investigations in control of hemipterous cotton insects in Arizona by the use of insecticides

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Title:
investigations in control of hemipterous cotton insects in Arizona by the use of insecticides
Physical Description:
19, 1 p. : ill. ; 27 cm.
Language:
English
Creator:
Cassidy, T. P
Barber, T. C
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

Subjects

Subjects / Keywords:
Cotton -- Diseases and pests -- Arizona   ( lcsh )
Hemiptera -- Control -- Arizona   ( lcsh )
Insecticides   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

General Note:
Caption title.
General Note:
"E-506."
General Note:
"July 1940."
Statement of Responsibility:
by T.P. Cassidy and T.C. Barber.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030271633
oclc - 778788572
System ID:
AA00023022:00001

Full Text


STALTS IU1A A
E-506 ARCUTRE July 1940


CTmoLOG AND
8MREAU Of .

PLANT QUARANTINE







INVESTIGATIONS IN CONTROL OF I-iIIPTEROUS COTTON
INSECTS IN ARIZONA BY TIM USE OF IYSEC7ICIDES

By T. P. Cassidy and T. C. Barber, Division of
Cotton Insect Investigations1i



Introduction

The problem of reducing the damage caused to cotton by hemipterous
insects in Arizona has been receiving serious consideration during recent
years. In 1938 a circular2/ was issued by the Bureau of Entomology and
Plant Quarantine giving the progress of experimental work up to and includ-
ing the season of 1937. That circular described the methods which had been
followed in determining the relative economic importance of each species
to the cotton crop, discussed the more economically important species, and
included a description of the character of the damage inflicted to the cot-
ton plant by the different groups of insects. It concluded with a resume
of the experiments in control with insecticides, which had been conducted
to that time, together with recommendations of measures which had been in-
dicated as practical and profitable as a result of these experiments.

Since Circular E-439 was published, 2 more years of experimental
control work have largely confirmed the correctness of the information
given therein. The present circular is intended to supplement the earlier
one by reporting the results of 2 more ;,ears of experiments, including,
last season, the use of airplane dusting.

The Kore Important Hemipterous Insects Attacking Cotton in Arizona

Out of 53 species of hemipterous insects collected on cotton in
Arizona, 8 were listed in Circular E-439 as being those most injurious to

_/ The writers were assisted in the field by !U. A. Stevenson, H. G.
Johnston, L. W. Sheets, J. MI. Breazeale, and H. J. Crawford.
2/ Cassidy, T. P., and Barber, T. 0. Hemipterous Cotton Insects
of Arizona and Their Economic Importance and Control. U. S. Dept. Agr.,
Bur. Ent* and Plant Quar. Circ. 2-439. (M-limeographed.)







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the cotton crop. These included three pentatomids, Euschistus impictiven-
tris Stel, Chlorochroa sayi Stal, and Thyanta custator Kirk.; four mirids,
Lygus hesperus Knight, r rtensis oblineatus (Sayr), Creontiades femor-
alis Van D., and Psallus seriatus (Reu.); and one pyrrhocorid, Dysdercus
mimulus Hussey.

A change has occurred during the past 2 years in the importance of
Dysdercus .iimulus. For some unknown reason this species, which was then
abi ant, has become so scarce, especially in the Salt liver Valley, that
amoa collections at thousands of points in 1939 only two or three speci-
mens were found. While this insect was so scarce that it was not consider-
ed of much economic importance in 1939, it must be recognized that at any
time it may reappear in damaging numbers.

The increasing importance of the mirid Creontiades femoralis should
also be emphasized. This species is ap:oarently increasing in the main
Arizona cotton areas, particularly in the south side of the Salt River Val-
ley, where for the past 2 years it has greatly outnumbered the combined po-
pulations oi :e two species of Lygus, which were formerly considered the
most com-on and destructive mirids. Repeated experiments have proved C.
femoralis to be more destructive to the cotton plants, insect for insect,
than either of the species of L !.oreover, Creontiades can maintain
itself and multiply readily on the cotton plants throughout the growing
season, whereas 'Lvgs can maintain itself in the cotton fields only after
the -lants have become large enough to furnish heaVy shade and are squaring
and fruiting heavily. Even then it does not multiply rapidly on cotton,
and ldiost of the population comes from migrations from other host plants in
the vicinity.

With the foregoing modifications the original list of the more in-
Jurious hemipterons in Arizona cotton fields is still accurate. No new
hemipterous insects of marked economic importance to the cotton crop have
been found in Arizona during the past two seasons.

Nature of Damage to Cotton by Pentatomids (Stink Bugs)

The three important species of stink bugs in Arizona cotton fields
are boll feeders, and feed but little on either the foliage or squares.
The damage caused by boll puncturing is greatly aggravated by lint stain-
ing, which follows as a result of pathogenic organisms that gain entrance
to the bolls through the *mnctures. Punctured bolls are shed in large num-
bers, but the ones not thrown off may exhibit varying degrees of injury from
a small stain in ona lock of the matured boll to what is termed an "unpick-
able boll," which is a unified, half-opened boll with the lint in every
lock i:a)acted, stained, short, weak, and of little or no market value. In
heavily infested fields a high percentage of the bolls are unpickable and
remain on the plants after the crop has been picked, and in extreme cases
the yield may be reduced b,, more than one-half.
Nature of Damage to Cotton by i-lirids (Leaf Bugs)
The d anage caused to cotton by Ls spp., Creontiades femoralis,
and other mirids differs from that of the pentatomids in that it is mainly







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concentrated upon the terminal buds, squares, and small bolls. The bud in-
Juries frequently result in a deformed vegetative type of growth, due to ex-
cessive branching of adventitious buds following the destruction of the
terminal buds. The square injury causes heavy shedding resulting in a re-
duction of the ultimate crop, although the squares shed are partially com-
pensated for by the tendency of the cotton plant to put on extra fruit to
replace early losses. Damage is also inflicted on small bolls, resulting
in considerable shedding and light lint staining, but the boll damage is
much less severe than in the case of the pentatomids, and the staining is
not so pronounced. Although the work of the mirids is not so conspicuous
as that of the pentatomids, the total amount of loss will closely approach,
if not exceed, that caused by the stink bugs.

Indirect Loss from iHemipterous Insect Damage

In addition to the direct injury to the cotton, a secondary source
of trouble consists of the dissatisfaction among the cotton pickers in
fields which have been heavily damaged by hemipterous insects. The cause
of the trouble is the sticking of the lint to the -proliferations within
the punctured bolls, augmented by the tendency of "'d.. punctured bolls to
open only partially, so that undue effort is required to pick the cotton
from them. These p-nctured bolls often require several 1'pulls," while in
a clean, unpunctured boll the lint can usually be gathered with a single
motion of the hand. Since in damaged fields the amount of cotton a picker
can gather is determined largely by the percentage of punctured bolls, the
pay is correspondingly reduced. This aspect sometimes assumes serious pro-
portions, the pickers migrating from camp to camp in an effort to locate
"clean" cotton fields.

The effect of hemipterous insect injury upon the Arizona cotton
crop was summarized in Circular 7-439 as follows:

"(I) It reduces the total amount of the crop by causing abnormal
cotton plants and heavy shedding of the squares and small bolls.

"(2) It reduces the grade and value of the lint on account of the
staining which follows the attacks of the boll-feeding species.

'(3) In cases of heavy infestation it renders a certain percentage
of the crop 'unpickable' and valueless through the almost complete destruct-
ion of many bolls.

"(4) It reduces the value of the seed for planting or milling, as
many seeds are injured in early development and fail to mature. iMany of
the faulty seeds are also broken in ginning and become mixed with the lint.

"(5) It causes much dissatisfaction among the cotton pickers by
slowing down their work and hence reducing their pay."






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Extent of Damage to Cotton by Hemipterous Insects in Arizona

Accurate estimates of the losses from bud, square, and small boll in-
juries are more difficult to obtain, but much information has been secured
on the damage inflicted by hemipterous insects upon the mature bolls. From
1934 to 1939, inlcusive, an intensive survey vas made each fall of the main
cotton-grow ng area of Arizon-. Representative cotton fields were selected
in all theve aieas, and cotton bo'!Is w-lee collectet frorm five points in each
field. Fai' thiou-:nds of cotton. bolls were thinis collect!c' each year, all of
which were ou~; into the laboratory and examined individually, both ex-
ternally and internally. A summary of the results of these annual surveys
is shown in table 1.

Table 1. -- Damage to cotton bolls by hemipterous insects
in Arizona cotton areas, 1934 to 1939, inclusive

Year Short-staple cotton Lon,7-,taole cotton
Number of Percentage Number Percentage
bolls of bolls of bolls of bolls
examined punctured examined punctured

1934 18,393 23.4 ....
1935 30,700 27.2 .....
1936 41,500 24.8 12,500 6.13
1937 21,200 2,3.5 5,000 7.7
193,? 43,810 31.5 30,958 14.63
1939 35,000 ?8.? '27,500 8.73

Total 190,603 75,958

Average 26.3 9.29

These figures show that over a period of 6 years an average of 26.3
percent of the short-staple bolls for the State had been punctured by hemip-
terous insects. In long-staple cotton the damage by boll-feeding insects is
materlaJily less, but considerable evidence has been gathered to indicate
that tne bucd and square injury is probably as great as if not greater than in
the short-staple cotton.

The comparative amount of boll injury varies greatly, yet consistently,
with the locality. For 6 consecutive years Yuma County, in the southwestern
corner of the State, has shown the heaviest hemipterous insect injury, ranging
from 40.3 percent in 1937 to 62.1 percent in 1939, with a 6-year average of
5347 percent. Pima County has as consistently shown the least injury, rang-
ing from 5.1 to 12.2 percent, with a 6-year average of 7.4 percent. The re-
maining cotton-producing counties have always fallen between these two ex-
tremes of infestation.

A number of factors are res-oonsible for the differences in the amount
of damage in different sections of the State, some of them unknown. The
boll-puncturing species are general feeders and attack many fruits and seeds.
They are frequently abundant in damaging numbers on other crops, such as al-
falfa, sugar beets, and grain sorghums, and they are found in considerable







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numbers on desert vegetation. The infestation in cotton is mainly due to
their migrations from these alternate host plants. The proportion of land
planted in other Crops and their proximity to the cotton fields, the time
they are harvested, the amount of rain and its effect on desert vegetation,
and the density of weed growth and other vegetation, all influence the mi-
grations of hemipterous insects to cotton and the time when damage occurs.

Control experiments

After preliminary tests with various insecticides in lantern globes
and cages, small field plots were dusted with hand guns and then larger
plots of 2 to 5 acres were dusted with a five-row power duster. For the
past 2 years particular attention has been given to sulfur and combinations
of sulfur and paris green or sulfur and calcium arsenate. The increase in
yields over the checks in the 53 plot experiments conducted during the period
1933 to 1939 are given by years for each locality in table 2 and are sum-
marized in table 3.






Table 2.--Sunrrary of all small-scale field control tests against heiaipterous cotton insects (includ-
ing all field-plot experiments of five acres or less in size), Arizona, 1933 to 1939, inclusive


insecticide tested


Calcium arsenate and
Paris green and sulfur

S:1 fur

Paris y7cen and calci-.-,
,ars.natc (1-3)

Le.ad arscnato

C-Acium arsenatc

Sodiwu fluosilicate




D:'ris and sulfur

.Pz' thrum and sulfur

Paliis grcon 7-1/2%, clay
9 2-1 / 2el


Increase in yield of seed cotton


Buckeye
1933


297

384


Buckeye
1934


189



454


517

328

151


Buckeye
1935


2o6



523


0

138

138

151
41


Buckeye
1936

27 4/


150

0

0

34


1937


11/


(pounds) per. acre in dusted plots over checks


Buckeye Yina Buckeye
1937 1937 193g

694-/2,333/ 791?/

gl5/2,6914- 392k/


Yuma Mesa Buckeye Mesa
1939 1939 1939, 1939


54./


178 1,078 1,274 1,620


58
120
43


1,is

310
818


169?!

3753

157


313_?!

57
375


812/
117 3/

91


6oo


-ICalciu. arsenat: 33-1/3%, sulfur 66-2/35.
,7aris greon 7-1/21%, Sulfur 92-1% (1-12-1/3)
aris grecn 5%, sulfur 95% (1-19).


.Calcium arscnatc 20%,
-'Paris green 10%, su


sulfur so0 (1-4).
ifur 90% (1-9).








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Table 3.-- Average gains from the use of different insecticides
tested upon a field-plot basis in Arizona, 1933 to
1939, inclusive



Insecticide tested Total number Average gain in seed
of expri- cotton,pounds per
ments:- acre.

Calcium arsenate and stilfur 8 683.2

Paris green and sulfur 10 528.6

Sulfur 11 525.2

Paris -reen and calcium arsenate 3 392.0

Lead arsenate 7 329.1

Calcium arsenate 5 258.4

Sodium fluosilicate 2 258.5

Pyrethrum 2 233.0

Derri s 2 144.5

Derris and sulfur 1 151.0

Pyrethrum and sulfur 1 41.0

Paris green 7-1/21, clay 92-1/2, 1 19.0
l/ In most experiments the treatments were replicated from one to
several times, and the number of plots treated is therefore much greater
than the number of experiments shown.







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It will be noted that the first three insecticides listed have
shown the largest gains year after year; these gains fluctuated greatly
in different localities and years, as they were affected by local condi-
tions and the intensity of insect populations. The calcium arsenate-sul-
fur mixtures in 8 experiments over a period of 4 years and in 3 localities
have given an average gain of 683.2 pounds of soed cotton per acre over un-
treated check plots. The paris green-sulfur mixtures in 10 experiments
over a period of 5 years in 3 localities have given an average gain of
528.6 pounds of seed cotton per acre. Dusting sulfur in 11 experiments
over a period of 7 years and in 3 localities has given an average gain of
525.2 pounds of seed cotton per acre. In addition to giving the best in-
sect control of all treatments tested, these three insecticides are avail-
able at a reasonable cost.

Airplane Cotton Dusting Experiments in Arizona, 1939

In the experiments reported above, the insecticides were applied
with hand dust guns and ground power dusting machines. However, neither
method of application if fully adapted for large-scale field dusting in
Arizona. The hand machines are too small to be practical and require too
much expenditure for labor. ',hile a powTer dusting machine can efficiently
dust some 50 or more acres of cotton in a night at an application cost of
about one-half of airplane dusting, the use of power ground machines pre-
sents definite difficulties. The irrigation schedules interfere seriously
with the use of a ground duster, as in some soils the machine cannot be
used for several days after an irrigation on account of the muddy condition
of the ground. When cotton reaches its maximum growth the latter Oart of
the season, insect populations have usually reached a peak and dusting is
most urgently needed, but the dusting machine cannot be drawn through the
fields without causing material damage to the cotton plants and fruit.
Then, too, in the event of a sudden insect migration to cotton, it may be
necessary to apply insecticides at a much faster rate than can be done
with a ground machine. For these reasons it is believed that hand and
power machines will not be entirely suitable for average conditions in
Arizona. Obviously a method of insecticide aolication is required which
will not be affected by the field irrigation schedules, which will not in-
jure the cotton plants when they attain large size, and moreover will
ermit the dusting of large acreages in the shortest possible time. The
use of airplanes promises to meet these requirements. The desired type
of dust cloud as applied with a ground power dusting machine is shown in
Figure 1. It has been found that under ideal climatological conditions
a satisfactory dust cloud and distribution of insecticides can be obtained
with air-olanes in Arizona. An airplane dusting cotton is shown in figure 2.

During 1939 a series of large-scale airplane dusting experiments was
conducted cooperatively with the J. G. Boswell Company and a number of cot-
ton growers to obtain information on the efficiency, practicability, and ex-
pense involved in this method of insect control, and the minimum number of
injurious hemipterous insects that would justify airplane dusting. The dis-
tribution of dusted cotton fields was planned to cover the major cotton-
growing sections of the State, and they included fields located in areas





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that were heavily and lightly infested in previous years. The fields were
selected and arrangements made for the experiments before the insect sbun-
dance could be determined. Later examinations showed that in some fields
the insects did not reach what are considered to be commercially damaging
populations, and in no fields were the populations as heavy as in some of
the previous'experiments dusted with ground machines. However, as one of
the aims of the a-irplane dusting experiment was to determine the insect po-
pulations that would justify control operations and -Produce a profit, it
was decided to carry through the season 8 large-scale field experiments as
planned, regardless of insect populations or cost. Each field consisted of
40 or 80 acres, half of which was dusted with a mixture of 7-1/2 percent
paris green and 92-1/2 percent sulfur and half left as an untreated check.
"'he gains over the checks in the 6 dusted fields in Maricopa County in 1939
are shonr. in table 4.


Table 4.--Summary of gains in the airplane dusting ex-
periments, Salt River Valley, Arizona, 1939


Field Type of Gains in seed cotton, dusted plots over checks
N Location cotton Pounds per acre Percent

1 Palo Verde Short 47 3.2
2 Buckeye Do. 34 2.5
3 Perryville Do. 87 4.1
4 Marinette'~ Do. 208 9.3
5 Marinette Pima 59 7.1
6 Ch,,ndler Do. 242 40.4
7 lilb e7t Do. 154 12.5
8 Me .q Short 240 15.7

Average 5 short-staple fields 123 6.9
Average 3 long-staple fields 152 20.0

It will be noted that despite the unfavorable insect conditions for
the experiments. Increases in yields ranging from 2.5 percent to 40.4 per-
cent were obtained. In the 5 short-staple fields an average gain of 123
pounds, or 6.9 percent, of seed: Cotton per acre was obtained by dusting,
while in the 3 long-staple fields the average gain was 152 pounds, or 20
percent, of seed cotton. These figures and the seasonal insect population
counts show that airplane dusting with the paris green-sulfur mixture will
reduct hemipterous insect populations and their injury to cotton but that
it will not be profitable under all conditions with low insect populations.

The population and yield records in the experimental fields of 1939
indicated that, while some increase in yields could be secured from dusting
fields with light infestations, a population of 12 to 15 of the injurious
species per 100 strokes with a standard sweep net is required to justify
control by airplane,, and that dusting should be discontinued when the in-
sects are reduced below these numbers. ?urther work is needed before de-
finite recommendations can be made as to the populations that will yield






10 -

profitable returns from control, the increase in yields that can be expected,
and the number of dust applicati6is'thatwill give the most economical control.

There have been so many requests for the results of the airplane dust-
ing experiments that the detailed records of two fields, one in short-staple
and one in long-staple cotton, are given in the following pages.

Seasonal History and Yield Records of Experimental
Field No. 8, Acala Short-Staple Cotton

This was an 80-acre field divided into four 20-acre strips, two of
which were dusted and two undusted for securing comparative records in the
treated and untreated cotton.

Dusting records:

Insecticide applied -- paris green 7 1/2 ,, sulfur 92 1/24, at
7-day intervals.

Yitmber of applications -- 7, at 15 pounds per acre-application.

Method of application -- airplane in early morning hours.

Dates of a oolication -- July 13, 20, 26, August 2, 9, 16, 23.

Cost of dusting -- $1.17 per acre-application, including insecticide.

Total amount of inseoticide applied -- 4,200 pounds

Hemipterous insect infestation records:

Twelve population counts made at weekly intervals.

First count made June 22 and final count made September 8.

Populations of injurious hemioterous insects:

Number of injurious insects -per 100 strokes

Dust ed Check

Seasonal average 8.21 10.25

Peak infestations 19 28

Period of commercial damage 3 weeks 4.5 weeks

Dusting reduced the infestation an average of 2.04 injurious insects
per 100 net strokes over the season, and reduced the peak infesta-
tions by 9 insects per 100 strokes. It also reduced the period of
severe damage by one-third.











Records of form counts:

Average number of forms perlolant

Date Dusted Check

June 23 9.77 9.33

July 19 32.08 27.69

August 26 17.85(15.88 bolls) 13.96(13.27bolls)

At the last count, the dusted plots exceeded the check plots on the
average by 2.61 bolls per plant.

Record of boll examinations for hemipterous insect damage:
Percent of bolls punctured

Date Dusted Check

August 10 21.75 31.25

September 6 34.25 52.00

Yield of seed cotton in comparable areas:

The average yield per acre was 1,770 pounds in the dusted lots and
1,530 pounds in the check plots. The average gain in the dusted plots over
the checks was 240 pounds, or 15.7 percent.

Rendition of lint:

On a field basis the gin records show that the dusted plots yielded
0.8 percent more lint from seed cotton than did the check plots.








- 1? -


Classing and grading records:

Dusted Check

No. of bales Percent No. of bales Percent

Total yield 47 -- 39 --

Grade

,Strict Middling 23 48.9 8 20.5

Middling 24 51.1 31 79.5

Color

""hit e 44 93.6 36 92.3

Spotted (last picking) 3 6.4 3 7.7

Staple

7/8" 2 4.3 2 5.1

15/16" 3 6.4 6 15.4

1" 14 29.8 16 41.0

1-1/32" 24 51.0 10 25.7

I11 16" 4 8.5 5 12.8

It is seen that a higher percentage of lint was produced and a bet-
ter grade and staple was obtained in the dusted cotton.

Value of Acala seed cotton

11ith a gin lint turn-out of 36.5 percent, 9.5 cents per pound for
the lint and l24 per ton for the seed, 100 pounds of seed cotton would
bring the following returns:

36.5 pounds of lint at t0.095 t3.47

63.5 pounds of seed at tO.012 0.76

Total $4.23







13 -

From the extra yield ettri'butable to dusting, however, the follow-
ing costs per hundred pounds of seed cotton would have to be deducted:

Picking and hauling 0.95

Ginning 0.30

sagging and ties 0.09

Total $1.34

The net value of 100 pounds of *.cala seed cotton would therefore
be 4.23 minus '1.34, or $2.89 per hundred.

Computing profit from the above figures, and not considering the
increased value of the dusted cotton due to an increase in lint turn-out
and a better grade and staple, the value of 240 pounds of seed cotton
gained per acre as a result of dusting Is $6.94. The cost of seven ap-
plications of dust at 'l.17 per acre-application is t8.19, which shows
a net loss of $1.25 per acre. However, at least three applications of
dust were made in the experiments before the insect population reached
damaging numbers, and it is believed that four applications would have
given the same yields and a profit of t2.26 per acre.

Seasonal History and Yield Records of Eroerimental
Field Yo. 6, Long-Staple Cotton

'This was a 40-acre field of Pima cotton divided into four 10-acre
strips, two of which were dusted and two untreated. The field was divid-
ed into 1-acre plots for securing yield records in the dusted and undust-
ed cotton.

Dusting records:

Insecticide aplied -- paris green 7 1/2, sulfur 92 1/21
at 7-day intervals.

Number of applications -- 7, at 15 pounds per acre-application.

Method of application -- airplane, in early morning hours.

Dates of application -- July 13, 20, 26 -- Aug. 2, 9, 16, 23.

Cost of dusting -- 1.17 per acre-application, including insecti-
cide



Total amount of insecticide applied -- 2,100 pounds.



-A;







- 14 -


Hemipterous insect infestation records:

Twelve population counts made at weekly intervals.

First count made June 22 and final count made September 8.

Number of injurious izsects per 100 strokes


Dusted Check

Seasonal Average 14.25 20.10

Peak infestations 27 37

Period of severe damage 6 weeks 7 weeks

Dusting reduced infestation an average of 5.85 injurious insects
per 100 net strokes over the season, and reduced the peak infestations by
10 insects per 100 strokes. It also reduced the period and intensity of
severe damage.

Records of form counts:

Average number of forms per plant

TDate Dusted Check

June ?4 3.83 3.96

July 19 14.01 12.75

August 24 42.55 (13.64 bolls) 36.78 (11.53 bolls)

At the final count, the dusted plots exceeded the check plots on
the average by 2.11 bolls per plant, although the long-staple cotton
had not yet reached the peak of the fruiting stage.

Record of boll examinations for hemipterous insect damage:

Percent of bolls punctured

bate Dusted Check

August 10 8.75 19.50

September 7 14.00 26.75

The amount of boll puncturing was reduced -ractically one-half through-
out the main fruiting season in the dusted plots as compared with check
plots.








15 -

Yield of seed cotton in comparable areas:

The average yield per acre was 841 pounds in the dusted plots
and 599 pounds in the check plots. The average gain in the dusted noots
over the checks was 242 pounds, or 40.4 percent.

Rendition of lint (gin turn-out):

On a field basis the gin records show that the dusted plots
yielded 0.7 percent more lint than did the check plots.

Classing and grading records:

Dusted Check

Yo. of bales Percent No. of bales Percent

Total yield (first picking) 8 -- 7

Grade

No. 1 5 62.5 0

No. 2 3 37.5 7 100.0

Staple

1-1/2" 2 25.0 4 57.1

1-9/16" 6 75.0 3 42.9

It is seen that a higher percentage of lint was produced and a bet-
ter grade and staple was obtained in the dusted cotton.

Value of Pima deed cotton:

1-ith a gin lint turn-out of 25 percent, 20 cents per pound for the
lint and '2. per ton -for the seed, 100 pounds of Pima seed cotton would
give the following returns:

25 -pounds of lint at t0.20 $5.00

75 pounds of seed at $0.012 .90

Total 5.90

From the extra yield attributable to dusting, however, the follow-
ing costs per 100 pounds of seed ,cotton would have to be deducted:







- 16 -


Picking and hauling $1.85

Ginning .60

Bagging and ties 0.06

Total 2.51

The net value of 100 pounds of Pima seed cotton would therefore
be $5.90 minus $2.51, or $3.39 per hundred.

Computing the value of the gains and costs of dusting from the above
figures, but without taking into consideration the increase in value of the
dusted cotton due to an increased lint turn-out and a better gTrade and
staple, the value of 242 pounds of seed cotton gained per acre as a result
of dusting is $8.20. The cost of seven applications of dust at '1.17 per
acre-application is t8.19, which shows a net gain of 1 cent per acre. How-
ever, it will be noted that insect populations in the dusted areas of this
field were present in da-.in ruLmbers for a period of 6 weeks, which
should have required only 6 enplications of dust instead of 7 and would
have left a profit of l1.18 per acre. The yields in this field were low,
the undusted check producing only 600 pounds of seed cotton per acre.
Ordinarily Pima cotton produces from three-fourths to one bale per acre on
suitable land for Pima in Arizona, and a gain of 40 percent in cotton from
such areas will justify several applications of dust and still give a
profit.

Definite information on the increased value of the lint resulting
from the improvement in grade and staple in the airplane-dusted fields is
not available at this time. A study of the classing and grading records
shows, however, that this should be a considerable item. In fact, one
large company that has been dusting with airplanes for several years con-
siders that the increased value of the cotton alone will pay for all costs
of dusting even though there is no increase in yield.

?ecommendations for Hemipterous Insect Control in Cotton

Experiments conducted over a period of 7 years have shown that
hemipterous insect damage to cotton can be profitably reduced by the use
of several insecticides applied by hand and ground machinery. The in-
creases in yields from 1 year's experiments with airplane dusting were not
enough to pay the costs of dusting. This is attributed to the comparative-
ly low insect populations in the experimental fields and the fact that more
applications of dust were made than were needed. It is believed that further
experiments will show that dusting with airplanes has certain advantages
over ground machinery and can be profitably used for the control of hem-
ipterous insects on cotton. A number of factors influence the results that
may be expected from dusting in various cotton-growing areas of the State,
such as the soil fertility, surrounding crops, wild host plants, size and
stage of cotton growth, the relative proportion of the different species of
injurious insects present, and the intensity of the insect populations. In
planning control for hemipterous insects the general recommendations that







17 -

follow are suggested.

Hemipterous Insect Populations in Cotton

Insect populations should be determined in all cotton fields be-
fore dusting operations are begun. The methods used for making popula-
tion counts are sweeptmg with a standard sweep net 15 to 16 inches in
diameter, and plant examinations. In fields that are to be dusted, sweep-
ings should be started the latter part of June or when the cotton plants
begin to set squares and bolls. The sweeping should be made at regular
weekly intervals by making 300 or 400 net strokes in representative areas
of the field. The sweeps should be made across the rows by hitting the
tops of about every other plant with the net. When 100 net strokes have
been made, the insects and debris should be shaken down to the bottom of
the net and sprinkled with while gasoline to kill or stunify the insects
so they can be counted and recorded. When the sweepings have been com-
pleted in a field, the total number of injurious hemipterous insects col-
lected should be divided by the number of 100-stroke units, and if it is
found that 12 to 15 specimens of injurious species are present per 100 net
strokes, dusting should be started and continued at 7-day intervals until
the numbers of injurious insects have been reduced below this point. Al-
though very few leaf bugs or mirids may be present, it has been found that
stink bugs often migrate into cotton fields in great numbers, especially
when sugar beets or alfalfa grown for seed is harvested. Since stink bugs
are heavy-bodied insects and feed principally upon the bolls located low
on the plants, a smaller percentage of those present are collected by the
sweeping method than of the lighter bodied mirids. In fields where heavy
stink bug migrations occur, the plant examination method is used for de-
termining the populations by examining 300 to 400 plants in representative
areas of the field. Wfhen 6 to 8 are found per 100 plants, poisoning should
be started and continued as described above until the stink bugs have been
reduced below this point.

Insecticides for Hemipterous Insect Control

The insecticide to be used will depend upon the insects present.
If the insects are almost entirely mirids.(Lytgs spp. and Creontiades
p.), dusting sulfur may give the most economical control. If pentatomids
are present in any appreciable numbers, as they usually are in all cotton
areas of Arizona, an arsenical-sulfur mixture will give better results.
Repeated experiments have shown that sulfur alone does not give satisfactory
control of stink bugs, while mixtures of paris green and sulfur and of cal-
cium arsenate and sulfur give economical control in fields where the popula-
tions are great enough to justify the expense. The arsenical mixtures are
also of value in coLtrolling the cotton leaf perforator (Bucculatrix thurb-
eriella Busck), the bollworm (Heliothis armigera (rbn.)), and the cotton
leaf worm (Alabama argillacea (Hbn.)). The perforator and bollworm are
nearly always present, and the leaf worm sometimes is present in Arizona
cotton when dusting is needed for hemipterous insects and it sometimes
causes considerable damage. Some of the gains that have been secured from
dusting are probably partly due to the reduction in damage caused by these
insects.








- 18 -


The problem of the most economical insecticide to use is further com-
plicated by costs. At present prices dusting sulfur (98 percent 325-mesh,
at least 95 percent pure) can be bough% in quantities at around 4 cents a
pound, the 20 percent cvlcium arsenate and 80 percent Vulfar mixture at
5 to 5-1/2 cents, and the 7-1/2 percent paris green and 92-1/2 percent
sulfur mixture at 5-1/2 to 6 cents a pound. The results of several years
ofexperiments show that for average conditions the calcium arsenate-sulfur
mixture or the paris green-sulfur mixture will give the most profitable re-
sults, the choice depending largely on the preference of the individual
grower and the availability of the materials. In both cases the materials
should be thoroughly mixed by machinery for best results. These recom-
mendations for insecticides are not to be considered as final, as they may
be changed from time to time as investigations progress.

Applications and Cost of Treatment

When insect populations reach commercially damaging numbers the
insecticide selected for use should be applied at the rate of 15 pounds
per acre per application at 7-day intervals until the injurious species
have been reduced below 12 to 15 insects per 100 sweeps, or, in the case
of stink bugs, below 6 to 8 per 100 plants by the plant-examination method.
In applying the insecticides with airplanes or any type of dusting machinery,
a thorough coverage and uniform distribution of the dust are necessary.
This can be best secured by dusting at night or early in the morning when
atmospheric conditions are more favorable. lfhere large acreages are to be
dusted, commercial airplane dusting companies will apply the insecticides
for 40 to 50 cents per acre per application. Where power dusters can be
used advantageously, growers could probably apply their insecticides cheap-
er than this. The expense of dusting will range from about $1.00 to $1.40
per acre per application. The number of insecticide applications required
may vary from 2 to 9 per season, depending upon the abundance of the in-
sects, but usually 5 or 6 dustings are sufficient.

Poi soning Bees

Considerable apprehension has arisen over the danger of poison-
ing bees by arsenical dusts used for the control of cotton insects,
especially when airplanes are used for dusting. A few cases of damage to
apiaries have been reported, but these have been due largely to the drift-
ing of dust to adjacent fields around the edges of the cotton. The danger
can be ,reatly reduced b- cutting off the dust in time when nearing the end
of the field and closing the hopper tightly while zooming and turning over
adjacent property. The State entomologist at Phoenix should be notified
several days in advance when dusting is to be done in a locality. He has
arranged to notify all beekeepers in the vicinity so they can move their
bees to other areas. Cooperation with beekeepers by cotton growers and
airplane pilots in taking precautions to prevent drifting of dust and giv-
ing advance information as to when dusting will begin will reduce danger
of damage to bees and the objections of beekeepers to dusting.





19 -

Summary

The more important injurious hemipterous cotton insects in Arizona
include three species of Pentatomidae, four species of Miridae, and one
species of Pyrrhocoridae. Several additional species inflict lesser in-
juries.

The damage consists of (1) injury to the small buds, causing mal-
formation in the growth of the plants; (2) injury to squares and small
bolls, causing them to shed; and (3) puncturing of the bolls, resulting
in shedding or in deformed and abnormal bolls. The boll injuries are fol-
lowed by lint staining, which lowers the quality and value of the crop;
and the lint from punctured bolls is more difficult to pick, causing dis-
satisfaction among the cotton pickers.

In addition to the damage to terminal buds and squares, annual
surveys of the cotton areas in the State have shown that on the average
one boll in every four is punctured by hemipterous insects, The heaviest
inju:4y invariably occurs in yama County, where an average of one-half of
the cotton bolls are damaged, while the lightest damage occurs in Pima
County, where only about 1 boll in 13 is damaged.

In dusting for the control of hemiterous insects on cotton, the
following general rules should be observed:

(1) Commence dusting when 12 to 15 injurious hemipterous in-
sects can be collected per 100 sweet-net strokes, or
when 6 to 8 stink bugs are found by examining 100 plants.

(2) Dust with calcium arsenate and sulfur (1-4), paris green
and sulfur (1-12), or straight dusting sulfur. The pres-
ent information indicates that dusting sulfur will give
the most economical control of the mirids, but for gen-
eral use where stink bugs and other insects are also prea-
ent the arsenical-sulfur mixtures are better.

(3) All insecticide applications should be made at the rate
of 15 pounds per acre per application at night or early
in the morning when atmospheric conditions are most favor-
able for dusting.

(4) Insecticide applications should be made at 7-day intervals
until insect populations have been reduced below damaging
numbers.

(5) The number of insecticide applications required may vary
from 2 to 9, depending on the abundance of insects.

(6) Under average conditions the cost of dusting will range
from about $1.00 to $1.40 per acre per application.



































Figure l.--Power ground chine in operation, showing satisfactory
dust cloud.






























Figure 2.--Duating airplane in operation. The dust cloud should settle
among cotton plants in the same manner as shown in figure 1.




UNIVERSITY OF FLORIDA

1262 09224 7708




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