CIRCULAR No. 42 AUGUST, 1919
ALABAMA
Agricultural Experiment Station
OF THE
Alabama Polytechnic Institute
AUBURN
Cotton Worm Control
By
W. E. HINDS
Entomologist
1.919
Post Publishing Comipany.
Opelika, Ala.
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(Orig;inal)
COTTON WORM CONTROL
By
W. E. HINDS, ENTOMOLOGIST.
INTRODUCTION
The cotton worm is also known by a number of other
,common names such as "army worm" and "cotton leaf
caterpillar" and "the caterpillar." It is the only species
that accomplishes the complete defoliation of the cot-
ton plant throughout large areas. There have been
seven serious outbreaks of this species since its first
occurrence in Georgia and South Carolina in 1793.
OUTBREAK OF 1911.
In the outbreak of 1911 the first stripping in Alabama
occurred during the last week of July, and before the
end of that season the cotton in 66 counties had been
practically stripped. Careful field studies in 1911
showed that the cotton worms prevented the opening of
approximately 10 per cent of the bolls throughout the
State. Nevertheless, the yield in 1911 was next to the
largest ever produced in Alabama in spite of the work
of the cotton worms. It happened that in 1911 from
90 to 95 per cent of the entire crop was set and the bolls
were well on toward maturity by the first of August.
The present condition is very different therefrom, and
unless cotton can be kept in fruiting during August
1919, the yield this season is bound to be very short.
PROSPECTS FOR 1919.
There are two important insect factors in the 1919
cotton crop. The first of these is the boll weevil.
Every indication during the present season has been
for heavy weevil damage, and conditions at the
present time indicate that it may prove to be heavier
than for any preceding year, except possibly 1916, in
this State. On top of this condition of boll weevil in-
festation, is the prospect that the cotton worm may
destroy the foliage over large areas before the end of
August so that squares will cease to form and small
bolls will be destroyed. If this happens, as seems likely
at the present time, the insect damage to the present
crop will far exceed that sustained in 1911. The boll
weevil damage alone to the 1918 crop was not less than
$12,000,000.00 and weevil work was exceptionally light
in 1918.
WHAT SHOULD BE DONE?
Watch cotton closely every year to detect the first
signs of cotton worm attacks. Report immediately to
64
the Department of Entomology, Auburn, whenever-
cotton worms appear, as it is of the utmost importance
that the extent of distribution of this species and
its abundance in every section of the State should be
known as soon as possible. This is necessary if proper
stocks of poison are to be arranged for and placed
where they can be easily and economically secured
when needed by the cotton planters. Merchants should
not be expected to carry the entire burden for placing
this stock of poison. Cotton planters should divide
this responsibility with the merchants by ordering,
enough poison to meet their immediate needs for pro-
tecting their rankest cotton, where the worms are most
likely to appear first.
The amount needed for cotton worms for each
application will be from three to five pounds per
acre, and if proper materials are used, such as
Calcium Arsenate and Arsenate of Lead, it is likely
that one application will be enough to control each
generation. A total amount of from six to ten pounds
per acre will therefore, provide fairly satisfactory in-
surance for the cotton crop against the cotton worm.
This amount will not be enough to provide for treat-
ment of the boll weevil, which requires approximately
twenty pounds per acre for adequate treatment. When-
ever there is a prospect of cotton worm occurrence,
as under present conditions, it becomes increasingly
advisable to treat for boll weevil wherever the fer-
tility of the field is such that there is a possibility of
the plant continuing to grow squares and bolls until
the early part of September.
WHAT POISON TO USE
There are only two poisons on the market at the
present time that we recommend for cotton worm con-
trol. The first and cheapest of these is Calcium Ar-
senate, which is a comparatively new insecticide and
has not been used extensively in Alabama until the
present season. It is being used increasingly for boll
weevil control, and the principal stock of poison in the
State henceforth may consist of this material. However,
Arsenate of Lead, which was used very extensively i
1911 may also be secured and will give practically as
good results for cotton worms as will Calcium Arsenate,
although it is somewhat weaker in killing power and'
more expensive. Both of these poisons adhere well
to the leaves and can be applied with safety to the
plants. They will have no effect in checking the set-
ting of squares, and will not burn foliage, neither are
they likely to cause sores on men or mules using these
65
materials. No other material is needed to mix with
either of these poisons.
We do not recommend Paris Green as it is now far
more expensive than either Calcium Arsenate or Arse-
nate of Lead. It is also far more injurious to the plant
and more dangerous for the workmen handling it.
METHODS OF APPLICATION.
The simplest method of application is that recom-
mended and widely used in 1911, consisting of the
home-made so-called "pole and bag outfit." For the
pole use a piece of board about three-quarters of an
inch thick and four inches wide by such length as will
cover two or four rows of the cotton upon which it is to
be used. Lay out on the board the plan for the entire
outfit, marking for each bag so that it will be about
eighteen inches long on the pole and placing the bags
so that the middle of each will come over the cent r
of a row. Bore a 114 to 1/2-inch hole at the middle of
the space for each bag so that the poison may be in-
troduced after the bag is completed. The holes may
be closed with cork stoppers or with corn cobs after
the poison has been put in place. For the ends of each
bag cut off two pieces of the same board each four inch-
es long. Nail these pieces endwise on the underside of
the board and brace by a small piece of 1-inch quarter-
round on the inside and underneath the board so that
the end blocks will not be drawn out of place by the
tension of the cloth and the weight of the poison. (See
Plate II). The proper cloth for use may vary accord-
ing to the method of distribution intended. There are
two factors that govern the amount of material applied
per acre. One of these is the rate of distribution from
the bag, and the other is the rate of progress across the
field. The rate of distribution depends upon the tight-
ness of weave of the cloth and the agitation given the
outfit. If the poison is to be distributed by a man riding
a mule, much will depend not only upon the jar given,
but upon the progress, whether the mule is walking or
trotting.
As a general rule for cotton worm control, one thick-
ness of unbleached domestic or two or three thickness-
es of cheesecloth can be used in the bags for the distri-
bution of either Calcium Arsenate or Arsenate of Lead.
With the two bag outfit to be carried by hand, three
thicknesses of cheesecloth will give about the proper
distribution. A longer pole may be used covering four
rows and carried by a man on a mule. In this case,
there is greater jarring to the bags at the end of the
66
pole than those nearest the rider. Therefore, two
thicknesses of cheesecloth may be used for the bags
nearest the rider and three thicknesses for those at the
ends of the pole. The cloth is stretched tightly over the
blocks forming the ends of each bag and tacked at a
distance of from one inch to an inch and a half apart.
The stretching of the cloth should be lengthwise of the
bag especially, so that the bottom of the bag will not
sag from the weight of the poison. This gives better
distribution than where the poison is allowed to accu-
mulate in a short portion of a loose bag. The construc-
tion of this outfit is plainly shown in the illustrations
on Plate II.
NUMBER OF APPLICATIONS REQUIRED.
For cotton worm control alone, a single application
for each generation given at the time the worms begin
to eat through the tissue of the leaf, should be suffi-
cient for control of that generation of worms. Two or
three applications for the season may protect the crop
completely from cotton worms. However, if heavy
washing rains occur within twenty-four hours after
the dusting has been applied, it is likely that an imme-
diate repetition of the treatment may be necessary. The
best time for application is from daybreak in the morn-
ing until the dew is off the cotton. Do not allow the
bags to touch wet plants. The second best time for
application is rather late in the evening after the air
has become comparatively calm and continuing until
dusk. In emergencies however, it becomes advisable
to continue the dusting for cotton worm throughout
the day, and treatments can easily be given during
moonlight nights. The generations of cotton worm
develop in slightly less than four weeks. More fre-
quent treatments should be given, however, if the
worms threaten the foliage.
CONTROLLING BOTH BOLL WEEVIL AND
COTTON WORM.
In the past it has been considered that the boll weevil
could not be profitably controlled by dusting arsenical
poisons on the plants. Therefore hitherto, it has been
believed that after the boll weevil has stopped the set-
ting of bolls, it was not advisable to poison. During
recent years however it has been found that with a new-
er and better poison and with better methods of apply-
ing it, the boll weevil can be controlled. Calcium Ar-
senate applied by means of a dust gun driving the
poison through the plants very thoroughly, and applied
at proper intervals, will control the boll weevil very
67
satisfactorily. The expense for this treatment usually
amounts to eight or ten dollars per acre for four ap-
plications. (See Ala. Sta. Cir. No. 31) Wherever the
treatment is applied for boll weevil there will be no
trouble whatever from the cotton worm. With both
weevils and cotton worms in prospect, farmers who
have productive lands which will continue the growth
of the cotton until the first to the tenth of September,
if the boll weevils are controlled, should by all means
provide the necessary poison and proper apparatus
and treat for the boll weevil, and thereby control both
boll weevil and cotton worm. The treatment for the boll
weevil is generally applied at weekly intervals, and if
properly given, plants may continue to bloom and set
fruit as long as the fertility of the soil will enable them
to do so. The treatment for cotton worm will cost ap-
proximately one-half of that for boll weevil. If treat-
ment saves an average of only two bolls per plant it
will pay a profit on four dustings with the present
prices for seed and lint. Surely this increase can be
reasonably expected wherever the yield promises to
be one-third bale or better to the acre.
WHEN IS IT TOO LATE FOR BOLL WEEVIL
CONTROL?
Not so long as the cotton contiues to grow and set
bolls, or is capable of doing so if the boll weevils are
controlled. In our most productive fields, two or three
applications of Calcium Arsenate for the boll weevil
may be given with expectation of profit after the 15th
or 20th of August, and a single late application will
in many cases give very profitable results. Prompt
action will of course give best results.
Under conditions of heavy boll weevil infestation
and with the prospect of cotton worm occurrence, we
believe that it is highly advisable for planters to use
the Calcium Arsenate without delay for boll weevil
control. Hand dust guns may be obtained in limited
numbers from the manufacturers or from some of the
wholesale druggists in the principal cities of the State.
Calcium Arsenate is also available. Do not wait until
the cotton worm stops all possibility of further setting
of fruit or the boll weevils infest all of the squares be-
fore applying this treatment. The expense for control-
ling both boll weevils and cotton worms is a very small
item when the present price of cotton is considered.
Prompt action may save several million dollars worth
of cotton to Alabama farmers this season.
IYI.A1l" 11.
?.6 sJ~C
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~d?7 C4?~&~
12 i 1, Dlin" ba-L Iin process(( of construciiti(,!. Eillici two
or fiurioi {Hile j,'niaN be used wxithi one ba for eachi ro-v.
Fig. 2., Dusoting bai, (uiihIctedi, 'radlx for1 fillip". funinel ini l)Iie.
Fig. :1, siuppl of Cailciumu \irseni
t
e or Ar'senate of Lead. big.
I, Sitmd of lablorer ax~ppl inu duist fromi imule-back. Bletter
use a1 four ban pole for this~ iicItid of applicationu.
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