during May, there being then an abundance of rain and a temperature fairly high.
The weather conditions here indicated were, of course, not exactly the same throughout the State, and variations will also occur from year to year. These observations, and others, indicate, however, about the time when we may expect to get a good start of Fungus and when we may expect to get only a poor start or none at all.
Table showing mean temperature in degrees Fahrenheit, precipitation in inches, and number of rainy lays at Orange Home, Sumter county.
J n Feb . M a r. April May I June I JulY -Aug. Sept. Ou '. N o,. flu . Mean terp . 51 598 638 70 766 813 80.7 816 81.6 726 678 596 Precipitatio. 5 41 1. 248 2 31 .525 9051 8.411 7 , 189 ' . 4f 14 Rainy days .S 6 6 8 1 10 15 20 15 12 5 3 1 M r. Budd's record' .1. . . . 0 1 0
Last half. Or more.








Wh iteflY Condition's in1 1906.


AFTER FREEZE SUGGESTIONS.

In trees and groves where the friendly fungi are found in abundance, it is advised to collect large quantities of the dead leaves still found clinging to the trees, or fallen leaves, with plenty of fungus upon them. These should be dried and stored for use in again starting the fungi the next spring or summer. Should the fungus upon the leaves prove useless by the time it is desired to use it, little labor will have been lost. Samples of such leaves sent to the Station at the proper time will be gladly tested for the vitality of the fungi.
Again, in view of the fact that freezing has begun the work of defoliating, it may be desirable to complete it, and thus as far as possible reduce the whitefly at one stroke. If but few green leaves remain upon a tree it is advisable to complete the defoliation by trimming, otherwise spraying with some good insecticide may he adopted. There being but relatively few leaves upon a tree it should be possible to spray successfully, at such a time. All wxhitefly larvae and pupae (the stages found under the leaves at freezing time) will die when the leaves dry, but to insure against the possibility of any nearly mature insects completing their development and aiding in reinfesting a grove, all fallen leaves should be carefullY plowed under or burned.

ACKNOWLEDGEMENTS.

Acknowledgement is due Mrs. E. W. Berger for criticisms and aid in preparing the manuscript. Also to Mr. H. S. Budd, of Leesburg, for advice and valuable data.




Full Text

PAGE 1

BULLETIN NO. 88 .., ~ , Ali~: : J~t9' Florida 4gricultural Experiment Station Whitefly Conditions in 1906 The Use of the Fungi ( . \l e yrmle ~ Citri,) Bv E. \ N. HER.Ci E R.. Ph.D . T h e HuH elins ol thi s St a tion wi ll ht> . 'icn l lrcc lo a n y a d dn : ss in F'lnr i cla 1 q .u111 appii('at in n 11, i i H ihr tdu r oJ th e. Exper iment Station . C a i ncs villc . Fla. ~ E. 0. P:iinf t'. r Pri n t in g Co. , D e La nd , Fla.

PAGE 3

BOARD OF CONTROL. N. P . BRYAN, C hairman .......... .. .. ... Jacksonville, Fla. P. K. YONGE.... . . . . . . . . . . . .. . ... ... .. . Pensacola, Fla. A. L. BROWN ... . .. .. . . .... . . . .. .......... .. Eustis, Fla. T. B. KING. . . . . . . . .. ...... . .... . .... Arcadia, Fla. J. C. BAISDEN .. . . . .. . . . . ... .... . . . . . .. .. Live Oak , Fla . STATION STAFF. P . H. ROLFS, M.S ... . . . . .. .. . . . ... . ... .. .. . ... Director. A. \V. BLAIR, A.M. . . . . .. . . ... . . . . . . .. . ...... Chemist. JOHN M. ScoTT, B.S . .. . . ....... . . ... .. Animal Industry. E . H SELLARDS, M.A ., Ph . D ...... . ......... . . . Geologist CHARLES F. DAWSON, M.D., D.V.S., Jacksonville , Consulting Veterinarian . E . W. BERGER , Ph.D ............. Assistant Entom o logist. H. S. FAWCETT, B.S . ......... Assistant Plant Path o logi s t. R. Y. \VI N TERS, B.S .. . . ... . ... . .. .. Assistant in Botany. K. H. GRAHAM. . . . . .... .. ... Auditor and Bookkeeper. R. D . AL G EE .. . .... . .. ..... ...... .. . .... Stenographer. M. CREWS .. . ...... . . . .. .. ..... . ....... Farm Forem a n. F. !'vf. STEARNS . .. . . . ....... ... . .. ...... . .... Gardener .

PAGE 4

CONTENTS. Important Facts .. Introductory ...... . ........... . .. . ............ . ..... . Page. 51 53 The Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Conditions favorable for the Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 The Red Aschersonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Introducing this Fungus . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Summary for the Red Aschersonia . . . . . . . . . . . . . . . . . . . . 59 By Sf>raying on Spores of the Fungus . . . . . . . . . . . . . . . . . . . 60 By Pinning on Leaves ................. . ... . The Yellow Aschersonia The Brown Fungus ....... . ....... . .. . .. . .. . Scale and Whitefly ... . .. . . . .... . .. . . Trimminfl; Trees ... . Spraying and Fumigation Copperas ... Sooty Mold .. . .. . . ... . . The Snail ............. . Life History of the Whitefly Food Plants .... . Quarantine ......... . Nursery Stock ...... . Vehicles and Private Roads .......... . . . .. . 63 64 64 65 66 66 68 69 69 70 7I 73 73 74 Picking Implements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Plants to be Condemned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Appendixes I. Where to Obtain Fungus . . . . . . . . . . . . . . . 82 2. The Fungi in Florida . . . . . . . . . . . . . . . . . . . 82 3. Spraying Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4. The Weather at Leesburg ... . ....... . ....... . 5. After Freeze Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . 84 Acknowledgments ..... . 86 PLATES. Plate l. Whitefly egg and Adult ............. . .. . .. . . 77 Plate II. Larvae and Pupa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Plate TTI. Fungi and Whitefly on leaf . . . . . . . . . . . . . . . . . . . . . . . . . 81

PAGE 5

Whitefly Conditions in 1906. 51 IMPORTANT FACTS. 1. The fungi parasitic on the whitefly larvae and pupae can be started in whitefly-infested trees by spraying the spores suspended in water, by pinning on leaves having pustules of the fungi upon them, or by planting infested trees. The writer's success by the first two methods during the past summer was 98 per cent. 2. There are three of these fungi-the Red Aschersonia, the Yellow Aschersonia and the Brown Fungus. The spores of the latter have not been discovered, hence this fungus can probably not be successfully introduced by spraying. Dried fungus pustules have been kept for a month and found efficient for starting the fungi. They probably will retain their vitality much longer. 3. All these fungi will apparently thrive in any part of Florida. The Red Aschersonia was observed to thrive well as far north as Lake City during the past summer, while the Brown Fungus was also successfully introduced. 4. A humid atmosphere in a grove is important for the thriving of the fungi. Suggestions for aids in accomplishing this are given in the test. Considerable warmth also appears to be necessary. 5. It appears from our present state of information that the best time for starting the fungi in whitefly-infested trees will be the months of May, June, July and August. March and April may also be good months. In general, periods of rain and summer temperature are considered favorable . . 6. To insure the efficiency of the fungi, repeated "plantings" should be made to get a good start. Keep the fungi abreast of the whitefly, instead of tandem, or at its heels, which is the general situation 'at present. 7. Trees of all kinds along roadways should be trimmed high to avoid the distribution of the whitefly by carriages brushing against the branches. 8. Not every tree, bush or weed in the hammock is a food plant of the whitefly. The number of authentic food plants can probably be counted on the fingers of two hands. g, The Cape Jessamine, Chinaberry, Umbrella Tree, Prickly Ash,

PAGE 6

B ull e ti n No . 88 . Privet, Trifoliate Orange, Mock Orange (Cherry Laurel) , and all useless and neglected citrus stock should be condemned and destroyed. These should be cut down and BURNED AT ONCE. IO . The "greatest injury done by the whitefly is during its several larval and pupal stages while it lives in a wingless state attached to the under surface of the leaves. u. Where it is desired to spray or fumigate for the whitefly, the best time for doing this is during the months of December , January and February; or better , after the fruit is picked and the danger from frost is past. All of the eggs are probably hatched by December. The eggs are not easily killed either by spraying or fumigating. 12. There appears to be no good evidence to show that copperas is of any value for reducing the whitefly, to say nothing of exter mination. 13. Snails in groves should be encouraged by providing mulch (coarse and fine mixed) under the trees , and burlaps in several of the narrower crotches . 14 . Snails do not destroy whitefly, except incidentally some eggs and a few larvae, but feed upon the sooty mold , other fungi and lichens. They keep the tree clean when in sufficient numbers. They appear to avoid the fungi parasitic upon citrus tree insects. 15. The picking implements and the clothing of pickers should be disinfected by one of the several methods described in the text , before being transferred to a noninfested grove. 16. See the Summary for the Red Aschersonia, which probably holds good for all the fungi.

PAGE 7

Whitefly Conditions in 1906-The Use of the Fungi. INTRODUCTORY. The whi te fly i s o n the increase and spreading to citrus gr c m ing sections o f th e St ate hitherto n o t infested . No doubt the mild winter o f 1 905 to 190 6 favored its spread a nd increase in the more n or therly sect ion s o f the State. Citrus trees that wer e ge nerally quite defoliated during m o re sev ere winters re tained so me of their le aves and of course the whitefly larvae with them. T hi s gaYe it an unc o mm only good start last Sprin g. Rail roa d train s . carri ag es and o ther le ss under s tood mean s o f di ssemi nati o n are sprea ding i t to all parts o f the State. T he situation i s ur g ent. and some ex citem e nt prevails i n oran ge growin g secti ons that have recently be come infe s ted. Some have "Hit the line hard " when thev found the fly pres ent last fall and winter , with very gra!ifyirig r es ults, going even t:o the extent of cutting dow,111 infested tree s, s uch as um brella , Chinaberry, and o thers. Such me a ns are ra ther dr as tic but a r e a c ert a in remedy where the s itu atio n ju st ifie s it. Oth ers have m ade strenuous eff orts. doin g everything in their power to keep the pest down. but found their eff orts mainly in effecti ve bec ause of th e indiffer e nce of thei r nei g hbors. There appears to be the expectation o n the par t o f some that a pan ace a wi ll be discovered, which will do away with the whitefly on short notice. This is something to b e hoped fo r , and p oss ble, but n o t very probable. It is o f no use to wa it : fighting in sects is much like fighting weeds in a garden, one must b e r eady to cut them, down with the m eans at hand whe11ez1er they raise their h ea ds. The main purpose o f thi s bulletin is to ur ge growers to do something and n o t t o wait. and especially 10 urge the intro ducti o n of the fungi. \Vhile many new facts and demonstra tion s are int rod uced. much of necessity fol low s in the nature

PAGE 8

54 Bulletin No. 88. of suggestions which only future experience can prove neces sary or erroneous. It would be well if growers generally fol lowed out some of the suggestions made by the Station, if only on a small scale, for by so doing they will be of great aid to the Station Staff.. The writer believes that future work upon the whitefly will consist, not so much in the discovery of new remedies and enemies, though this is desirable, but in a better understanding of how to use the remedies at hand. THE FUNGI. Plate III, Figs. 2 and 3. Broadly speak . ing, the fungi belong to the lowest order of plants known, and are devoid of the green coloring matter ( chlorophyll) so characteristic of the higher plants . Mush rooms, toadstools, mildews and the several molds are familiar examples of fungi. The majority of fungi generally propagate themselves by minute mic roscop ic bodies called spores. These are produced in countless millions and chiefly relied up on when we desire to propagate , or start, fungi. These spores take the place of seeds produced by the higher plants. but structurally they are not seeds. There are three fungi at present known to be parasitic upon the whitefly larvae and pt1pae. These are the Red Ascher sonia ( Aschersonia aleyrodes), the Yellow Aschers o nia ( As chersonia -/lmJo-citrina) and the Brown Fungus. Each oc curs on the under surface of citrus leaves and transforms (kills) the larvae and pupae o f the whitefly living there into pustules having the color characteristic of each fungus named, except that the young pustules of the Red Aschersonia are pink and only develop the sca rlet red fruit bodies as they become mature. There is another fungus that occasionally destroys a few whitefly larvae, namely the Red Scale Fungus (Sphaero stible coccophila), but this occ urs only rarely upon the whitefly and will not be further discussed in this paper. None of these are known to attack either the eggs or the adult whitefly. It appears to be the observation of some that the Brown Fungus works more rapidly than the Red Aschersonia. On the other hand, the observation of others is quite the reverse, that the Red Aschersonia spreads more rapidly and is more efficient. This last is also the writer's personal observation to

PAGE 9

Whitefly Conditions in 1906. 55 date. The Yellow Aschersonia appears to be quite the equiva lent of the Red so far as present observations indicate. CONDITIONS FAVORABLE FOR THE FUNGI. All fungi thrive best in the presence of ari abundance of moisture, and observations show that the Red and Yellow As chersonias and the Brown Fungus work best in destroying the whitefly where the ground is sufficiently moist; or where the surrounding conditions are such as to retain the moisture in and about the trees and the ground. Plenty of dense vege tation ( trees, shrubs, tall grass etc.) about and in the grove, will do this to a great extent. The trees and shrubs should be arranged in the nature of windbreaks, while the grass and beg garweed should be permitted to grow tall and rank at the proper se ason as a cover crop. It appears also, that where the fungi tl11ive best, there is frequently some decaying rubbish s uch as weeds, gra ss, etc ., in the nature of mulch near or about the tree s . which help s to conserve the moisture. That it is not s uch a difficult matt e r to reproduce these conditions, in some degree at least . will be admitted. It is easy to mulch a grove, and still easier to grmv tall cover crops. \Vindbreaks can, of course, be planted. An occasional wetting in dry weather of both the trees and soil, where convenient, will add to the efficiency of the above provisions. \Vhere groves are irrigated the problem is simple. Even a s light daily wetting of the tree s and ground would no d o ubt be very favorable for the thriving of the fungi. Such a sprinkling outfit would have its other uses . To say n o thing of its va lue for irrigation, it would above all be effective in reducing the reel spider and fa,or the activities of the snail wherever present, besides be ing a possible protection against frost. But these problems are beyond the scope of thi,paper. The conditions above se t forth appear t, _i be those very generally exi s,ti ng in groves on hammock Janel, and this no doubt accounts for the fact that the fungi thrive there so much better than on high pine land. If then. the grower can succeed in approximating these conditions in groves on pine land, by a liberal mulching and wetting when possible and the growJng of tall cover crops and windbreaks , he will s~c ceed in helping the fungi a long way toward the destruction of the whitefly. The main object is to produce a moist atmos

PAGE 10

phere in the grove, and the mulch aids in this respect not only by conserving the moisture, but by actually adding a cer tain amount of water produced by the decay of the mulch. The question of a temperature s ufficiently high to meet the requirements of the fungi is also important. But the con trol of this is wholly beyond any means possessed by the grower. Careful observations covering the months of the dry seaso n fr o m some time in September. 1906 , until January, 1907, indicate that the fungi have spread but little during this period. These months have been very dry this season, there oc curring on l y one or two slight rains at Lake City, and in many other parts of Florida. The temperature, furthermore, probably averaged something like 70 degrees F. The fact, hO\ ,v ever, that heavy de,,ns were quite frequent during these . m o nths. points to a high temperature as an important factor for the grow•th of t_hese fung i. Efforts to start the Red and Yellow Aschersonia during the months of September, October and Nove mber have so far been only partially successful. Summing up the conditions favorable for the growth and starting of the fungi, it is clear that abundant moisture together with a Florida summer temperature are important. THE RED ASCHERSONIA. Plate III, Ag. 2. The Reel Aschersunia, otherwise kn o wn as th e Red Fungus of the Whitefly. has been known to occur in Florida since 1892. ( See appendix 2.) H was observed to be d oing good work then. and is doing good work now. It is at present reducing the whitefly in a yard near Lake City. On July 8th it was found on this place (Agnes Jones') and August 6th 47 .2 per cent. ( counting all larvae. purpae, and empty pupae cases) were infected and killed by the fungus. This is the count upon eighteen leaves that were brought t o the laboratory. Not counting the empty cases upon the leaves the per cent. of infecti o n wa s 59.9 per cent. This shcnvs that ov er one half of all the living larvae and pupae upon the leav es brought to the laboratory had been killed iby the fungus and the work is still going on. Dr. H , erbert J. \Vebber wrote, for Gainesville (about 1895): "On many leaves it was difficult to find a liv ing larvae or pupa nf the mealy w'ing [ whiteAy] and in such

PAGE 11

fl'/1itcfl_,, Co11ditio11s i11 1906. 37 cases the leaYe:i ,Yere thickly clotted over with th e pustules o f Aschersonia .. , The destructive freeezs during the winter of 1894 to 1895 killed all the citrns trees to the ground, but left unharn,ecl a number nf species o f h o st plants upon which t-he insect sur,ivecl the "inter. From the s e plants the new citrus sprouts \Yere again infested the follo,Ying spring and smn mer . The large quantity 1) f fine fruit s hipped from the :.fan atee section and the large acreage o f ne,y grove s being set o ut, indicate that any rep o rts nf the citnis industry being ruined in that section by the whitefl). are nut ,, ell founded. Many of th e most successful growers of this s ection depend upon the fungi t o keep their trees clear from the whitefly, while others are ahandoning spraying and are going t o permit the fungi to take their course. Summing up all the facts and o b s erva tions. it is difficult t o understand why a more general effort has n"t been made tn spread this useful remedy. It is admitted that in some grmes the c o nditions are not as favorable for the growth of the fungi as in ot hers . but extensive observations in dicate that " here conditions are naturalh unfavorable. thev can lie greatly impnwed, so that the fung i ,~ ill thri, e hevter. INTRODUCING THIS FUNGUS. The chief dra,vhack to introducing the fungi ha s been the supposed difficulty of starting ("planting") then in whitefly infested tree s. The matter appears to be mnch m o re simple than "as heretofore s npp osec l. . ..\t Lake City the writer succeeded ( June 20th and Augnst 8th) in introducting the Reel . \scher sonia into four out o f five trees hy pinning leave s, W'ith an abundance of fungus pustules upon them, to the leave s of the trees. In two instances the fungus started in another part of the tree some distance from the pinned leaves, but as no oth e r infected trees could be found within one-half mile of these. it is considered safe to assume that the fungus started from the infected leaves placed there. In two of the successful instances the leaves with the fungus pustules u1xm them ,L ' crc dr : \' ancl had been picked about a month before being pinned into the trees, shO\ , ving that the spores of the fungus retained their vitality for at least a month and no doubt longer. It was also found that the fungus had started in three different trees at Leesburg, into which Judge J.B. Gains had pinned snme leave~.

PAGE 12

58 Bulletin No. 88. No Red Aschersonia had hitherto been observed at Leesburg, Since writing the first part of this paragraph, the writer has found the fungus started in each of thirty-seven trees into which he had pinned leaves of the Red Aschersonia six weeks previously (August 15th) at Leesburg. In all, forty-two trees had been treated in this manner, but five of them were not examined for lack of time. In many of these trees the fungus had made good headway, and in one instance Judge Gaines reported that it had started at the end of two weeks from
PAGE 13

Whitefly Conditions in 1906. 59 damage before the fungus gets it under control. The situation appears to be about as follows. During one year the fungus cleans up the fly; the second year the grove is generally clean, also the fruit; the third year the fly reinfests the grove, and the trees and fruit are again black with sooty mold; then the fungus does its work again; etc. Now, in view of the fact, that the fungus can be introduced by pinning on leaves or by spray ing on spores, the fungus should be started at the same time that the wh i te-fly larvae are first observed, and while the progress and injury of the fly may not be wholly offset, yet I believe a great deal can be done in this way to lessen the injury. It is purely a question of helping nature ( the fungus) along by guiding her at the critical moment. This is an important point. A grower should not wait for the fungus to start of its own ac cord but should start it himself as soon as he discovers the presence of the whitefly, and this should be done whether the fungus has previously been present or not. The fungus should be introduced and handled with the same ratioHal considera tion with which spraying or fumigation is carried on . Because the fungus is a natural remed y and will of itself (generally) spread and reduce the whitefly is no reas o n why rational means for artificially spreading the same should not be used. The problem o f getting sufficient fungus many involve some difficulty , but a number of nurserymen advertise citrus stock having the fungus upon it for sale , and these no doubt will be glad to furnish leaves at reasonable prices. ( See Appendix . ) SUMMARY FOR THE RED ASCHERSONIA. I. Get it into your whitefly infested trees at almost any price, 2. By spraying on the spores, 3. By pinning on leaves, 4. By planting trees with fun g us upon them, 5. Mulch the trees and where convenient keep the mulch damp by an occasional wetting. 6 . Spray the trees often with water in dry weather, where convenient, 7. Permit the cover crop to grow tall in the grove and let it remain there as long as possible, 8. Plant windbreaks. 9. Spray again with fungus spores and oftener, if neces sary, in order to get a good start of fungus.

PAGE 14

60 Bitlletin No. 88. BY SPRAYING ON SPORES OF THE FUNGUS. lf it is decided to introduce the fungus by means of spray ing on spores, care should be taken to spray against the under surface of the leaves . Future experiments may show that this precaution is not necessary but we are not likely to go very far astray by adopting it for the present. Forty well de veloped pustules having the bright red spots upon them are sufficient for a pint of water. Two well infected leave~ may be taken as representing the forty pustules but one leaf will frequently have the required number and often more. A pint of the solution, I believe, should be sufficient for a tree of ordi nary size where a very fine spray is used. From this it will be seen that spraying is the most economical in so far as infecting material required is concerned. Three thousand leaves will about fill a bushel measure . Two leaves per tree to make the spray, gives us fifteen hundred trees that can be treated with this number of leaves. Where an abundance of leaves are available the spraying solution may be made stronger; it can not be made too strong. After having poured the water over the leaves and stirred the s ame about for a few minutes, fifteen to thirty minutes sh o uld be allowed for the spores to become dissolved out of the reel spots on the pustules of the fungus. Then the mass should be stirred again, thoroughly, in order to wash out all the spores possible. Do not permit the solu tion to settle but strain the liquid at once through a piece of cheesecloth or fine wire sieve. An atomizer spray is to be pre ferred because it does not require so much liquid to spray the tree. At all events, a nozzle that produces a very fine spray should be used. The above estimate of one pint of liquid per tree was based upon an atomizer spray. If on the other hand, no atomizer is available, a spraying machine may be employed. The spraying solution should under no conditions be permit ted to stand in a copper or brass tank, for the amount of cop per that would go into the solution might be fatal to the spores, as these are very sensitive to copper. If a spraying ma chine made wholly or in part of copper or brass, must be used, the same should be thoroughly cleaned before using, and then the work should be done as expeditiously as p o ssible. If it is necessary to use the copper or brass reservoir co nnected with the spray pump or spraying machine this should be partially filled with the solution, enough only being put in. to spray three

PAGE 15

Whitefly Conditions in 1906 . 6r or four trees . Spray the solution on the under surface of all the infested leaves giving special attention to the heavy infec ted new growth. If it happens that only a limited amount of the spraying solution is available it may be diluted with water. Thoroughly sp raying all the trees with a weaker solution is considered preferable to spraying half the trees, or only part of each tree, with a str o nger solution. It goes without saying, that it would be futile to intro duce fungus into a tree not infested with whitefly. The fungi in questi o n , so far as known, can thrive only upon the whitefly, so that there \Youlcl b e nothing for them to live upon in a non-infested tree. It will al so be well to wait before introduc ing fungus into a tree until the whitefly larvae can be abundant ly found under a considerable number of leaves. To spray every tree in a grove regardless o f the individual requirements of each tree would frquently lead to waste of material and labor. The writer's plan of campaign would be as follows: Start the fungus in all the trees in which the whitefly larvae can be readily found. Later, say in three or four weeks, in spect the grove and spray all the trees not previously sprayed and which now show the presence o f whitefly. In another three or four weeks inspect again and spray. Each tree should be considered individually and treated accordingly. Any trees not showing a good start of fungus in three to six weeks should be sprayed again. wholly or in part. This kind of pro cedure should be continued from year to year, and the pre diction is made that in a comparatively few years, when the citrus growing sections of the State have in this manner been thoroughly saturated w it h the fungi, there will be no whitefly problem. I have stated above that the fungi in question can thrive only upon the whitefly larvae and pupae and this is probably true in nature. In the laboratory, however, Professqr H. S. Fawcett has been successful in growing the Yellow and Red Aschersonias and to produce spores, upon several of the media generally used for such work. There is but little doubt that the Brown Fungus can be cultivated on the same media. This opens up the possibility of producin g sp o res of the fungi in the laboratory for use upon trees . But as an abundance can generally be obtained from infected groves it is not likely that we shall very soon he compelled to depend upon artificial means for a supply . The fact, however, that a fungus can be

PAGE 16

62 Bulletin No. 88. cultivated artificially gives the scientific investigator greater opportunity for careful and varied experiments and observa tions that may eventually lead to broad scientific principles of practical value. It is considered important, especially on the drier soil, to mulch the grove or trees treated , and the more liberal the mulching the better. As already stated, this not only has the effect of permitting the ground moisture to evaporate slowly and during a longer period of time, thus increasing the humidi ty of the grove , but also some water is actually formed during the process of the decay of the mulch, and this too adds to the humidity or dampness of the atmosphere. An occasional wet ting of the mulch in dry weather is also rec o mmended, or the trees can be sprinkled, as previously suggested. Reference to the usefulness of tall cover crops and windbreaks has already been made and also to the fact that the conditions herein set forth very clo s el y approximate those existing in many groves on hammock land. The mulch, may furthermore, serve other purposes , such as harboring insects that aid in the distribution of the sp o res o f the fungus throughout the tree, or as a possible medium for the development of other stages of the fungus. I wish to state again that if the first attempt at introducing the fun g us fails t o produce a good start in a g rove , or in indi vidual trees of a grove , a second attempt s hould be made and a third one if necess a ry. This kind of sprayin g is much cheaper ( and I belie v e spraying on the spores is preferable to pinning on the leaves; but both meth o ds can be used , ) than spraying with insecticides, and is perfectly harmless to the trees. This point, furthermore , should not b e lost sight of, that the in crease of the fungu s in a tree ( other things being equal) is in the same proporti o n that we succeed in starting it in that tree . Thus, if we succeed in starting 100 pustules of fungus in one tree and 300 in another, it will be evident that the spread of the fungus in the last tree will be three times as rapid as in the first one, and hence the importance of making as good a start of fungus as possible by repeated sprayings. Attention should also be directed to the fact, that for sub sequent sprayings, fungus from the trees previously treated may be used , provided it i s sufficiently developed. This will be evident as the pustules increase in size and become a bright scarlet red in the Red Aschersonia or a bright yellow in the Yellow Aschersonia.

PAGE 17

Whitefly Conditions in 1906. When is the best time for doing this work? Future ex periments will give us more information. The months of June, July and August , as the experiments previously indi cated show, are favorable months. Ordinary periods of cold and dry weather generally have only the effect of retarding the growth of fungi. \Ve know that neither ordinary cold nor dry ing kills the fungi parasitic upon the whitefly. Note the fact already stated that leaves with fungus, and dried for a month, were as efficient as fresh leaves for starting the Red Ascher sonia and the Brown Fungus. The m o nths of September (last half) , October , November and December ( 1906) were found unfavorable, probably be cause of drought and cooler weather. No experiments in starting the fungi have been tried during January, February, March and April, yet it is hardly to be expected that these will be exceptionally favorable. l\fay being generally quite warm and immediately preceding the rainy season is believed to be a good month. and any one beginning work with the fungi at this time will hardly go far wrong. Prospective warm summer weather and rains may be taken as a guide for starting the work, and since the spores are to be mainly sprayed on the under surfaces of the leaves there is little danger that they will be washed off during heavy rains. BY PINNING ON LEAVES. To introduce the fugus by pinning on leaves I would sug gest that from one to a dozen or more well infected leaves be pinned to a tree. The number will be determined by the amount available. As Leesburg 12 leaves per tree were used. Each infected leaf should be pinned to the under surface of the leaf on the tree, with its under surface down, that having been its position before it was removed from the tree and is in closest keeping with nature. The in fected leaves might be pinned with the infected ( or under) side against the under side of the leaves on the tree, and I have ob tained good results in this way, but for the sake of keeping close to nature I advise the other way for the present . Each infested leaf should be pinned as high up in the tree as is convenient, that is, at least as high as a man can reach. To pin it higher is desirable. It should, furthermore, be so placed that the drip from it, when it rains, will drop onto a cluster , or s everal clusters , of leaves beneath it . Use two pins

PAGE 18

Bulletin No. 88. for each leaf. I have observed that the fungus sometimes starts on the leaves beneath the pinned leaf rather than at the leaf to which the infected leaf was pinned. It is well to pin a small piece of paper on the upper surface of the leaves to which the infected leaves are pinned as a mark. This will greatly facilitate later inspections. THE YELLOW ASCHERSONIA. This fungus, known at present to occur at \Vinter Park, Orlando and :Mims is very much like the Red Aschersonia, but the pustules are of a rich yellow color. It appears to spread rapidly; ninety per cent. of the larvae on some leaves examined in the laboratory being infected. It should be treat ed exactly like the Reel Aschersonia, as the conditions under which it thrives seem to be the same, and each produces spores in abundance. THE BROWN FUNGUS. Plate III. Fig. 3. \\That has been said for the Aschersonias applies ( with one probable exception) also to the Brown Fungus. The spores of the Brown Fungus have not been discovered, and this fact makes it uncertain whether it can be successfully intro duced by spraying. This leaves two methods available for in troducing the Brown Fungus: (I) to pin leaves having white fly larvae infected with the fungus upon them onto the leaves of the tree into which it is to be introduced; ( 2) to plant small trees, having the fungus upon them, into the grove as previously explained for the Reel Aschersonia. Since writing the above paragraph I have been agreeably surprised to find that the Brown Fungus has started in four of the eight trees sprayed at Leesburg (August 15th '06) with spores of the Reel Aschersonia and previously noted in this paper. Some Brown Fungus was scattered over the leaves with the Red Aschersonia, used in preparing the mixture of spores and water for this spraying, and this clearly indi cates that the Brown Fungus can be started by spraying. In spection of these trees September 29th, 1906, did not reveal any of the Brown Fungus, but at a later inspection (December 21st, 1906) leaves having an abundance of this fungus upon them were found in four of the trees. Further experiments

PAGE 19

TVhitefi3 Conditions in 1906. will be necessary to determine whether the method of starting the Brown Fungus by spraying can be made practical. How ever, in preparing a mixture of spores and water of the Red or Yellow Aschersonias for spraying. it will not be amiss to mix in any leaves at hand having Brown Fungus upon them. It may be well, however, to thoroughly triturate the pustules of this fungus to insure getting an abundance of small particles of it into the mixture. As already stated we are not certain that we have discovered the spores of this fungus, and it may have started in tte trees at Leesburg from small particles that were in the mixture sprayed into the trees. I do not think that the infection could have come from another source since inspection of neighboring trees that had not been sprayed showed no signs of it. It has been suggested that the Brown Fungus probably spreads more rapidly in cool weather that the Aschersonias, and this observation at Leesburg seems to be corroborative of this suggestion. Further observations will determnie this point. That this fungus can be introduced by planting small trees having the Brown Fungus upon their leaves was first demon strated by Dr. H. T. \Vebber and this method has since been successfu.lly emplo}ed by many individuals throughout the State. It will be preferable, however, to use the method of pin ning on leaves as it is easier and more practicable. The writer has something like seven instances on record where he succeed ed in starting this fungus by pinning on leaves. Dr. H. J. Vv ebher, also notes an instance where this fungus was started bv this means (Bull. 13, U. S. Dept. Agri., Div. Veg. Phys. a;1d Path.). SCALE AND WHITEFLY. The question is sometimes asked, "If I depend upon the fungus to keep down the whi,tefly, what shall I clo to keep down the scale? If I spray for the scale then I will kill the fungus." There are several fungi that are very effective in reducing the scale, and it may be desirable to introduce some of these. These fungi are the Red Headed Scale Fungus (Sphaerostilbe coccophila. See Bulletin 41), the Gray Headed Scale Fungus ( Ophfonectra coccicola), and the Black Scale Fungus ( M yrangi11111 Duryii). and material can be obtained without nmch diffict1lty in many parts of the State. The best

PAGE 20

66 Bulletin No. 88. present known method for introducing them is to tie leaves and twigs having some of these fungi upon them into the scale-infested trees. If the case requires immediate and drastic measures a thor ough spraying of the tree with some good spray should be ef fective in reducing both scale and fly. Then, when the fly again shows signs of increasing in the tree one of the whitefly fungi should be introduced as previously directed. TRIMMING TREES, Trees infested with the whitefly and located where ve hicles and persons pass, should be trimmed sufficiently high to give free passage; so that the flies cannot be brushed off and in that manner carried about the country. There is no doubt that this is one of the chief means by which the fly is carried from place to place, and it would require but very little effort along this line to reduce this source of infection. Everybody owning infested trees should become awake to the situation and do their part. In towns the city officials could compel the proper trimming of trees, while Boards of Trade could warn people, and instruct them in the desirability of keeping their premises in proper condition. I desire here to commend the Leesburg Board of Trade for their efforts in getting infor mation and their foresight in issuing a circular to interest the people. The railroad trains carry the fly farther than perhaps any other agent , and something could be done to lessen this means of distribution if railorad officials as well as people along the line would see to the proper trimming and destruction of infested trees and bushes on and near the right of way. This suggestion is important and should receive attention. SPRAYING AND FUMIGATION. For more complete directions in regard to spraying with contact insecticides, I shall refer the reader to the following bulletins: Press Bulletins 4 and 56 treat of the whitefly and methods of repression, and are both available for distribu tion; Bulletin 67 is the standard bulletin on the whitefly and is , out of print but thousands of copies have been distributed throughout the State; Bulletin 76 is on Insecticides and Fungi

PAGE 21

Whitefly Conditions in 1906. cides, and is full of valuable information on spraying and fumigation in general. Judicious spraying with insecticides should be effective in reducing the ravages of the whitefly provided a grower can persuade his neighbors to spray at the same time. Co-operation is absolutely necessary for effective spraying. December, January and February are the best months to spray for the whitefly as it is then in one or the other of its several larval stages or pupae under the leaves , and is more readily killed in these stages . It is practically useless to spray for the adults since the females lay their eggs when they are from 18 to .30 hours old, so that the g-rower would have to spray every day during the swarming periods to insure killing them before they laid their eggs. The eggs are not readily killed either by spraying or fumigation. Spraying to be effective should, furthermore, be drastically thorough, and one such spraying in -zcti11ter after the fruit is picked and danger from frost is past will be worth more than several less thorough applications. To postpone spraying until danger of frost is past may save much labor and spraying material, since, should the leaves be dropped by freezing but little if any spraying would be necessary. In case of a freeze sufficiently severe to cause many leaves to drop, these should be plowed under or burned to insure against the possibility of any nearly mature whitefly from completing their development. It will thus be evident that a freeze may be a blessing to a whitefly infected grove. Summer spraying may be practiced when conditions re quire it. The difficulty with spraying lies not so much in getting an insecticide that will kill the insect as in applying it so that all or a very large percei:it. will be killed. Any of the contact insecticides ( including whaleoil soap) generally used for destroying insects on citrus trees, will be found useful. However, all kinds of spraying with emulsions and other chem ical compounds generally in use, appear to be more or less in jurious to orange trees. Of these, whaleoil soap is probably the least injurious. Before spraying, all excessive foliage should be removed from the trees by a thorough trimming. Spraying with insecticides is, also, more or less harmful to the Fungi, so that having decided to use the Fungi, spraying should be discontinued. Fumigation has not been sufficiently tested in this State to

PAGE 22

68 Bulletin No. 88. warrant its being" 'boomed' into disfa, , or," as Professor H. A. Gossard has aptly put it. COPPERAS. Much has recently been said and written in regard to the use of copperas for killing the . whitefly . Examination by com petent persons of groves treated with coppera$ indicates that the latter is not efficient for reducing the whitefly, to sav nothing of extermination. In one , instance (Orlando) it wa's reported that an application of copperas had killed the whitefly. but examination showed the trees treated to be just as full of larvae and pupae as the trees hot treated. The following is taken )rom the Florida Farmer and Fruit Grower of August 31st, 1906 . "ROYAL PALM NURSERIES, REASONER BROS., Oneco, Fla., August 22, 1906 . Editor Farm and Fruit-Grower: * * * I will again state, however, that I think it sim ply impossible to kill or drive away the whiteflies by any such mild measure as spreading copperas under the trees. I have evidence that it will not affect them at all! In Bradentown hvo of the best known citizens used copperas liberally on the soil, giving several applications through the year; 2 to pounds per tree on from 100 to 200 trees each were used by them about six years ago and no effect whatever was no, tived on the flies which continued as thick as ever for some years thereafter. Now that the natural fungoid enemie s of the flies are present, the groves look very well and are carry ing a fair crop of fruit. The fungus ( two species) keeps groves generally clean in the infected localities o-f thi s, Ma11atee county, where the flies have been known about fiften years. Parts of the count~ have never had the flies present at all, ancl if we have normally wet summers the flies can never get bad again wherever the fungus has been introduced . It remains the only knnwn suc cessful "cure" for whiteflies." (Signed). E. N. REASONER.

PAGE 23

11 )1itefly Co11ditions 1 1906. SOOTY MOLD. This mold ( a species of meliola) of a sooty black, as its name implies, is found wherever whitefly or other insects, that excrete a sweet solution (honeydew) occur. As this sweet secretion ( also relished by ants ) nearly ahrnys collects on the upper surfaces of leaves, it follows that the mold. which thrives in this secretion, also occurs on the upper surface. Other insects that are accompanied by the sooty mold are: mealy bugs. plant lice (aphids), soft scale (Lecaniums), wax scales, cottony cushion scale , and others, so that sooty mold visible upon a tree is not necessarily a sure sign of whitefly. This fungus does not ordinarily become visible until after the trees have been infested by the whitefly for some months. THE SNAIL. There appear to be several species of snails that will feed upon the sooty mold accompanying the whitefly. Besides the .\tianatee Snail (B11Hm11/11s Dor111ani), another species brought from Miami by Professor Rolfs and spoken of by us as the Miami Snail. is also a good feeder upon the sooty mold and may become of considerable value. Their usefulness consists mainly in the fact that they will dean the rnoty mold from all parts of a tree and the fruit. They do not feed upon the white fly la1vae as sometimes repoPted. That they will swallow and destroy some larvae and eggs is a fact but this is only inci dental, the laraw and eggs being swept off the leaves with the mold. This is, however, not of frequent occurrence since the snails seldom feed on the under surface of the leaves where the eggs and larvae are found, except when food is getting scarce. To those who have or suspect the presence of snails in their trees, the following may be recommended: Keep a lib eral amount of mulch. coarse and fine mixed, around the base of the trees and hang pieces of burlap into several of the narrowest crotches oi each tree. The purpose of the above i,to provide moisture-conserving places in and about the trees in which the snails can lay their eggs and conceal themselves. The above directions are important.

PAGE 24

Bulletin No. 88. LIFE HISTORY OF THE WHITEFLY. Pla!es I, II and Ill. The name whitefly is a misnomer, the insect in question not being a fly at all but a member of the Hemiptera, the order to which the plantlice and scale insects belong. Flies have only two wings, but the whitefly has four, which fact at once sepa rates it from the Diptera, or flies proper. There are three well defined broods of the whitefly, with an interval of several days to several weeks between each brood, when few or none are seen on the wing. The first brood generally appears sometime during March, April or May, the second during June, July or August, although this summer it appeared as two quite distinct divisions at Lake City, and the third during September and October. Variations that occur are due to variations in the seasons and the locality. No doubt many people supposed that they had exterminated the whitefly by means of some treatment ( copperas) when one or another of the several broods disappeared from the wing-. Larvae ( the young stages) and pupae ( the transformation stage) of the whitefly can, however, always be found on the under surfaces of the leaves, and seldom elsewhere . The lar vae are scale-like ( Plate III, Fig. 1.) and closely appressed against the leaf. They vary in size from the very young, just visible to the unaided eye, to the fully matured larvae which measure about one-sixteenth of an inch in length. The larvae are white and translucent with a tinge of yel low, and almost invisible upon the leaf . By holding a leaf ( under surface up) at the ends, with the thumb and forefinger o f each hand and then rubbing lengthwise along the leaf with o ne of the unused fingers, the larvae will appear as flattened whitish scales. The pupa ( Plate II, Fig 8) ( plural pupae) is the tran s formation stage from the larva ( plural larvae) to the adult, winged fly. The pupae are readily visible as yel lowish white, plump, oval bodies with a dark reddish spot on the back. From the pupa emerges the adult winged fly. The little white cases, with a T-shaped split on the back, and found on the under surface of a leaf , are the empty pupa cases from which the adults have emerged ( Plate II, Fig IO). The eggs ( Plate I, Fgs. 3, 4) are just visible to the unaided eye as a fine dust upon the under surface of the leaves . An ordinary hand

PAGE 25

Whitefly Conditions in 1906. lens ( magnifying glass) will show them as little egg-shaped bodies much resembling grains of wheat. There are, therefore. four stages in the life history of the whitefly: The egg visible as a fine particle of dust; the larva, a flattened scale; the pupa, plump and readily visible; and the adult winged insect. All of these stages are nearly always confined to the under surface of the leaves. ( Plates I, II, III.). The following facts are a summary from Professor H. A. Gossard's Bulletin 67. Twenty thousand eggs have been esti mated on a large orange leaf . From observations made in the laboratory, egg laying begins when the female is from eighteen to thirty hours old, and from seventeen to twenty-five eggs are deposited. These eggs are generally all laid within twenty-four hours after the first egg has been laid. Her length of life has been estimated at from three days in warm weather to three weeks in c o ol weather, and the complete length of life cycle from egg to adult is from forty or fifty days in summer to six months in winter. It will thus be evident that in order to spray successfully for the adult fly it i s necessary to spray practically every day to catch the females before they lay their eggs; an impossible task when a man has more than a few trees. FOOD PLANTS. There appears t o be a great deal of misapprehension in regard to the number of food plants of the whitefly. Every tree, bush, or weed in the hammock is not a food plant, as many suppose. The definitely known number of food plants is a relatively small o ne. I cannot do better, perhaps, than to quote verbatim the page on Food Plants from Professor Gos sard's Bulletin 67. "Vvhite flv o c curs upon all varieties of citrus . C. trifolia ta is, of course: only infe s ted during the summer months, being a deciduous varietv. The deciduous character of some of the C. trifoliata hybirds 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 ovestocked. The adult flies as well as the larvae sap the leaves, and their taste for certain varieties leads them to oviposit on these when pos sible, going to less favored plants only as they are driven by

PAGE 26

72 Bulletin No. 88. necessity to do so. Besides citrus, the Chinaberry tree (Melia Azederach), Viburnum nudum, the Cape jessamine ( Gardenia florida), the Japan persimmon ( Diospyros kak-i), California privet (Ligustruin Amurense), Golden privet (Ligustrum sp.) and Mock orange (Pnmus Caroliniana) are food plants. Va rious species of Ficus are said to be food plants; I have seen it on two species, F. altissima, and on an unknown species introduced from Costa Rica. The water oak ( Quercus aquatica) is ocsasionally infested, according to Quaintance, and I have taken two or three larvae advanced to third and fourth stage on sc rub palmetto. Their presence upon the latter plant is very rare, having been ob served but once, though opportunities have been plentiful. Prickly ash (Xanthoxylum sp.) is reported as a food plant upon what 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." To this list but few if any additi o ns can be made at this tinie. The Umbrella tree, a variety of the Chinaberry, be comes as much infested as the latter. During the past summer the Prickly ash ( F agara C lava-H erculis) has been observed to be an undoubted food plant and several badly infested trees were found at Lake City. A similar observation was made at Leesburg. Specimens of whitefly were also found upon the wild persimmon. ( Diospyros Vrginiana) along a roadside south of Orlando. The umbrella tree and the wild persimmon . seem thus to be about the only additions that we can make at this writing. That a definite knowledge o f the food plants of the white fly is important in devising means for its control will be evident to all, and all persons interested should send samples of any in fested ( or supposedly infested) plants, not in the above list, to the Experiment Station at once upon their discovery, so that we can make our knowledge as complete as possible. Were we to count all plants upon which a few larva•e may occasionally mature, the number of food plants would be increased to two or three times the number lisited; but the majority of these would represent plants that become slightly infested only when in close proximity to some tree that is badly infested. Thus Dr. Webber states (verbally to the writer) that larvae will occasionally mature upon magnolia under such conditions, It appears that plants, in their food relations to ,the white

PAGE 27

TVhitefly Cond , itions in 1906. 73 f!y may be div id ed into three classes: ( r) Food plants proper, ( 2) Partial food plants ( those not generally infested or but little infes , ted) and ( 3) Plants immune. The majority of plants listed above belong to the first class , and all but six, are of Oriental origin, which furthermore , suggests that the fly is of Oriental origin. These six native plants, Viburnum nudium Mock Orange ( Cherry Laurel,) Water Oak , Scrub Palmetto, Prickly Ash, and ' Wild Persimmon become only slightly infested ( Prickly A s h excepted) and belong to class two . QUARANTINE. In localiti es ,,here the, whitefly is n ot present , or where the amount present is very small and the chances for its elimi nation by a v i goro u s application of drastic method s are favor able, quarantining should be effective to a great degree, at least in putting off the evil day, and thu s be the means of s aving thousands of dollars. This could be, and in fact has been , made effective in several different ways: by keeping out suspi cious nursery stock; clo sin g up pr ivate roads and gates and keeping o ut vehicles corning from infested districts; keeping out pickers' implements when coming from infested district s, or compelling their disinfection at some safe point. NURSERY STOCK. In buying nur s ery stock the buyer can well afford to tra,el to any part of Florida to determine for himself the condition of the stock he desires to buy , provided the section in which he desires to plant the trees is free from the whitefly. If the section i s already i nfested this is not so important. On the other hand , th e present status of our knowledge indicates that it would be perfectly s afe to buy nursery stock from any infested district provided the same be cut back , defoliated , and as a special precaution , fumigated with hydrocyanic acid gas. \Vhile eggs are frequently laid upon the tender wood of growing shoots , yet no larvae ha ve ever been known to be come mature there, and whenever this wood is cut back and the rest defoliated, and the tree fumigated as a special precau tion, reasonable safety can be assured, especially during De cember, January and February , when absolute safety can be guaranteed. During the s e months all the eggs ' have hatched

PAGE 28

74 Bulletin No. 88. and proper fumigation can be depended upon to kill any stray larvae or pupae that might be attached to the bark. VEHICLES AND PRIVATE ROADS. Private roads should simply be closed to all vehicles, at least to any whose previous whereabouts are uncertain. This has been done in many places and no doubt has saved growers thousands of dollars by delaying infection, even if it was not effective in keeping out the whitefly permanently. PICKING IMPLEMENTS. The picking implements u s ed by pickers, coming from an infested district have been excluded, from at least one section, ( the Subpeninsula) of Florida, and this no doubt was one of several important factors that aided in keeping this section practically free from the whitefly for many years. On the other hand, a thorough disinfection of the implements, includ ing ladder s, sacks, etc ., a s well as the outer clothin g of the picker s should be effective in reducing the chances of infection from thi s source to nothing. It has been sugge s ted that where picing o f c i trus fruits is let by contract a clause requiring dis infection of the implement s and clothing should be included . It i s the writer's opinion that thi s i s a very valuable su g gestion . Ladders could be best d i sinfected by painting or spraying them with kerosene or kerosene emulsion, whaleoil soap, linseed oil , or by slowly passing them through the flames of a fire when the other means are not at hand. For disinfecting the picking bags, clothing, etc., n o thing, perhaps , would be simpler than placing these in an air tight barrel or box , pouring a liberal quantit y of gas o lene over them , and cl o sing the barrel or bo:x: tightly for several hours. If carb o n bisulphide is at hand this can be used instead of the gasoline, and a treatment of an hour is sufficient. Three ounces ( about one-fifth of a pint) of carbon bisulphide will be sufficient for a case the size of a bar rel. If gasoline is used the dose should be several times as large. Finally, if a fumigating box is at hand, such as is used for fumigating nursery stock with hydrocyanic acid gas, the implements etc., can be fumigated in this, using the normal dose of the gas for forty minutes . The picking bags, etc. , should be arranged loosel y and with s paces between them to

PAGE 29

Whitefly Conditions in 1906. 75 insure a perfect circulation of the vapor or gas used, whether in barrel, box, or fumigating box. PLANTS TO BE CONDEMNED. The following plants should be condemned by every citrus grower and by all people in any community where citrus grow ing is an industry. These plants are: the Cape Jessamine, the Chinaberry, the Umbrella Tree, the Prickly Ash, Golden Priv et, California Privet, the Tri foliate Orange ( Citrus trifoliata) and any useless and abandoned citrus of all kinds. The Mock Orange ( or Cherry Laurel) should be included in this list whenever it is observed to become badly infested. These plants are generally of little value and can well be spared and re placed by others not subject to attack by whitefly. Including the trifoliate orange in this list does not preclude its being used as a foundation stock in nurseries. Of course anyone having only one or two of these trees may overcome the danger of their becoming a source of infection by spraying them to the extent of defoliation, or they can be defoliated by trimming; but in either case the work must be done thoroughly, every leaf must come off, and as a special precaution the tree should be sprayed besides, to insure the killing of any larvae that might be on the buds and elsewhere. Such an operation, however, might have to be repeated each year, and possibly oftener, so that cutting down and burning such trees and shrubs is the better plan. Do not cut them dmmi and then let them remain about the premises so that the fly can continue to develop, but burn them at once! It may seem akin to vandalism to be expected to sacrifice some of our garden and orchard pets, but all successful warfare consists in some degree at least in reducing the number of the enemies' strongholds. One Cape jessamine and two or three umbrella trees in a certain yard in New Smyrna seem to be responsible for the spreading of the whitefly in that place. In looking over this ground one is soon impressed with the fact that these trees were the focus of infection.

PAGE 30

EXPLANATION OF PLATE I.* Aleyrodes Citri. Fig. r.-Adult female with expanded wmgs much en larged. Fig. 2.-Aclnlt female with wings folclecl over the body in normal roof-like position. Fig. 3-Egg and footstalk of same, greatly magnified. Fig. 4.-Eggshell, showing the split through which the larva emerged. Fig. 5.-Tip of male abdomen, showing claspers. Fig. 6.-~\ntenna, showing annula:ted joints. Fig. 7.-Fore margin of front wing. INSECTS SOMETIMES MISTAKEN FOR A. CITRI. Fig. 8.-Larva of Aleyrocles floridensis greatly magnified. Fig. ro.-Greatly enlarged section of waxen fringe sur rounding A. floridensis Fig. r r.-Outline of Lecanium hcspcrid11111. (A soft scale). *All _plates are the same as in Bulletin 67. By Prof. H A Gossar cl.

PAGE 31

JO 11 PLATE I.

PAGE 32

EXPLANATION OF PLATE IL Aleyrodes Citri. Fig. I .-Larva, first 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 operculum with lingua in the center. Fig. 8.-Pupa, showing embryo an(! distribution or 0 1w . 1ge colorec~ areas, waxen tufts extending from the breathing tubts are sho~vn. Fig. 9.-Adult with folded wings, emerging from the pupa case. Fig. 10.-Empty pupa case, showing split through which the fly emerged.

PAGE 33

\ ' l I r -----------I --------------I I ~/, \ ~/ ~ ' \ } PLATE IL

PAGE 34

EXPLANATION OF PLATE III. Fr01n Photographs. Fig. I .-Larvae and Pupa of Whitefly on Orange. Fig. 2.-Recl Fungus, Aschersonia Aleyrodes, Webber. Fig. 3.-Brown Fungus on Orange. Ag. 4.-Aclult Flies and Eggs on Orange.

PAGE 35

Flg. r . Fi g 3. F i g. 2. Fig 4 . PLATE III.

PAGE 36

Bulletin No. 88. 81 APPENDIXES. I. WHERE TO OBTAIN FUNGUS. The following persons living in Florida have consented to furnish leaves having fungus-infected whitefly larvae and pu pae upon them at fifty cents per one hundred leaves. A. J. Pettigrew. :Manatee, (Red and Brown), A. F. \Vyman. Braclentown, (Red and Brown), F. D. Waite, Palmetto. ( Red and Brown), C. A. Boone, Orlando, (Red, Yellow and Brown), C. B. Thornton. Orlando , (Yellow and Red). Larger quantities can no doubt be obtained at reduced rates. 2. THE FUNGI IN FLORIDA. The following data have been taken from Bulletin No. 13, U. S. Dept. Agr., Div. Veg. Phys. ai1d Pathology, by Dr. H. T. \Vebber. Red Aschersonia first observed: Panasoffkee, ; Crescent City, August 1893; Bartow, January 1894; Citra, December 1894*; Myers, June 1895*; Gainesville, Man atee, 1893-1897*. (Years with stars may be too great by one or several years) . Brown Fungus first observed: Manatee, March 1896. Yellow Aschersonia first recognized as distinct from the Reel Aschersonia by Professor P. H. Rolfs on specimens sent from Winter Park by J. F. Adams, September, 1906. 3. SPRAYING APPARATUS. For those who expect to give the fungi a thorough trial it will be desirable to have a special outfit for spraying the mixture of fungus spores and water. Having a special outfit and using it only for the fungi, there will be no risks of poi soning the spores by small traces of any chemicals that may re main in an old outfit, especially one used for spraying fungi cides. The writer has found the Lowell Fountain Compressed Air Sprayer, made by the Lowell Specialty Company of Lowell

PAGE 37

82 Whitefly Conditions in 1906. Michigan, a very desirable machine. The tank holds three gallons and is furnished with nozzles giving three sprays of diffrent degrees of fineness, and a solid spray. The finest spray makes a mist and this is the one to use for spraying the fun gus spores. It should be ordered with about ten feet of ex tension pipe for spraying in the tops of trees. It is made of brass or galvanized steel. The latter metal should be ordered for spraying the fungi. E . 0. Painter & Company, Jackson vi!le, are the agents. C o st complete about six dollars. The "Auto" Compressed A,ir Sprayer sold by Peter Hen derson &Company, New York, appears also to be a desirable machine. It can be obtained, made from galvanized steel, for $6.oo, extension pipe extra. Order with nozzle oapable of producing spray as fine as mist. 4. THE WEATHER AT LEESBURG. The following is an abstract from notes kindly kept for the writer by Mr. H. S. Budd, of Leesburg, during the period of the observations at that place noted in the text. These ob servations were begun August 15th and terminated December 22nd, 1906. Unles s otherwise mentioned, the weather was fair during this period. August: 17th , s o me rain; 19th, light shower; 23rd, 53/2 hrs, rain; 24th , cloudy; 25th, heavy rain o ne hour, then steady; 26th, cloudy all day with frequent rains ; 27th, cloudy all day, some rain; 28th, heavy showers and rain all day; 30th , rain and thunderstorm ; 3 rst , fine but rain after dark. September: 3d, partly cloudy and heavy storm; 8th, fine but one half hour rain at 7 p . m.; 9th , heavy storm p. m.; 10th, little rain; 18th , rain; 23d , light rain for one hour; 24th, rain; 25th, rain; 26th, rain; 27th , light rain. October: rst , rain and thunderstorm; 2nd , rain; 5th, rain; 8th, little rain; 9th , slight rain; I 5th , s o me rain; 16th, fine and cloudy; 17th, wet; 18th, rain, 19th , cloudy; 20th, mostly cloudy; 21st, rain; 22nd, cloudy; 23d, drizzle; 24th, dull; 28th, colder; 29th, colder. December: Drought broken night o f 19th; 19th and 20th cloudy with light rains .

PAGE 38

X4 /fo//cti11 Xo. 88. _ '\PPENDIX 4. THE WEATHER AT LEESBURG. The following notes have been inserted for the pnrpose of showing the contrast between the weather conditions as they existed during the mouths of June, July, August and part o f September, when the Fungi started readily and spread rapidly, and the conditions during September, October, November and December. when this was not the case. There being no W eath e r Bureau Station at Leesburg, Vfr. H . S . Budd kindly kept a record of the rainy clays for me. but as I have since been able t o get a complete rec o rd taken at Orange H o me, only about eight miles from Lee9burg, I haYe decided to let the latter r e cord represent the conditions at Leesburg. but giving also Mr. Budd's rec o rd. It will be •>bsened from the table that during the month s most fan,rable for the Fungi. the mean temperature was above 80 ancl the precipitation (rain) very abundant; that dur ing the les s fa,orable ( 01 unfa vo rable) month s th e temperature either dropped considerably bel o w 80 o r the amount of precipi tation became strikingly less, or both. No experiments in s tarting the Fungi have been tried during January, February , March, April or May. hut judged by the conditions repre sented in the table, the first four months were very likely un fav o rable. On the other hand. the Fungi would probably have done well during May. there being then an abundance of rain and a temperature fairly high. The weather conditions here indicated were, of course, not exactly the same throughout the State , and variations will also occur from year to year. These observations, and others. indicate, however, about the time when we may expect to get a good s tart of Fungus and when we may expect to get only a poor start o r none at all. Table showing mean temperature in degrees Fahrenheit. precipitation in inches . and number of rainy days at Orange Home, Sumter county . ==== I JaM. F;i;_ M,,. , April I May I June I July A~~~ -, S,pi ., Oc t ~ N ., . , ll,~ :Meai:i ~emp ........... -59 1 . W . 8 6;18 7? . 7 G 8 1.3 8 0 . 7 81 6 81.6 72 67 .8 f>9 .6 Prec1p1tation .. .. . 5G . 4 1 . 0 2.48 2 31 1 fi 25 1 9.05 1 8.41 7 8 l.89 I 1.23 .4 . 14 Rainy days . . .. _ o 6 8 1; JO , 15 20 15 12 r, 3 l Mr. Budd's record' ..... ! .. i ..... , . . . . . . . : . ... ; ~• ' 10 11 1 0) 2 * Last half. f Or mor e.

PAGE 39

H / hitcfly Conditions in 1906. AFTER FREEZE SUGGESTIONS. In trees and groves where the friendly fungi are found in abundance, it is advised to collect large quantities of the dead leaves still found clinging to the tre es, 01 fallen leaves, with plenty of fungus up on them. These should be dried an