EI
3iu
Progress Report Series No. 44 April 1950
AGRICULTURAL EXPERIMENT STATION
of The Alabama Polytechnic Institute, Auburn, Ala.
. .* * , M. J. Funchess, Director
CONTROL of COTTON INSECTS with DUSTS and SPRAYS
F. S. ARANT, Entomologist
The boll weevil, Anthonomus grandis
Boh., was more abundant and more de-
structive in Alabama during 1949 than in
any other season during the 23 years that
control experiments have been conducted.
Other cotton insects were of minor impor-
tance, except in localized areas or where
populations of cotton aphid, Aphis gossypii
Glov., developed from use of calcium ar-
senate without an aphicide.
The previous winter was exceptionally
mild, and a large population of over-win-
tering weevils emerged in the spring and
early summer. Cloudy weather and fre-
quent rains produced ideal conditions for
multiplication of boll weevil during the
cotton-growing season .. Rainf 11 -mnrde con-
trol of insects extremely difficult in some
sections. Applications of insecticides were
washed off and the soil was frequently too
wet to repeat applications with ground ma-
chinery before additional rainfall occurred.
This progress report gives results of con-
trol experiments with organic insecticides
in 1949 and summaries of some principal
results during the 3-year period, 1947-1949.
1949 EXPERIMENTS
Experiments in the control of boll weevil
and other cotton pests were performed at
five localities in the State, namely: Mon-
roeville and Atmore in the southwestern
section, Headland in the southeastern area,
Prattville in the central area, and Tallassee
in the east central part.
Dusting at Monroeville
The 1949 cotton-growing season was
more nearly normal at Monroeville. than
in any other part of the State. Although
a high population of boll weevil adults
emerged from hibernation, weather was
favorable during late June and early July
for fruiting of cotton. As the over-win-
tered adults died, the infestation on cotton
declined and approximately one-half bale
per acre was set before serious damage
occurred. However, dusting was necessary
at frequent intervals between July 8 and
August 17. A total of nine applications
of dust was applied at the rate of approx-
imately 12 pounds per acre to cotton on
small plots. Treatments were replicated
five times in randomized blocks. Infesta-
tion counts were made at approximately
5-day intervals and yield records were ta-
ken at the end of the experiment.
Summarized results of experiments at
Monroeville Experiment Field are present-
ed in Table 1. Bollworm, Heliothis armng-
era (Hbn.), cotton aphid, and red spider
mites were minor factors in this experi-
ment, except where aphids became numer-
ous on plots dusted with calcium arsenate
containing no aphicide. Satisfactory con-
trol of boll weevil was obtained with all
insecticides. However, it was found neces-
sary to increase the rate of application of
organics above 10 pounds per acre in order
to effect control. Gains from dusting rang-
ed from 414 pounds per acre on the cal-
cium arsenate plots to 1,000 pounds per
acre on the areas dusted with 20 per cent
toxaphene. Toxaphene, BHC-DDT, and
calcium arsenate with nicotine appeared
about equally effective.
It will be noted 
that four applications
of 20 per cent toxaphene applied June 6
to 18 at the time cotton plants were just
beginning to square did not increase yield
of cotton.
Dusting at Headland
The season at Wiregrass Substation,
Headland, was somewhat similar to that
at Monroeville, except that the weevil in-
festation was much higher and rainfall
AI I)II II I I II II Al VI1 ll
rI L -
TABLE 1. SUMMARIZED RESULTS of COTTON-DUSTING EXPERIMENTS, FIVE
REPLICATIONS, MONROEVILLE EXPERIMENT FIELD, 1949
Av. Infestation Insects Per Sq. In Yield Seed Cotton Per Acre
Treatment 1/ Av. Gain Over
B. Weevil Bollworm Aphids R. Spiders Yield Check
Pct. Pct. No. No. Lb. Lb.
Check --------------------------------------- 73.7 2.0 2.44 2.42 1,742
20% toxaphene,
early and late 2/ --------------- 46.5 
2.2 0.27 0.34 2,640 898
20% toxaphene, late ----- 47.4 1.1 0.33 0.34 2,742 1,000
BHC-DDT, 3-5 -- ------------------ 49.4 1.3 0.32 1.79 2,548 806
Calcium arsenate
alternated BHC-DDT ------------- 50.6 0.9 1.30 2.51 2,508 766
Calcium arsenate
alternated calcium
arsenate + 2% nicotine - 49.0 0.7 0.95 0.66 2,631 
889
Calcium arsenate - 52.4 1.0 6.80 1.18 2,156 414
L. S. D., 5 per cent level 217
1/Dusts all inert, applied approximately 12 pounds per acre: July 8, 15 (rain), 18, 23, 28; August 2,
5, 11, 17 (rain).
2/Dusted June 6, 11 (rain), 13, 18 in addition to the dates given in footnote 1*
much more frequent. Also, temperatures procedure. Four check plots, located on
were lower, either side of the experimental area, were
The experiment was conducted on a field used to estimate the theoretical yield for
basis and insecticides were applied by Ne- each plot in the area.
gro labor using mule-drawn, 2-row dusters. Almost daily rainfall made application
No personnel of the Entomology Depart- of insecticides very difficult. A 
total of 11
ment was stationed in the vicinity of this applications of dusts was made 
at the rate
experiment, but trips were made at 5- to 7- of 10 to 15 pounds per acre between 
July 7
day intervals to make infestation counts and August 16. Seven 
of 11 treatments
and give instructions on application of in- were washed off by rainfall within 24
secticides. hours after application.
Treatments were replicated four times Summarized results of the experiment
in a linear series to simplify the dusting at Headland are presented in Table 2. Boll-
TABLE 2. SUMMARIZED RESULTS of COTTON-DUSTING, FOUR REPLICATIONS,
NON-RANDOMIZED, WIREGRASS SUBSTATION, 1949
Boll Weevil Bollworm Yield Seed Cotton
Treatment 1/ Infestation Infestation Per AcreGain Over
Dusted Check Dusted Check Dusted Check Check
Pct. Pct. Pct. Pct. Lb. Lb. Lb.
Calcium arsenate 74.1 87.4 2.2 2.4 1,125 597 528
BHC-DDT-inert, 3-5 48.1 88.3 0.0 2.9 1,550 448 1,102
20 toxaphene-inert 51.5 87.8 0.1 2.7 1,457 523 934
i/Dusts applied at rate of 10 to 15 pounds per acre with mule-drawn equipment as follows: July 7
(rain), 14 (rain), 18, 22 (rain), 26 (rain), 29 (rain); August 2 (rain), 5, 8 (rain), 11, 16,
-2-
worm, cotton aphid, and red spider mites
were of little importance in this experi-
ment. Where calcium arsenate was used
without an aphicide, the aphid population
was too low to warrant taking infestation
counts. The most effective control under
the condition of this experiment resulted
from use of BHC-DDT mixture, with 20 per
cent toxaphene second, and calcium arsen-
ate third. This is the second consecutive
year that BHC-DDT and toxaphene have
been more effective against boll weevil
than calcium arsenate at Headland. Dur-
ing both years the temperatures were mild.
Insect migration was extremely heavy and
frequent rainfall made it difficult to keep
insecticides on the plants. These condi-
tions were quite different from those en-
countered at Monroeville where tempera-
tures were higher, and very few applica-
tions of dusts were washed off by rain.
Tractor Spraying and Dusting at Prattville
Field-scale experiments were carried on
at the Murfee and Dismukes farms 
near
Prattville to determine effectiveness of tox-
aphene sprays and dusts for control of cot-
ton insects. Insecticides were applied with
tractor equipment 1/ to plots approximate-
ly 1 to 3 acres in size, depending upon the
length of the rows. All treatments were
replicated four times. Each replicate was
in a separate field.
1/Department of Agricultural Engineering coop-
erated in this work.
The cotton was planted following a
heavy crop of winter legumes in 
two of the
fields. Cotton in these two fields was very
rank, reaching a height of 6 to 7 feet on
undusted areas. The other two fields had
grown no legumes and the plants were con-
siderably smaller.
Frequent rainfall together with the
heavy, sticky nature of the soil made the
application of insecticides with ground ma-
chinery difficult. A total of 16 applica-
tions was made between July 1 and August
30. Seven of these applications were
washed off within 24 hours by heavy rain-
fall. The insect population was extremely
heavy, and it was necessary to shorten the
interval between applications of insecti-
cides in order to reduce infestation. Sprays
were applied at the rate of 6 gallons per
acre, while dusts -were applied at approx-
imately 12 pounds per acre.
Results of the tractor dusting and spray-
ing at Murfee and Dismukes farms are pre-
sented in Table 3. The toxaphene emul-
sion spray and the toxaphene-DDT emul-
sion spray appeared to be slightly more
effective than the dust in controlling boll
weevil. However, the differences in yield
from the three treatments were not signifi-
cant. The average gains resulting from
application of insecticides ranged from
1,043 pounds per acre of seed cotton on
the areas dusted with toxaphene to 1,230
pounds on the plots receiving toxaphene-
DDT spray.
The tractors used for applying sprays
TABLE 3. SUMMARIZED RESULTS of TRACTOR SPRAYING and DUSTING of COTTON
at MURFEE and DISMUKES FARMS, 1949
Amt. Insects Per Yield Seed Cotton
Treatment 1/ Tech- Average Infestation Square Inch Per Acre 2/
nical Boll Boll- Red Av. Gain Over
Per Acre Weevil worm Aphids Spiders Yield Check
Lb. Pct. Pct. No. No, Lb. Lb.
Check......----------------------------. 71.6 77 1.0 0.2 620
Toxaphene dust ------------------ 2.5 3/ 42.7 0.9 0.4 0.1 1,663 1,043
Toxaphene spray -- ---------------- 2 40.7 1.3 0.2 0.1 1,744 1,124
Toxaphene-DDT 2 Tox.
spray.------------------------- 1 DDT 35.8 0.2 0.1 0,0 1,850 1,230
L. S. D., 5 per cent level 308
1/Insecticides applied: July 1, 6, 11 (rain), 20 (rain), 25,
(rain), 13, 17 (rain), 22, 26, 30 (rain).
2/Based on undamaged rows.
28; August 2 (rain), 3, 6, 10 (rain), 12
3/Approximate rate; varied from 1.6 in first applications to 3 in last.
and dusts were equipped with guards de-
veloped at the Stoneville Laboratory of the
U.S.D.A. Bureau of Plant Industry, Soils,
and Agricultural Engineering. T h e s e
guards were manufactured, installed, and
adjusted by the U.S.D.A. Farm Tillage
Machinery Laboratory and the Experiment
Station's Department of Agricultural En-
gineering. However, some difficulty was
encountered in the use of these guards,
particularly in crossing terraces with the
equipment.
Considerable damage occurred to the
cotton as a result of the frequent applica-
tions of insecticides. Data showing results
of this damage are presented in Table 4.
It will be noted that the sprayer caused
much more severe damage than the duster.
The sprayer used was new equipment,
which rested low on the back of the trac-
tor. Damage was severe in cotton having
very rank growth, particularly in fields
East I and East II. The large number of
applications was another factor in the
amount of damage that occurred. How-
ever, these data emphasize the need for
more suitable machinery for applying in-
secticides in Alabama. In many sections,
well fertilized land produces a rank growth
of cotton. Hilly land and terraces add to
the difficulty of effective application of
insecticides with ground machinery.
Dusting and Spraying at Tallassee
Failure to get a stand necessitated aban-
doning the field of cotton originally plant-
ed for insect-control experiments. A sec-
ond planting on a smaller area was mad.e
the last week in May. This date is con-
sidered by farmers as too late to plant
cotton in Alabama and expect a crop.
However, the cotton grew rapidly and was
not seriously infested with the boll weevil
until migration began in early August. In-
festation after that time was extremely
heavy and the interval of application of
insecticides had to be shortened to 3 days
;a s0 
-insects. 
A total of
in order to control the insects. total of
12 applications was made between August
9 and September 9.
One spray and four dust mixtures were
used in the experiments. The spray was a
BHC-DDT emulsifiable concentrate con-
taining 10 per cent gamma BHC and 16.7
per cent DDT. The concentrate was dilut-
ed with water and applied with a hand-
sprayer at the rate of approximately 0.36
pounds gamma and 0.6 pounds DDT per
acre in 30 gallons of spray. The emulsion
tended to settle out in the spray tank unless
agitated continuously. Dusts were applied
with hand-dusters at the rate of 10 to 15
pounds per acre per application,.
Bollworm was a minor factor in this ex-
periment and practically no red spiders
TABLE 4. EFFECT of TRACTOR DAMAGE on YIELD of SPRAYED and DUSTED 
COTTON,
MURFEE and DISMUKES FARMS, 1949
Yield Of Seed Cotton Per Acre
Treatment Gain
Dismukes East I East II Church Average Over Check
Lb. Lb. Lb. Lb. Lb. Lb.
Check.----------------- .......-------------------- 640 508 340 993 620 
---
Toxaphene (tractor
dust (rows 920 1,556 1,332 1,008 1,204 584
(no tractor
(damage -- 1,226 1,836 2,136 1,456 1,663 1,043
Toxaphene (tractor
spray (rows 737 1,088 584 844 813 193
(no tractor
(damage 1,136 2,228 1,996 1,618 1,744 1,124
Toxaphene- (tractor
DDT spray (rows ------ - 831 1,212 1,160 750 988 368
(no tractor
(damage 1,490 2,088 2,308 1,515 1,850 1,230
L. S. D., 5 per cent level 308
-o
were found. Near the end of the experi-
ment, the aphid population on the calcium-
arsenate plots was high and the plants lost
most of the leaves early enough to reduce
the yield of cotton.
Summarized results of the dusting and
spraying experiment at the Station's Plant
Breeding Unit, Tallassee, are presented in
Table 5. These results are based on records
made from the four inner rows from each
plot. All insecticidal treatments reduced
boll weevil infestation and increased the
yield of seed cotton above that on the un-
dusted checks. Twenty per cent toxa-
phene dust and BHC-DDT 3-5 dusts were
the most effective treatments. Calcium
arsenate dust was the least effective treat-
ment in terms of seed cotton yield. An
aphid population of over 16 insects per
square inch of leaf surface developed on
plants dusted with calcium arsenate (Table
5), as compared with 3 insects on the un-
dusted checks. The leaves dropped from
the aphid-infested plants and prevented
many of the bolls from maturing properly,
thereby reducing yield on the calcium-ar-
senate plots. A new material, aldrin.
showed promise in the control of the boll
weevil in this experiment. The infestation
was lower than on the calcium-arsenate
plot and no build-up in apids occurred. A
gain of 1,066 pounds of seed cotton per
acre resulted from the use of 2 per cent
aldrin and 5 per cent DDT in an inert car-
rier. It is believed from thts experiment
that 2 per cent concentration is not quite
sufficient for best results from use of al-
drin.
While the BHC-DDT spray showed
promise, it was not as effective as the dust.
The high gallonage used in applying the
material may have been a factor in the re-
sults obtained with the spray.
Airplane Dusting and Spraying
Experiments were conducted on the con-
trol of cotton insects with sprays and dusts
applied by airplane at the Murfee and Dis-
mukes farms near Prattville and on the At-
more State Prison Farm.
Prattville. In the experiment near
Prattville, 20 per cent toxaphene dust, tox-
aphene emulsion spray, and toxaphene oil
solution were applied with aerial equip-
ment. The insecticide was applied at the
rate of 2 pounds of the technical material
per acre. A bi-plane was used in applying
the spray, with nozzles adjusted to delivei
2 gallons of spray per acre. Dusts were
also applied with a bi-plane at the rate ol
10 pounds per acre.
Four applications of the insecticides
were applied on a field basis between July
1 and 20, and infestation counts of insects
were taken at intervals of approximately
5 days. The owner and operator of the
plane left the project and went into conm-
mercial spraying in Mississippi about July
24. The project was discontinued and nc
picking records were made.
Average boll weevil infestations during
TABLE 5. SUMMARIZED RESULTS of COTTON DUSTING and SPRAYING, FOUR
REPLICATIONS, PLANT BREEDING UNIT, TALLASSEE, 1949
Yield Of Seed
Treatment 1/ Average Infestation Aphids Per Cotton Per Acre
Square Inch Average Gain Over
Boll Weevil Bollworm Yield Check
Pct. Pct. No. Lb. Lb.
Check ------- -- - 88.6 5.87 3.12 643 . ------
20 toxaphene dust -49.6 1.37 0.15 1,886 1,243
BHC-DDT spray 67.9 1.50 0.18 1,482 839
BHC-DDT, 3-5 dust ------------------- 52.2 1.37 0.09 1,864 1,221
Calcium arsenate ------------------ 65.4 2.37 16.16 1,120 477
2 / aldrin + 5(/, DDT dust -- 62.1 1.50 0.78 1,709 1,066
L. S.S. D., 5 per cent level 282
I/Insecticides applied: August 9 (rain), 13, 16, 19 (rain), 20, 23, 25, 29, 31 (rain); September 2, 7
(rain), 9.
5-
the pefiod of spraying are presented in
Table 6. All dusts and sprays reduced the
infestation of boll weevil, and sprays ap.
peared to be equal to the dusts in weevil
control.
Atmore. Seven applications of insec-
ticides were applied with aerial equipmeni
on the Atmore Prison Farm between July
29 and August 22. Boll weevil adults were
migrating in large numbers throughoul
most of this period. Rates of application
of insecticides and insect infestations are
given in Table 7. Infestation in the area
sprayed with toxaphene was slightly lower
than where 20 per cent toxaphene dust and
1.5 per cent dieldrin were used. All of the
insecticides reduced the boll weevil infesta-
tion well below that on the checks. Yield
records were not obtained in this experi-
ment at Atmore.
THREE-YEAR AVERAGE GAINS
from DUSTING
New organic insecticides have been 
used
experimentally in Alabama over a period
of 3 years. In one series 
of experiments,
tests were made to determine effectiveness
of insecticides applied during the 
time the
crop was being set and matured. In an-
other series, studies were made to deter-
mine the relative effectiveness of early and
late applications of dusts. Summarized
data on both series are herein presented.
Dusting While Crop Was Being
Set and Matured
Four insecticidal treatments have 
been
found to be effective in control of boll wee-
vil. Results of all experiments with four
leading insecticides, Table 8, show that 20
TABLE 6. AVERAGE BOLL WEEVIL INFESTATIONS in 
FIELDS DUSTED and SPRAYED
with AIRPLANE EQUIPMENT, MURFEE and DISMUKES 
FARMS, 1949
Amount Of Technical Infestation
Treatment 1/ Per Acre 
50 A Field Silo Cut East Road
Lb. Pct. Pct. Pct.
Check --- ------------------------- 
0 -- 55.3 
57.3
Toxaphene dust ------- ------- ---- 
2 47.6 17.2.
Toxaphene-oil emulsion 2 
21.0 35.8
Toxaphene-oil solution ---- 2 
30.6 14.7 39.9
I/Sprays applied at rate of 2 gallons and dusts 
at 10 pounds per acre per application: July 1, 
6, 11
(rain), 20 (rain).
TABLE 7. AVERAGE BOLL WEEVIL and BOLLWORM 
INFESTATIONS in FIELDS DUSTED
and SPRAYED with AIRPLANE EQUIPMENT, 
ATMORE PRISON FARM, 1949
Treatment 1/ Amount Of Technical Infestation
Per Acre Boll Weevil 
Bollworm
Lb. Pct. Pct.
West check ----------------------------- - 0.0 
89.3 1.0
Toxaphene spray ----------------------- 2.0 
41.5 0.5
Center check -------------------------- 
0.0 76.3 3.0
20% toxaphene dust -----------.. _. 2.0 
52.7 0.6
1.5% dieldrin 2/ ----------------- 0.15 
47.7 4.3
East check --------------- ---- 
0.0 81.7 1.3
I/Insecticides except dieldrin applied: July 
29 (rain); August 2, 6 (rain), 11, 15, 19 (rain), 
22.
2/Applied: August 6 (rain), 11, 15, 
19 (rain), 22. This area had been 
dusted with toxaphene July 29
and August 2.
per cent toxaphene dust and BHC 3-5 mix-
ture increased the yield of cotton approx-
imately one-half bale per acre in a large
number of experiments. Gains from alter-
nate applications of calcium arsenate and
calcium arsenate containing 2 per cent ni-
cotine were considerably less in a smaller
number of experiments. Severe damage
from bollworm reduced the yield on the
calcium-arsenate plots during one season.
During another season, very light boll-
weevil infestation occurred and the gains
were small in all experiments. For these
reasons, the average gains from calcium
arsenate and calcium arsenate-nicotine are
somewhat smaller than might be expected.
Where calcium arsenate was used without
an aphicide, the average gain from dusting
was only 205 pounds of seed cotton per
acre.
It is realized that the data in Table 8 are
taken from a large number of experiments
conducted under different conditions. In
any exact evaluation of the results, insects
present and conditions under which the ex-
periments were conducted must be taken
into account. However, the averages given
in the table are indicative of yields and
gains that may be expected from control
of cotton insects on good land in Alabama.
Tabulated results of experiments, where
the four commonly used insecticides oc-
curred together in the same field, are pre-
sented in Table 9. With one exception
gains from dusting are lower than in Table
8, which includes more tests. However, the
yields in Table 9 should represent a fair
measure of relative efficiency of treat-
ments against major cotton pests under
Alabama conditions during the 3-year per-
iod, 1947-1949.
TABLE 8. THREE-YEAR AVERAGE YIELD of SEED COTTON on ALL DUSTED AREAS and
CORRESPONDING CHECKS, 1947-1949
Yield Of Seed Cotton Per Acre
Treatment Replications Gain From
Dusted Undusted Dusting 1/
No. Lb. Lb. Lb.
Calcium arsenate ----------------- 36 1,749 1,536 213
Calcium arsenate alternate with
calcium arsenate-2% nicotine 25 2,135 1,821 
314
BHC-DDT, 3-5 dust 39 2,085 1,425 660
20 ( toxaphene dust-------------- 73 2,103 1,349 754
1/These gains may not be strictly comparable, since all treatments did not always occur together in the
same experiment.
TABLE 9. THREE-YEAR AVERAGE YIELD of SEED COTTON in ALL EXPERIMENTS WHERE
FOUR INSECTICIDES OCCURRED TOGETHER in the SAME TEST, 1947-1949
Treatment Replications 
Yield Of Seed Cotton Per Acre
Yield Gain Over Check
No. Lb. Lb.
Check --- 21 1,946.211
Calcium arsenate -- 21 2,048 102
Calcium arsenate alternate with
calcium arsenate-2 (' nicotine ------ 21 2,292 346
BHC-DDT, 3-5 dust 21 2,385 439
20( toxaphene dust------------------ 21 2,459 513
-7-
Timing Applications of Dusts
For many years entomologists and 
farm-
ers alike have been interested in the possi-
bility of applying insecticides early 
to kill
over-wintered boll weevils. In theory, the
elimination of these over-wintered 
adults
should reduce damage later in the year. 
In
practice, profitable control of boll weevil
has not resulted from use of calcium 
arsen-
ate in the form of pre-square mopping and
pre-square dusting.
Introduction of new organics again 
fo-
cused attention upon early application of
insecticides. Early application on county-
wide basis has been recommended 
in some
sections of Texas. Experiments have been
conducted in Alabama during the past 3
years in order to determine the 
effective-
ness of early applications with new insec-
ticides. In general, the procedure has been
to apply three to four applications of insec-
ticides at 5-day intervals, beginning 
just
before the first squares are 
large enough
for boll weevil egg punctures. 
This pro-
cedure should permit a maximum 
number
TABLE 10. EFFECT of TIME of APPLICATION of 20 PER CENT TOXAPHENE DUST on INSECT
CONTROL and COTTON YIELD, FOUR to FIVE REPLICATIONS, 1947-1949.
Average Insects Per Yield Of Seed
Year Treatment Infestation Square Inch Cotton Per A.
Boll Boll- Red
Weevil worm Aphids Spider Yield Gain
Pct. Pct. No. No. Lb. Lb.
Undusted check .............---------------- 48.5 12.8 7.1 .... 3/ 762
3 dustings, June 17-
1947 1/ July 2 2/ ...........------------------- 45.8 18.6 7.3 ---- 629 -133
5 dustings, July 11-
August 21 2/ --------------- 20.0 4.5 2.2 1,165 403
Undusted check ........---------------- 45.8 ..... 3/ 2.7 ---- 3/ 1,616
3 dustings, June 2-12 ------ 38.8 1.7 - 1,609 -7
3 dustings, June 2-12,
1948 plus 7 dustings, July 12-
August 14 ......... ..------------- 26.7 -- 0.7 2,018 402
7 dustings, July 12-
August 14 --- .. ...--------------- 24.6 0.7 ---- 2,075 459
Undusted check .----------------. 54.7 5.5 0.3 1,760
3 dustings, June 1-15,
1948 plus 7 dustings, July 7-
August 12 --------..----------. . 48.9 3.0 2.9 1,892 132
7 dustings, July 7-
August 12 ----- .........------------- 46.8 3.3 1.1 1,898 138
Undusted check ---------------- 73.7 2.0 2.4 2.4 1,742
4 dustings, June 6-18,
1949 4/ plus 9 dustings, July 8-
August 17 -------------------- 46.5 2.2 0.3 0.3 2,640 898
9 dustings, July 8-
August 17 ..----------- - - 47.4 1.1 0.3 0.3 2,742 1,000
1/Population of over-wintered weevils June 14 averaged 502 per acre over the experimental 
areas.
2/Plus one application washed off.
3/Practically no damage.
4/Population of over-wintered weevils averaged 130 per acre over the experimental 
area June 6 before
dusts were applied.
of over-wintered weevils to emerge and
then kill the insects with insecticides before
they have an opportunity to infest cotton
squares.
Results of field-scale and small-plot ex-
periments on timing of applications are
presented in Table 10. No gains have re-
sulted from the early applications in Ala-
bama. During one season, the plots re-
ceiving three early dustings produced less
cotton than undusted checks in each of
four fields near Prattville. The reduction
in yield resulted from bollworm coming
into the area after the dusting operation
had ceased. Insect predators had been
destroyed by the insecticides and boll-
worms caused more damage on dusted
than on undusted areas. In all other tests,
the yields on plots treated early have been
slightly but not significantly lower than
those on the corresponding plots receiving
no early application.
It is concluded from these experiments
that insecticides applied to young cotton
having a few or no squares were ineffec-
tive in increasing the yield. There is evi-
dence that setting of bolls occurred a little
earlier where the early applications were
made.
SUMMARY
Gains in cotton yields resulting from
dusting and spraying for control of boll
weevil, Anthonomus grandis Boh., and
other cotton pests ranged from 766 to 1,243
pounds of seed cotton per acre on well fer-
tilized land in 1949, a season of extremely
high insect populations and adverse weath-
er conditions. Materials giving the most
effective control and highest yields were:
(1) 3 per cent gamma benzene hexa-
chloride-5 per cent DDT dust, (2) 20 per
cent toxaphene dust, and (3) 
sprays pre-
pared from emulsifiable concentrates of
toxaphene or toxaphene and DDT.
Dust containing 2 per cent aldrin 
and 5
per cent DDT was effective, but plots re-
ceiving this mixture yielded 
slightly less
cotton than plots treated 
with toxaphene
or BHC-DDT dust. A spray 
prepared from
an emulsifiable concentrate of 
BHC and
DDT was somewhat less effective 
than tox-
aphene sprays. Dieltrin applied as a 1.5
per cent dust showed promise against 
boll
weevil.
Over a 3-year period, 73 replications of
20 per cent toxaphene dust resulted 
in an
average gain of 754 pounds of 
seed cotton
per acre over undusted cotton; 39 replica-
tions of BHC-DDT mixture resulted in 
a
gain of 660 pounds of seed cotton per acre.
Thirty-six replications of calcium 
arsenate
without an aphicide resulted in a 
gain of
213 pounds of seed cotton per acre.
Three-year average results on timing 
of
applications of insecticides on 
cotton re-
sulted in yields as follows: Cotton 
receiv-
ing three applications before and 
just after
squaring begins without later treatment
averaged 70 pounds of seed cotton 
per
acre less than cotton receiving no 
insecti-
cide. Where three early applications 
were
followed by an average of seven 
dustings
during the time the crop was being 
set and
matured, the average gain was 
483 pounds
of seed cotton per acre over 
undusted
areas. Cotton receiving no 
early treat-
ment, but dusted an average 
of seven times
while the crop was being set and 
matured,
produced 508 more pounds of 
seed cotton
per acre than undusted areas-in 
the same
experiments.
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