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THE COMMON MEALY3UG AN
CONTROL IN CALIFORNIA
-5
R. S. WOGLUM AND J. D. NEULS
Entomological Assistants, Investigations of Insects
Affecting Tropical and Subtropical Fruits
rJ* ~
FARMERS' BULLETIN 862
UNITED STATES DEPARTMENT OF AGRICULTURE
Contribution from the Bureau of Entomology
L. O. HOWARD, Chief
Washington, D. C.
September, 1917
Show this bulletin to a neighbor. Additional copies may be obtained free from the
Division of Publications, United States Department of Agriculture
WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917
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NO ONE METHOD for the control of the common mealybug
can be recommended under all conditions. The remedy
or remedies to be used will depend upon whether the trees
are in house lots or orchards, whether few or many, and the
infestation light or severe. In the case of severe infestation
it will depend also upon the kind of fruit. This insect infests
oranges of all varieties, grapefruit, lemons, and all other kinds
of citrus fruit grown in California, causing deformity, weak-
ening and dropping of much immature fruit, and the dis-
coloration and weakening of the rind of the fruit maturing.
This bulletin discusses the three remedies which have been
widely used; namely, fumigation, spraying, and the artificial
spread of insect enemies, points out the sphere of usefulness
of each method, and shows, on pages 14-15, how they may be
combined so as to secure complete control.
An important part of the procedure recommended is the
banding of trees with a mixture consisting of sulphur and a
sticky material used to protect trees from insects. This keeps
off the Argentine ant and other ants which attend and foster
the mealybug and hinder or prevent the good work of insect
enemies which otherwise might hold it in check. The method
of preparing the mixture and applying the bands is described
on pages 12-14.
Where the insect enemies are few or absent, or where they
are themselves heavily parasitized, the trees should be sprayed
or fumigated, and colonies of effective enemies should be in-
troduced.
THE COMMON MEALYBUG1AND ITS CONTROL
IN CALIFORNIA.
CONTENTS.
Page. Page.
Nature of injury and host fruits preferred.... 3 Control of the mealybug-Continued.
Characteristics and life history In brief....... 4 Control by natural enemies ............ 10
Control of the mealybug.................... General recommendations .............. 14
Fumigation ........................... 5 Preventing spread through picking boxes
Spraying ............................... 7 and by pickers........................ 15
F AILURE of control methods against the common mealybug in
California, together with its continued spread and the recent
severe outbreak at Uplands, Cal., of a previously unknown species,2
has caused mealybugs to be probably the most feared insect pests of
citrus fruits in southern California to-day. The common mealybug
is reported as destructive in Los Angeles, Orange, Santa Barbara,
San Diego, and Ventura Counties. Fortunately, however, only a
small percentage of the citrus acreage in these counties is now in-
fested by this insect.
'The common mealybug is of world-wide distribution and omnivo-
rous habits. It appears first to have been reported in California as
an orchard pest near Los Angeles more than 30 years ago, and sub-
sequently came to notice in Paradise Valley, San Diego County. Its
sporadic outbreaks continued to be of mere local concern until an
extensive and severe infestation appeared in Ventura County in
1907-8, simultaneously with new but lesser areas of infestation in
Los Angeles, San Diego, and Orange Counties.
NATURE OF INJURY AND HOST FRUITS PREFERRED.
A severe infestation of the common mealybug is well illustrated in
figure 1 and in the illustration on the title-page. Immature fruit
may be deformed or may become so weakened that it drops. Ma-
turing fruit is frequently discolored, resulting in a high percentage
of culls or fruit of low grade. The cottony secretion covering the egg
masses is unsightly, and the sooty mold which develops in the honey-
dew exudations necessitates washing the fruit. Abnormal decay
1 Pseudococcus citri Risso. 2 Pseudococcus citrophilus Clausen.
FARMERS' BULLETIN 862.
FIG. 1.-Lemon infested with the common mealybug.
usually follows the washing of this rind-weakened fruit. A severe
infestation may result in partial or even complete defoliation of the
trees. The lemon, grapefruit, and navel orange are preferred host
fruits, although other varieties may be attacked severely.
CHARACTERISTICS AND LIFE HISTORY.
An idea of the superficial appearance of the common mealybug
may be obtained from figure 2. The body of the insect is covered
with a white waxy secretion, which is most pronounced in a bordering
fringe of short filaments. The female retains the same general ap-
pearance through all stages of development from larva to adult.
The male in its early stages is very similar to the female, but about
four weeks after hatching it forms a cocoon, and from this it emerges,
from 10 days to two weeks later, as a very small and delicate, light
olive-brown, winged, gnatlike adult. Reproduction takes place from
eggs deposited in a cottony sac secreted by the mature female. The
number deposited depends on the size of the insect and varies from
less than a hundred to more than a thousand, the average production
of a female mealybug on green fruit being between 300 and 600 eggs.
The length of a single generation on orange trees under the climatic
conditions of Pasadena, Cal., during 1914-1916, varied,from a mini-
mum of 36 days during the summer to approximately six months
'during the winter. There are three more or less distinct generations
a year on the citrus trees of southern California.
As a rule the infestations in the late winter and spring are so
light as to escape notice, but later the crowding of the young insects
on the small fruit, followed by the production of egg sacs in early
summer, readily reveals the presence of the pest, and the maximum
infestation and injury usually come in the early autumn with the
second generation of mealybugs.
THE COMMON MEALYBUG IN CALIFORNIA.
CONTROL OF THE MEALYBUG.
Three methods of control-fumigation, spraying, and the coloni-
zation of natural enemies-have played -an important part in com-
bating the mealybug on citrus trees and have been esteemed variously
as the most promising. The studies carried on in southern Cali-
fornia by this department indicate that no one of these control
methods is applicable or preferable under all conditions of infesta-
tion, but by proper combination of these methods, and with the addi-
tion of banding to exclude ants, satisfactory control may be accom-
plished.
FUMIGATION.
Fumigation with hydrocyanic-acid gas as generally practiced for
the black and red scales is a failure against mealybugs. No instance
has been observed where the usual commercial treatment of an in-
fested orchard with this gas has controlled this pest. Although
records taken within a few weeks after fumigation have shown a
reduction of the mealybug, such reduction was found invariably to
be due largely to the action of natural agencies and doubtless would
have occurred even though the trees had not been treated-a consider-
ation seldom taken into account by the orchardist or commercial
operator.
FIG. 2.-A group of common mealybugs. Enlarged about 9 times.
6 FARMERS' BULLETIN 862.
Table I sets forth the general results of experiments made to test
the value of fumigation. The work was performed during the years
from 1909 to 1917, under the climatic conditions normal to orchard
fumigation in southern California.
TABLE I.--Rsults of fumigation cithl hlydrocyanic-acid gas against the common
mealybug.
A. 8-OUNCE U. S. ARMY DUCK TENT.
SINGLE CHARGE.
Dosage
schedule. Exposure. Results.
No.11...........1 hour......... Small percentage killed. Commerciallyineffective.
Two and three .....do........ 85 to 95 per cent killed.
times No. 1.
REPEATED CHARGE UNDER SAME TENT.
First charge. Second charge.
Results.
D Exposageure. Dosage exposure.
schedule. sure, schedule. Exposure.
No.1............. 30 minutes.... No. 1...... 30 minutes.... Small percentage living.
One and one-half .....do......... No.1 ..... 1 hour ...... 99 per cent killed.
times No. 1.
No,1............. 1 hour.. ... No....... ..do........ Do.
B. GAS-TIGHT TENT.
Sodium cvanid
peSr 1 ca ee Exposure. Results.
1 ounce.......... 1 hour......... Sometimes a few living; usually all killed.
1 ounces ........ .....do......... All killed.
C. GAS-TIGHT BOX OF 100 CUBIC FEET CAPACITY.
ounce .......... 45 minutes.... A number living.
ounce .......... hour........ A few living.
ounce.......... 2 hours........ Sometimes a few living.
Sounce......... 4 hours........ All killed.
1 ounce......... 45 minutes.... Usually a few living.
1 ounce .......... Ihour......... All killed.
1 This schedule is given on page 34 of Bulletin No. 90 of the Bureau of Entomology, U. S. Department
of Agriculture.
These results show the ineffectiveness of single-dosage fumigations
under army duck tents, even where excessive dosages are used. Re-
peated charges give better results but can not be recommended except
in the case of a limited number of trees where other control measures
are not readily available, or where cost and possible injury are sec-
ondary to immediate control. Since 8-ounce United States Army
duck retains hydrocyanic-acid gas better than any other cloth of
which fumigation tents are constructed at present, results equally
THE COMMON MEALYBUG IN CALIFORNIA.
poor in comparison with those tabulated are to be expected under
drill or double-filled duck covers.
Treatment under gas-tight tents is eminently successful from the
standpoint of general control, it being possible to secure complete
eradication on a small number of trees, and such treatment would
be recommended in preference to any other means of artificial
control but for the fact that no gas-tight tenting material practical
for commercial usage is known at present. It is to be hoped and
expected that a suitable gas-tight cloth will be forthcoming in the
future. The dosage should be 1 ounce of sodium cyanid to each 100
cubic feet of space beneath the tented tree; for eradication, 11 ounces.
Citrus trees in dormant condition during the winter months will
withstand safely a dosage as high as 11 ounces of sodium cyanid to
100 cubic feet of space under gas-tight covers. Heavy, repeated
dosages under ordinary commercial tents have been used at this time
with little damage to the trees. It is unsafe, however, to apply such
concentrated gas to orange or grapefruit trees during the growing
season.
Eradication of the mealybug can be effected in a gas-tight box
or room with a dosage rate of 1 ounce of sodium cyanid to each 100
cubic feet of space.
SPRAYING.
RECOMMENDED SPRAY FORMULAS.
More than 100 different sprays have been tried against the mealy-
bug, including insecticides formerly used and others developed during
this investigation. Several preparations, including the resin wash
and a 2" per cent paraffin-oil emulsion, have given fairly effective
results; but two new sprays, cresolated distillate emulsion and soap-
powder emulsion, are recommended as best measuring up to orchard
requirements in mealybug control. The formulas for the preparation
of these sprays are given below.
CRESOLATED DISTILLATE EMULSION.
Distillate (280 Baum) ____--------gallons. 22
Liquor cresolis compositus, U. S. P _____----- ___ quarts__ 1
Liquid fish-oil soap ---------------------- quart-_ 1
Soap powder (sodium carbonate 40-60 per cent, caustic soda
40-60 per cent) ------------------ ----- pounds 3
Water to make---------------------------- gallons 100
Preparation.-When the bottom of the spray tank is covered with water,
start the agitator and sift in the finely ground soap powder, which dissolves
while the tank is filling. Prepare the stock by first measuring the distillate, then
pour the liquor cresolis compositus into the distillate and stir. Pour into the
liquid soap twice as much of the foregoing mixture as of the soap and beat with
a paddle until of uniform consistency. Then add remainder of mixture and
stir thoroughly, after which the preparation is ready to be poured into the spray
tank.
FARMERS' BULLETIN 862.
This spray has been used with success for more than a year and is
recommended as the preferred insecticide for mealybugs. It has been
applied to a very large variety of plants during the winter season
without injury. Oranges and lemons are treated safely, though
grapefruit has been known to be stained slightly. The grade of dis-
tillate is very important, and only that of a gravity approximating
28 Baumb should be purchased. This is an untreated black oil, very
distinct from the stove distillate (320-34: Baum6), which is com-
monly used for spraying. The cost of cresolated distillate emulsion
is about 1 cents a gallon.
SOAP-POWDER EMULSION.
Distillate emulsion _-_------gallons__ 5
Soap powder -------------------pounds 10
Water to make -- -------------gallons 100
Preparation.-When the bottom of the spray tank is covered with water, start
agitator and sift in the finely ground soap powder. The distillate emulsion is
added when the tank is almost filled.
Soap-powder emulsion is effective against the mealybug as well as
against citrus scales. It is more injurious to the foliage than creso-
lated emulsion, however, and may cause moderate or even severe
dropping of the leaves unless applied under favorable climatic con-
ditions. (See Season for spraying," p. 9.) The cost is about
| cent a gallon.
HOW TO SPRAY A TREE.
Trees first should be pruned of all dead wood and opened up so
as to allow the ready use of the nozzle on the inside. In spraying
for mealybug control the results accomplished are quite as dependent
upon the method of application as upon the insecticidal properties of
the material used. The upper, or dorsal, surface of the mealybug is
tough and resistant to most commercially usable dips and sprays,
the place of greatest vulnerability appearing to be a series of tubes
which lie beneath the fringe of wax. This protective fringe, which
is very resistant to most insecticides, must be removed by the spray
to insure quick destruction of the insect; and to effect this removal
careful treatment with a driving spray is required.
A power machine capable of maintaining 200 to 250 pounds
pressure should be used. A very satisfactory type of nozzle is shown
SFormula for distillate emulsion:
Distillate (280 Baume) --- -- -- -------- allons 20
Liquid fish-oil soap ------------------------------- do-- 4
Hot water ------------------------ -------------do 16
Pour hot water into spray tank. Start agitator, then add soap. Next slowly pour in
distillate. Pump back into itself through nozzle for 20 minutes, after which pump through
fine nozzle into storage tank. This emulsion keeps indefinitely.
THE COMMON MEALYBUG IN CALIFORNIA.
in figure 3. The rods for spraying the inside and lower parts of the
trees should not exceed 6 feet in length.
Mealybug infestation is confined in large part to the fruit, espe-
cially that toward the inside of the tree. It is recommended that
the inside of the tree be sprayed first, starting at the lower part and
moving upward, and then finishing over the outside of the tree.
Especial effort should be made to spray the top of the tree, where
the insects are most likely to escape treatment. Trees more than 10
feet in height should have their tops sprayed from a platform on
the sprayer or from a light tripod ladder which can be carried from
tree to tree. The nozzle should be moved rapidly about the tree, the
spray being directed against both sides of the leaves, against the
FIG. 3.-A type of nozzle well adapted to mealybug spraying.
fruit from at least two directions, and in all crevices which may
harbor mealybugs. Thoroughly to spray a citrus tree 10 to 15 years
old usually requires fully 20 gallons of material.
SEASON FOR SPRAYING.
Insecticidal sprays of the strength required to destroy the common
mealybug may be applied safely to citrus trees in California only
during the cool months of the year, when the fruit is either maturing
or has been picked. This season generally extends from November to
April, though the months of greatest plant resistance to sprays are
December, January, and February. It is unsafe to apply the insecti-
cidal sprays advocated in this bulletin when the temperature is above
10 FARMERS BULLETIN 862.
800 F. or during the summer when the trees are laden with immature
fruit. Should it appear advisable to employ a spray during the
summer, water under pressure should be used, as this can be applied
safely, even when the highest summer temperatures prevail.
WATER SPRAYING.
An increasing number of growers are using successfully water
under pressure so as to dislodge the mealybugs forcibly from citrus
trees. This method of control was demonstrated in several orchards
during the years 1915 and 1916, with varying degrees of success.
Control of mealybugs by water spraying is practicable in the case
of all citrus fruits excepting possibly the navel orange, but its suc-
cess depends on thorough and repeated applications. Especially is
this true of the navel orange, which requires such a large number of
applications that the method is generally impractical in extensive
and severe infestations.
Water has one important advantage over all other sprays in that
it may be used with safety in unlimited quantities at any time
of the year, thus affording a means of combating mealybugs during
the summer months when practically all insecticides of value are
too injurious to fruit and foilage to justify their application.
Several matters have a very important bearing on the successful
commercial use of water spraying. In orchards the cost can be
reduced materially by installing a system of piping, the power
being derived from the water main, a stationary pump, or a power
sprayer. The piping should be of-a diameter to give ample force.
The best type of nozzle allows an uninterrupted flow through an
aperture not larger than one-fourth of an inch. The writers
devised a very satisfactory direct-discharge nozzle having a rec-
tangular opening 6 by 2 millimeters and capable of delivering 6 to
7 gallons a minute under 100 pounds pressure. The common garden
type or a j-inch fire nozzle, however, will serve the purpose. Nozzles
with small openings, as those of the Bordeaux type, are unsuitable
for water spraying, as the stream of water will strip the leaves and
cut off fruit. The tops of the trees should be sprayed from a ladder.
Twenty to thirty minutes are required for spraying thoroughly a
tree 10 to 15 years old.
CONTROL BY NATURAL ENEMIES.1
No important citrus insect pest in California seems to be attacked
by more natural enemies than the mealybug, and efficient control of
1The more effective enemies of this species, including both predators and parasites,
given in the order of their importance, are: Sympherobius barber Banks, 8. californicus
Banks, Hyperaspis lateralis Muls., Cryptolaemus montrouzieri Muls., Chrysopa califor-
nica Banks, Leucopis bella Loew, and Paraleptomastim abnormis Girault.
THE COMMON MEALYBUG IN CALIFORNIA.
the mealybug by these natural enemies is often noted. For example,
one severely infested orchard was observed to be cleaned in less than
two months to an extent satisfactory in commercial control by tvo
species of predatory brown lacewing flies.1 Other groves have enjoyed
similar respite from mealybug injury through the activity of these
brown lacewings, aided by one. or the other of two species of ladybird
beetles.2 Undeserved credit is often given to insecticides, in the case
of orchards that have contained these natural enemies in large num-
bers at the time of spraying or fumigation, while in fact the mealy-
bugs have been destroyed by these predatory enemies unobserved
by the orchardist or operator. The natural enemies are most effica-
cious during the autumn and early spring.
RELATION OF ANTS TO NATURAL CONTROL.
Since the mealybug is beset with so many efficient natural enemies,
it has been the cause of considerable wonder that the pest is not more
generally kept in check. The infestation may be reduced during
the autumn or spring to a point bordering on control or even eradi-
cation, yet it is a matter of common observation in some localities
that in spite of these conditions one severe infestation follows an-
other year after year. This failure of the natural enemies to hold
the mealybug in check throughout the year has been found to be due
mainly to the presence on the trees of large colonies of ants, the
Argentine ant being the greatest offender. The experimental work
reported in this bulletin has been confined to the Argentine ant,
which has been observed to carry living mealybugs, to destroy and
carry off the larve and eggs of natural enemies, to interfere with
the free movement about the tree of certain beneficial insects, and by
their constant attendance upon the mealybugs to prevent normal
egg laying and feeding of the adult parasites and predatory enemies.
Remarkable results have been secured by keeping the Argentine
ant off of trees infested with mealybugs by banding with a sticky
mixture. In Los Angeles County during 1915 and 1916 trees that
when first freed from ants were infested severely with the mealybug
became commercially clean, without exception, within a period of six
weeks to three months. The mealybug remained under control
throughout the year or during the period of the experiments, while
trees in adjacent check rows only a few feet away continued to be
severely infested. The natural enemies responsible for this control
were the two brown lacewings and a ladybird beetle.4
1 Sympherobius barber Banks and Sympherobius californicus Banks.
2 Either Hyperaspis lateralis Muls. or Cryptolaemus montrouzieri Muls.
3 Iridomyrmeo humilis Mayr.
4Hyperaspis lateralis Muls.
FARMERS BULLETIN 862.
An experiment typical of many others is given in Table II.
TABLE II.-Relation of the Argentine ant to the natural control of the mealybug.
Experiments at Sierra Madre, Gal., July to October, 1916. [Percentage of
fruit infested with the mealybug on each tree. Twenty orange trees to each
test.]
I. NO INSECTICIDAL TREATMENT.
Tree No. 1 2 3
Infestation at start of test, July 25. All
trees frequented with ants:
a. Check row, unbanded........... 100 100 94
b. Banded...................... 92 96 92
Six weeks after start, Sept. 6:
a. Check row, unbanded........... 100 92 80
b. Banded......................... 1 3 2
Eleven weeks after start, Oct. 11:
a. Check row, unbanded........... 100 82 45
b. Banded I...................... 0 1 0
4 5 6 7 8 9 10
80 34 90 100 100 91 100
86 100 73 82 75 93 100
91 73 100 100 86 90 100
1 15 1 2 1 ...... 24
50 32 61 96 76 42 86
0 1 0 1 0 0 1
1 Only 8 infested fruit on entire 10 banded trees.
II. TREES SPRAYED WITH WATER ON JULY 25.
Condition before water spraying, July 24:
a. Unhanded....................... 94 100 97 100 100 100 85 100 100 100
b. Banded......................... 30 98 100 90 55 93 89 100 100 86
Six weeks after start, Sept. 6:
a. Unbanded....................... 100 5 94 99 100 98 100 9 100 94
b. Banded.......................... 2 1 9 2 1 4 14 1 3 3
Eleven weeks after start, Oct. 11:
a. Unbanded.... 90 93 92 90 94 100 100 20 100 100
b. Banded.......... ............. 1 0 1 0 0 0 1 0 0 0
HOW TO KEEP ANTS OFF OF TREES.
To free trees of ants the ideal procedure would be to eradicate
these insects from the area affected. The writers have not carried
on any such tests, but the published results of work carried on by
the Department of Agriculture against the Argentine ant1 would
indicate the feasibility of freeing orchards of this pest.
The procedure followed with noteworthy success in municipal
control work was the distribution throughout the affected area of a
poisoned sirup in a suitable container. A paraffined paper bag, with
perforations for the passing of ants, containing about a gill of sirup,
was used as a container for nailing to trees.
The sirup is made as follows:
Granulated sugar ---- ---------------- ----_pounds- 15
Water -------------_ ------------pints-- 7
Tartaric acid (crystallized) -----------------_-------ounce- I
Boil for 30 minutes. Allow to cool.
Dissolve sodium arsenite (C. P.) -------------------ounce-
In hot water--------------------------------------pint 1
Cool. Add poison solution to sirup and stir well. Add to the
poisoned sirup:
Honey----------- --------------pounds_ 1
Mix thoroughly.
1Barber, E. R. The Argentine Ant: Distribution and Control in the United States.
U. S. Dept. Agr. Bul. 377. 23 p., 4 fig. 1916. Newell, Wilmon, and Barber, T. C. The
Argentine Ant. U. S. Dept. Agr. Bur. Ent. Bul. 122. 98 p., 13 pl., 13 fig. 1913.
THE COMMON MEALYBUG IN CALIFORNIA.
A number of experiments with banding in orchards infested with
the Argentine ant have proved the practicability of this method of
keeping trees free of ants during their active season, and this method
of control is recommended (see fig. 4) as the most effective one tried.
Before the band is applied the tree should be pruned so that the
lowest branch is fully a foot above the ground, and all rubbish should
be removed from beneath the tree and the soil cultivated to destroy
all grass and weeds. The only banding material which has given
satisfaction is a mixture 2 made up as follows:
Finely powdered flowers of sulphur ----------part by weight__ 1
Commercial tree-banding sticky material --_- parts by weight__ 6
The two ingredi-
ents are mixed to-
gether thoroughly
with a wooden
paddle until of a
uniform color and
consistency. Th at
possible injury may
be avoided, this is
not applied directly
to the bark, although
direct application of
the commercial sticky
tree-banding ma-
terial alone has never
been noted in Cali-
fornia to affect citrus
trees seriously. First
coat the trunk with a
thin layer of paraffin
and apply the mix-
ture of sulphur and
sticky tree banding
material over this. .
Paraffin that has a FIG. 4.-Keeping ants off citrus trees. A 5-inch band of
high melting point is sulphur and commercial sticky tree-banding material
preferable, and it is ver a wider coating of paraffin.
preferable, and it is
applied with a brush while melted. It hardens almost immediately,
after which the mixture just referred to can be applied in a band
about 5 inches wide and almost one-fourth inch thick. A single
application of this material has kept trees free of ants for several
months during warm weather.
2 Compounded by Mr. J. R. Horton of the Bureau of Entomology, U. S. Department of
Agriculture. (See Horton, J. R. Some weatherproof bands for use against ants. In
Mo, Bul, Cal. State Com. Hort., v. 5, no. 11, p. 419-421, 1916.)
14 FARMERSS- BULLETIN 862.
Ants that are on trees at the time of banding usually drop off
within a day or two unless nests are in the trunk or branches. If
nests are present, however, they should be destroyed by applying
pyrethrum or some other ant powder, or with a fine spray of gasoline
from a plumber's torch, or with cresolated emulsion applied with a
3-gallon compressed-air sprayer. This should be done early in the
morning, while the ants are least active.
Inspection should be made weekly for the discovery of reinvested
trees, the bands being renewed where necessary and the branches of
the trees kept from coming in contact with weeds or the ground.
GENERAL RECOMMENDATIONS.
In view of the success secured in the foregoing experiments in con-
trolling the mealybug by keeping ants off of the trees, the impression
might be conveyed that banding alone is all that is necessary to keep
orchards commercially free of this destructive pest. Under present
conditions this would probably prove true in most cases; nevertheless,
two important factors must be kept in mind when a general scheme
of control for the common mealybug in southern Califbrnia is under
consideration: (1) The possible scarcity or absence of effective bene-
ficial insects in the infested orchard and (2) heavy parasitism of the
beneficial natural enemies themselves in some localities at certain
seasons of the year. Control of the mealybug under either of these
conditions could not be effected quickly except by spraying or other
artificial control, unless it should be possible to introduce promptly
large colonies of effective natural enemies.
General recommendations for control are given below, and it is
believed that complete success will result if they are followed closely
in all details. Frequent examinations to detect ant reinfestation
must be made, and colonization of natural enemies, where not present
already in noticeable numbers, is essential. The trees should be
sprayed wherever the conditions demand it.
PROCEDURE RECOMMENDED FOR THE CONTROL OF THE COMMON MEALYBUG.
TREES IN ORCHARDS.
1. Where there are very few trees.
a. Prune heavily for spraying, with lowest branches at least 1 foot above
ground.
b. Band trees with sulphur-sticky mixture and keep them free of ants.
c. Attempt eradication by spraying with cresolated emulsion or by fumiga-
tion under a gas-tight tent.
d. Inspect weekly. If living insects are present, respray or refumigate
until they are eradicated,
THE COMMON MEALYBUG IJ; CALIFORNIA. 15
2. Where there is a light general ilute-tation.
A. Where no trees are severely infested.
1. Pick navel fruit, including all (.111 and off bloom, before March 1.
2. Band trees with sulphur-sticky nxture, preferably in February or
March. Free trees of ants.
3. Introduce large colonies of the I' r most useful insect enemies,1 if
these are not present in n,'t i el~ .e numbers. This should be done
preferably in March or April. lt introduction can be continued
throughout the season, if neces rv.
4. Inspect weekly for ant reinfestatiu.
5. Spray with water during summer if infestation becomes severe.
B. Where there are a few severely infested trees in an orchard otherwise
lightly infested.
1. Such trees should have the inflation greatly reduced during the
month of February, either by spraying with cresolated or soap-
powder emulsion or by fumigation under a gas-tight tent. After-
wards they can be handled lii' the rest of the orchard, as ex-
plained in A above.
3. Where there is severe infestation.
A. Treatment of navels, grapefruit, and-nmonis.
1. Navels and grapefruit.-Pick all fthit, including culls and off bloom,
before treatment. Leave culls and off bloom on the ground.
Lemons.-Picf all marketable f1-t before treatment.
2. Prune heavily for spraying, with he lowest branches at least 1 foot
above the ground.
3. Following removal of fruit, sprLy with cresolated or soap-powder
emulsion, or fumigate under a gas-tight tent, prefer;! il in
February.
4, 5, 6, 7. The same as for A 2, 3, and 5, respectively, in section 2.
B. Treatment of Valencias.
The procedure is the samR a : ,-_celsy grapefruit, and lemons,
except that the fruit is ni r;~, while the spraying should be done
with cresolated dij'Ollate emulsion.
TREES IN HOUSE LOTS.
1. Pick all fruit during the winter.
2. Prune heavit' and keep free from ,Aui!ings, other plants, etc.
3. Fumigate with eradication dosage i.;nicr gas-tight tent if available.
Otherwise spray it-ivily with -resolated or soap-powder emulsion.
4. Band with sulphur-st:!,::, mixturee and keep free of ants.
5. Spray fr. 1loiirl.I with water if living insects continue on trees.
TPRVENTING SPREAD THROUGH PICKING BOXES AND BY PICKERS.
The present localization of the common mealybug renders advis-
able the adoption of some means to prevent its spread to new
regions through such controllable agencies as picking boxes and
picking sacks. Picking boxes which have been known to carry fruit
infested with the mealybug should be treated before use in uninfested
1 Sympherobits californicus, S. barberi, Hyperaspi lateralis, and Cryptolaemis m nt
trouzieri,
16 FA PAIMF BULLETIN 862.
orchards. Eradicatioh of tb' insect on boxes is secured by fumi-
gation in a gas-tight room vith hydrocyanic-acid gas at the rate
of 1 ounce of sodium cyanid P each 100 .ubic feet of space, or with
sulphur at the same strength
Dipping picking sacks, gve':, and jumpers in gasoline for five
minutes will destroy all irll:' and eggs. As the gasoline evapo-
rates in a few minutes, the,cloth or leather will be ready for use
again before the next orchard3 y reached.
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