(Reprinted 1937)
Control of Cotton Insects and Diseases
C OTTON 
is often seriously 
damaged by such 
insects as the 
boll
weevil, leaf worm, flea hopper, red spider, and boll worm, and
by such diseases as rust, wilt, and anthracnose. It is the purpose of
this leaflet to discuss briefly the habits and appearances of some of
these pests and to give 
control measures for 
them.
COTTON INSECTS
Boll Weevil
The boll weevil is the most widely known and the most im-
portant insect pest of cotton. The females puncture the squares and
deposit their eggs in them; later in the season they also deposit eggs
in the bolls. The larvae (grubs) which emerge from the eggs feed
in the squares causing them to turn yellow, flare open, and usually
drop from the stalk. Infested bolls usually do not drop but fail to
produce a full boll of cotton. The yield of cotton may be reduced
50 to 75 per cent if weevils are very numerous at the time the crop
is being set.
How to Dust Cotton.-Although such cultural practices as
the liberal use of fertilizers, the growing of small, early maturing
varieties, and the destruction of all cotton stalks early in the fall
are helpful in controlling the boll weevil, it is often necessary to
dust cotton with calcium arsenate to prevent serious damage. When
dusting is necessary, the calcium arsenate should be applied with a
dust gun at the rate of 5 to 6 pounds per acre. The distributors of
the dust gun should be set a few inches above the tops of the cotton
plants and the dust gun should be adjusted to put out the dust in a
thin cloud which completely covers the plants. Cotton may be dust-
ed with good results at any time during the day or night, provided
the air is calm. If a heavy rain occurs within 24 hours after dusting
the application should be repeated.
When to Dust.-The most difficult problem in controlling the
boll weevil is that of knowing when to dust and when not to dust
the cotton. In general it is profitable to dust cotton only when the
expected yield is one-half bale or more per acre, when boll weevils
are numerous during the fruiting season, and when the price of
cotton is ten cents a pound or above. If sufficient fertilizer has
been used to produce one-half bale per acre and cotton is approxi-
AGRICULTURAL EXPERIMENT STATION
OF THE
ALABAMA POLYTECHNIC INSTITUTE
M. J. FUNCHESS, Director
AUBURN
LEAFLET No. 10 JULY 1934
mately ten cents a pound, the
problem then becomes one of de-
termining whether or not weevils
are nlumerous enough to warrant
dusting with calcium arsenate.
The only way to know whether
or not boll weevils are numerous
enough to warrant dusting is to
make infestation counts of the
squares. In making these counts
100 squares are examined in each
of several places in a field. Stalks
of cotton are selected at random
and each square is examined for
)punctures (Fig. 1) before counting
is begun on a new one; squares on
the ground are not counted. The
number of punctured squares a-
miong 100 examined is the per cent
infestation at a given place.
FIGUTRE' 1. IlIIH.tild <jUHic ut
Infestation counts are begun as C o t t o n (enlar'ied
soon as the cotton is squaring free- 
(bout e3 ctiimes). his
lyv and are made at weekly 
inter- punctures.
vals until the average per cent in-
festation in a field reaches 10 per cent or above. Three applications
of calcium arsenate are then made at intervals of four to six days.
Following this series of dustings, infestation counts are again made
each week and an additional dusting is made whenever needed to
keel) the infestation below 20 per cent. This method of determin-
ing infestation and applying calcium arsenate is continued until the
crop is set. If weevils are numerous late in the season when the
squares are becoming scarce but before many of the bolls are ma-
ture, one or two applications of calcium arsenate may be made to
protect the young bolls.
Kind of Dust Gun to Use.-The kind of dust gun needed will
depend upon the amount of cotton to be dusted. An ordinary one-
row hand gun, selling for about $15, is satisfactory for dusting 3
to 5 acres of cotton. A mule drawn two-row or four-row dust gun,
however, is more satisfactory for the average farmer. Such a dust
gun may be purchased through the Farm Bureau or elsewhere at
prices ranging from $40 to $70 each, depending upon the make and
the type of the gun. A four-row dust gun usually diffel's from a
two-row gun only in the number of distributors for the dust; the
dusting machinery proper is the same. The cost of the four-row
gun is $5 to $10 more than that of the two-row gun. Several
factors, such as the abundance of rainfall and the presence or
absence of numerous short rows in a field, will affect the acreage
that may be dusted with any dust gun. In general, however, a
two-row gun will dust 20 to 30 acres of cotton and a four-row
gun, 40 to 60 acres throughout the season.
Amount of Calcium Arsenate Needed.-The total amount of
calcium arsenate required to dust an acre of cotton varies greatly
from year to year. The largest amount ever used during a season
in experiments at Auburn was 75 pounds per acre; the average
amount was approximately 40 pounds. It is suggested, there-
fore, that 40 pounds of calcium arsenate be purchased in the
spring for each acre of cotton to be dusted. If part of the dust is
not needed, it may be stored in a dry place and used later.
Calcium arsenate, stored in the tightly closed steel drums in
which it is purchased, will keep 5 to 6 years or longer without
losing its power to kill insects.
Cost of Dusting.-The 
average cost of dusting 
an acre of
cotton was approximately $5 a year in experiments conducted at
Auburn. This cost included the following: $3.20 for 40 pounds
of calcium arsenate at 8 cents a pound, $1.20 for 4 hours of man
labor and 4 hours of mule labor, each at 15 cents an hour, and
$0.60 for depreciation on the dusting machinery. In figuring the
cost of depreciation, it was assumed that a $60 two-row dust gun
would dust 25 acres of cotton for each of four years. It should
be remembered that the costs given here are average figures and
that the total cost of dusting an acre of cotton may be consider-
ably more or considerably less during any given year, depending
upon the price of calcium arsenate and labor and upon the num-
ber of dustings required.
Profits to be Expected.-Reasonable profits may be expected
from properly dusting cotton. In experiments conducted by this
Station the gains from dusting have varied from no gain to 931
pounds of seed cotton per acre. The large gains were made on
fertile soils during years that boll weevils were very numerous
and the small gains on poor soils or during seasons that boll
weevils were not numerous. The six-year average gains on three
types of soil receiving from 300 to 500 pounds fertilizer per acre
were 240 pounds of seed cotton per acre on sandy loam, 252
pounds on Black Belt clay, and 282 pounds on red clay. Since
the average yearly cost of dusting an acre of cotton was $5, or
$3.80 exclusive of labor, profits of $5 to $15 per acre may be ex-
pected. These profits are at least sufficient to pay for the ferti-
lizer applied to the cotton.
Pre-Square Poisoning.-Although the usual procedure in
controlling the boll weevil is to dust the cotton with calcium
arsenate at the time the crop is being made, it may be necessary
to protect cotton by applying
poison before the p)lants begin
to square. If weevils are very
numerous early in the year, pre-
square poison may be dusted or
mopped on the young plants be-
fore the squares al)l)ear. In pre-
square dusting, calcium arsenate
is applied with a dust gun at
the rate of 4 to 5 pounds per
acre. In pre-square mopping,
calcium arsenate is applied in a
syrup mixture to the buds of the
cotton plants. The mixture used
consists of 1 pound calcium ar-
senate. 1 gallon of water, 
and
FIGURE 2.- Lalrae of the Cotton
Leaf Worm (natural
size). Note the v\aria-
tions in color.
1 gallon of syrup thoroughly mixed together. 
In making the
poison mixture, the calcium arsenate should be 
stirred into a
small amount of water. The remaining 
part of the water and
the syrup should then be added. 
The sweet poison should be
applied with a small cloth mop on the 
end of a stick two to
three feet long. One pound of calcium 
arsenate will make
enough of the mixture to cover two acres 
of cotton. The cost
of mopping is apl)roximately $0.25 
per acre. Mopping is of
no value after the cotton begins to square.
Pre-sqluare poisoning is of some 
value in controlling boll
weevils if they are numerous on young 
cotton but is no insurance
against boll weevil damage later in the season.
Leaf Worm
The cotton leaf worm may do serious damage 
to cotton in
the summer or early fall by eating the leaves 
of the plants be-
fore the bolls are mature. This insect passes the winter 
in tropi-
cal regions and many of the adults, 
which are brownish-colored
moths, fly northward in the spring and 
summer to lay their eggs.
The eggs are deposited on the underside of cotton 
leaves; they
hatch in four to five days to form caterpillars, sometimes 
called
army worms. These laivae (worms) vary 
considerably in color
and general appearance (Fig. 2) but 
are green or yellowish in
color with light and dark stripes running lengthwise 
the body
and with black dots occurring on the head 
and in rows on the
sides near the back. When disturbed these worms 
jerk or jump
in a ve ry characteristic manner. After feeding on 
the leaves of
the cotton for ten days to two weeks the worms reach 
a length
of about I l. inches and are full grown. The worms 
then fasten
themselves to the plant with webs and are later transformed 
into
moths. Three to four weeks after the apl)earance 
of the first
leaf worms on cotton, a second generation is likely 
to appear;
the worms of this and succeeding generations are usually much
more numerous than those of the first. Serious damage will be
done if the worms become numerous before the bolls mature.
The. cotton leaf worm can be controlled by dusting the cotton
with calcium arsenate. Dusting should be done whenever worms
appear in large numbers on cotton with immature bolls. The
dustmay be applied undiluted with a dust gun at the rate of
5 to 6 pounds per acre, or it may be shaken from cloth bags on
the ends of poles. If bags are used each pound of calcium
arsenate should be mixed with 9 pounds of hydrated lime to
prevent wasting large quantities of the arsenical. An application
made with a dust gun is cheaper and more effective than one
made with poles and bags.
Flea Hopper
The cotton flea hopper has become a pest of considerable im-
portance during the past few years, although only an occasional
outbreak occurs. This insect (Fig. 3) is a pale green bug which
is about 18 inch long when full grown. The adults have four
wings and are able to fly from plant to plant, whereas the
nymphs (young) are wingless.
Injury is produced by the insect attacking the terminal buds
and the very small-squares 
of cotton. Both young and 
adults
14
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t : , 
..
ij 
I
1 
J / \
Young Adult
FIGURE 3.-Nymph (young) and adult of the Cotton Flea Hopper (enlarged
about 16 times).
suck the juices from buds and squares causing them to drop off.
The cotton plants set little or no fruit and have a characteristic
upright growth.
The cotton flea hopper may be controlled by dusting cotton
with superfine sulphur at the rate of 10 pounds per acre. The
sulphur should be applied with a dust gun at intervals of 4 to 6
days until the insect is under control. If boll weevils are num-
erous the, sulphur may be mixed with calcium arsenate in the
proportion of 2 pounds of sulphur to 1 pound of the arsenical
and the mixture applied at the rate of 16 pounds per acre.
Red Spider
The red spider is not a true insect but is a tiny mite that
sometimes becomes numerous on the leaves of cotton during dry
summer months. The leaves assume a red or rusty color, be-
come dry, and finally drop from the plants.
Red spiders pass the winter and early spring on green plants
that may grow along fence rows or in yards, gardens, or waste
places. When the weather becomes warm in the spring the mites
multiply and spread to other plants by crawling on the ground
or from leaf to leaf. Thus cotton is infested by the mites crawl-
ing from the winter host plants to the adjacent cotton plants. As
the red spiders become more numerous they migrate to other
cotton plants and thereby gradually spread the area of infesta-
tion. The infestationmay also be spread by man or domestic
animals passing from infested to uninfested areas in a field.
In controlling the red spider it is helpful to keep down all
weeds around the cotton fields. This practice destroys many of
the breeding places and greatly decreases the chances of a seri-
ous outbreak of red spiders. If an infestation is discovered just
as the mite begins to spread to the cotton, the infested plants
should be pulled up and burned or they should be thoroughly
sprayed with kerosene to destroy both mites and plants. If the
red spider has spread over a considerable area of cotton before
the infestation is discovered, the infested cotton should be dusted
with sulphur as recommended for the cotton flea hopper. Should
there be a few days of rainy weather, however, the dusting may
not be necessary as cool, damp weather is detrimental to the
red spider.
Boll Worm
The boll worm is also called the corn ear worm and the toma-
to fruit worm. It is a green to brownish-colored caterpillar which
is about two inches long when full grown and is marked with
alternating light and dark stripes running lengthwise the body.
The cotton boll worm eats holes in the squares and bolls,
causing the squares to drop and the bolls to rot. Cotton may be
7
at least partially protected against boll worm damage by dusting
with calcium arsenate. It is desirable that this dusting be done
as a part of the boll weevil control program so that the control
of the boll worm is incidental.
COTTON DISEASES
Rust
This disease of cotton, which more commonly appears on the
poorer soils throughout the State, has been called by several
names, such as black rust, yellow leaf-blight, and potash hunger.
The cotton plant usually shows little signs of this trouble until
mid-season at which time yellowing, reddening, curling, and
dropping of the leaves may occur in sequence. Plants in large
areas may be completely bare of leaves by late summer or only
a few leaves may remain at the ends of the branches, while the
plants in the rest of the field have complete foliage. The pre-
mature shedding of leaves may reduce the yields of such plants.
Control.-Where this disease is general in a cotton field a
soil-building program should be followed, that is, a rotation with
other crops by which humus is added to the soil. The plowing
under of summer green-manure crops, such as cowpeas, velvet
beans or of winter cover crops such as Austrian peas or vetches
will aid materially in the control of this disease. In addition to
the above practice, the cotton should be fertilized with 50 pounds
of muriate of potash per acre. If these recommendations are
followed the disease should be controlled in a few years.
Wilt
This disease of cotton is more or less generally known as wilt
or black root. Both names are very appropriate since the first
sign of disease is a general wilting of the plant or a portion of
it, which eventually ends in the death of the plant. When closely
examined the plant tissues just under the bark appear blackened
instead of being the normal yellowish to greenish color. The
disease is far more common on sandy soils than on the clay soils;
however, it may sometimes be found on the latter. This disease
is becoming very common throughout Alabama. The damage is
usually more severe where nematode injury or "root knot" ap-
pears 
in the 
same field.
Control.-The best control is the use of a highly wilt-resistant
variety of cotton. There are a number of such varieties but the
following have proved more satisfactory in Alabama: Dixie-
Triumph, Clevewilt I, Cook 27-54, Cook 307-92, and Cook 307.
When nematodes are present, nematode-resistant crops
should be used in a rotation with cotton. The following resistant
crops are desirable to use in the rotation: corn, oats, and other
grasses followed by or accompanying such legumes as Brabham,
Iron, and Monetta cowpeas, velvet beans, Laredo soybeans, or
peanuts.
Anthracnose
The most conspicuous stage of this disease is a boll rot or
boll spot, which, under favorable climatic conditions of high
temperature and abundance of moisture, may cause considerable
loss. On the bolls the disease first appears as small, water-soak-
ed spots, which soon increase in size and may completely destroy
the boll; however, as the disease develops the spots change into
brown or black spots with reddish borders and pink centers.
Badly diseased bolls never open; slightly diseased bolls may
open but will show a pink staining of the lint or a matting of
the locks. In some cases only one lock is destroyed,
The fungus causing the disease grows into the bur, lint, and
seed where many small spores are formed. These spores may
live from year to year in or on the seed. When such seed are
planted the fungus grows into the seedlings, killing them before
they appear above ground, or it may cause a type of "damping-
off" by attacking the young plants near the soil line. The fungus
may also live from one year to another on old cotton plants in
the field.
Control.-The practical methods of control are: Use at least
a one- or a two-year rotation of crops and use seed that are free
of disease. Disease-free seed may be obtained by selection of
seed from disease-free fields or by storage of seed for at least
three years.
DEPARTMENTS OF ZOOLOGY-ENTOMOLOGY AND BOTANY AND
PLANT PATHOLOGY