June 1942 U.R E-569
CONTROL OF COTTON INSECTS
Prepared by the Division of Cotton Insect Investigations
The control ot injurious insects is an important factor in the profit-
able production of cotton, It is estimated that an average of 15 percent
of the United States cotton crop, or one bale out of every seven, is destroyed
by insects. Much of this loss could be prevented and the quality of lint
improved by intelligent use of approved methods of control. Often the dif-
ference between insect control and no control means the difference between
a substantial profit and a loss on a cotton crop. Growers, merchants, bank-
ers, and others interested directly and indirectly in increased cotton pro-
duction per acre should realize the importance of planning ahead to pro-
vide funds and supplies for insect control,
The boll weevil is the most notorious of the cotton pests and causes
the greatest total damage, but other insects are at times injurious in all
cotton-producing areas. Insects vary in abundance from year to year and
from field to field, and it is necessary to determine which insects are pres-
ent in damaging numbers before insecticides can be used properly. Applying
insecticides when insects are not abundant enough to justify it is a waste
of time and money, and not to use them when needed may mean the loss of the
crop. Insecticides must be properly applied to get the highest degree of
control and to conserve vital war materials. Many cultural practices are
also of great value in reducing insect damage and should not be neglected,
especially under war conditions. Proper cultural practices reduce the quan-
tities of insecticides needed and at times enable growers to produce good
crops without using other control measures.
Recommendations are given in this circular for the control of several
of the important cotton insects. They are based on experimental work by
the Bureau of Entomology and Plant Quarantine and State experiment stations
and are suitable for a wide range of conditions in the Cotton Belt. When
more than one insecticide or method of application is recommended, follow
the recommendation of your State experiment station or use the remedy which
experience has shown to be effective in your locality.
War conditions have limited the supply of certain insecticides, such
as paris green. The use on cotton of derris and other insecticides contain-
ing rotenone is at present prohibited, as it is necessary to conserve the
available supply for use on important food crops and for military purposes.
Normal supplies of calcium arsenate, nicotine, and sulfur are expected to be
available for 1942. Allotments of materials for dusting machinery are suf-
ficient for the manufacture of a slightly larger number of machines and near-
ly twice the quantity of repair Darts made in 1941. The situation with ref-
erence to insecticides and equipment may change materially almost from day
to day, and cotton growers must be ready to resort to substitutes, some of
which are suggested herein.
CULTURAL PRACTICES THAT HELP PREVENT INSECT DAMAGE
(1) Plant cotton on good land that has been well prepared.
(2) Use fertilizer as recommended for your community by the State ex-
(3) Select an early-maturing, disease-resisting variety, recommended
for your section.
(4) Plant as early and space as closely as recommended by your nearest
(5) Cultivate thoroughly and use timely farm practices.
BOLL WEEVIL CONTROL
(1) Stop all fruiting by plowing out, cutting, or grazing cotton
stalks as early as possible before frost in the fall. This will reduce the
weevils on next year's crop.
(2) Select fields as far as possible from the fields that were in cot-
ton last year. It is also helpful to select fields in large cleared areas
where the. opportunities for boll weevils to hibernate are not good. Many
weevils pass the winter in woods and other protected places close to the
cotton fields in which they developed.
(3) The most practical direct method of control after boll weevils
reach the fields is to protect the cotton with calcium arsenate dust during
the time the plants are fruiting. As a general rule it will not pay to dust
cotton growing on soil that is not capable of producing at least a third of
a bale per acre if no boll weevils were present.
Presquare or Early-Season Treatment
(1) Early in the season, before squares are large enough for weevils to
puncture, examine the plants for boll weevils. If weevils are found at the
rate of 25 or more per acre, presquare poisoning may be used as a preliminary
(2) For presquare poisoning calcium arsenate may be'applied as a dust
or as a liquid mixture with a mop or sprayer.
(3) Dust with 4 to 5 pounds of calcium arsenate per acre, or mix it
with equal parts of lime, talc, clay, or sulfur and apply at the rate of 6
to 7 pounds of the mixture per acre.
(4) If no dusting machines are available, less satisfactory results can
be obtained by shaking the calcium arsenate or the calcium arsenate dust
mixtures on the plants from a can with small holes in it, or from a cloth bag.
(5) The mixture most generally used for mopping consists of 1 pound of
calcium arsenate, 1 gallon of blackstrap molasses or zrp, and 1 gallon of
water, applied at the rate of 2 to 3 gallons per acre with a homemade mop.
Other liquid mixtures containing calcium arsenate are also used for mopping.
(6) Dust or mop every 5 or 6 days until 2 or 3 early applications have
been made. By that time large squares or blooms will be present and treat-
ments should be stopped until square examinations show that the weevils are
abundant enough to require dusting.
Mopping with sweetened poison early in the season has been helpful in
weevil control in some sections but of little value in other sections. In
many experiments in South Carolina, extending over a 12-year period, the
average returns were only slightly larger from midseason dusting preceded by
early mopping than from dusting alone. Mopping alone did not give satisfac-
tory weevil control, and in years when weevils were abundant there were severe
losses where mopping alone was used. Mopping is an early-season treatment
that may delay for a week or 10 days the time when dusting is needed for
boll weevil control, but mopping alone does not give satisfactory control in
summers when conditions are favorable for boll weevils.
Mid-Season Dusting for Boll Weevil Control
(1) After cotton begins to fruit, examine the squares once a week or
oftener for weevil-punctured squares. To determine the percentage of weevil-
injured squares, walk diagonally across the field and pick 100 squares from
the plants. Select squares large enough for weevils to puncture (half grown
or larger). Pull only 1 square from each plant and take about the same num-
ber from the top, the middle, and the bottom branches. Keep the squares
until 100 have been pulled and then examine them carefully for egg and feed-
ing punctures. The number of squares found punctured in 100 squares ex-
amined is the percentage of square infestation. In a large field the counts
should be made in several places to determine which parts of the field
should be dusted.
(2) Begin dusting with calcium arsenate when 10 to 25 percent of the
squares are infested. On light soils, where the cotton does not grow rank
and where it matures early, dusting should begin when 10 to 15 percent of the
squares are infested. On fertile soils, where cotton continues growing and
fruiting until late in the season, it is safe and often more profitable to
wait until 20 to 25 percent of the squares are infested, before dusting.
(3) Dust with 5 to 7 pounds of calcium arsenate per acre every 4 or 5
days until the weevils are brought under control or a crop of bolls is set.
(4) Repeat the application if the dust is washed off by rain within
24 hours. Three to five applications that remain on the plants will usually
control the weevils and result in the setting of a crop, From one to three
later dustings are sometimes needed to protect bolls from weevil damage.
(5) Dusting may be done at any time of day or night when the air is
quiet. It is more important to dust when the air is calm or nearly so than
when the plants are wet with dew,
(6) On the light sandy soils of the Southeastern States, use only as much
calcium arsenate as necessary to give satisfactory boll weevil control, in
order to reduce the danger of arsenic injury to the soil. l/ For cotton
growing on light sandy soils where soil injury may occur, a mixture of
equal parts of calcium arsenate and slaked lime, talc, clay, or sulfur is
recommended. The mixtures do not kill the weevils so quickly as does cal-
cium arsenate alone, but when used at the rate of 7 to 10 pounds per acre
they have given satisfactory control duringyears of average weevil abundance.
(7) When cotton flea hoppers. rapid plant bugs, tarnished plant bugs,
or other sucking bugs are present with boll weevils, dusting with 12 to 15
pounds per acre of a mixture of 1 part of calcium arsenate and 2 parts of
sulfur is recommended.
(8) Low winter temperatures and hot, dry summers help control the boll
weevil. Watch for a rapid increase of weevils during rainy spells in the
growing season. The largest gains and most profitable returns from dusting
are obtained in years when weevils are most abundant. Dusting usually pays
better in wet than in dry seasons.
Cotton aphids (plant lice) often occur in damaging numbers, especially
following the use of arsenical insecticides. They reduce the yield and
grade of cotton.
(1) Aphids can be held in check if nicotine is added to the calcium
arsenate or other dusts used on cotton.
1/ No soil injury has been noted from the calcium arsenate used for
boll weevil control on clay soils, red soils, or dark soils, but there has
been some injury to light sandy soils. In most cases of soil injury that
have been investigated, excessive quantities of calcium arsenate had been
(2) Adding i percent of nicotine to the calcium arsenate used for
each dusting or adding 2 percent of nicotine to the calcium arsenate used
for every other dusting are equally effective in preventing serious aphid
(3) Preventing aphids from becoming abundant is more profitable than
controlling them after a heavy infestation has built up. However, if a
heavy infestation develops it may be necessary to use a 3-percent nicotine
dust or a spray to check it.
(4) Liquid nicotine sulfate containing 40 percent of nicotine can be
mixed with calcium arsenate to make the 1-percent. 2-percent, or 3-percent
nicotine dust by adding 1 quart, 2 quarts, or 3 quarts of nicotine sulfate
to approximately 100 pounds of calcium arsenate, 2/
(5) If spraying machines are available, 1 quart of 40-percent nicotine
sulfate in 100 gallons of water to which about 5 pounds of laundry soap has
been added can be applied at the rate of 30 to 40 gallons per acre in place
of the 3-percent nicotine dust.
(6) Best results are obtained from nicotine dusts or sprays applied
for aphid control when the air is very quiet, the temperature high, and the
The bollworm is also called the corn earworm and tomato fruit worm.
The bollworm moths prefer rapidly growing succulent cotton on which to lay
their eggs. Generally bollworms do not cause serious damage to cotton until
comparatively late in the season, that is, about the time corn silks are
drying out and after dusting for boll weevils is over. Each bollworm de-
stroys a large number of squares and bolls, and when thc worms are numerous
a crop of cotton may be ruined in a short time. Damage often occurs so late
in the season that the plants do not have time to mature another crop of
(1) When it is about time for bollworms to appear, examine the tips
of the plants frequently for eggs and newly hatched worms. The eggs are
about half the size of a pinhead and pearly white when first laid but change
to a darker color before hatching. They are laid singly on the tender
growth and squares. When 20 to 25 eggs that are beginning to hatch, or
such a number of eggs and very small worms, are found per 100 plants, dusting
should be started immediately. Small worms feed largely on the tender buds
and leaves and the outside of squares for several days after hatching and
can be controlled. Large worms feed mostly inside the bolls, and it is very
difficult if not impossible to poison them.
2/ In a limited number of experiments a dust containing 10 percent of
free nicotine has been used instead of the nicotine sulfate for mixing with
calcium arsenate in making 1-percent and 2-percent nicotine dusts, with
(2) Heavy dosages of dust-properly-applied when the eggs are begin-
ningto hatch and before the worms enter the bolls is the secret of suc-
cessful bollworm control.
(3) Dust with 8 to 10 pounds of calcium arsenate, lead arsenate, or
cryolite per acre at 5-day intervals. Use more pounds per acre when the
infestations are heavy and the plants large.
(4) Two or three applications will usually control a brood of boll-
worms. However, there may be more than one brood or a steady movement of
egg-laying moths to cotton from other crops with no distinct broods. In
such cases several additional applications may be needed to keep the plants
covered with insecticides for killing the newly hatched worms.
(5) Arrange the dust nozzles with one over each row and a few inches
above the cotton so that the tops of the plants will be well covered with
(6) Ladybird beetles and other natural enemies and extremely hot,
dry, and windy weather often destroy large numbers of eggs and young boll-
worms and control threatening infestations without the use of insecticides.
(7) Sometimes the normal destruction of aphids, bollworm eggs, and
small bollworms by natural enemies is upset by the use of arsenicals, with
the result that increased aphid and bollworm populations follow. However,
this complication that occurs at times should not discourage the proper
use of the control measures recommended for various insects.
COTTON FLEA HOPPER
The cotton flea hopper occurs over the entire Cotton Belt but causes
the most damage in Texas, Oklahoma, and Louisiana. Severe damage from this
pest also occurs at times in other areas. The flea hoppers feed mostly on
the growing tips and very small squares of young cotton. Injured squares
turn brown or black and are shed when they are very small, often no larger
than a pinhead.
(1) If cotton is not squaring properly or if young cotton fails to
"set" the small squares, examine the tips of the main stem (terminal buds)
of the plants for flea hoppers. Begin dusting when 15 to 25 flea hoppers
(the number depending upon the size of the plant) are found per 100 termi-
(2) Dust with 12 to 18 pounds of finely ground dusting sulfur (325-
mesh or finer), or with 12 to 15 pounds of a mixture of 2 parts of sulfur
and 1 part of calcium arsenate, per acre. Sulfur alone is satisfactory
for young flea hoppers (wingless nymphs), but the sulfur-calcium arsenate
mixture gives a better kill of the winged adults and will also control
the boll weevil when both insects are present.
(3) Two or three applications at 5- to 7-day intervals will ordinar-
ily give control, but where the infestation is heavy or large numbers of
flea hoppers are continually moving into the cotton, from four to six
dustings are sometimes needed.
(4) Often 2 or more weeks must elapse after flea hoppers are killed
before the plants recover and squares again become noticeable,
(5) The rapid plant bug and the tarnished plant bug resemble the
cotton flea hopper but are larger and cause more damage per insect. Their
injury to cotton is similar to, and is sometimes mistaken for, that caused
by the flea hopper, but they also cause the shedding of large squares and
bolls. These insects are widely distributed, and if they are present in
injurious numbers, the sulfur-calcium arsenate mixture recommended for
flea hopper control should be used.
COTTON LEAF WORM
Early outbreaks of the cotton leaf worm, which strip the leaves from
the plants before most of the bolls harden, require control. Late i4fes-
tations, after the crop is nearly mature, cause little damage and are some-
times helpful by destroying the food for boll weevils late in the season,
thus reducing the number of weevils that survive the winter and enter the
cotton fields the following spring.
(1) Small to half-grown leaf worms are easily killed by any of the
arsenical insecticides. Large worms are harder to kill and when numerous
they cause serious "ragging" or completely strip the plants unless con-
(2) Dusting with calcium arsenate as for boll weevils or bollworms
will keep the leaf worms under control. Lead arsenate as a spray at the
rate of 4 to 6 pounds in 50 gallons of water for about 3 acres, or as a
dust at 5 to 6 pounds per acre, is also satisfactory. If a quick kill of
large worms is needed to prevent stripping, add 7 to 8 pounds of paris
green to each 100 pounds of calcium arsenate, or use 8 to 10 pounds of
paris green mixed with 100 pounds of lime. Other arsenicals are also
effective. White arsenic mixed with lime is sometimes used by growers,
but is not recommended, as it is apt to burn the plants. Cryolite is not
so effective against leaf worms as arsenical poisons.
For dusting cotton no method of application has been found that is so
satisfactory as properly designed dusting machines. There are dusting
machines varying in size from small hand guns to large power dusters and
airplane dusters. The type and size of machine needed for different acre-
ages are discussed in Farmers' Bulletin 1729, Machinery for Dusting Cotton,
which may be obtained free from the United States Department of Agriqixre,
Washington, D. C. If you are planning for cotton insect control, suffi-
cient dusting machines should be available to dust the entire acreage
every 4 or 5 days, with due allowance for unfavorable weather and break-
downs. The demands for war materials have restricted the manufacture of
dusting machinery, and growers should order parts early to repair their
dusting machines before the dusting season begins.
Machines with one nozzle for each row to be dusted are recommended.
"Side delivery" or "broadcast" dusters do not give an even distribution,
are wasteful of dusts, and are not recommended for the control of cotton
insects. The nozzle should be directly over the row and slightly above
the tops when the plants are wet, or touching the tops when the plants are
dry. Most machines tend to put out more dust than is needed for small cot-
ton. It is not necessary to "whitewash" the plants to secure good cover-
Time of Day to Dust
In the past the Bureau has recommended dusting for boll weevil control
when the plants are wet with dew and the air is calm, This has usually
limited to the late afternoon, night, and early morning the hours during
which dusting could be done, and has reduced the acreage that a machine
could dust. Tests over a 6-year period at Tallulah, La., have shown that
the average gains from cotton dusted during the middle of the day for weevil
control were as large as from cotton dusted in the early morning. Gains
from the late afternoon dusting (between 6 and 7:30 p.m.) were practically
as good as from the early morning or midday applications. Experiments in
Texas have shown that sulfur and sulfur-arsenical mixtures can also be
satisfactorily applied for flea hoppers when the plants are dry, although
better results were obtained when the plants were wet with dew. Dusting
should not be done when there is enough breeze to cause any considerable
drifting of dust beyond 3 or 4 rows, but it can be done at any time of day
or night when the air is quiet, regardless of whether there is dew on the
plants. Dust mixtures containing nicotine give best results during a hot,
calm period of the day when the plants are dry.
Calcium arsenate and sulfur mixtures are sold by many insecticide
dealers, and in some localities calcium arsenate-nicotine mixtures can be
obtained ready mixed. The nicotine mixtures tend to lose their strength
after standing for some time and should be mixed during the year they are
to be used. In closed steel calcium arsenate drums they can be safely kept
for at least a dusting season. If factory-mixed dusts are not readily obtain-
able, the dusts can be made on the farm in a mixer such as is used on many
farms for treating cottonseed; or a homemade mixer that will hold 100 pounds
of dust can be made from a 50-gallon barrel fitted with supports and a
crank. In mixing insecticides, from 40 to 50 pounds of stones about the
size of eggs should be placed with 100 pounds of dust and the mixer turned
slowly for at least 5 minutes to insure uniform mixing. Another method of
mixing insecticides is to roll the barrel on the ground. This can be done
by making a mule-drawn frame sled so arranged that the barrel fits into the
opening between the runners and is held by cross pieces so as to allow it
to roll on the ground. The stones and lumps should, of course, be care-
fully screened out before the mixture is placed in the dusting machine.
Nicotine fumes are irritating and cause nausea when inhaled in auan-
tities. Mixing should be done out of doors or in an open room or shed.
Keep to the windward side when filling or emptying the mixer and dust
UNITED STATES DEPARTMENT OF AGRICULTURE
OFFICE OF THE SECRETARY
WASHINGTON, D. C.
BUREAU ENT & PLANT QUAR
COLLABORATOR IN CHARGE
507 JOHN F SEAGLE BLDG
33 GAINESVILLE FLA
PENALTY FOR PRIV
PAYMENT OF P
UNIVERSITY OF FLORIDA
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