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ONE HUNDRED

TWENTY YEARS

OF RESEARCH

ON COTTON INSECTS

IN THE UNITED STATES

.^>v UNITED STATES

%{àm} DEPARTMENT OF

'' AGRICULTURE

AGRICULTURE PREPARED BY

HANDBOOK AGRICULTURAL

NUMBER 515 RESEARCH

SERVICE
ONE HUNDRED TWENTY YEARS OF

RESEARCH ON COTTON INSECTS

IN THE UNITED STATES

By C. R. Parencia, Jr., research entomologist

Agriculture Handbook No. 515

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE

Washington, D.C. Issued March 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 — Price
PREFACE

This handbook summarizes research information developed on cotton

insects and their control largely by researchers in the Agricultural

Research Service and its predecessor organizations and in the State agricultural experiment stations. It gives results of early and current research

on cotton insects and their control for growers, processors, research and

extension personnel, and others interested in the production of cotton.

This publication reports research involving pesticides. It does not

contain recommendations for their use, nor does it imply that the

uses discussed here have been registered. All uses of pesticides must

be registered by appropriate State and/or Federal agencies before

they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals,

beneficial insects, desirable plants, and fish or other wildlife—if they

are not handled or applied properly. Use all pesticides selectively and

carefully. Follow recommended practices for the disposal of surplus

pesticides and pesticide containers.

rOLLOW THK LABBU

Trade names are used in this publication solely to provide specific

information. Mention of a trade name does not constitute a warranty

or an endorsement of the product by the U.S. Department of Agriculture to the exclusion of other products not mentioned.
CONTENTS

Page

Research 1854 to 1940 2

Boll weevil 2

Thurberia weevil 17

Bollworms 18

Cotton aphid 21

Cotton fleahopper 23

Cotton leafperforator 25

Cotton leafworm 26

Lygus bugs 29

Pink bollworm 30

Spider mites 34

Stink bugs 36

Thrips 37

Miscellaneous cotton insects 38

Research 1941 to 1974 44

Attractants 44

Biological control 46

Biology and ecology 48

Collections of insects in the upper air 49

Genetic control 49

Host plant resistance 51

Insecticides 53

Juvenile hormones 57

Pathogens 58

Physiology and morphology 60

Rearing , 61

Pilot boll weevil eradication experiment 62

Field laboratories 65

Annual conference on cotton insect research and control, 1947-74 __ 68

Status of cotton insect control 69

References 70
ONE HUNDRED TWENTY YEARS OF RESEARCH

ON COTTON INSECTS IN THE UNITED STATES

C. R. PARENCIA, Jr., ARS research entomologist^

In the United States problems with cotton

insects did not begin in 1892 with the introduction of the boll weevil, Anthonomus grandis

Boheman. The early colonists cultivated cotton

and had problems with cotton insects. T. Glover,

the first Government entomologist under the

Commissioner of Patents, mentions cotton insects in his first and second reports for 1854

and 1855.

Pursuant to an Act of Congress, Professor

C. V. Riley, appointed entomologist of the Department of Agriculture in 1878, started a

special investigation of cotton insects. Professor

J. H. Comstock continued this investigation

and in 1879 published a large, practical volume

on the cotton leafworm, Alabama argillacea

(Hübner), and the bollworm, Heliothis zea

(Boddie), entitled **Report on Cotton Insects."

The investigations on cotton insects were

transferred to the U.S. Entomological Commission under the Department of the Interior and

assigned to C. V. Riley. In 1885, Riley published another large volume on the cotton leafworm and bollworm as the "Fourth Report of

the U.S. Entomological Commission." Both

Comstock's and Riley's reports had large editions and contained much useful information

on the occurrence of outbreaks, methods of control, and spraying machines.

These two insects continued to be important

pests of cotton until the boll weevil reached the

United States. Many references to the cotton

leafworm and other insects affecting cotton are

found in the early entomological publications.

^ Bioenvironmental Insect Control Laboratory, U.S.

Delta States Agricultural Research Center, Stoneville,

Miss. 38776.

Since the boll weevil entered Texas about 1892,

it has been the most important pest of cotton,

receiving most of the attention focused on insects attacking cotton.

Some results of boll weevil investigations,

also, have been helpful in the development of

control measures for other insects. Of particular

importance have been the development of calcium arsenate and organic insecticides, the improvements in ground application equipment,

and the development of applying calcium arsenate in a dust formulation and later other insecticides in dust, as well as in spray formulations, by aircraft.

With the advent of the organic insecticides

in the mid-1940's, tremendous improvements

were made in the control of all cotton insects.

However, as the boll weevil built up resistance

to the organochlorine insecticides in the mid1950's and other species developed resistance

to various insecticides, the need for alternate

methods of control became apparent. Budget

constraints, however, permitted research only

on solving immediate problems. As more money

became available for research, basic research

and development of alternatives to conventional

insecticides for control of insect pests that

attack cotton were emphasized.

In the 1960's research was expedited on the

boll weevil, resulting in a Pilot Boll Weevil

Eradication Experiment in South Mississippi

and in adjoining areas of Louisiana and Alabama, which began in July 1971 and terminated

in August 1973. Results indicated that eliminating the boll weevil from the continental United

States was technologically and operationally

feasible, and plans were submitted to the Secretary of Agriculture on December 12, 1973.
AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Though much progress has been made, new

problems are continually arising and the need

for more effective and economical control of

most cotton insects continues.

This handbook consists of a brief discussion

of progress made in research on the various

cotton insects. The first section covers the period

1854 to 1940 and lists cotton insects and research achievements about each of them. The

last section lists areas of research about all

insects attacking cotton from 1941 to 1974. The

outstanding research findings reported by authors of Federal and State agencies^ are summarized here, including some unpublished observations.

The author is indebted for much of the early

information to an unpublished manuscript, entitled ''Report on the Accomplishments of the

Work on Cotton Insects Investigations of the

Bureau of Entomology and Plant Quarantine

and Preceding Organizations of the United

States Department of Agriculture from 1954

to 1938.'' This manuscript v^as found in the

Waco, Tex., Cotton Insects Laboratory files.

RESEARCH 1854 TO 1940

Boll Weevil

The boll v^eevil {Anthonomus grandis Boheman) v^as described by Boheman in 1843

from specimens received from Vera Cruz, Mexico, and was recorded by Suffrian in 1871 as

occurring in Cuba. Its food plant was not

known, and the first association of this species

with cotton was a note by C. V. Riley in 1885

stating that the boll weevil had been reared

from cotton bolls sent to the Department by

Dr. Edward Palmer from near Monclova, Mexico, where it was causing serious damage. In

the mid-1960's archeologists working in Oaxaca,

150 miles south of Mexico City, found cotton

bolls on the floor of a cave once inhabited by

Zapotee Indians. An adult boll weevil was discovered in a lock of one boll. The carbon-14

dating process established beyond doubt that

the weevil was alive about 900 A.D. making it

at least 1,000 years old.

The first report of the occurrence of the boll

weevil in the United States was received in the

Department of Agriculture in the fall of 1894

from Brownsville, Tex. The Division of Entomology immediately dispatched C. H. T. Townsend to Texas. He found several counties infested with the boll weevil causing serious

damage to cotton since 1892. His report, published in March 1895, dealt with the area infested and the life history and habits of the

boll weevil that were previously unknown. He

concluded his report with recommendations for

the destruction of cotton stalks to kill the overwintering weevils and the establishment of a

noncotton zone to prevent further spread. The

Department reported the seriousness of the pest

to the Governor of Texas and urged immediate

legislation to permit quarantine and remedial

work. These recommendations were not

adopted, and in 1895 the boll weevil had spread

as far north as San Antonio and as far east as

Wharton, Tex.

The Division of Entomology continued its

investigations, and in 1896 and 1897 L. 0.

Howard published the results. These publications and many earlier ones on the boll weevil

were published in English, Spanish, and German for the benefit of the large foreign population of Texas. Townsend was stationed in Mexico in 1897 to study the parasites and diseases

of the boll weevil, but he found none that appeared promising to control the insect.

The boll weevil was a newly introduced pest

causing almost total loss of the crops in the

infested areas and rapidly spreading to new

territory. Therefore, to meet the demand for

immediate information, the Department issued

frequent publications on this subject matter.

L. 0. Howard in 1896 first suggested the importance of early planting and clean cultivation

as control measures. These recommendations

were based on his knowledge of the habits and

life history of the weevil. Marlatt and Townsend in 1896 experimented in poisoning the boll

weevil by spraying with paris green and sweetened poisons. Howard reported these results in

- See References, p. 70.
RESEARCH ON COTTON INSECTS

1898. Because results indicated that the weevil

could not be controlled by poisons then available,

special emphasis in most of the early work was

placed on other methods of control and on the

economic phases of the problem.

The year 1898 was important in the history

of the boll weevil in several ways. The season

was favorable for the development of the boll

weevil and it spread rapidly, causing serious

damage over a large area.

The first of a long series of boll weevil conventions attended by many cottongrowers,

merchants, and bankers was held on October 12,

1898, in Victoria, Tex. The Legislature of Texas

appointed a State entomologist to investigate

means of controlling the pest. At the end of the

1898 season, the Division of Entomology discontinued its work in Texas.

The boll weevil continued to spread, however.

In 1901 when it became evident that other

States were threatened, Congress appropriated

money for the first boll weevil investigations

to discover means of preventing its spread.

From 1901 until his death in 1925, W. D. Hunter

was in charge of this work. In addition to other

work. Hunter inaugurated cooperative work on

eight farms in 1901 to demonstrate the cultural

methods controlling the weevil that had been

recommended by the Division of Entomology.

These farm demonstrations of boll weevil control developed into the Farmers' Cooperative

Demonstration Work of the Bureau of Plant

Industry and, later, into the present Extension

Service of the Department.

The work was expanded in 1902, and a laboratory was established at Victoria, Tex., to

obtain much needed information on the life

history, habits, and hibernation of the boll

weevil. So much attention was devoted to the

immediate economic phases of the problem that

detailed studies of the insect had not been possible up to that time. The results of the first 2

years' work were published by Hunter and

Hinds in 1904, and Howard in his letter of

transmittal stated it was the most complete

treatise on the life history of a single insect

species published.

Development,—The boll weevil has four

stages in its life cycle—egg, larva, pupa, and

adult. Under favorable conditions, it completes

the cycle in 21/2 to 3 weeks. High temperatures

and humidity result in faster development, while

low temperatures slow it down. As many as

seven generations may develop in a year in the

extreme southern part of the Cotton Belt. The

adult boll weevil is one-eighth to one-third inch

long. It ranges in color from tan to dark gray,

or sometimes to dark brown.

Starting in the spring, the female lays eggs

singly in cotton squares (flower buds). When

the boll weevil population is high and a shortage of squares exists, two or more eggs may be

laid in one square. Late in the season, eggs are

laid both in squares and in young bolls.

Eggs hatch in 3 to 5 days. The larvae feed

7 to 12 days inside the squares or bolls. The

pupal stage lasts 3 to 5 days. Adults cut their

way out of the squares or bolls. After feeding

3 to 7 days and mating, females begin laying

eggs. This cycle is repeated until the cotton

plants are killed by cold weather (fig. 1).

Adult boll weevils hibernate in surface woods

trash and along ditchbanks near cottonfields

and in trash and litter around gins and farm

buildings. In the spring they return to the

cottonfields.

Jaws at the end of an adult weevil's snout

enable it to eat into a square or boll. Both males

and females make feeding punctures. Females

make egg punctures, which are deeper than

feeding punctures, in which they lay eggs.

Both kinds of punctures cause damage. After

a square is egg punctured, the bracts around it

flare, the square turns yellow, and after a few

days, usually drops to the ground.

Many punctured small bolls drop to the

ground, but punctured large ones usually remain

on the plants. If the large bolls have egg punctures, however, they will be damaged by the

weevils developing in the locks where the eggs

were laid. Weevil-infested locks produce little,

if any, cotton, and the quality of that produced

is inferior.

Early research,—Congress in 1904, after becoming aware of the great damage inflicted by

the boll weevil, appropriated $250,000 to enable

the Secretary of Agriculture to meet the boll

weevil emergency. Of this amount, $100,000

was allotted to the then Bureau of Entomology

and the rest to the then Bureau of Plant Industry. Much of the money was used to expand the

demonstration work in newly infested areas.
AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

' c%

f

PN-4418

Figure 1.—Cotton plant showing (a) punctured squares on ground; (b) square showing egg puncture; (c) larva

in square; (d) pupa in square; (e) adult emerging from square; (f) larva and pupa in boll; (g) adult.

(Punctured squares on ground about one-fourth actual size; adult about 6 times actual size. Other stages

actual size.)
RESEARCH ON COTTON INSECTS

testing control recommendations on a large

scale, and experimenting with insecticides. The

weevil had spread to Louisiana in the previous

year, and a special session of the Louisiana

Legislature, called in 1904, established the Crop

Pest Commission of Louisiana. This commission

made many contributions toward controlling

the pest.

Early in 1905 the boll weevil laboratory was

moved from Victoria to Dallas, Tex. Many

farmers' bulletins, circulars, and articles for

farm papers containing information of practical

value to farmers were published in 1904 and

1905 and distributed in large numbers. A comprehensive publication by Hunter and Hinds in

1906 brought together the more fundamental

information that had been accumulated on life

history, dissemination, and natural and artificial control of the boll weevil.

The State of Texas offered a reward of

$50,000 for an effective control for the boll

weevil, and numerous remedies and devices

were proposed. The Bureau of Entomology tested all remedies that were submitted and reported the results to the originator. Although

these tests required a great deal of time, they

were of immense aid to farmers in reducing

the amount of money spent for ineffective concoctions and devices, as not a single new method

of any value resulted.

Extensive tests with paris green showed that

some weevils could be killed, but under field

conditions the benefits were too slight to recommend its use. A satisfactory method of fumigating cottonseed by vaporizing carbon bisulphide was developed so that seed could be moved

from infested territory. Numerous machines

and traps for controlling the weevils were

tested, also. Government entomologists studied

the relation of temperature and climate to

damage, dissemination, and areas where the

weevil would become a pest. Results of biological studies indicated that the boll weevil could

infest most of the Cotton Belt.

With the apparent ineffectiveness of insecticida! and other direct methods of control, emphasis was placed by the Bureau of Entomology

on ^'cultural methods," which included various

modifications of the cropping system that

studies of the pest indicated might be useful in

avoiding damage. The most important cultural

methods developed for reducing boll weevil

damage were the early maturity of the crop

before the weevils become abundant by selecting

an early maturing variety, planting early, fertilizing and cultivating properly, and destroying

stalks as early as possible in the fall. Early

destruction of stalks in the fall prevented the

large, late season increase in weevil populations,

thus reducing the numbers that entered hibernation sites and survived the winter.

Other investigations were also started. Studies were made on the abundance and distribution of some 50 species of native parasites and

predators of the boll weevil, but efforts to

increase their usefulness were unsuccessful.

Estimates from many sources of the damage

caused by the boll weevil during this period

varied greatly. The most reliable estimates

placed the losses in newly infested areas at

about 50 percent of the crop, but after a few

years growers were able to reduce this considerably by adopting the recommended cultural

control practices. About one-third of the acreage planted to cotton in Texas was then infested,

and the loss to the 1904 crop was conservatively

estimated by the cotton industry at $22 million.

The boll weevil crossed the Mississippi River

into Mississippi in 1907. All cotton-growing

States had previously enacted quarantines

against the introduction of infested material,

and the spread was almost entirely by natural

dispersal. Only a few isolated infestations became established at any distance ahead of the

general line of advance, with most of these

being eradicated. It was then generally accepted

that the boll weevil would continue to spread

over the Cotton Belt, and growers became concerned as the weevil entered the large plantations in the Mississippi Delta.

The spread of the boll weevil year by year

was of paramount interest to the people in the

line of advance. The most severe damage was

usually caused during the first few years before

the infestation became stabilized and growers

learned the best methods of growing cotton in

the presence of weevils. One great service of

the Bureau of Entomology was in determining

the limits of infestation each season. Maps and

articles giving this information were widely

distributed each fall that greatly assisted farmers, businessmen. State authorities, ginners,
AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

and many others in planning for the next season. This service was rendered from the beginning of the investigations in 1904 in south

Texas until the weevils reached Virginia in

1922.

The advance varied from 40 to 160 miles a

year, although in several instances adverse

winter conditions caused a reduction in the

infested areas. Spread was more rapid to the

north and northeast during the early years,

and then faster to the east as unfavorable

climatic conditions were reached in western

Texas and Oklahoma. The semiarid areas with

high summer and low winter temperatures are

unfavorable for weevil development and survival, and infestation have never become established in the High Plains of Texas, New Mexico,

Arizona, and California. A suppression program

to prevent the establishment of infestations on

the High Plains has been underway, however,

because the boll weevil was found able to survive

the winter above the caprock. By 1922 the boll

weevil had spread over North Carolina and into

Virginia, thus covering over 600,000 square

miles of territory since its entry into the United

States 30 years previously (fig. 2). About 85

percent of the cotton in the United States was

produced in the infested territory, and the rapid

expansion of cotton production to the West was

partly due to the absence of the boll weevil in

that area.

As the boll weevil continued to spread to new

areas, it became more and more apparent that

the ''boll weevil problem" was a series of problems and that investigations should be conducted under different climatic, ecological, and

agricultural conditions. Consequently, in 1909

the laboratory moved from Dallas, Tex., to

Tallulah, La., until it closed on June 30, 1973.

Figure 2.—Spread of boll weevil in the United States, 1892-1934.
RESEARCH ON COTTON INSECTS

This location was selected because it was near

the southern edge of the Delta section where

the boll weevil was expected to cause as much

damage as anywhere in the South. The soils

were fertile and with the abundant rainfall

plants normally continued to produce cotton

until late in the season. Large areas of dense

forests afforded good hibernation quarters, and

with comparatively mild winters heavy infestations were the general rule.

The policy of investigating the boll weevil

''on the spot'' was followed throughout the work

and additional laboratories were established by

the Bureau of Entomology in Mississippi,

Florida, South Carolina, Oklahoma, and

Georgia. As the weevil spread to new areas,

work also moved to these areas. Information on

habits, damage, and control measures best

adapted to different local conditions fully justified this procedure. The State agricultural experiment stations, particularly Texas, Oklahoma, Alabama, Arkansas, Florida, and South

Carolina, did a great deal of work on the boll

weevil, but the Tallulah laboratory was the

leader in these investigations.

The many phases of the boll weevil investigations and the interest in this insect are

indicated by bibliographies compiled by Bishopp

in 1911 (7), Dunn in 1964 {25), and Mitlin in

1968 (7^), all of which contain titles or abstracts of important papers by both Federal

and State entomologists.

Research for the first few years at the Tallulah laboratory continued somewhat along the

same lines as the previous work in Texas.

Whether the cultural methods that had given

good results in Texas would be effective under

the ecological and farming conditions of the

Delta had to be determined. Every phase of the

control methods then in use was based on biological facts, and life history studies had a

direct economic bearing on the boll weevil problem. Consequently, biological studies were made

at Tallulah from 1910 to 1915. In 1913 another

series of biological studies, also, were made at

Victoria, Tex., to check those made 10 years

previously. Because of the shorter developmental periods, the same number of generations

(7) were produced at Tallulah as at Victoria,

although the breeding season at Tallulah was

more than a month shorter.

The discovery of the Thurberia weevil. Anthonomus grandis var. thurberia Pierce, a close

relative of the boll weevil, in the ''wild cotton''

of Arizona led to further studies on the host

plants of the boll weevil. In experiments conducted at Victoria, the boll weevil developed in

Hibiscus syriacus, a common ornamental shrub,

and fed and partially developed on two other

species of native Malvaceous plants under cage

conditions. This was the first record of rearing

the boll weevil on plants other than cotton.

A method of control consisting of collection

of weevils and infested squares was thoroughly.

tested in the Mississippi Delta in 1915 and 1916.

Considerable reduction in damage and fair increases in yield resulted from this practice, but

it was impractical because of the great amount

of labor and expense involved.

Research with insecticides.—Although the

Bureau of Entomology had been concentrating

its efforts on cultural control based on biological data, research had also started on use of

insecticides as a control measure. In addition

to the Bureau's work, the Louisiana Crop Pest

Commission began conducting tests with paris

green in 1905. A certain amount of control was

obtained, but paris green seemed to have some

adverse physiological effect on the plants and

increases in yield were not commensurate with

the reduction in weevil infestation. Arsenate of

lead was coming into general use as a substitute

for paris green for use on fruit trees, but this

insecticide was then made only as a paste and

could be used only as a spray. Since spraying

was considered impractical for cotton, Wilmon

Newell conceived the idea of making lead

arsenate as a powder that could be dusted on

cotton for boll weevil control.

The first powdered lead arsenate was prepared for Newell by the Grasselli Chemical

Company in 1908 and was used in cage tests

against the weevil in that season. Field tests

conducted in 1908 and 1909 showed considerable increases in yield and profits from dusting

with lead arsenate under some conditions. Emphasis was placed on the value of dusting early

in the season and forcing the dust inside the

bracts of the squares and into the terminal

buds of the plants where it would be ingested
8 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

by the weevils while feeding on the external

tissues. Dusting was recommended as a useful

supplementary measure to cultural methods.

The results were the most successful that had

been obtained to that date with insecticides,

arousing considerable public interest as well

as stimulating renewed interest in insecticides

by the Bureau of Entomology. Results from

subsequent tests of dusting with lead arsenate

were erratic, and the method was neither

recommended nor used extensively by growers.

In 1916, however, tests with tri-plumbic arsenate of lead dust resulted in good gains in

yield when applied late into the season.

In 1916, the new insecticide, calcium arsenate, was first compared in field tests against

the boll weevil with di-plumbic arsenate of

lead. Calcium arsenate in a dust formulation

was being made by a few manufacturers but

was a comparatively unknown insecticide. Its

physical properties were poor, having a density

of about 40 cubic inches per pound, and when

applied it did not form a good dust cloud for

plant coverage. Excessive quantities of watersoluble arsenic often made it phytotoxic. Considerable experimenting was done at Tallulah

in cooperation with manufacturers to improve

its physical and chemical properties. Dusts,

ranging in density from 80 to 160 cubic inches

per pound, were prepared. Those with densities from 80 to 100 cubic inches per pound gave

better coverage and were better suited for cotton. Some increases in yields were obtained

from most of the treated plots in 1916, but the

most striking results were obtained in a plot

in a field of heavily weevil-infested cotton that

was treated with calcium arsenate in August.

The weevils were effectively controlled, and a

fair crop produced on cotton the owner had

abandoned as an absolute loss. The late season

poison applications resulted in good gains in

yield, whereas gains from the early season

applications were slight.

Results of studies at Tallulah in 1917 to

obtain information on the efficacy of different

poisons, the time of day of applications, the

proper intervals between applications, and

other phases were inconclusive because of the

light weevil infestation, but tests with calcium

arsenate conducted in Mississippi and Arkansas again gave good control, with gains ranging from 250 to 1,000 pounds of seed cotton

per acre. A large-scale field test in Arkansas in

a heavily infested field of late cotton demonstrated for the first time the value of a late

application of poison for protecting the bolls

from weevil damage.

Who first made calcium arsenate is not

known. Apparently, the first records of its use

as an insecticide were in 1907 by John B. Smith

of New Jersey and by Bedford and Pickering

of England, who tested it as a substitute for

lead arsenate during the same year. Pickering

stated, however, that calcium arsenate had already been used in the United States, and

Smith reported that combinations of arsenic

and lime were well known and easily prepared

by farmers. Bedford and Pickering used a

homemade product and gave the proportions

of an arsenate and a calcium salt, with the

recommendation that an excess of lime be used

to prevent an excess of soluble arsenic in the

calicum arsenate. Smith used a calcium arsenate sent him by Dr. Fred P. Dewey, a chemist

of Washington, D.C., thought to have been connected with the U.S. Mint.

The next reports of calcium arsenate as an

insecticide were by Scott and Siegler, of the

Division of Deciduous Fruit Insect Investigations of the Bureau, who used it in laboratory

tests in comparison with many other arsenicals

against the fall webworm, Hyphantria cunea

(Drury), and in orchard tests against the codling moth, Laspeyresia pomonella (Linnaeus),

in 1912 at Benton Harbor, Mich. The calcium

arsenate used in 1912 was a ''chemically pure"

powder, applied as a spray (0.5 pound to 50

gallons of water). Against the fall webworm

the results were about equal to that obtained

with lead arsenate, and against the codling

moth the results were somewhat below that

obtained with lead arsenate.

In 1913 further tests were made by Scott

and Siegler with two homemade formulations

of calcium arsenate prepared in the laboratory

from sodium arsenate and calcium acetate, and

a commercially prepared calcium arsenate paste.

The commercial calcium arsenate paste was as

effective as the lead arsenate paste against the

tent caterpillar (Malacosoma spp.).

An interesting account of the first commercial manufacture of calcium arsenate for insec-
RESEARCH ON COTTON INSECTS

ticidal use was furnished by E. H. Siegler.

While the tests at Benton Harbor were in

progress, Scott's brother, W. M. Scott, of the

Thompson Chemical Company, Baltimore, Md.,

became interested in the new insecticide. He

made a calcium arsenate paste to test as an

insecticide in 1913. In 1914, the Thompson

Chemical Company also furnished a commercial

calcium arsenate powder, which was as effective

as lead arsenate against the fall webworm in

laboratory tests at Benton Harbor. The powdered calcium arsenate was also furnished to

several investigators for use against the codling

moth, and over 2,000 pounds were used against

shade tree insects in 1914.

Although calcium arsenate was first used in

experiments against fruit insects, it was still

a comparatively unknown insecticide when

tested against the boll weevil. It gave better

control than the other arsenicals then in use.

The improvements in the physical and chemical

properties of calcium arsenate and the rapid

expansion in its use were due almost entirely

to the work of the Bureau of Entolomogy on

the boll weevil.

The results of the tests with calcium arsenate

dust against the boll weevil in 1916 and 1917

were so successful and aroused so much interest

and demand for information that USDA Bulletin 731, ''Recent Experimental Work on Poisoning Cotton Boll Weevils,'' was issued in July

1918, although it was felt that further details

should be worked out before recommendations

were made to the public.

The machines then in use for applying dust

formulations were as crude as the insecticides.

From the beginning of the dusting experiments

it was evident that improvements in machinery

were necessary before application of dust formulations of insecticides to cotton on a large

scale would be feasible. In 1916 Elmer Johnson,

an engineer with the Bureau of Public Roads,

was detailed to the Bureau to improve and

develop dusting machines adapted to cotton.

He was invaluable in improving the design and

developing machines suitable for various

acreages and types of farms. These improvements were covered by Public Patents and were

available for use by all manufacturers.

In 1918 several thousand acres of cotton were

dusted with calcium arsenate under the supervision of Bureau personnel. As a result of the

success of this work, over 3 million pounds of

calcium arsenate were used for weevil control

in 1919 and about 10 million pounds in 1920.

The increase in the use of calcium arsenate for

control of the boll weevil was phenomenal,

probably the most rapid of any insect control

measure ever developed up to that time. Emphasis in lines of work changed almost entirely

from cultural control to direct control by insecticides and development of dusting machines.

Two new industries—the manufacture of calcium arsenate and of dusting machinery—were

expanding simultaneously. Over 30 companies

were making calcium arsenate in 1920, and

many models of dusting machines were available.

With such rapid expansion in use, much of

the calcium arsenate and machinery placed on

the market were not suitable. The physical

quality of some early calcium arsenate was

poor and contained so much water-soluble arsenic that it was phytotoxic, or so little total

arsenic that it was not sufficiently toxic to kill

the weevils. The Tallulah laboratory tested all

samples for growers or others, and in 1920

had tested over 2,000 lots. It also tested new

models of dusting machines and suggested

improvements to the manufacturers before they

were placed on the market.

These services saved the growers much

money that would have been expended for unsuitable insecticides and dusting machines. In

addition, an educational campaign was urgently

needed to advise growers, county agents, and

others on the use of the new methods of control.

Consequently, in 1921 most of the personnel at

Tallulah were stationed at representative sections of several States to demonstrate dusting

with calcium arsenate and to obtain additional

information on its use under different conditions. Arrangements were made through the

States Relations Service whereby the men

worked with the county agents and issued

timely advice on local insect conditions and

dusting schedules.

Work on refinements in methods of applying

dust formulations to cotton were delayed as

every possible effort was made to help farmers

in controlling the boll weevil. During this period of rapid expansion in the use of calcium
10 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

arsenate, a shortage of white arsenic used in

its manufacture occurred. The Bureau of Entomology surveyed available supplies and prospective insect conditions to aid in the proper

distribution of calcium arsenate and dusting

machines to meet critical needs. This action led

to the annual installation of a large series of

hibernation cages in different States to study

the emergence and abundance of weevils in

the new cotton-growing season. Such information was valuable to manufacturers in planning

to meet the demand for calcium arsenate and

dusting machines and to the farmers in stabilizing prices and preventing scarcity of

materials.

The next important step in boll weevil control occurred when the method of applying dust

formulations of insecticides with airplanes

was developed. The possibility of using airplanes for this purpose was suggested by the

work of the Ohio Experiment Station in distributing lead arsenate for the catalpa sphinx

Ceratomia catalpae (Boisduval) in 1921. The

first tests for control of cotton insects were

against the cotton leafworm in 1922, through

the cooperation of the Air Service of the

United States Army that furnished planes and

personnel.

In the first flights, calcium arsenate was

dropped by hand from the planes, but it was

soon evident that methods had to be developed

to distribute the poison evenly at a controlled

rate. After several years' work in cooperation

with engineers of the Bureau of Agricultural

Engineering, U.S. Department of Agriculture,

hoppers were developed that would evenly distribute dust over a swath 150 to 200 feet wide,

and aerial applications were equally as effective

as those applied by ground equipment for boll

weevil control.

Treatment with airplane was much faster

than with ground equipment, as one airplane

could treat from 750 to 1,000 acres per day.

This treatment was especially important when

the fields were too wet for use of ground equipment or when large acreages had to be treated

quickly. Commercial airplane companies, under

contract, did most of the aerial dusting. Growers did not need to purchase planes or other

dusting equipment. These costs compared favorably with that of ground equipment and

was much more convenient for the growers. At

least 1,000 acres to be treated in a community

were needed for economical operation of airplanes, and the dust companies contracted for

treating fields within a radius of several miles

of a landing field. This method of insect control

for cotton was used extensively in Texas,

Arkansas, Louisiana, Mississippi, and in other

States for truck crops and orchards. Expansion

in the use of airplanes was rapid, and many

commercial companies maintained fleets of airplanes equipped for crop treating with as many

as 100 planes ready for instant call. Treating

with airplanes was spectacular, but at the

same time entirely practical, economical, effective, and the most convenient method ever devised for treating large acreages of cotton or

other crops (fig. 3). In December 1931, the

Bureau of Entomology discontinued its work

and disposed of its airplanes after such method

of treatment was established commercially as

a result of the research done by the Division

of Entomology.

Following the first successful demonstrations

with calcium arsenate for boll weevil control,

experiments on insecticidal control by the various State agencies renewed. Information on

treatment schedules best adapted to each locality and on the profits that could be expected at

different points was in great demand. Many

new remedies appeared on the market as a

result of this renewed interest. A large part

of the Bureau of Entomology's work during the

next several years consisted of demonstrations

in many areas to bring the results to growers

and State officials by seeing that control methods were properly used and testing many

proprietary remedies that appeared on the

market.

There was such a lack of uniformity in the

methods of experimentation and recommendations by the various agencies that the Association of Southern Agricultural Workers

(ASAW) appointed a Cotton Council in 1922

to review the boll weevil situation thoroughly

and to standardize the control recommendations. The Council adopted the following resolutions in 1924, which were slightly modified in

1926:
RESEARCH ON COTTON INSECTS 11

Figure 3.—Applying insecticides as dusts with aircraft.

PN-4419

For the bell weevil, one presquare poisoning may

be applied if it appears there are numerous overwintered weevils present. This should be given just

as squares begin to form. Then apply the regular

series of three or more dust applications of calcium

arsenate at 4- or 5-day intervals, beginning when

an average of approximately one-tenth of the

squares show weevil punctures. Dusting should be

continued as needed to keep this infestation low

until a full crop is set and matured beyond the

probability of further weevil injury (Proceedings,

ASAW, 1926).

This action by the ASAW did much good in

gaining the cooperation and coordination of

the work of all agencies engaged in boll weevil

control.

The boll weevil had spread over most of

South Carolina by 1920 and, as usual in newly

infested territory, was causing serious damage.

The South Carolina Legislature made a special

appropriation to conduct control investigations

in cooperation with the Bureau of Entomology.

This was an excellent opportunity for the Bureau of Entomology to obtain additional information on the weevil under the conditions in

the Southeastern States, since most of the previous work had been done west of the Mississippi River. In 1922 a laboratory was established in Florence, S.C., which has operated

continuously. In the first few years of operation, the work in the laboratory consisted

largely of tests to determine the gains and
12 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

profits that could be obtained under local conditions.

In 1925 a thorough study of the biology of

the boll weevil in South Carolina began with

the results published in 1929. Only four generations a year developed at Florence compared

with seven at Tallulah. Studies on dispersal

showed that the temperature and intensity of

infestation were the principal factors causing

the migration or flight of weevils from field to

field and to new areas. After 1928 the attention

of the Florence personnel was devoted largely

to such phases of control as the value of the

mopping technique of reducing the amount of

calcium arsenate needed for control and the

effect of calcium arsenate used for boll weevil

control on aphids and on the soil. Root aphids

and other insects affecting cotton, also, were

studied.

From 1926 to 1940 several laboratories conducted research on improving and refining

methods of boll weevil control to increase the

efficiency of control and reduce the cost. Tests

of applying insecticide dust formulations at

various time intervals, at different times of the

day, and in reduced quantities were conducted.

Special attention was given to developing combinations of insecticides that would control some

other insects that occurred simultaneously with

the boll weevil. A mixture of calcium arsenate

and sulphur was found to control combination

infestations of the boll weevil and certain other

insects such as the cotton fleahopper Pseudatomoscelis seriatus (Reuter) and other mirids.

Each year a large series of cage toxicity

tests were conducted to compare other insecticides with calcium arsenate for effectiveness

against the boll weevil. The promising materials from these tests were then tested under field

conditions. Many arsenical, rotenone, nicotine,

fluorine, and other insecticides were tested, but

none were as effective and economical as calcium arsenate. Results of studies showed calcium arsenate was a complex material with

varying physical and chemical qualities. This

finding explains why some commercial calcium

arsenates were more effective than others

against the boll weevil although they all met

the required specifications.

Commercial calcium arsenates with a high

percentage of water-soluble arsenic by the Geneva method were more toxic to weevils in cage

tests than those medium or low in water-soluble

arsenic but were no better than those medium

or low in water-soluble arsenic in field tests.

The three forms found in the commercial products—mono-, di-, and tri-calcium arsenate—

were separated and tested separately. Samples

were fractionated into different sizes of particles. The indicated results of the tests were that

if the most desirable physical and chemical

properties could be determined they could be

incorporated into commercial practice by modifying the manufacturing processes without increasing the cost of production.

Parasites.—Parasites of the boll weevil were

studied again from 1932 to 1935 to determine

the change in native parasites during the 20

years since the previous studies. About 20

species of parasites were found, 3 of which

were new. Findings from these studies indicated little increase in the control of the boll

weevil by parasites since the previous investigations. An average of 5.5 percent of the weevil

larvae collected in several States were parasitized, and there was little hope of increasing

the native parasites so that they would give

greater control.

Effects of calcmm arsenate on aphids, soils,

and crops following its use for boll weevil control.—The use of calcium arsenate dust at first

appeared to have solved the problem of controlling the boll weevil. However, soon after it

came into extensive use, a conspicuous and

often injurious increase in infestations of the

cotton aphid Aphis gossypii (Glover) occurred

following its use on cotton. This was noted in

1920 in Texas and about the same time in

South Carolina and in other States. In some

instances where large amounts of calcium arsenate were applied, the aphids increased to

the extent that the gains from weevil control

were offset by the damage caused by them.

Investigations conducted from 1922 to 1929 to

determine the reasons for the increase in aphids

indicated that several factors were probably

responsible for this complex problem. The

initial increase in aphid infestation was

thought to be due to the attraction of the

winged females to the white deposit of calcium
RESEARCH ON COTTON INSECTS 13

arsenate or other white dusts on the plants. The

aphid population then increased because the

hymenopterous parasites were killed when they

emerged in the presence of the arsenical. Later

tests with calcium arsenate colored with aniline

dyes did not prevent the buildup of aphids. The

aphid problem on cotton became more serious,

especially in the Southeastern States. Rotenone

dusts were not very effective against the cotton

aphid and control with nicotine sulphate, the

most effective aphicide, was expensive and

somewhat erratic unless weather conditions

were ideal.

Research on varietal resistance or tolerance

of cotton to aphids started in 1934 with the

establishment of a Cotton Insects Research

Laboratory at Stoneville, Miss. The Bureau of

Plant Industry maintained a large collection of

exotic and domestic species, varieties, and

crosses of cotton here. An endeavor to find

strains of cotton or individual plants that were

immune or resistant to aphid buildup showed

that varieties with more pilose leaves retain

the calcium arsenate for a greater time and

that the aphids increased more rapidly than

on the smoother leafed cottons.

The amount of damage actually caused was

difficult to determine. Most farmers considered

the benefits from boll weevil control more important than the aphid damage following use

of calcium arsenate. There were some, however,

who were reluctant to use calcium arsenate

because of this factor.

About the same time that the effect of calcium arsenate on the increase in aphids was

observed, a few cases were reported on the

reduction in yield of cotton and other crops

following its use on the light sandy soils of

South Carolina. Later, similar reports were

received regarding arsenical injury to soils on

the ricelands of Louisiana. The injury from

arsenic in South Carolina was manifested by

poor stands of cotton and, more particularly,

by the adverse effect on the germination and

growth of oats and legumes. Workers from the

Louisiana Experiment Station found that cotton treated with calcium arsenate was not affected, but rice following treated cotton was

rather seriously injured. Other crops such as

rye, corn, sweet potatoes, and tobacco were

rather tolerant to arsenic, and some growth

was even stimulated where considerable quantities had been applied. Injury from arsenic in

South Carolina seemed to be correlated with

soil deficiencies of iron and magnesium, and no

injury was reported on dark or reddish soils.

Also, all the reported injury in South Carolina

were where larger quantities of calcium arsenate than recommended were used for boll

weevil control, although there was no proof that

the recommended quantities might not also

cause damage in the future.

In experiments to determine the types of

soils that would be affected and methods of

overcoming the injury, 500 pounds of calcium

arsenate per acre were applied to the soil at

Tallulah, La., for 4 successive years, or a total

of 2,000 pounds, without decreasing the yield

of cotton. However, after this quantity was

applied there was some deleterious effect on

the germination and growth of vetch planted

as a winter cover crop. Of the principal soil

types in Mississippi, 7 were treated with calcium arsenate at rates from 50 to 1,600 pounds

per acre and planted to cotton, corn, and soybeans in the spring, and to vetch, Austrian

peas, and oats in the fall as winter cover crops*

The germination and yields of some crops were

reduced somewhat on the light sandy soils when

100 pounds of calcium arsenate were applied

per acre, and when 200 pounds or^more were

applied per acre on some of the heavier soils.

Analysis of the soils showed that large quantities of water-soluble arsenic were lost by

leaching or fixation in one year. Not more than

30 pounds of calicum arsenate per acre per

year were estimated as needed to control the

ordinary infestations of the boll weevil. With

the rapid reduction in arsenic in the soils, there

was little danger of soil injury to any of the

soil types tested in Mississippi. No corrective

measures were found for arsenic injury to the

soil, but the damage naturally disappeared by

fixation or leaching of the arsenic in a few

years.

Progress was also made in avoiding soil injury by decreasing the amount of calcium arsenate dust used for boll weevil control by

diluting it with sulphur, lime, or other inert

materials. Injury was likely to occur only on
14 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

certain soil types found in comparatively small

areas of the Cotton Belt, and while danger of

soil injury was recognized as being serious

under certain conditions, the danger seemed

to be overemphasized.

The two disadvantages in the use of calcium

arsenate were factors in preventing its wide

acceptance for boll weevil control.

Sweetened poison.—Besides dusting with

calcium arsenate, the only other material generally used for weevil control was a mixture

of calcium arsenate, molasses or syrup, and

water—"sweetened poison^' or ''mopping'' as it

was usually called because the mixture was

applied to the tops of the plants with a mop.

The advantage of the mopping method was that

the overwintered female weevils feeding in the

terminal buds of the plants before the squares

were present could be killed by ingesting the

poisoned mixture before they oviposited.

Sweetened arsenicals were tested in the early

investigations at Victoria, Tex., but were neither

found to attract the weevils nor to give satisfactory control and were not recommended.

After the weevil reached South Carolina, the

use of sweetened poison was revived and was

more extensively used in that State and in

Florida than elsewhere. This method was advocated by some growers and State officials who

claimed that it was a cheap method of control

requiring no expensive application equipment.

A great many of the early emerging weevils

were killed by the presquare applications of

sweetened poison, but enough weevils usually

emerged from hibernation sites after squares

formed, and sweetened poison was no longer

effective to cause serious damage.

Mopping was extensively tested in Texas,

Oklahoma, Louisiana, South Carolina, Georgia,

and Florida. Its effectiveness varied somewhat

in different localities, apparently depending on

the time weevils entered the fields from hibernation shelter and climatic conditions. The more

open type woods of the Southeast appeared to

warm up earlier in the spring than the denser

woods of the Middle Cotton Belt, and caused

the weevils to emerge earlier over a shorter

period. Under these conditions the sweetened

poison seemed to be somewhat more effective.

More extensive tests with mopping were conducted in South Carolina than elsewhere because it was more generally used and recommended by the South Carolina Extension Service. In tests at Florence, S.C., over an 9-year

period (1928-36), the average gain from

mopping alone was 41.5 pounds of seed cotton

per acre ; from mopping followed by later dusting with calcium arsenate, 294.3 pounds per

acre; and from dusting with calcium arsenate

after 10 percent of the squares were infested,

270 pounds per acre. In tests in other States,

the results were similar to those in South

Carolina. On the basis of these results, the

Bureau of Entomology did not recommend

sweetened poison alone as a satisfactory control

but did recommend presquare mopping to be

followed by later dustings with calcium arsenate

in the South Atlantic States. Later demonstrations showed that effective control of overwintered boll weevils could not be obtained in

small-plot experiments, which no doubt influenced the poor results obtained.

Hibernation and survival.—Hibernation was

considered to be the most critical period in the

life history of the boll weevil and was studied

under a great variety of conditions. In the extreme southern part of the Cotton Belt, cotton

continued to fruit and weevils bred continuously all the year, but in most areas they passed

the winter as adults in the old cotton bolls,

weeds, and surface trash in fields and surrounding woods. Weevils entered hibernation in the

fall when the mean temperature dropped to

40° to 50° F and emerged in the spring when

the mean temperature averaged about 60°.

Some activity occurred during warm days in the

winter—weevils left hibernation sites, became

active, and entered hibernation sites again when

the temperature dropped. The hibernation and

survival studies were of value in determining

when boll weevils emerged from hibernation

sites in the spring and early summer to enter

cottonfields.

In 15 years of studies at Tallulah with various

types of shelter material and dates of installation, survival ranged from 0.01 to 6.14 percent,

with an average of 1.22 percent. The minimum

temperature was the most important winter

weather condition affecting survival, the lower

the temperatures or the greater number of times

the temperature was below freezing, the lower

the survival. Hibernation experiments also
RESEARCH ON COTTON INSECTS 15

were conducted at several other places to obtain

information on survival, especially at Florence,

S.C, Stoneville, Miss., and College Station and

Waco, Tex., representative of the different sections of the Cotton Belt.

Many boll weevils hibernated in Spanish moss

although it is not very favorable for weevil

survival because it is open and subject to sudden

changes in temperature. Examinations were

made of moss collected near cottonfields in the

fall and again in the spring for many years as

an index of weevil abundance at time of entering hibernation and spring survival and for

predicting weevil abundance.

In 1957 Brazzel and Newsom of Louisiana

State University found that the boll weevils

developed diapause to survive the winter in

hibernation sites. Much of the survival data

developed in cage studies before that time became suspect since there was no way of knowing

whether the weevils were reproducing or diapausing when they were installed in the cages.

The diapause finding did not adversely affect

results of surface woods trash examinations

because most of the weevils that entered hibernation sites had developed diapause, enabling

them to survive the winter.

Since about 1935 examinations had also been

made of surface woods trash collected near

cottonfields at Tallulah, La., and Florence, S.C,

and in later years at Stoneville, Miss., and Waco,

Tex. Machines have been developed that separate most of the trash and greatly reduce the

labor involved in examining surface woods

trash. These examinations have also shown that

most of the weevils occurred in trash within 50

feet of the edge, and no weevils were found

more than 300 feet from the edge of the woods.

Weevils have emerged from hibernation, fed

throughout the summer in the insectary, and

entered hiberation again the second winter, but

no survival over two winters was recorded.

Varietal resistance to boll weevil.—Another

line of investigation was the study of immunity

or resistance of cotton varieties to the boll

weevil. The reduction in damage by the boll

weevil through the development of improved

varieties was due to the shorter fruiting periods

and earlier maturity of the plants, and the

morphological characters that might offer resistance were studied very little previously. Investigations of such characters as the thickness

of boll walls, the toughness of the carpel lining,

pilosity of leaves, amount of leaf area (shade),

and early shedding of leaves were started at the

Stoneville, Miss., laboratory in 1934.

No resistant varieties were found and special

attention was given to the characters most likely

to increase the difficulty of oviposition. Thickness of boll walls and toughness of carpel linings

resisted oviposition, but as a strong negative

correlation existed between the two characters,

both were not present in any one variety.

Toughness of the carpel lining without the

protection of boll wall thickness was of little

value in resisting weevil damage, and the least

damage was caused to varieties with walls intermediate in thickness and toughness. This work

was continued in cooperation with plant geneticists, as the development of a variety with only

a slight degree in weevil resistance would mean

a great saving to growers. The work on resistant varieties received increased emphasis in the

1960's and 1970's and is discussed under that

section in this report.

Attractants.—Considerable attention was

given to studies of the chemical constituents of

the cotton plant that attract boll weevils with the

hope of isolating and using them as baits. Chemists assigned to this work at Tallulah in 1923

distilled large quantities of cotton plants and

separated the distillate into a number of constituents. As ammonia and trimethylamine were

in greatest abundance, they were considered to

be the most likely materials to attract weevils

to cottonfields. Extensive tests with these materials in a chemotropometer and a specially

designed apparatus for exposure in the field did

not indicate that they would be of any practical

value in attracting weevils though a few weevils

were attracted. Recent work is discussed in the

attractants section of this publication.

Boll weevils and Sea Island cotton,—The boll

weevil caused more serious damage to Sea

Island cotton than to short-staple and upland

cotton for the following reasons: Sea Island

cotton fruits over a much longer period; the

boll walls are thinner and softer, bolls require

longer to mature, and bolls are subject to attack

almost until they open. Very little work was

done on the boll weevil on Sea Island cotton, as

production was discontinued shortly after the
16 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

boll weevil reached the areas in Florida and

Georgia where this cotton was grown. A movement was started in 1934 to revive the once

prosperous Sea Island cotton industry, and one

of the most important problems to be solved

was the control of the boll weevil. The biology

and habits of the weevil on Sea Island cotton

had previously been studied in 1918, and experiments on control were undertaken at Tifton,

Ga., in 1936 and in 1937 at Gainesville, Fla. The

results indicated that the same methods that

were successful on short-staple cotton could be

used, although control was more difficult and

expensive because of the longer growing season.

Spraying instead of dusting calcium arsenate

also appeared to be more effective on the

smoother leafed Sea Island than on upland

cottons. Most of the Sea Island cotton was

produced in light sandy soils of low productivity, and despite the higher price per pound for

Sea Island cotton, weevils could not be controlled profitably. Pima, long-staple varieties,

are now grown only in western areas where the

boll weevil does not occur.

Host plants other than cotton,—The boll

weevil develops on the cultivated and wild cotton

of the genus Gossypium and closely related

genera. Fortunately, these are the only plants

on which the weevil breeds in sufficient numbers

to be of importance under normal conditions.

However, plans proposed for eradication of the

boll weevil with noncotton zones in the early

days raised the question whether the elimination of cotton would force the weevils to other

hosts and enable them to maintain populations

in the absence of cotton. In the early investigations weevils were noted to feed and to deposit

eggs on several malvaceous plants of the genus

Hibiscus, but the larvae did not reach maturity.

In 1913 weevils were bred for the first time on

plants other than cotton when two completed

development on althea. Hibiscus syriacus L., and

others partially developed on two species of

Callirrhoe under laboratory conditions. Weevils

are also known to breed in G. thurberia, but it

occurs only in New Mexico and Arizona and is

infested with the thurberia weevil.

In 1932 when several States were considering

legislation to eradicate the weevil, host plants

studies were again started to determine changes

in their status. Weevils were reared for the first

time from buds of H. syriacus growing in a field

of infested cotton and adults fed, and some

oviposited, on several other species of Hibiscus

although no larvae reached maturity. It was felt

that in an eradication program other host plants

could not be overlooked. Althea is an ornamental shrub that is generally distributed

throughout the South.

In 1956 at Brownsville, Tex., M. J. Lukefahr

noticed that several flower buds of Thespesia

populnea (L.) Soland were turning yellow and

shedding from the tree. He found that these

buds were infested with boll weevil larvae and

four adults were on the foliage. All the flower

buds and seed pods eventually became infested.

Several infested buds were collected, and 14

adult boll weevils emerged from them. Nine of

them were placed in a cage containing potted

cotton plants, and in a short time all the fruiting forms showed evidence of feeding or egg

punctures. Thespesia populnea belongs to the

family Malvaceae and is commonly called portia

tree. Locally, it is referred to as the tulip tree.

J. K. Walker of the Texas Agricultural Experiment Station in 1957 found that boll weevil

eggs removed from cotton squares and implanted individually in buds of the wine cup,

Callirrhoe involucrata (Nutt.) A. Gray, produced adults. The wine cup is a common malvaceous plant in central Texas and blooms in

April and May. Although boll weevils were

forced to feed and oviposit on this plant, they

produced no adults in this manner. It is doubtful that the wine cup is a significant host of the

boll weevil.

After finding that boll weevils developed on a

caged Cienfugosia drummondi (St. Hil.) Garcke

plant, Lukefahr and Martin reported that four

adults developed from 182 capsules of this plant

collected on July 14, 1961, on the Welder Wildlife Refuge near Sinton, Tex. The nearest cottonfield was approximately 10 miles away and

was fruiting at the time the seed capsules were

collected.

On July 31, capsules and flower buds were

collected from six locations in Nueces County,

Tex., and plants from three of the locations

were infested. Thirty-flve weevils were reared

from 104 fruiting forms that were collected

from plants growing about 500 feet from a

heavily infested cottonfield located near Port-
RESEARCH ON COTTON INSECTS 17

land, Tex. Twenty-eight adult weevils were

collected with an insect sweep net in an area 30

by 50 feet, containing approximately 100 plants,

at this location. Another area near Gregory,

Tex,, yielded 15 adults from 61 fruiting forms,

and the third infested collection made near

Corpus Christi, Tex., yielded 16 adults from

133 capsules. The plants in the three noninfested

locations were widely scattered and were not in

close proximity to cotton.

C. drummondi belongs to the family Malvaceae and occurs primarily in the Coastal Bend of

Texas. It is a perennial, low-growing plant,

about 8 inches high with runners as long as 2

feet. It is found in poorly drained places that

have been undisturbed by cultivation. This plant

has been observed blooming from April to October in Nueces County and in February at

Brownsville, Tex. Its flowering cycle seems to

be dependent on rains, but the plant is very

drought resistant. Twenty immature fruiting

forms and four mature capsules have been observed on one plant. A fully developed capsule

has five locules ^^âth seven or eight seeds per

locule. Each seed is covered with light-brown

fibers that are closely appressed to it.

How long the boll weevil has been associated

with Cienfugosia is unknown, but it seems probable that this insect may be able to maintain

itself on some species of this genus and be

entirely independent of cotton. The weevil infestation on C drummondi plants growing on

the Welder Wildlife Refuge may be an example

of such a population. These plants were surrounded by mesquite trees and brush in a rangeland widely separated from cultivated land;

however, they were found to be infested when

examined during midseason. Collections of

weevils in pheromone traps in the spring in

these areas indicate that weevils can survive

from one year to the next on hosts other than

cotton.

Five additional species were found to be hosts

of the boll weevil by Lukefahr and Martin.

These were Cienfugosia argentinia Garcke and

C sulphurea (A. Gray), C. hildebrandtii Garcke

of Africa, Thespesia lampas Cav. of Asia, and

Hampea sp. of Mexico. Fryxell and Lukefahr

postulate that the geography and ecology of the

infested Hampea sp. trees in Veracruz, Mexico,

suggest that they may be the long-sought primary host of the boll weevil. Large numbers can

develop on one male tree.

In reviewing the hosts of the boll weevil

other than cotton it seems that only Althea,

(Hibiscus syriacus), Thespesia populnea, and

Cienfugosia would pose much of a problem in

an effort to eliminate the boll weevil as an

economic pest from the United States. Insofar

as Althea is concerned, it could be handled with

regulatory procedures. Though homeowners

may be reluctant to give up this ornamental,

hopefully through education and information

they could be persuaded to do so. Inspection of

the many properties could be quite difficult.

Thespesia populnea would be handled in the

same way in the Lower Rio Grande Valley of

Texas. Cienfugosia would pose some problem in

a boll weevil elimination program. All colonies

would have to be located and delimited. However, since infestations usually are light, they

might be eliminated with release of sterile males

or with pheromone traps or with a combination

of the two techniques.

Thurberia Weevil

The Thurberia weevil {Anthonomus grandis

var. thurberiae Pierce) was discovered by Dr.

0. F. Cook of the Bureau of Plant Industry and

the novelist, Harold Bell Wright, on Thurberia

or ''wild cotton" in the Arizona mountains in

1912. At first the boll weevil was thought to be

breeding on a new host plant under climatic

conditions where it had not previously been

able to exist, and it was feared the weevils

would spread to the large noninfested cotton

areas of the West. Subsequent studies showed

the Thurberia weevil was a variety or biological

race of the boll weevil, difficult to distinguish

from the true boll weevil.

Explorations were made to determine the

distribution of the weevil and its host plant, and

research on the biology, habits, and economic

importance of the species was undertaken in

1913. These studies showed that the Thurberia

weevil would readily attack cotton and would

interbreed with the boll weevil. No commercial

plantings of cotton were made at that time near

the mountains where the weevils occurred, and

the infestation was confined to Thurberia

plants. However, an experimental planting of
18 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

cotton became infested in 1914, indicating that

the weevils would infest commercial cotton in

the future. Following the development of irrigation, commercial planting of cotton was extended in the Santa Cruz Valley nearer the

mountains, and in 1920 Thurberia weevils were

found infesting cotton north of Tucson, Ariz.

In 1924 the State of Arizona attempted to

establish a noncotton zone in the infested areas,

but farmers took this matter to the courts and

were granted a permanent injunction against it.

The trial attracted much attention and disclosed

the lack of entomological information on many

of the issues involved. Since about 2 million

bales of cotton, or about 15 percent of the U.S.

crop was grown in the West where the boll

weevil does not occur, the Bureau decided to

obtain the much needed information on the

importance of the Thurberia weevil. A laboratory was established in Tucson in 1925 to (1)

delineate more thoroughly the range of the

Thurberia plants and weevils in the United

States, and (2) determine if the Thurberia

weevil could maintain itself on cultivated cotton

in the absence of Thurberia plants, and the

damage it would cause to cotton.

An experiment was planned to rear the Thurberia weevil exclusively on cotton for at least

10 years to study any changes in its biology

and habits. The study was to be made on a

ranch isolated about 25 miles from any cotton

or Thurberia plants. The work was delayed,

however, as most of the weevils from the 1925

crop were used in working out fumigation and

sterilization methods for use in movement of

cotton products from the area to be quarantined.

A Federal quarantine was promulgated in 1926,

and the farmers filed suit to restrain the Department from enforcing it in the Maraña district of Arizona. The case, which was finally

won by the Department in 1928, was an important step in establishing the legality of Federal quarantines.

Detailed surveys in 1926 and 1927 and later

studies showed that the Thurberia plants were

found only in the mountains of eight counties

in southeastern Arizona and Hidalgo County of

southwestern New Mexico, while the weevil was

limited to portions of the plant range in five

counties in Arizona. Both the plants and the

weevil also extended into Mexico, although the

limits of distribution are not known.

Biological studies on the Thurberia weevil

bred continuously on cotton for 10 years indicated that it was not likely to become a major

pest of cotton in the irrigated sections of the

Southwest. The weevils hibernate as adults

within the pupal cells in old cotton bolls, and

the necessary preplanting irrigation causes the

weevils to emerge and die before cotton begins

to fruit. Experiments extending over 4 years

showed that agricultural practices used to produce the crop could eradicate the weevil in one

year from cotton in the irrigated section not

subject to reinfestation from Thurberia plants.

Damage to commercial cotton plantings never

was severe and occurred only where infestations

occurred from Thurberia plants. Dispersal by

flight is limited and the removal of infested

Thurberia plants for 1 mile or more from cotton

fields greatly reduces the infestation. Research,

also, showed that the Thurberia weevil can be

controlled with calcium arsenate.

A flareup in infestations in the 1960's caused

renewed interest in research on the boll weevil.

Results of the research substantiated much of

the early data. It was determined that if ''soca"

or stub cotton was not grown in Arizona the

problem would be eliminated or greatly minimized. State regulations now ^forbid growing

stub cotton.

Bollworms

The bollworm is very generally distributed

throughout the world and has been recorded as

a cotton pest in the United States since 1820.

Entomologists have devoted considerable attention to it since about 1854, and many early publications of the Patent Office and the Department deal with the bollworm.

The bollworm feeds also on corn, tomatoes,

grain sorghums, peas, alfalfa, lespedeza, beans,

soybeans, flax, peanuts, and many other plants.

It is called the corn earworm on corn and the

tomato fruitworm on tomatoes.

Development.—The bollworm has four stages

in its development : Egg, larva, pupa, and adult.

Only the larvae are destructive. Between spring

and early fall, this insect produces 4 to 6 generations. The last generation remains in the
RESEARCH ON COTTON INSECTS 19

pupal stage and passes the winter in the soil.

For about a month in the spring, moths emerge

from overwintered pupae. Moths are yellowish

or brownish and have a wingspread of 1 to IV2

inches.

Female moths of the season's first generation

lay eggs on clover, alfalfa, bluebonnets, winter

peas, young corn, and other plants. Secondgeneration moths lay eggs on silks of young

ears of corn, if they are available. If corn silks

are not available, the second-generation moths

lay eggs on other plants—on cotton in some

areas. Third and later generations of moths

(which often overlap) lay eggs on cotton.

On cotton, moths usually lay eggs on the

tender, growing tips of plants and on the top

sides of leaves. Sometimes they lay eggs on

squares, bolls, and stems. Eggs, which are white,

ribbed, and dome shaped, are about half the

size of a pinhead. Larvae hatch from the eggs

in 3 to 5 days.

Color of the larvae varies. It may be pale

green, rose, brown, or almost black. Full-grown

larvae are 1 to II/2 inches long. For a day or

two after hatching, larvae feed on the nearest

tender growth. Then, larvae on terminal buds

of the cotton plant move downward; those on

fruiting branches move toward the center of the

plant. The larvae eat out the squares and tunnel

into and eat the contents of the bolls. Mature

larvae enter the ground and change into mahogany-brown pupae, from which moths emerge

(fig. 4).

Research.—In connection with the boll weevil

investigations, work on the bollworm started in

1903 at the Victoria, Tex., laboratory. This

work was expanded in 1904 with headquarters

at Paris, Tex.

Fortunately, most methods of control developed for the boll weevil were of value, also,

against the bollworm. In the early investigations special attention was given to cultural

methods, trap crops, and poisoning with paris

green, the arsenical then in general use. Fall

plowing of the land to destroy overwintering

pupae and early maturity of the crop reduced

infestations considerably. Investigations on the

bollworm as a cotton pest were resumed in 1928

with headquarters at College Station, Tex. In

1939 the headquarters moved to Waco, Tex., and

the work continued until June 30, 1973, when

the laboratory closed. Work on the bollworm

continued at other locations, however.

The bollworm is difficult to control because of

the large number of wild and cultivated host

plants and its habit of feeding within the

squares and bolls, and because the damage

extends over a long period. The larvae often

are not sufficiently numerous at any one time

on cotton to justify the expense of control yet

the accumulative damage may be severe. Cotton is not the preferred host, and the abundance

and succession of other crops such as corn,

grain sorghum, cowpeas, vetch, alfalfa, and

others from which the moths migrate to cotton

are important factors in the damage caused

to cotton.

The use of trap crops, especially corn, to

prevent the early infestation on cotton was

recommended but was not successful in actual

use because of the reluctance of growers to

destroy the crops sufficiently early to prevent

maturity of the larvae. Studies of the factors

attracting moths to cotton for oviposition have

shown that the more succulent plants are favored for oviposition. Consequently, cotton on

river bottom land that had been overflowed or

had abundant moisture was usually the most

seriously damaged. In control experiments with

insecticides, the most important factor was the

timing of applications so that the plants would be

covered with insecticides when the larvae were

hatching so as to kill them while they are small.

The best early criterion for timing applications was egg deposition on plants. Treatments

for control were recommended to begin when

25 to 30 eggs are found per 100 terminal buds.

Unfortunately, egg counts are difficult to make

and growers usually did not recognize the

presence of injurious infestations until the bollworms were too large for successful control.

Tests were made with most of the common

insecticides including arsenicals, pyrethrum,

rotenone, sulphur, fluorine compounds, and

others. Calcium arsenate or a mixture of calcium arsenate and paris green gave the best

results. Cyrolite dust was not as effective for

bollworm control on cotton as it was on lima

beans. The most economical control on cotton

was obtained by treating with 10 to 12 pounds

of calcium arsenate per acre. Treating with

hand-dust guns or ground machines that con-
20 AGRICULTUEE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

PÎÎ-4420

Figure 4.—Bollworm and damage (a) eggs; (b) egg (15 times natural size); (c) young larva in square; (d)

damaged square; (e) full grown larvae; (f) pupae in soil; (g) adult. (Eggs about 15 times natural size; other

stages about natural size.)
RESEARCH ON COTTON INSECTS 21

centrated the arsenicals in the tops of the

plants gave better results than aerial dusting,

although thousands of acres were successfullytreated by aerial dusting in the Brazos River

bottom of Texas each year.

Naturally occurring predators and parasites

often keep infestations of the bollworm at subeconomic levels. However, insecticides applied

for the control of other insects, such as the

cotton fleahopper and boll weevil, kill off the

beneficial insects. Thus, continued use of protective measures is necessary until the crop

matures and is no longer attractive to bollworms and tobacco budworms even though the

target insect has been controlled.

In the 1940's organic insecticides such as

DDT, toxaphene, endrin, methyl parathion,

and carbaryl, and later monocrotophos were

very effective. At the end of 1972, however, use

of DDT on cotton was banned.

The tobacco budworm, Heliothis virescens

(F.), which is even more difficult to control

than the bollworm, did not become a serious

pest of cotton until the 1960's. It developed

resistance to available effective insecticides,

creating a serious problem in several areas of

Texas and Louisiana. The problem superimposed on other adverse factors resulted in

abandoning cotton production in several localities in Mexico.

Cotton Aphid

The cotton aphid. Aphis gossypii Glover, occurs wherever cotton is grown. It was described

by Glover in 1877 although he made previous

references to an aphid observed on cotton in

South Carolina, Florida, Georgia, and Mississippi in 1855 and in subsequent years. It

attacks many plants in addition to cotton and

is sometimes called the melon aphid because it

is a serious melon pest.

Development—The adult cotton aphid is a

soft-bodied, sucking insect that ranges in color

from light yellow to dark green or almost black.

In the spring, it is dark green on the tender,

growing leaves and terminal buds of cotton and

about i/i4-inch long. Later in the summer, it

is usually found on the undersides of mature

leaves and is light yellow and much smaller. In

the fall, when plants often put on new terminal

growth, the aphids are dark green to almost

black, and about the same size as the spring

aphids (fig. 5).

The cotton aphid multiplies rapidly under

favorable conditions. Enormous populations

may build up in a short time. New generations

may occur every 5 days during summer months.

Reproduction is slower and the lifespan longer

during cold weather.

Only female cotton aphids occur in the Cotton Belt. They give birth to living young. As

reproduction is continuous, generations are not

distinct. These insects may spend part of the

winter as winged adults, hibernating in field

debris or in cracks in the soil. When warm periods occur, they fly to weed hosts on which

they feed and continue to reproduce.

In the spring, winged adults develop on the

weed hosts. They fly to cotton and melon plants,

where they give birth to living young that

develop into wingless females. Winged forms

are produced on any host when crowding occurs

or when food becomes scarce.

Males and females occur in the Northern

States, where they feed on melons, cucumbers,

and many other plants, both wild and cultivated.

Females lay eggs that survive the winter and

hatch in the spring.

This insect damages cotton by sucking juices

from the plants, reducing both yield and quality, and often causes severe losses to growers.

When heavy infestations occur on seedling cotton, the leaves curl or crinkle; plants become

stunted and may die. This often happens in

early spring, before natural enemies of the

aphid become active.

When heavy infestations occur during the

main fruiting period (from early bloom to full

bloom), the older leaves turn yellow and shed,

causing premature opening of bolls and immature development of fiber. Also, honeydew secretions from the aphids drop on the fiber,

making it sticky. Often, a fungus develops in

the honeydew deposits, causing the plants to

appear black or sooty. Fiber picked from such

plants is stained and sticky and of low quality ;

seeds are low in viability and lightweight.

The cotton aphid often is controlled by its

natural enemies. It seldom increases to damaging numbers unless its natural enemies are

killed or reduced to low numbers. When heavy
22 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

PN-4421

Figure 5.—Cotton aphid and damage (a) curled leaves; (b) aphids on under side of leaf; (c) aphids on stem;

(d) honeydew on leaf; (e) winged female; (f) wingless female; (g) young. (Actual size depicted for a, b, c,

and d; females and young, about 14 times actual size.)
RESEARCH ON COTTON INSECTS 23

infestations occur on seedling cotton in early

spring, the cool weather prevents natural enemies from becoming active and numerous

enough to control the aphids. When warm

weather arrives, the natural enemies if left undisturbed, increase sufficiently to bring the

aphids under control. However, severe damage

may occur before natural enemies take over.

Research.—Use of calcium arsenate for boll

weevil control was limited because of the buildup of cotton aphid populations following its use

over wide areas (see p. 1). The only aphicide

available was nicotine sulfate, which was expensive, difficult to apply, and effective only under

ideal conditions. The new organic insecticides

replaced calcium arsenate for boll weevil control; most organophosphorus compounds effectively control the cotton aphid.

Cotton Fleahopper

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter), was known as a cotton pest in

local areas in southern Texas since about 1900,

but its importance was not recognized until a

serious general outbreak occurred in 1923 over

a rather large area. The fleahopper is generally

distributed over the Cotton Belt but causes the

most serious damage in the Blacklands of Texas

where it is often more injurious than the boll

weevil.

Development.—The cotton fleahopper has

three life stages—egg, nymph, and adult. In the

fall, adult females lay eggs in weeds, usually

in stems of crotón. This plant, known as goatweed, is common throughout the Cotton Belt.

The cotton fleahopper overwinters in the weeds,

in the egg stage.

The eggs hatch in early spring. Newly

hatched nymphs, which are about one twentyfifth of an inch long, are white and translucent.

After feeding they become pale green. They

have prominent, scarlet-colored eyes. Nymphs

progress through five instars before becoming

adults. The last nymphal stage resembles the

adult but does not have fully developed wings.

Adult cotton fleahoppers are about oneseventh of an inch long and are winged. They

are pale green with small, dark spots on the

body and- four black marks near the wingtips.

These insects feed and reproduce on tender

weeds, such as evening primrose and horsemint.

As the weeds mature and become less juicy,

adults fly to cotton plants, which are usually

in the presquaring or early fruiting stage. The

pests stay on cotton as long as the plants are

succulent. When cotton becomes tough, the fleahoppers generally leave it and go to crotón and

other weeds to feed and lay eggs. This insect

may produce six to eight generations in a season. Cold weather kills both adults and nymphs.

The cotton fleahopper injures the entire cotton plant by feeding on juices from the tender

parts. Leaves become ragged and deformed.

Squares turn brown or black and are shed when

they are the size of a pinhead. Heavy infestations of fleahoppers restrict the growth of

fruiting branches. Vegetative branches may develop abnormally in length or in number. Affected plants often grow tall and whiplike (fig.

6).

If the cotton fleahopper is not controlled early

in the season, fruiting is delayed. Cotton plants

then may be attacked for a longer time later in

the season by other insects, particularly by the

boll weevil, bollworm, and pink bollworm.

Research.—Investigations started in south

Texas on the biology, host plants, and control

measures soon after the outbreak in 1923. These

were followed by more detailed studies at Tallulah, La., of the habits of this and other species

of mirids and their effect on the plani^ tissues.

In 1933 a laboratory was established at Port

Lavaca, Tex., to develop control measures for

the cotton fleahopper. In the earlier Texas work

sulphur had been used with fairly good results,

but the details of application had not been

worked out.

Extensive cage and fleld tests with many insecticides showed that sulphur was the most

effective insecticide against the nymphs, but

that a mixture of sulphur and an arsenical was

more effective and gave quicker kill of the

adults. Mixtures of paris green and sulphur (1

part to 13 parts) or calcium arsenate and sulphur (1 part to 2 parts) were almost equal in

effectiveness against the fleahopper, but the calcium arsenate-sulphur mixture was recommended because it was somewhat cheaper and

was also effective against other insects such as

the boll weevil and cotton leafworm that usually

occurred at the same time. Calcium arsenate
24 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Figure 6.—Cotton fleahopper and damage (a) blasted square

from blasted square; (c) injured leaf. ((A) and (c) actual size

nymphs 15 times natural size.)

PN-4422

(b) whiplike plant and lack of fruit resulting

(b) about ^ne-fourth actual size; adult and
RESEARCH ON COTTON INSECTS 25

and paris green alone killed a high percentage

of fleahopper adults, although it was not determined how arsenicals kill these sucking insects.

Results of field tests over a number of years

showed that from 2 to 3 applications of 15

pounds per acre of the calcium arsenate-sulphur

mixture gave good increases in yield in the Port

Lavaca, Tex., area. The development of the

arsenical-sulphur mixtures was the most popular control used for cotton insects since the

discovery of calcium arsenate for the boll weevil. Large quantities of the mixtures were applied both with ground-dusting machines and

airplanes. In Calhoun County, where most of

the experiments were conducted, over twothirds of the cotton acreage was treated with

power dusters, primarily for ñeahopper control.

Attention was also given to cultural methods

of controlling the ñeahopper since the insect

overwinters in the egg stage in the stems of

plants with approximately 99 percent overwintering in the stems of crotón or ^'goatweed.''

In the winter of 1933, crotón on 10,000 acres of

ranchland in Calhoun County, Tex., was destroyed through a Civil Work Administration

grant. The following spring practically no fleahoppers were found on cotton until a heavy

migration of adults occurred. Results showed

that fleahoppers migrated for at least 20 miles

and that destroying crotón would not be a

feasible method of control.

In the spring of 1939, the Cotton Fleahopper

Laboratory was moved from Port Lavaca to

Waco, Tex., where this work was combined

with that conducted at College Station, Tex.,

for the bollworm. A sublaboratory was maintained in Port Lavaca, however, until 1942.

The cotton fleahopper continues to be considered a key pest of cotton in many areas of

Texas because treatment for control in the early

fruiting stage often results in increased subsequent infestations of the bollworm and tobacco budworm. Beneficial insects that often

keep the bollworm complex infestations below

economic levels are killed off by the treatment

for control of cotton fleahoppers, necessitating

the continued use of protective measures until

the crop matures and no longer is attractive to

bollworms and tobacco budworms. The bollworm complex problem often can be avoided if

treatment for cotton fleahoppers is needed in

the early fruiting stages of the cotton plants.

Treating in the early fruiting stages permits

the reestablishment of beneficial insect populations before injurious bollworm complex infestations occur. This can only be done if horsemint matures early enough to result in migration of cotton fleahoppers to cotton by that

time.

Cotton Leofperforator

As a result of the severe cotton losses in the

Yuma and Imperial Valleys in 1925 from the

cotton leafperforator (Bucculatrix thurberiella

Busck), a substation of the Tucson, Ariz., laboratory was established at Calexico, Calif., in

1926 to investigate this insect. Very little information was available, and the work during

1926 and 1927 was devoted largely to life history studies reported but not published.

Work was resumed in 1930 to 1932 with particular attention to practical control methods,

and while control measures were not satisfactorily worked out, considerable information was

available. Barium fluosilicate was the most satisfactory insecticide used, and eliminating soca

or stub cotton was valuable in reducing the

overwintering populations.

Development.—Eggs of the perforator are

laid on both the upper and lower leaf surfaces,

with an occasional one being placed on a petiole. The extremely small, whitish, elliptical egg

is attached to the leaf by one end with the

longitudinal axis then being perpendicular to

the leaf surface. The incubation period averages about 2.25 days under greenhouse conditions of 70° to 90° F. The first instar larva

emerges directly through the attached end of

the egg and into the leaf, thus becoming a leaf

miner. The first three instars are spent mining

through the leaf, feeding primarily on the palisade tissue. A larva seldom crosses a main leaf

vein, and avoids gossypol glands. The feeding

channels are most readily visible on the upper

surface of the leaf, becoming progressively

wider with each of the two subsequent mining

instars. The duration of the first three instars

(mining stages) averages 3.45 days (fig. 7).

After completing the third instar, the larva

emerges from within the leaf and begins the
26 AGRICULTURE HANDBOOK 515, U.S. DEPT. OP AGRICULTURE

'H'¿,

'#7-'

PN-4423

Figure 7.—Third-stage larva of the cotton leafperforator, almost full grown, feeding upon a cotton

leaf (natural size). Two mines, one large and one

small, can be seen in the leaf. The large mine is

empty; the small one contains a miner, or first-stage

larva, which is busily extending the large end of the

mine.

fourth stage, feeding on the leaf surface. During the feeding of the fourth and fifth instars,

the larva eats only to the opposite epidermis.

Feeding occurs on either upper or lower surfaces, but during daylight hours the larvae

generally feed on the lower surface of the leaf.

When disturbed, both fourth and fifth instar

larvae wriggle vigorously, usually dropping

from the leaf on a silken thread and returning

when the disturbance is over.

At completion of the feeding stage of the

fourth instar, the larvae spins a weblike cell

on the leaf surface and assumes a "horseshoe"

shape during this resting stage. The duration

of the fourth instar is 2.1 days, 1.0 day in

the feeding stage and 1.1 days in the resting

•stage. After molting, the fifth instar larvae

emerges from the cell and feeds on the leaf

surface, as in the fourth instar, until mature.

This requires about 2.6 days.

The fully grown fifth instar larva then spins

an elongate silken cocoon. This may be on the

leaf but is usually elsewhere such as on a main

branch, dead leaves on the ground, or even in

the soil. The pupal period averages 1.7 days.

The moth that emerges from the cocoon is

about one-fifth inch long and covered with whitish scales with a few black or brownish spots.

The head is concealed by a tuft of white hairs

on the upper surface. After a preoviposition

period of 4 days, the females begin laying eggs.

Adult activity occurs at twilight or after

dark. Eggs are laid singly and usually near a

leaf vein. The egg is white but darkens before

hatching. The newly hatched larva (leaf miner)

usually feeds in a tight circle before initiating

its meandering course through the leaf. The

first external feeding stage (fourth instar)

spends less time feeding and does relatively

little damage as compared with the fifth larval

instar. The fifth instar does considerably more

feeding in a single spot, thus creating larger

"windows" in the leaf. As this stage completes

development, it usually becomes restless and

leaves the leaf in search of a suitable place to

spin its cocoon.

One difficulty in controlling this insect with

insecticides appears to be related to the disproportionate amount of time that the insect

spends in protected areas. For example, the

life cycle (egg to egg) in the greenhouse required 21.5 days. Only 3.6 days were spent as

an exposed, feeding larva.

Research.—With the advent of the organochlorine insecticides, the cotton leafperforator

rarely became a problem. However, when these

insecticides were replaced by the organophosphorus insecticides because of resistance, the

problem intensified and occurred, also, in far

west Texas and in the Lower Rio Grande Valley. Research on the pest was resumed by the

Arizona Agricultural Experiment Statin and

the ARS Western Cotton Insects Laboratory

in the 1970's. Field tests for the evaluation of

insecticides for its control were conducted, also,

in the Lower Rio Grande Valley by the Texas

Agricultural Experiment Station land the ARS

Southwestern Cotton Insect Investigations

Laboratory.

Cotton Leafworm

Though the cotton leafworm, Alabama argillacea (Hübner), is now considered to be a
RESEARCH ON COTTON INSECTS 27

pest of little or no economic importance, it was

a major pest in the early days and received

equal billing with the bollworm in Professor

J. H. Comstock's report in 1879 (18), Re stated :

The first appearance of the cotton worm in this

country now on record was in 1793 in Georgia and

South Carolina after cotton had been grown for

150 years.

It was recognized as the first serious pest of

cotton.

The cotton leafworm is a tropical species

that does not overwinter in the United States.

Every year the moths migrate into this country

from Central or South America or from Mexico. Each year since 1922 cotton leafworm larvae first have been found in southern Texas,

usually in May but in some years in April,

June, or July.

The cotton leafworms spread out from southern Texas. Usually by the end of a cotton growing season, they are present in every cottonproducing State from Arizona eastward. Larvae

never have been reported in California or

Nevada.

Before the organic insecticides came into

general use in the late 1940's, the cotton leafworm often was one of the most destructive

cotton pests. In outbreak years, supplies of

insecticides, largely calcium arsenate, used in

control were usually exhausted before the end

of the season. Since then, the widespread use

of organic insecticides for the control of other

cotton insects in southern Texas usually delays

population buildup so that migration to other

areas occurs too late to be of much importance.

In the years before and through World War

II, first findings of the pest in the United States

were of considerable significance. Usually economic damage and migration to other areas

could be expected from later generations. The

planting period of the cotton crop in Texas

ranges from February 1 in the Lower Rio

Grande Valley in the extreme southern tip into

June on the High Plains. Thus, population

buildups in southern areas often resulted in

injurious infestations in all other areas of the

State as well as in Oklahoma and other States

as the cotton-growing season progressed. Tremendous amounts of insecticides were often

required to prevent defoliation of the crop by

the pest. It was of utmost importance that industry be prepared to make sufficient quantities

of insecticides available to meet the growers'

needs.

Development,—The cotton leafworm has four

stages in its life cycle—egg, larva, pupa, and

adult.

The female moth lays bluish-green eggs,

singly, on the undersides of cotton leaves. They

hatch in 3 or 4 days. Newly hatched larvae are

pale, dingy yellow. They feed only on the undersides of leaves.

There are five larval instars. In the summer

the larvae usually become full grown in about

2 weeks and are about II/2 inches long. Their

color varies with some being yellowish green,

without prominent stripes, while others have a

broad, black stripe and a fine central yellow

stripe down their backs. All cotton leafworm

larvae have a distinguishing characteristic—on

the top of each segment are four black dots

that form a square.

When a larva has completed its feeding, it

*Vebs up" in the fold of a leaf and becomes a

pupa. Other larvae may eat away the leaf,

leaving the pupa hanging by a thread from the

leaf vein or stem (fig. 8).

The pupal stage lasts about 1 week in midsummer, but it may last up to 4 weeks in the

fall. The moth, which is olive tan, has a wingspread of about IV2 inches. It is a strong flier

and, frequently, is found in the northernmost

States and in Canada. In these areas, it feeds

on ripe fruits, such as peaches, grapes, and

cantaloups.

The life cycle of the cotton leafworm is completed in about a month with two to eight

generations in a year.

Female cotton leafworm moths lay their eggs

only on cotton in this country. However, in the

mid-1960's Hampea sp. was discovered as a

host in Mexico.

Damage is first evident when the leaves start

to appear ragged. Larvae feed between the main

veins and often skeletonize the leaves. When

leaves become scarce, the larvae eat the bracts

surrounding the squares and bolls. Finally, they

may gnaw into the bolls. There is a characteristic, pungent odor in infested fields. Early

infestations, if not controlled, prevent bolls

from setting.
28 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

\A.

PN-4424

Figure 8.—Cotton leafworm (actual size stages) : A, Damaged branch; (a) full-grown larvae; (b) pupae; B,

terminal bud with (c) eggs; (d) young larvae; (e) eggs (15 times natural size) ; C, adult.
RESEARCH ON COTTON INSECTS 29

Leafworms may cause defoliation before the

crop is mature. Then some young bolls shed;

older bolls open prematurely; and the quality

of both fiber and seed is lowered. Lint often is

stained by excrement from the larvae. Leaf

skeletons become entwined in the lint and are

difficult to remove.

The cotton leafworm has many natural enemies that help control it. Birds, wasps, ants,

spiders, beetles, robber flies, mantids, and aphis

lions are among the predatory enemies.

It has an egg parasite and several pupal parasites. Hot, dry weather causes many leafworm

eggs to dry up, and the unhatched larvae die.

Diseases often destroy leafworm larvae.

Research.—In the early years materials used

for the control of this pest were mixtures of

paris green or london purple with lime or flour

applied primarily with the pole and bag method. The author as a small boy in Texas in the

early 1920's observed his father controlling

cotton leafworm infestations many times with

paris green applied with the pole and bag

method from his best saddle horse. This was

usually done early in the morning or late in

the afternoon with a slight cross breeze, if

possible. Lead arsenate applied as a high volume spray was popular and effective. When

calcium arsenate was developed in the 1920's,

it was also found effective against cotton leafworms and was used to control this pest until

the organic insecticides were developed in the

mid-1940's.

Lygus Bugs

Lygus bugs are the principal insect pest of

cotton in western areas of the United States.

They are especially destructive where extensive alfalfa hay and seed crops are produced

near cottonfields and where large pasture areas

dry up in early summer. In the South lygus

bugs often become abundant on weeds and leguminous crops and may mov,e to nearby cotton

and cause severe damage.

Development.—Lygus hésperas Knight is the

predominant species in western areas ; L. lineolaris (Palisat de Beauvois), known as the

tarnished plant bug, is prevalent in the South.

Other species of lygus bugs damage cotton, but

usually they are of minor importance.

Lygus bugs develop in three stages—egg,

nymph, and adult. Female adults use their

swordlike ovipositors to lay eggs in plant tissues, particularly in stems and leaf petioles.

Eggs are tiny, elongate, and slightly curved.

Nymphs develop through five instars before

becoming adults. The life cycle is completed in

about 4 weeks in summer with a longer time

in other seasons.

Adults are flat and about one-fourth inch

long. They range in color from straw green to

dark brown and have a conspicuous lighter colored triangle between the wings (fig. 9).

When disturbed by the cutting of a host crop

such as alfalfa, or when the plants are no

longer attractive as food, adults fly to another

host crop. They hide in plant foliage during

the day when the weather is hot.

Lygus bugs feed by inserting their long,

needlelike mouthparts into plant tissues and

sucking out the juices. On cotton, they attack

the tender terminal growth, squares, flowers,

and young bolls. Injured squares and small

bolls usually shed. Injured bolls that do not

Figure 9.—Adult lygus bug.

PN-1425
30 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

shed may open abnormally and produce inferior

lint that clings to the warty carpels that result

from lygus feeding.

Lygus damage reduces the yield. It causes

the lint to be spotted and lower in grade. Injured plants develop abnormally, becoming tall

and whiplike, with fewer fruiting branches

(fig. 10).

In western areas of the United States, lygus

bugs may develop on weeds such as wild mustard. They develop large populations on alfalfa,

especially when the alfalfa is grown for seed.

When lygus bugs infest an alfalfa hay crop,

they have time to produce one generation between cuttings. The crop is cut several times

in a season and is a constant source of infestaPN-4426

Figure 10.—Damage to cotton plant exposed to lygus

bugs for 7 weeks in a ñeld cage.

tion for cotton. An alfalfa seed crop requires

at least 60 days before the seeds are mature

and ready to harvest. This allows time for two

or more generations of lygus bugs to develop

in very large numbers. If uncontrolled, they

may destroy the entire seed crop.

Lygus adults leave alfalfa soon after a seed

crop matures or a hay crop is cut. If cotton is

growing nearby, the pests may move to it in

large numbers and gradually disperse over the

entire cottonfield. If other alfaljfa is growing

in the vicinity, they may move into it in preference to remaining in the cotton.

In southern areas, alfalfa and other legumes

may serve as hosts for lygus bugs. Weed hosts,

however, are more often responsible for the

lygus populations that move to cotton. The

more important weed hosts are butterweed,

fleabane, goldenrod, aster, and dog fennel.

When weed hosts mature or become otherwise

unsatisfactory for feeding purposes, lygus bugs

usually migrate to cotton if it is growing

nearby.

Research.—Work on the biology and control

of lygus bugs was conducted in Louisiana and

in Arizona in the 1930's. Mixtures of calcium

arsenate or paris green and sulphur gave effective control but were replaced by the new organic insecticides in the 1940's. Lygus bugs are

key insect pests as insecticides applied for their

control often result in subsequent injurious infestations of the bollworm complex necessitating continued treatment until the crop matures

and is no longer attractive to boUworms.

Pink Bollworm

The pink bollworm, Pectinophora gossypiella

(Saunders), was described in 1843 from specimen collected in India in 1842 and is probably

indigenous to that country. It was reported

as a serious pest of cotton in 1904, when it

caused damage in what was then known as

German East Africa. It has since become the

most injurious insect pest of cotton in many

cotton-growing regions of the world. Potentially, it is a serious pest of cotton in the United

States. Quarantine regulations and cultural and

chemical controls have reduced economic damage in most years in the infested areas of this
RESEARCH ON COTTON INSECTS 31

country and have retarded the spread of this

insect to new areas.

The pink bollworm was introduced into Mexico in 1911 through importing infested cottonseed from Egypt for planting and into the

United States in 1916 in cottonseed from Mexico for milling. The pink bollworm was first

found in Texas at Hearne near an oil mill that

had received seed from Mexico.

Research on the pink bollworm first started

in Hawaii. In February 1918, the Department

established a laboratory for pink bollworm research at Lerdo, Durango, Mexico, where the

insect populations were sufficient for such

studies. The work in Mexico was interrupted

late in 1919 until early 1921 and then resumed

at Tlahualilo, Durango, until April 1925. At

that time the Tlahualilo laboratory closed because infestations in southwestern Texas had

built up to the extent that work on the pest

could be conducted there.

In July 1927, headquarters for research on

the pink bollworm by the Department was

established at El Paso, Tex. Since that time,

other Federal laboratories in Texas have conducted research in cooperation with the Texas

Agricultural Experiment Station.

The first experiment conducted with the insect in this country began in the fall of 1927

at Castalon, now in the Big Bend National

Park. A laboratory staffed by both Texas

and Federal personnel was established at Presidio in April 1928, and it became headquarters

for this work in 1933. In August 1928, a sublaboratory of the Presidio laboratory resumed

work at Tlahualilo, Mexico, where it was operated until 1936. A sublaboratory established at

Brownsville in 1939 became the headquarters

laboratory in 1941. Then, the Presidio station

became a sublaboratory and was operated as

such until it closed in 1947. A sublaboratory

w^as operated at Ysleta, El Paso Valley, from

the fall of 1944 until the spring of 1952 and

another at San Benito from 1944 to 1951.

Later sublaboratories were operated at Lubbock and Port Lavaca, both from 1953 to 1956.

Some phases of the work, coordinated by the

Brownsville laboratory, were carried out by

personnel of the cotton insect laboratories at

College Station and Waco from 1954 to 1957

and 1954 to 1962, respectively. In 1965 a new

laboratory was established at Phoenix, Ariz.,

to conduct research on the pink bollworm.

Although the infestation at Hearne, Tex.,

was eradicated, the insect later crossed the Rio

Grande from Mexico into Texas, and its occurrence has been general throughout the State.

Since 1952, this pest has caused considerable

damage to cotton periodically in southern, central, and parts of western Texas. In 1958 and

1959 it caused heavy damage on some acreages

in the El Paso Valley of Texas.

The pink bollworm soon spread to other

States. General infestations have occurred

throughout Oklahoma and New Mexico. Infestations in some parts of Louisiana and Arkansas have been light.

Since 1940, the pink bollworm has caused

heavy cotton losses in some areas of Arizona.

In 1958 and 1959, severe outbreaks of the pest

occurred in the Gila Valley and in the Salt

River Valley of that State, and extended into

Pima County. In these same years—1958 and

1959—this insect caused serious cotton losses

in some parts of the Mesilla Valley of New

Mexico. In the 1960's, it became a serious pest

in the Imperial and Coachella Valleys of California.

Development,—The pink bollworm has four

stages of development: Egg, larva, pupa, and

adult (fig. 11). Adults are small, grayish-brown

moths with a wingspread of about one-half

inch. The average life of the adult is about 2

weeks.

Early in the cotton season, females lay eggs

on cotton stems, squares, and terminal buds.

When green bolls are present, they usually lay

most of their eggs in masses beneath the glovelike calyx at the base of the bolls. A moth lays

100 to 200 eggs, which are white and oval. In

4 to 5 days, the eggs hatch into larvae. Newly

hatched larvae are glossy white and have lightbrown heads. They eat their way into squares

or bolls, where they feed 10 to 14 days. At the

end of this period they are light cream, and

about one-half inch long. They have fairly welldefined, transverse bands of mottled pink on

the dorsal side.

Larvae feeding in squares usually complete

development by the time the bloom opens and
32 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

PN-4427 PN-4428

Figure 11.—Pink bollworm: Left, larvae; right, adult.

rarely damage the developing boll. These larvae

produce the typical rosette bloom that is readily recognized. Many of these larvae drop to

the ground and pupate in cracks in the soil or

in surface trash. A few remain in the bloom

until it sheds. Occasionally, a square or young

boll may shed as a result of feeding injury.

Larvae in bolls feed on the seeds. When a

larva has finished feeding in a green boll, it

either cuts a small hole through the carpel wall

and drops to the ground to pupate or remains

in the seed in which it completed feeding.

A larva that remains in the seed may hibernate in a single seed, or it may pull two hollowed-out seeds together and unite them by

spinning a continuous cocoon within the two

cavities. Seeds thus united are called double

seeds. They become apparent after ginning and

usually are an indication of the presence of

the pink bollworm.

The larvae change to pupae, and the pupae

transform to moths. In 3 or 4 days the female

moths begin laying eggs. The moths are active

only at night. In the daytime they stay under

trash or clods of dirt or in cracks in the soil.

In midsummer the pink bollworm completes

its life cycle in 25 to 30 days. As many as six

generations may occur in a year.

Pink bollworm damage to cotton is caused by

feeding of the larvae (fig. 11, left). Only minor

damage results when larvae feed in squares,

since blossoming is not hindered and the resulting young bolls usually are not damaged.

Severe damage occurs when larvae feed

within the bolls, moving from one seed to another and eating out the kernel of each. This

causes a loss of seed viability, and a reduction

in the volume and quality of oil. Some bolls—

often a high percentage of late-produced bolls

—are damaged so severely that they are unpickable and therefore are a total loss.

When larvae feed within the bolls, they cut

and stain the fibers resulting in low-grade lint.

Fibers so damaged, when mixed with undamaged lint in the harvesting and ginning processes, reduce the average grade of the crop.
RESEARCH ON COTTON INSECTS 33

Some larvae may leave the bolls to pupate or

hibernate by cutting exit holes in the carpels.

This increases damage because a single hole

permits entrance of moisture and disease organisms that cause boll rot. In fields heavily

infested by the pink bollworm, boll damage may

be so severe that the cotton may not be worth

harvesting.

Control with cultural practices.—The pink

bollworm is the only major cotton insect that

passes the winter in cotton or okra residues

left in the field after harvest, or in cottonseed

and seed cotton taken from the field.

Many larvae left in the field in crop residue

can be destroyed by using recommended cultural practices. To be more effective, cultural

practices should be used as a community,

county, State, or regional program and followed by every grower in the control area.

Control of the pink bollworm can be made

more effective if other insects are controlled

and if other sound production practices that

promote rapid, early setting, and maturity of

fruiting forms are used. Early bolls escape

severe damage because they mature before the

pink bollworm infestation builds up to its seasonal maximum intensity.

A thick, vigorous stand will hasten maturity

and increase the efficiency of mechanical harvesting. Seed should be treated with fungicide,

the variety of cotton recommended for an area

should be planted, and a suitable fertilizer

should be used. In a generally infested area,

the insecticide-control practices recommended

for that area in the State guide should be

followed. At the proper time, chemical defoliants or desiccants to speed up harvest should

be used.

Cotton should not be irrigated late in the

season to prevent late-season generations of

pink bollworms (and boll weevils, if they are

present) from going into winter hibernation.

The possibility of a high winter carryover of

the pest, plus the cost of additional insecticide

applications, usually makes the production of

a late top crop unprofitable to the cotton

grower. The production of a top crop of bolls

with resultant fall breeding of the pest seriously jeopardizes the efforts to suppress or

eliminate the pink bollworm, and may greatly

increase damage the following year.

Cotton should be produced in the shortest

time possible and harvested promptly and completely. Most larvae in cotton taken to gins

are destroyed in the ginning process, but approved sanitation practices should be followed

to prevent carryover in waste cotton on the gin

premises. Clean harvesting reduces the number

of larvae left in the field.

Stalks should be cut promptly after harvest

with a power-operated shredder (fig. 12). The

flail-type shredder is preferred. It is quite effective in killing pink boUworms, and it spreads

the residue evenly on the ground, thus aiding

plow-under efficiency (fig. 13).

Crop residue, including infested material

knocked to the ground at harvest, should be

plowed under promptly to a depth of at least

6 inches—^the deeper, the better.

Prefrost stalk destruction increases winter

mortality of the pink bollworm. It reduces the

pest's reproduction in the fall, sometimes by

two or three generations.

Fields left fallow or unplowed in fall or

winter should be plowed early in the spring.

Survival of the pest is highest in bolls lying

on the ground. In areas that have sustained low

temperatures, high mortality occurs in bolls on

standing stalks.

Soil moisture helps to kill pink bollworms.

So in cold, arid climates, fall or early winter

plowing of the dry soil may not be as effective

against pink bollworms as it is in other climates. Under arid conditions, irrigation after

winter plowing increases mortality of the pest.

Many pink bollworm moths from overwintered larvae emerge early in the spring and die

before cotton squares become available for their

reproduction. Thus, the degree of infestation

can be influenced by the date of planting. Extremely early, scattered plantings attract moths

emerging from hibernating larvae in surrounding fields; therefore, heavy infestations occur

in these early plantings. When early plantings

mature, the moths emerging in them migrate

to later fruiting, more attractive cotton.

Usually, late plantings are severely damaged

because moths migrate into them in large numbers. The potential overwintering population is

increased because an abundance of green bolls

are available for pink bollworm development

after the early and intermediate plantings have
34 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Fignire 12.—Horizontal blade stalk destruction machines.

FN-4429

matured. An increase in the number of pink

bollworm generations results when cotton is

planted over a long planting period. Then, the

increased population of the pest causes increased crop damage. Because of this, cotton

should be planted within a short, uniform

planting season for a given area. Planting

should not be started until near the time when

soil temperature becomes favorable for rapid

seed germination and seedling growth. This is

considered the best planting time whether or

not an insect problem is present.

Control with insecticide.—For many years

after it first appeared as a cotton pest, nothing

was known of how to control effectively or

eliminate the pink bollworm. Today, cultural

methods of control can be effectively supplemented in either control or eradication programs by properly timed and adequate applications of insecticide. Effective insecticides did

not become available until the organic insecticides were developed in the 1940's.

Research.—^A detailed discussion of the research on the pink bollworm is given in "Fifty

Years of Research on the Pink Bollworm in the

United States" (78).

Spider Mites

Spider mites attack many plants. A number

of species of these pests attack cotton, and

often cause serious damage. The most important ones are carmine spider mite, Teranychus

cinnabarinus (Boisdval) ; desert spider mite, T.

desertorum Banks, T. ZO&OSîîS Boudreaux; pacific spider mite, T. pacificvs McGregor ; schoene

spider mite, T. schoenei McGregor; strawberry

spider mite, T. turkestani Ugarov and Nikolski ; tumid spider mite, T. tunddiis Banks ; and

two-spotted spider mite, T. urticae Koch and

T. ludeni Zacker.

The mites, which are barely visible, are red,

green, orange, or straw colored. Usually, they

are kept under control by weather, beneficial

insects that kill the mites, other species of

mites that prey on them, and disease (fig. 14).

Outbreaks of spider mites are most likely to

occur following application of a pesticide that

destroys the beneficial insects and mites.

Development.—Spider mites develop in five

stages—eggs, larva, two nymphal stages, and

adult. Females are able to reproduce without

mating and when they do, the offspring always

are males.
RESEARCH ON COTTON INSECTS 35

'^^^i^

'^v ^'

# -( '

PN-4430

Figure 13.—Stalk shredding with flail shredder (top) and machine lifting bolls from ground and shredding

them (bottom).

Where winters are mild, as in the cottongrowing regions of the United States, spider

mites may remain active and reproduce

throughout the year. Under favorable conditions, some species complete a generation in 7

to 12 days. As many as 16 generations may

occur in a year.

Spider mites may attack cotton at any stage

of its growth, but usually they are most injurious from about July 1 until early September. Infestations are prevalent during periods

of hot, dry weather. They may be detected by

inspecting the undersurfaces of leaves of plants

in different parts of the field—^particularly in

areas that were infested in previous years.

Severe infestations may be recognized by

dust collecting in webs that the pests spin over

PN-4431

Figure 14.—Microphotograph of female twospotted

spider mite. Note conidia of fungus Entomophthora

attached to legs.
36 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

leaf surfaces for protection as they feed and

lay eggs. Such infestations may enclose plant

terminals in the webbing.

Spider mites damage cotton in all active

stages of their life cycle.. Larvae, nymphs, and

adults suck the juices from leaves, stems, and

fruits of the plants. Their feeding causes plant

parts to become blotched or stippled and leaves

to become discolored and drop prematurely (fig.

15). When plants are severely attacked, they

may become defoliated and devitalized.

Research.—Before the advent of the organic

insecticides, spider mites were minor pests of

cotton. Infestations, when they did occur, often

were confined to a small area within fields.

Sulphur dust was an effective acaricide. Application of the organic insecticides for other

cotton insects often resulted in subsequent infestations of spider mites. However, several organophosphorus compounds were effective.

Some species, however, have developed resistance to these compounds.

Stink Bugs

Stink bugs that are sometimes serious pests

of cotton are Brown stink bug, Euschistus servus (Say) ; the onespot stink bug, E. variolarius

(Polisat de Beauvois) ; conchuela, Chlorochroa

ligata (Say) ; dusky stink bug, E. tristigmus

(Say), and E. conspersus (Uhler) ; green stink

bug, Acrosternum hilare (Say), T. pallidovirens

spinosa (Ruckers) ; Say stink bug, Chlorochroa

sayi Stal; southern green stink bug, Nezara

viridula (L.) ; and western brown stink bug,

Euschistus impictiventris Stal.

The importance of these pests and the species

involved vary from year to year and from area

to area. The damage is confined principally to

/f

Figure IB.—Damage to cotton foliage by spider mite.

PN-4482
RESEARCH ON COTTON INSECTS 37

the bolls and results in reduced yields and

lower quality of both lint and seed.

Research,—Lint staining, causing serious

loss in reduced grades and values, was found

in much of Arizona cotton in the 1920's and

1930*s. Several species of hemipterous insects

were responsible for the reduction in yield

through the shedding of squares and bolls and

the production of nonpickable lint. The brown

stink bug, the conchuela, and the redshouldered

plant bug caused most of the staining. Surveys

over a 4-year period showed an average of 25

percent of the bolls of short-staple cotton produced in Arizona were punctured. This group

of insects are general feeders and frequently

caused considerable damage to sugar beets, alfalfa, grain sorghums, and tomatoes.

Population buildup occurred in desert vegetation. Seasonal intercrop migrations of insects

occurred, and the proportion of other crops, the

time of harvest, and the effect of rain on desert

vegetation all influenced the amount of damage

to cotton. Indications were that migrations occurred for considerable distances from wild

host plants. Staining of lint, which caused reduction in grade and, thus, the value of the

crop, was caused by several micro-organisms

that entered through the punctures made by

the insects.

Plants caged with insects and field surveys

of the seasonal abundance gave much information on the nature and extent of damage caused

by the several species in different localities of

the State.

Research on methods of control started in

1933 in cage tests and later in small plot and

large-scale field experiments. Evaluation of a

large number of insecticides showed that sulphur and mixtures of sulphur and arsenicals

gave the best results and, in some cases, more

than doubled the yield where the infestations

were high. Mixtures of calcium arsenate and

sulphur or paris green and sulphur applied at

the rate of 15 to 18 pounds of dust per acre

were about equal in effectiveness. The work on

hemipterous insects aroused a great deal of

popular interest among cottongrowers of Arizona. One company in 1939 cooperated in a

large-scale experiment of airplane dusting by

furnishing the planes and insecticides for dusting several thousand acres under the supervision of the Bureau of Entomology. Several

organic insecticides give effective control of

stink bugs, but stink bugs have not been a

major problem in recent years.

Thrips

Thrips are small winged insects that injure

plants by feeding on their juices. The following

species of thrips attack cotton plants : Frankliniella exigua Hood; tobacco thrips, F. fusca

(Hinds) ; F. gossypiana Hood; F, occidentallis

(Pergande) ; flower thrips, F, tritici (Fitch) ;

onion thrips, Thrips tabaci Lindeman, and Sericothrips variabilis (Beach). Most common of

these are the flower thrips and their closely

related species, tobacco and onion thrips. Two

or more species may be found in the same

cottonfield, often on the same plant, although

one species usually predominates in a population.

Thrips are found on cotton in all the major

cotton-producing States. Some species, such as

onion thrips and F, exigua, occur across the

entire Cotton Belt. Tobacco thrips are confined

to approximately the eastern half of the United

States with F. occidentalis occurring in the

western half. The latter two species overlap in

occurrence in western Oklahoma and in slightly

more than the central third of Texas.

Tobacco thrips usually are predominant on

seedling plants, but other species may become

more numerous on plants beyond the seedling

stage of growth. Onion thrips rarely cause serious injury to cotton in the eastern part of the

Cotton Belt, except where onions are grown

near cotton.

The duration and intensity of thrips infestations vary greatly in different seasons and

locations. Experience is the best guide in predicting damage to cotton in an area.

Development.—Thrips develop in four life

stages—egg, larva, pupa, and adult. Female

adults lay their eggs in the tender tissues of

plants. Eggs are creamy white and minute—

about i/ioo-inch long. In about 4 days, the eggs

hatch into tiny, white larvae. The larvae feed

for about 6 days, shedding their skins twice

during that time. Then, they burrow into the

soil and transform into pupae. The pupae
38 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

transform into adults and emerge from the soil

in about 4 days.

Adult thrips may be yellow, brown, or black,

depending on the species. They are slender and

about i/i 6-inch long. They have two pairs of

fringed wings and fly from plant to plant and

from field to field.

Thrips complete a generation in about 2

weeks and produce many generations in a year.

In southern areas, they breed all year on various host plants. In other areas, they pass the

winter in plant residues and resume the life

cycle when hosts become available in the spring.

Both thrips larvae and adults damage cotton

plants. They pierce the leaf tissues with their

sharp mouth parts and suck out the juices.

These insects injure cotton seedlings and sometimes older plants. They attack leaves and terminal buds. Severely infested young plants may

die, and the stand may be destroyed or reduced

to the point where the crop must be replanted.

This condition may occur when heavily infested

onions, growing near cotton, are harvested.

Heavy feeding on cotyledons gives the plants

a silvery appearance. A field of severely injured

young cotton may appear to have been scorched

by fire. Thrips injury to leaf tissue in terminal

buds results in ragged, crinkled leaves that curl

upward. (Aphid injury would cause leaves to

turn downward.) The terminal buds may be

killed. When this occurs, new buds develop and

the plant becomes distorted and excessively

branched.

Infestations usually abate after cotton plants

are 4 to 6 weeks old. The plants recover from the

injury, but those that are severely injured may

continue to shed squares for a week or more

after recovery seems apparent.

If an infestation occurs on seedling cotton

and does not destroy the stand, it may retard

plant growth and delay fruiting and maturing of

the crop. The same is true if an infestation attacks cotton that has progressed beyond the

seedling stage. In some western cotton-growing

areas, cotton in the late-season stage of growth

is sometimes severely attacked by thrips.

Thrips attack many wild and cultivated host

plants. Large numbers of adults migrate to

cottonfields in spring and early summer after

other host plants begin to mature.

The abundance of thrips, extent of their damage, and need for their control vary greatly in

different years and areas. Thrips may retard

seedling growth and delay fruiting. They may

be responsible for reduction in yield where

droughts in late summer limit production or

where boll weevils, boUworms, or pink bollworms are prevalent.

Research,—Considerable information on the

species, host relationships, and factors causing

outbreaks of thrips on cotton was accumulated

at various research locations. Effective control

measures were not developed, however, until

organic insecticides were developed in the

194œs (fig. 16).

Miscellaneous Cotton Insects

All parts of the cotton plant are attacked by

insects. In addition, the sweet liquid secreted

by the nectaries of the leaves and bracts attracts a great variety of harmless and beneficial

insects that are often mistaken for pests. The

Department over the years has studied many

minor pests. Some outbreaks are sporadic in

local areas, and in others the species are generally distributed but are usually present in such

limited numbers that their damage is not serious. Because of the great diversityy of species

that attack cotton, the total damage caused by

the minor insect pests is considerable. About 50

species of miscellaneous cotton insects were

studied in connection with the early boll weevil

investigations.

Research.—Damage to cotton by the field

cricket led to studies of the biology and methods

of controlling this common species. The saltmarsh caterpillar, beet armyworm, cutworms,

blister beetles. Fuller's rose beetle, and many

other insects that attack cotton have been

studied to some extent. The nature of the damage caused by about 40 species of Coleóptera

and Lepidoptera that occur on cotton in Louisiana was studied at the Tallulah laboratory as

late as 1934 and 1935. Many of these had not

been recorded previously on cotton.

The brown cotton leafworm, Acontia dacia

Druce, was collected on cotton from three counties in Texas in 1953. Damaging infestations

have occurred through the 1950's over wide
RESEARCH ON COTTON INSECTS 39

'^iäiüaSisi'A^

_. PN-4483

Figure 16.—Thrips injured plants (foreground) and plants grown from cottonseed treated with systemic insecticide

(background).

areas of Texas and in Louisiana. Recoveries

have been reported from Arkansas.

Several Anomis leafworms are known to

occur in the cotton-growing regions of Africa,

Asia, all of the America's, and the East and

West Indies. Three species—A. erosa Hübner, A.

flava fimbriago (Stephens), and A. texana Riley

—occasionally damage cotton in the United

States. They are often mistaken for the cotton

leafworm and are sometimes found on the same

plants with it.

Several species of cutworms, including the

following, may develop in weeds or crops, esspecially legumes, and then attack adjacent cotton or cotton planted on land previously in

weeds or legumes : Black cutworm, Agrotis Ípsilon (Hufnagel) ; palesided cutworm, A. malefida Guenée; variegated cutworm, Peridroma

saucia (Hübner) ; granulate cutworm, Feltia

subterránea (F.) ; rough-skinned cutworm,

Proxerms mindara, Barnes and McDunnough;

and army cutworm, Euxoa auxilUaris (Grote).

Recommended control measures include thorough preparation of seedbed, elimination of

weed host plants, and the use of insecticides. In

western areas, irrigation forces the subterranean forms to the surface, where they may

be treated with insecticides or destroyed by

natural factors. If the vegetation in an infested

area is plowed under 3 to 6 weeks before the

cotton crop is seeded, insecticides may not be

needed.

Root aphids known to attack cotton are the

corn root aphid. Aphis maidiracidis (Forbes),

Smynthurodes betae (Westwood), and Rhopalosiphum rufiabdominalis (Sasaki). So far as is

known, injury before 1956 was confined to the

eastern seaboard. S. betae destroyed spots of

cotton up to 1^ acres in fields in Pemiscot

County, Mo., in 1956. In 1961, root aphids caused

some damage to cotton in the northeastern

counties of North Carolina and Arkansas. Several species of ants are known to be associated

with root aphids, the principal one being the

cornfield ant, Lasius alienus (Foerster). Root

aphids injure cotton chiefly in the seedling

stage. Since cotton in this stage shows injury

without any evidence of insects being present,
40 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

the underground parts should be examined

carefully. Ant mounds at the base of these

plants indicate the presence of root aphids.

The cowpea aphid, Aphis craccivora Koch,

the green peach aphid, Myzus persicae (Sulzer), and the potato aphid, Macrosiphum

euphorbiae (Thomas), are common on seedling

cotton. Cotton is not believed to be a true host

of these species. However, in 1963, A, craccivora caused severe and permanent stunting of

cotton plants in the San Joaquin Valley of

California.

Darkling beetles, Blapstimus spp. and Ulus

spp., the adults of false v^ireworms, occasionally

adversely affect the stand of young cotton in

western areas.

The garden springtail, Bourletiella hortensis (Fitch), has caused injury to cotton

locally in Hertford County, N.C. Another

springtail, Entomobrya unostrigata Stach, has

occasionally damaged seedling cotton over a

wide area of the southern high plains of Texas

and New Mexico.

Leaf beetles of the genus Colaspis are widespread and often found on cotton, frequently

on the foliage or near the base of squares and

bolls where they usually feed on the bracts

surrounding them.

The corn silk beetle, Calomicrus brunneus

(Crotch), has been reported as a pest of

cotton in localized areas in South Carolina,

Georgia, Alabama, Mississippi, and Louisiana,

but little is known about it.

The cowpea curculio, Chalcodermus aeneus

Boheman, sometimes causes damage to seedling cotton.

A curculionid, Compsus auricephalus (Say),

damaged young cotton plants and foliage in

Grady County, Okla., in 1961. It also appeared

in large numbers in cottonfields in Pope County,

Ark. In 1963, heavy populations caused considerable foliage damage to young plants in

localized areas of Grimes, Robertson, and

Brazos Counties in Texas and in Obion and

Lake Counties in Tennessee. A curculionid,

Conotrachelus erinaceus (LeConte) caused

damage to stems of seedling cotton in isolated

instances in Marion County, Ala. in 1962. A

curculionid, Otiorhynchus cribricollis (Gyllenhal), caused spotted heavy damage to cotyledons of seedling cotton in New Mexico in 1967

and 1972.

The cotton stainer, Dysdercus suturellus

(Herrich-Schaifer), is found within the United

States in Florida only. However, probably owing to mistaken identity, the literature also

records it from Alabama, Georgia, and South

Carolina.

Several leafhoppers of the genus Empoasca

are often abundant on cotton in many sections

of the Cotton Belt. Serious injury has been

reported only in California, however, and this

was caused by two species, southern garden

leafhopper, E, solana DeLong, and potato leafhopper, E. fabae (Harris). These species are

known to be phloem feeders on some crops and

cause damage typical of this type of feeding on

cotton.

The saltmarsh caterpillar, Estigmene aerea

(Drury), is a late-season pest of cotton principally in western irrigated areas. Occasionally,

the yellow woollybear, Diacrisia virginica (F.)

and the hairy larvae of several other tiger

moths, Arctiidae, including Callarctia phyllira

(Drury), C. arge (Drury), and C, oithona Strk.,

cause serious damage to cotton.

The striped blister beetle, Epicauta vittata

(F.), sometimes causes severe foliage damage

in small localized areas. Damage usually results when weeds, which are preferred host

plants, are cleaned out of cotton. Total loss of

foliage may result in small areas before the

insects move out of the field.

Field crickets, Gryllus spp., occasionally feed

on cotton bolls and seedling plants in the Imperial Valley of California and in Arizona.

During periods of drought late in the season,

they may feed on the seed of open bolls, especially in the Delta sections of Arkansas, Louisiana, and Mississippi. This feeding is usually

done at night as the crickets hide during the

day in deep cracks in the soil.

Whitefringed beetles, Graphognathus spp.,

are pests of cotton and many other farm crops

in limited areas of Alabama, Florida, Georgia,

Louisiana, Mississippi, North Carolina, South

Carolina, and Tennessee. Infestations in recent

years have been discovered in Maryland, Virginia, and Texas. The larvae feed on the roots

of young plants.
RESEARCH ON COTTON INSECTS 41

The seedcorn maggot, Hylemya platura

Meigen, may seriously affect the stand of cotton, particularly when planting closely follows

the turning under of a green manure crop or

other heavy growth.

The whitelined sphinx, Hyles lineata (F.),

occasionally occurs in large numbers in uncultivated areas and migrates to cotton.

Several species of wireworms are associated

with cotton. Damage is caused by the sand wireworms, Horistonatus uhlerii Horn, in South

Carolina and Louisiana and by the Pacific Coast

wireworm Limonius canus Leconte, in California. Adults of the tobacco wireworm, Conoderus vespertinus F., are frequently found on

the cotton plant, and the larvae may cause

damage to cotton. Wireworms, together with

false wireworms and the seedcorn maggot,

sometimes prevent the establishment of a stand.

Approved crop-rotation practices, increased soil

fertility, and added humus help to reduce

damage to cotton by the sand wireworm.

Serpentine leafminers, Liriomyza spp., and

L. pictella (Thomson), in California have been

present in large numbers in some areas during

the last few years. Drought conditions favor

infestations of these pests. Heavy infestations

may result in considerable leaf shed. Infestations often are brought under control by rain

or irrigations.

Damage to cotton by periodical cicadas,

Magicicada spp., in the United States was first

reported in 1905. Damage is caused by the

deposition of eggs in the stems of young plants,

branches of older plants, and occasionally in

leaf petioles. The parts of the plant above the

oviposition puncture usually die. Growth below

the puncture results in low bushy plants. Severe

local damage to cotton by Diceroprocta vitripennis (Say) occurred in the river bottoms of

nine counties in Arkansas in 1937. An undetermined cicada caused light damage to cotton

in some areas in Maricopa County, Ariz, in

1961.

The harlequin bug, Murgantia histrionica

(Hahn), heavily infested a few cottonfields in

Graham County, Ariz., in August 1959. Feeding was similar to that of other stink bugs. No

immature stages were noted.

The barberpole caterpillar, Mimoschima rufofascialis (Stephens), a pyraustid larva, is reported occasionally attacking cotton bolls in

Imperial and San Joaquin Valley of California.

It also has been reported from Ariozna, Oklahoma, and Texas.

Bugs of the genus Nysiics, N. ericae (Schilling), N, californicus Stal, and A^. raphanus

Howard, commonly called false chinch bugs,

frequently migrate to cotton from adjacent

weed hosts. Stands of seedling cotton may be

destroyed by adults and nymphs.

Snowy tree crickets, Oecanthus spp., infestations caused alarm to some southwestern Oklahoma cottongrowers in mid-July 1958. Approximately 3-percent lodging of plants occurred in the Blair area. There is evidence that

this group of insects may be predaceous on

aphids.

The European corn borer, Ostrinia nubilalis

(Hübner), was first reported on cotton in the

United States on July 3, 1955, in Franklin

County, Tenn., in a 3-acre field adjacent to one

that was in corn the previous year. A few plants

near the edge of a field were severely damaged.

The cotton plants were only 8 to 10 inches high,

and the larvae had entered the stems 2 to 6

inches from the ground and burrowed up

through their centers. In August light infestations were reported in cotton in Dunklin, New

Madrid, Pemiscot, Butler, Stoddard, and Mississippi Counties, Mo., and in Madison County,

Tenn. The insect had bored into the upper third

of the stems, and second- and third-instar larvae were attacking small bolls. These records

were of special interest because the European

corn borer was apparently spreading in the

Cotton Belt. No reports of this insect on cotton

were received in 1956 and 1957.

In 1958, the European corn borer was found

in cotton stalks in Autauga and Madison Counties, Ala., and in Washington County, Miss., in

late July. In 1959, as many as 10 percent of the

plants were infested in a 10-acre field of cotton

in Etowah County, Ala. This field had been

planted to corn in 1958. The borer was found,

also, in Madison Parish, La., in 1959. Damage

was confined to the terminal 6 to 8 inches of

the plant. Other infestations were found in

cottonfields in Autauga County, Ala. In 1961,

larvae were found in cotton in Hardeman, Lin-
42 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

coin, and Fayette Counties in southern Tennessee. In 1966, larvae were found in cotton in

Florence, S.C. In other parts of the world, particularly in Russia, Turkestan, and Hungary,

it has been reported as a serious pest of cotton.

One reference, Annual Conference Report on

Cotton Insect Research and Control (100),

states, ''In Turkestan it is principally cotton

which is attacked by the larvae and in which

they bore long tunnels in the upper part of the

stems.''

The Fuller rose weevil, Pantomorus cervinus

(Boheman), occasionally is a pest of cotton.

It is a leaf feeder and usually attacks cotton in

the early season, causing ragging of the leaves

and partial defoliation. It overwinters as an

adult in about the same habitat as the boll

weevil. Examinations of surface woods trash

for hibernating boll weevils often reveal specimen of the Fuller rose beetle. It has been reported from cotton in Georgia more frequently

than from any other area.

The stalk borer, Papaipema nebris (Guenée),

is widely distributed east of the Rocky Mountains. It attacks many kinds of plants, including

cotton, and is so destructive that one borer in a

field may attract attention. The borers are most

likely to be found near the edges of cottonfields.

Light marginal injury occurred in scattered

fields in Missouri during June 1957. It was also

reported as causing some injury to cotton in

Mississippi and Tennessee in 1956. In 1961 it

caused some damage along the edges of many

cottonfields in western and southern counties in

Tennessee. It is sometimes mistaken for the

European corn borer. Clean cultivation and

keeping down weed growth help to hold them

in check. The use of stalk shredders early in the

fall should reduce their numbers.

A white grub, Phyllophaga ephilida (Say),

was reported to have destroyed 5 acres of cotton

in Union County, N.C., in 1956. As many as 20

larvae per square foot were found. P. zavalana

Reinhard is also reported to be a pest of cotton

in the Matamoras area of Mexico, where the

adults feed on foliage, particularly in the seedling stage. It is known to occur in Zavala and

Dimmit Counties, Tex. P. cribrosa (LeConte),

sometimes known as the '% o'clock bug" in west

Texas, has also been feeding on young cotton

in that area. Moderate damage was caused to

young cotton plants in the Arkansas Delta area

in 1962 by larvae of P. implícita (Horn).

The cotton stem moth, Platyedra subcinerea

(Haworth), a close relative of the pink bollworm, was first discovered in the United States

in 1951, when larvae were found feeding in

hollyhock seed in Mineóla, Long Island, N.Y.

It is recorded as a pest of cotton in Iran, Iraq,

Morocco, Transcaucasia, Turkestan, and the

U.S.S.R., and as feeding on hollyhock and other

malvaceous plants in England, France, and central and southern Europe. Collections made in

1953 extended its known distribution in this

country to a large part of Long Island and limited areas in Connecticut and Massachusetts.

Extensive scouting during 1954 disclosed that

it had reached 11 counties in four States as

follows: Hartford and New Haven, Conn.;

Essex and Plymouth, Mass. ; Monmouth, Ocean,

and Union, N.J.; Westchester and all counties

of Long Island (Nassau, Queens, and Suffolk),

N.Y. There has been no reported spread since

1954 until 1965 when it was reported from

Rockingham County, N.H. Although this species

has not been found in the Cotton Belt in the

United States, it is desirable to keep on the

lookout for it on cotton, hollyhock, and other

malvaceous plants. In 1956 it was collected from

a natural infestation on cotton growing on the

laboratory grounds at Farmingdale, N.Y.

Several of the leaf rollers, Tortricidae, occasionally damage cotton. Platynota stultana

(Williamson) and P. rostrana (Wilkerson) are

the species most commonly recorded, but P.

flavedana (Clemens), P. idaeusalis (Wilkerson),

and Sparganothis nigrocervina (Williamson)

have also been reported. These species are widely distributed and have many host plants. P.

stultana has at times been a serious pest of

cotton in the Imperial Valley of California and

part of Arizona and New Mexico.

Heavy feeding on cotton by the Japanese

beetle, Popillia japónica Newman, was reported

in Sampson County, N.C., in 1961. Adults of the

Japanese beetle caused 30- to 35-percent defoliation of cotton plants in fields in the more

heavily infested areas in North Carolina in

1970.

A giant appletree borer, Prionus sp., caused
RESEARCH ON COTTON INSECTS 43

isolated root damage to cotton in one county in

Arkansas in 1962.

Adults of a buprestid beetle, Psiloptera druTri^

mondi Lap., occasionally cause damage to cotton.

The damage consists of partly girdled terminals

that break over and die.

The pink scavenger caterpillar, Sathrobrota

rileyi (Walsingham), is one of several insects

that resemble the pink bollworm and is sometimes mistaken for it by laymen. The larvae is

primarily a scavenger in cotton bolls and corn

husks that have been injured by other causes.

Several species of grasshopper, including the

follov^ing, sometimes attack cotton: American

grasshopper, Schistocerca americana (Drury) ;

Trimerotropis pallidipennis pallidipennis (Burmeister) ; differential grasshopper, Melanoplus

differentialis (Thomas) ; lubber grasshopper,

Brachystola magna (Girard) ; migratory grasshopper, M. sanguinipes (F.) ; redlegged grasshopper, M. fermurrubrum (De Geer) ; and twostriped grasshopper, M, bivittatus (Say).

The American grasshopper overv^inters as an

adult and in the spring deposits eggs in the

fields. Other species of grasshoppers overwinter

as eggs in untilled soil, fence rows, sod waterways, around stumps, and similar locations. The

species overwintering in the egg stage can be

best controlled with early treatment of hatching

beds before the grasshoppers migrate into the

fields. Sprays or dusts have largely replaced

poison baits, particularly where grasshoppers

must be controlled on lush or dense vegetation.

The beet armyworm, Spodoptera exigua

(Hbn.), is often a pest of seedling cotton, but

it may also attack older plants. Squares and

blooms may be destroyed, and feeding on the

bracts may cause small bolls to shed. Although

the beet armyworm has been a pest in the West

and Southwest for many years, it was reported

in Louisiana and Mississippi in 1962. Injurious

infestations occurred in some localities in Alabama and Georgia in 1963, and in Alabama, Arkansas, and Mississippi in 1969. It was a serious

pest of cotton in Georgia in 1973 and 1974.

The fall armyworm, Spodoptera frugiperda

(J. E. Smith), occasionally occurs in sufficient

numbers to damage cotton.

The yellowstriped armyworm, Spodoptera

ornithogalli (Guenee), and western yellowstriped armyworm, S. praefica Grote, sometimes

cause considerable damage to cotton.

The cotton square borer, Strymon melinus

(Hübner), occurs throughout the Cotton Belt,

but rarely causes economic damage. The injury

it causes to squares is often attributed to the

bollworm.

The palestriped flea beetle, Systena blanda

Melscheimer, the elongated flea beetle, S. elongata (F.) and S. frontalis (F.), sometimes cause

serious damage to seedling cotton in some areas.

The sweetpotato flea beetle, Chaetocnema confinis Crotch, injured seedling cotton in the Piedmont section of South Carolina in May 1954.

The striped flea beetle, Phyllotreta striolata

(Fabricius), caused damage to cotton in Alabama in 1959. Other species of flea beetles have

been reported from cotton, but records regarding the injury they cause are.lacking.

Whiteflies, the bandedwing whitefly, Trialeurodes abutilonea (Haldeman), the greenhouse

whitefly, T. vaporariorum (Westwood), and the

sweetpotato whitefly, Bemisia tabaci (Gennadius), are usually kept in check by parasites

and diseases, but occasionally may be serious

pests late in season. Bemisia tabaci is reported

to be a vector of the leaf crumple virus of cotton.

Whiteflies have caused damage to cotton in

northwest Louisiana since 1964. Infestations

have increased in Alabama and IVKssissippi in

the early 1970's.

The cabbage looper, Trichoplusia ni (Hübner), is a pest of cotton in many areas. It is

difficult to control with insecticides. It is frequently controlled by virus and fungus organisms. When diseased loopers are commonly

found, chemical control may be delayed or omitted. The cabbage looper became more of a problem in cotton in the 1950's and less so since

then.

The greenhouse leaftier, Udea rubigalis

(Guenee), also known as the celery leaftier, has

occasionally been abundant on cotton in the

San Joaquin Valley of California. Despite the

heavy populations, damage was generally slight

and restricted to foliage on the lower third of

the plants in lush stands. This pest caused considerable damage in three fields near Yuma,

Ariz., in 1964.

The false celery leaftier, Udea profundalis
44 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

(Packard), caused considerable defoliation of

cotton in some fields in Tulare, Kings, and

Fresno Counties, Calif., in 1962. Control was

difficult because of the insect's feeding habits

on the lower part of plants within a web.

Damage to cotton stalks by termites, undetermined species, was reported in western

Tennessee in 1961, and in previous years in

Texas. Termites, Reticulitermes sp. (Rhinotermitidae), partly destroyed a stand of cotton

in Little River County, Ark., in 1961.

Insects in or among cottonseed in storage,—

Insect infestations in cottonseed during storage

can be minimized if proper precautions are

followed. Cottonseed, or seed cotton, should be

stored only in a bin or room thoroughly cleaned

of all old cottonseed, grain, hay, or other similar

products in which insects that attack stored

products are likely to develop. Among the insects that cause damage to stored cottonseed or

to cottonseed meal are the cigarette beetle,

Lasioderma serricorne (F.), the Mediterranean

flour moth, Anagasta kuehniella (Zeller), the

almond moth, Cadra cautella (Walker), and the

Indian-meal moth, Plodia interpunctella (Hübner). Other insects commonly found in cottonseed are the flat grain beetle, Crytolestes

pusillus (Schönherr), the red flour beetle, Tribolium castaneum (Herbst), and the sawtoothed

grain beetle, Oryzaephiltts surinamensis (L.).

The pink bollworm may be found in stored

cottonseed, but such infestations would be present in the seed before they were stored.

RESEARCH 1941 TO 1974

Attractants

Boll Weevil

In the 1950's an observation was made at the

Stoneville, Miss., Cotton Insects Laboratory that

the female weevil sought the male rather than

the usual procedure, most male insects seeking

the female. This was verified in laboratory studies at the Boll Weevil Research Laboratory in the

mid-1960's, and the attractant named grandlure was identified and synthesized. Now commercially available, grandlure is widely used in

migration, survey, and detection procedures.

Hopefully, it will be registered in the future for

use in population management and eradication

programs. A trap baited with grandlure was

developed to capture female boll weevils. Grandlure is also an aggregant as early in the year

males as well as females are attracted to it.

As cotton plants begin to square, however, response to the pheromone is predominately by

female boll weevils. Traps baited with grandlure placed along the edges of cottonfields capture tremendous numbers of overwintered boll

weevils.

In the Pilot Boll Weevil Eradication Experiment conducted in south Mississippi and in adjoining areas of Louisiana and Alabama in

1971-73, traps baited with grandlure at the

rate of two per acre were used as one of the

suppression measures in the core or eradication

area. Trap crops consisting of cotton planted

some 2 weeks earlier than that of the grower

cotton were baited with grandlure at 100-foot

intervals. Plants in the trap crops were treated

in-furrow at planting with aldicarb and sidedressed with it at early squaring to kill overwintered weevils attracted to them. The trap

crops were treated with methyl parathion during periods when the aldicarb treatment was

considered not to be effective. Very few weevils

were found in the grower cotton before it began

to fruit. Even after grower cotton began to

square, weevils continued to be attracted to the

trap crops as evidenced by the collection of

sterile males released in the grower cotton being

collected in the trap crops. The development of

infield traps, those that can be used within fields

without interfering with cultivation, baited

with grandlure has great potential as a tool in

population suppression or elimination programs.

In the previous discussion of the boll weevil,

efforts to develop attractants from cotton plants

to control the pest were unsuccessful. Interest in

boll weevil attractants from the cotton plant

was revived by researchers in the 1960's.
RESEARCH ON COTTON INSECTS 45

Water and chloroform extracts of cotton plant

parts were attractive. A powerful arrestant and

feeding stimulant was found in water extracts

of all cotton parts and square components

tested. A feeding deterrent was found in the

calyx of an alternate host, Hibiscus syriacus.

However, the chemistry of the arrestant and

attractant compounds in the cotton plant is so

complex that chemists have been unable to identify and synthesize all of them for use in control, suppression, or survey programs.

Pink Bollworm

In the mid-1960's research on the female pink

bollworm moth showed that the female emitted

a substance attractive to males. The chemists

identified and synthesized the substance and

named it propylure. Unfortunately, propylure,

though attractive ^o males in the laboratory,

failed to perform in the field. Apparently, something was missing in the synthesized compound.

A somewhat structurally related compound,

called hexalure, was found to be attractive to

males and was widely used in the West in

survey and detection operations. Though not

as attractive as the natural pheromone, hexalure

was sufficiently attractive to be used to bait

traps so that use of live females was obviated.

An intensive effort was made by ARS chemists

to identify and synthesize the pheromone. However, progress was slow and in late 1973 researchers at the University of California, Riverside, identified and synthesized the compound.

ARS chemists verified the finding. Named gossyplure, it has considerable potential for use in

survey detection and population suppression programs and has been used in a large-field experiment as a confusant. When applied to a field of

cotton, the male then cannot locate the female.

Tobacco Budworm and Bollworm

Females of the tobacco budworm and bollworm produce powerful sex pheromones or sex

attractants to call males of the respective species for mating. Research has continued since

1963 on these pheromones with the ultimate

goal of producing synthetic materials that could

be used for population survey and suppression.

The pheromone of the female tobacco budworm was identified and synthesized. A crude

extract of the pheromone from females had very

short activity, and a similar problem has been

found with the synthetic material. Research is

currently directed toward development of a

stable formulation of the synthetic pheromone

to give long-term activity in the field.

A similar attractant has recently been discovered for the bollworm ; however, it is as yet

uncertain whether the synthesized compound is

the natural sex pheromone.

Once stable formulations of the pheromones

of the two species are devised, the possibility

for developing population suppression schemes

will be opened. Among the methods suggested

for use of these materials are elimination of

males by trapping or dispensing the attractant

on an insecticide-treated substance, luring the

males to substrate treated with chemosterilants,

or saturating an environment with the pheromone, thus, interfering with the mating orientation of the males. However, it will be several

years before these systems can be put to practical use. Development of methods of using the

pheromones in traps to anticipate outbreaks of

the pests for timing of insecticide applications

is apparently more immediately promising.

A related approach has been the search for

chemicals that will disrupt the chemical communication between sexes. Researchers have

shown that the attractiveness of female tobacco

budworms is greatly reduced if certain organic

chemicals are released into the environment.

However, these studies are in the preliminary

stages.

Researchers have reported that the male

tobacco budworm, when preparing to mate with

a female, produces a substance that suppresses

the emission of the female sex pheromone, but

no work has been done on isolating the active

agent. Possibly such a substance would be useful in combination with some of the previously

noted techniques.

Results of recent research have shown that

certain egg and larval parasites of Heliothis

spp. are attracted to the host by host-seeking

stimulants named kairomones.

Tarnished Plant Bug

In the early 1970's a researcher at the Stoneville. Miss., laboratory found that the female
46 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

tarnished plant bug produced a substance attractive to males. Research is underway to

identify the substance.

Biological Control

Predators, parasites, and diseases play an

important role in the control of insect pests of

cotton. The role of natural enemies in cotton

insect control programs should be maximized

by utilizing insecticides, cultural practices, and

other agents and techniques in supportive ways.

The role of beneficial insects in the field should

be evaluated when possible. Some predaceous

and parasitic insects of prime importance are

discussed in this section.

Predators

Hemiptera

Orius insidiosiis and 0. tristicolor, often

called minute pirate bugs or fiower bugs, are

predators of eggs and first instar larvae of the

bollworm, thrips, and other small insects. Populations often build up in such crops as corn and

grain sorghum. Big-eyed bugs, Geocoris pallens

and G, uliginosus, are common predators of

eggs and small larvae of the bollworm as well

as of other Lepidoptera, mirids, and aphids.

Damsel bugs of the genus Nabis are efficient

predators of a wide range of prey including

mirids, leafhoppers, aphids, and eggs and larvae of Lepidoptera. They attack bollworms as

large as the second instar. Assassin bugs, particularly the genus Zelus, feed freely on eggs

and larvae of the bollworm, tobacco bollworm,

and cabbage looper. However, these insects are

usually less abundant in cottonfields than those

discussed previously. Podisus maculiventris is

a common stink bug that preys on large bollworms and other caterpillars in the West.

Neuroptera

Larvae of green lacewings, Chrysopa spp.,

are important predators of eggs and small larvae of bollworm and other Lepidoptera and of

many soft-bodied insects.

Coleóptera

Ground beetles of the family Carabidae have

considerable potential as predators in the cottonfield, but knowledge is lacking on the habits

and factors affecting abundance of the many

species. Lady beetles (Coccinellidae) are common predators in cottonfields. The large species,

including Coleomegilla macúlala, Hippodamia

convergens, and Coccinella novemnotata, feed

on eggs and small larvae of bollworms, other

Lepidoptera, and on aphids. Some smaller species in the genus Scymnus and all Stethorus

spp. are primarily predators of mites. Collops

beetles (Malachinnae in the family Malyridae)

are often abundant in cotton. They reportedly

feed on the eggs and small larvae of the bollworm and other lepidopterous species.

Díptera

Many families contain species predaceous as

adults or larvae. Best known as predators in

the cottonfields are the larvae of syrphid flies

that prey primarily on aphids.

Hymenoptera

Ants (Formicidae) include many predaceous

species ; Iridomyrmex pruinosus is a predator

of bollworm eggs. Paper-nest wasps, Polistes

spp., and solitary wasps of the genera Zethus,

EumeneSy Rygchium, and Stenodynerus provide

their young in the nests with Lepidopterous

larvae. Wasps of the genus Sphex nest in the

ground and provide their young with grasshoppers and related insects.

Spiders

All spiders are predaceous and many species

are common in cottonfields. Orb weavers capture many moths in their webs. Wolf spiders

and lynx spiders capture moths and other insects. Larvae and adults of the bollworm and

boll weevil adults are among the prey of jumping spiders.

Parasites

Hymenoptera

Numerous hymenopterous parasite species of

several families are of great value in the biological control of most cotton pests. These

parasites vary tremendously in size, behavior,

ecology, and host preference. Within their

ranks, however, effective or potentially effective
RESEARCH ON COTTON INSECTS 47

parasites of nearly every developmental stage,

egg through adult, of the majority of cotton

pests may be found. Many of them occur naturally in great numbers in certain geographical

areas. Some are nov^^ and many will eventually

have to be augmented in the field by means of

habitat management or mass release techniques

so as to concentrate their populations at the

time and in the place required for most effective

control.

Díptera

Flies of the family Tachinidae are parasites

primarily of larvae of Lepidoptera and Coleóptera. Several species are of value as parasites

of cotton pests and should be examined with the

same goals of augmentation through laboratory

or field practices.

Control with Predators and Parasites

Native predators and parasites are often

highly effective against aphids, the bollworm,

beet armyworm, tobacco budworm, cabbage

looper, cotton leafworm, cotton leafperforator,

cutworm, lygus bugs, saltmarsh caterpillar,

spider mites, whiteflies, and certain other pests.

Diversified crops and uncultivated areas serve

as refuge and reservoir areas for predators and

parasites, and unfortunately for some pests.

The need for controlling such insects as the

boll weevil, lygus bugs, and the cotton fleahopper with insecticides often results in increased subsequent infestations of the bollworm

and tobacco budworm because beneficial insects

that might hold such infestations below economic levels are killed off by the insecticides.

The continued use of an insecticide then is

necessary even though infestations of the primary insect have been reduced below injurious

levels. If insecticidal control was not needed

for these insects, the control problem with the

bollworm complex would be eased considerably.

Augmentation of food for lacewings has

shown promise in field experiments in California.

Naturally occurring parasitic and predaceous

insects frequently destroy sufficient Heliothis

to prevent outbreaks of these pests on cotton.

However, supplementing natural control may

be necessary to insure that adequate numbers of

these entomophagous insects will be available

to prevent the pests from causing economic

damage.

Recent experiments have demonstrated that

augmentation of entomophagous insects through

mass rearing and release holds promise as

an effective means of controlling Heliothis.

Releasing large numbers (100,000) per acre

of the predator, Chrysopa carnea Stephens,

controlled Heliothis in field cages, which was

confirmed in small field plots. Similar results

were obtained with large releases of the egg

parasite Trichogramma. A large-scale pilot

test of augmentation was, therefore, undertaken. A mass-rearing facility was developed

for producing Chrysopa and Trichogramma by

using Sitotroga eggs as host material. In addition, development of an encapsulated artificial

diet was undertaken.

In 1972-73, Chrysopa and Trichogramma

were produced for a large-scale test of the

augmentative release method in Frio Co., Tex.

Methods of shipping and releasing the insects

were devised, and releases were made on about

1,700 acres. However, failure of a diapause boll

weevil control program to reduce populations

necessitated insecticidal treatment for the boll

weevil and negated much of the effect of the

releases of the entomophagous species.

Results of this pilot test brought out several

points to be considered in using this technique.

Effective and economical use of this method

will require the design and operation of a pest

control system which makes possible the management of pests over large areas. Production

practices on all farms in the area must be

compatible with the- management of parasites

and predators. Releases of beneficial insects in

cotton cannot be effective if conventional insecticides are applied at the same time to control other pests such as the boll weevil. Methods

of determining and anticipating the numbers

of pests and entomophagous species needed for

release must be improved.

Two hymenopterous parasites, Bracon kirkpatricki (Wilkinson) and Chelonus blackburni

(Cameron), were tested as control organisms

for the pink bollworm in approximately 100

acres of irrigated cotton near Tucson, Ariz., in

1971 and 1972. The parasites were reared on
48 AGEICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

the pink bollworm at the Biological Control

Investigations Laboratory in Tucson. The pink

bollworm populations were suppressed in the

early season with releases of B, Kirkpatricki,

but C. blackburni was somewhat less effective

later in the season. These parasites were reared

in the Animal and Plant Health Inspection Service, Methods Development Laboratory, Phoenix, Ariz., in 1973 and were released in the

wild cotton in the southern most area of Florida. A few pink bollworm larvae infested with

the parasites were recovered. Though the parasites show promise against low-level populations of the pink bollworm, the technique cannot be exploited until techniques for rearing

them artificially are developed. An effective egg

parasite is needed.

Additional research is needed to reduce the

cost of rearing and to improve the quality of

the released insects in various ways. More

engineering research is needed to improve

mechanization of the systems. It is anticipated

it will be a number of years before all of the

necessary components can be developed to the

extent that this method can be used effectively

by cottongrowers.

Biology and Ecology

Much of the biological work conducted on

the boll weevil, bollworm, and pink bollworm

in the early days continues to have validity.

Progress has been considerable, however, in

ecological studies as more sophisticated techniques became available. Sex attractants, light

traps, and marking techniques, genetic as well

as physical, have been invaluable in the furtherance of ecological studies.

Migration

Migration of the boll weevil usually occurred

late in the season when populations developed

in extremely large numbers and new sources

of food and oviposition sites were needed. With

the advent of the more effective insecticides

and their widespread use, migration as occurred previously was not so pronounced. Surveys in the early days showed that the boll

weevil moved eastward across the Cotton Belt

at an average rate of about 50 miles per year.

In Georgia in 1959, boll weevils infested a cottonfield 25.5 miles from other cottonfields. In

1968 boll weevils were captured in male-baited

wing traps along the highway from Juarez to

Chihuahua in Mexico though the traps were

located 25 to 45 miles from .otton. During midseason in South Carolina, Fi and succeeding

generations of the weevil dispersed at least 19

miles to find new cotton. In south Mississippi,

genetically marked weevils were collected in a

pheromone-baited trap 25 and 35 miles from a

release site.

Pink bollworms have long been known to

move long distances when food supply became

scarce late in the season. The collection of pink

bollworm moths in traps operated from an airplane at 3,000 feet over cottonfields in Mexico

indicated that moths could migrate several hundred miles from Mexico to the United States.

Though in small numbers pink bollworm moths

were collected in light traps early in the season,

almost none were caught after cotton plants

began to fruit, an indication that early-season

movement was a search for oviposition sites in

fruiting cotton. Collections in light traps increased as cotton plants began to mature and

oviposition sites became scarce. Large numbers

were captured when late season infestations

were heavy. Results of teiçts conducted in

Riverside County, Calif., in 1970 showed that

moths from overwintering larvae were capable

of migrating at least 35 miles to infest cotton

in areas not previously infested. This finding

will be of considerable value if any elimination

program for the pest is ever undertaken.

Though the bollworm is known to migrate

for considerable distances, definitive data have

been difficult to obtain. Hibernation and survival studies in the early 1940's in central Texas

showed that a generation developed in the

field before moth emergence from hibernating

pupae occurred in the cages. It was assumed that

the field generation resulted from migrants

from the South where earlier emergence occurred. Use of black light traps to which the

moths are attracted has been most helpful in

such studies. Results of studies in the Mississippi Delta area in the 1960's were similar.

Moths were collected in the light traps some 30

days before moths emerged from hibernating
RESEARCH ON COTTON INSECTS 49

pupae. In 1968 moths from larvae developing

on a plot of radiolabeled sv^eet corn on St.

Croix, U.S. Virgin Islands, dispersed in a nonrandom pattern for distances up to 10 miles

to locate suitable hosts. In the same year, data

for released marked moths at Tifton, Ga., indicated that moths dispersed over an extended

distance, at least 16 miles in one night and at

least 45 miles over a period of 1 to 4 days. Collections of moths in light traps at different

heights indicated that bollworms are capable

of obtaining controlled flight altitude in excess

of 1,000 feet. A moth was collected in traps

from aircraft at 500 feet. In the fall of 1973

three moths v^ere captured in light traps on

unmanned oil platforms in the Gulf of Mexico

100 miles from land.

In 1971 laboratory-reared adult tobacco budv^orms marked with dyes fed in the larval diet

and sterilized with CO^^ irradiation were released in northeastern Mexico and southern

Texas and recovered in sex-lure traps at known

distances at cardinal compass directions. In

Mexico, male moths dispersed 10 miles north in

24 hours, and a distance-dilution effect was

indicated. In southern Texas, moths dispersed

as much as 70 miles from the release point

within an estimated 4 to 5 days.

Collections of Insects in the Upper Air

In addition to being used for applying insecticides, the airplane equipment of the Department, also, was used for collecting insects in

the upper air to obtain information on the flight

or carriage of insects by air currents. Special

traps were designed based on the principle of

camera plat holders with screen-covered frames

coated with adhesives carried in compartments

for protecting the screens before and after exposure. The traps were mounted on the wings

of the planes and controlled by wires to the

cockpit so that exposures could be made for a

specified time at known elevations.

Systematic flights were made during the 5

years, 1926-31, in which over 150,000 miles

were flown and 1,007 hours spent in actual

exposure of the traps. Most of the 1,385 separate flights were in Louisiana, but 44 were

made in the Laguna section of Mexico. Flights

were made during the day and night at all seasons of the year at elevations of from 200 to

15,000 feet, during which 30,033 specimens of

insects, spiders, and mites were collected. The

weaker fliers were taken in greater numbers

at the higher elevations than the stronger fliers,

and numbers of wingless adults, nymphs, and

larvae were collected at elevations up to 14,000

feet. A spider was taken at 15,000 feet, the

highest elevation at which flights were made.

Temperature, surface vapor pressure, intensity

of air currents, direction of the wind, and convection were the most important factors in

determining the abundance of the insects in the

upper air. These flights were the most extensive

ever undertaken for studying insect abundance

and distribution in the upper air. Additional

flights were made over the Lower Rio Grande

Valley and King Ranch areas of Texas in 1954.

Late in the cotton season of 1956, flights were

made over central Texas and in the Tri-State

areas of Texas, Arkansas, and Mississippi.

Much information of scientific interest and

practical value was obtain'^d. The collection of

pink bollworm moths at 3,000 feet in the air

over the cottonfields of Mexico, for example,

confirmed evidence that the moths were migrating several hundred miles from Mexico to the

United States and were responsible for the

failure of the eradication measures and the

increase in infestation in the Big Bend area

of Texas. Later flights over Texas resulted in

captures of pink bollworm moths, which

showed that they could disperse into Arkansas

on wind currents from infested fields in central

Texas. A boll weevil was taken at 2,000 feet in

Louisiana and at 200 and 500 feet in the Lower

Rio Grande Valley of Texas.

Genetic Control

Research on genetic control of cotton insects

has centered on the sterile insect release approach that was so successful against the screwworm fly, Cochliomyia hominivorax (Coquerel).

In this approach large numbers of insects are

reared and exposed to ionizing irradiation or

to chemosterilants to induce sterility; then,

they are released among native populations at

sufficient ratios to insure a high proportion of
50 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

sterile matings. Developing this technique includes devising methods for rearing and sterilizing large numbers of insects with minimum

effect on their competitiveness in securing

mates, for shipping them from the rearing

facility to release sites and releasing them so

that they disperse among the native population,

and for monitoring the effectiveness of the

program. Frequently, preliminary application

of other population reduction measures, such as

insecticides, are needed to reduce native populations to levels low enough so that an effective

overflooding ratio can be achieved.

Boll Weevil

Much research has been conducted on sterilizing the boll weevil. Effective doses of gamma

irradiation reduce competitiveness and result

in high mortality. Similar results were obtained

with some chemosterilants. Finally, workers at

several laboratories found that busulfan could

achieve sterility in the male when incorporated

in the adult diet for a 6-day feeding period.

Two disadvantages of busulfan were the long

feeding period and not sterilizing the female.

Thus, in the Pilot Boll Weevil Eradication

Experiment, the weevils had to be sexed for use

of the sterile male component. Sexing has to

be done manually and is, therefore, laborious

and costly. In an elimination program, the cost

of sexing would be prohibitive. An intensive

effort, then, was made to find a chemosterilant

effective against both sexes. A combination of

a 4-day feeding of busulfan-treated diet to

adults plus a few hours of fumigation with

hempa appeared to sterilize both sexes satisfactorily. However, research continued because

the long holding and feeding period needed to

be reduced or eliminated. Thompson-Hayward's

TH 6040 N-(4-chlorophenyl)-Ni-(2.6-diflurobenzoyl)urea has exciting possibilities. Use of

fractioned doses of gamma irradiation applied

at 4-hour intervals also appears promising.

Chances are good that the problem will be

solved before an elimination program is undertaken.

Bollworm and Tobacco Budworm

A great deal of research has been done on

methods of sterilizing Heliothis and the effects

on various aspects of sexual competitiveness.

Gamma irradiation has been pursued most extensively because it is relatively easy to use

and presents minimum environmental hazards

when proper equipment is used.

A limited field test of this method against

the bollworm conducted on St. Croix, U.S.

Virgin Islands, was a partial success, but problems with rearing interfered.

More extensive tests were carried out on

the same island in 1972-74. The results of these

tests indicated that released mass-reared insects, whether irradiated or not, competed

poorly for native mates, especially the males.

However, populations of the bollworm were

reduced to low levels because the sterile females

mated earlier in the night than the native females. Since the sterile males were essentially

noncompetitive with the native males and since

both types of males were ready to mate at any

time of night, the native males mated with

sterile females when these females were ready.

When the native females began mating at

the later hour, the available native males had

already mated and, as a result, the sterile males

mated with these females >vith little competition. Since populations of the bollworms were

limited to a few small plantings of corn on the

island, relatively high ratios of sterile to native

insect were achieved, and the population could

be manipulated easily. Whether this procedure

could be used on a large scale is questionable.

The test with the tobacco budworms showed

that the sterile males were about 25 percent as

competitive for mates as native ones. This resulted from the mass-rearing conditions and

irradiation. A lack of synchrony in mating

times of sterile and native insects of both sexes

was noted, thus making the system used against

the bollworm ineffective in this case. Also,

populations of the tobacco budworm were much

larger and more widely distributed than those

of the bollworm, with the result that the sterile

to native insect ratios were generally too low

(5 to 1) to have much impact on the native

populations when the competitiveness problem

was considered.

Research is continuing on development of

this method for use against the tobacco budworm with emphasis on defining and overcom-
RESEARCH ON COTTON INSECTS 51

ing problems related to the poor competitiveness of the sterile insects. It will probably be

a number of years before this method can be

considered feasible for practical use.

Pink Bollworm

Gamma irradiation for sterilizing pink bollworms has been under study for some time.

Research continues, and doses have been reduced to 20 kr, which has improved competitiveness of treated males with nonsterile males for

females. The pink bollworm has been mass reared at the Methods Development Laboratory, Animal and Plant Health Inspection Service

(APHIS), USDA, Phoenix, Ariz., since 1967.

Migrants from the Imperial and Coachella

Valleys have been detected in relatively low

numbers in certain localities of the San Joaquin

Valley in California each year since 1967. Sterile moths have been released in these localities

annually beginning in 1968. Approximately 100

million were released annually from 1970

through 1973, but rearing problems reduced the

numbers released in 1974. The releases apparently have prevented establishment of infestations in this important cotton producing valley.

Such treatment must continue until the pest is

eliminated or populations are reduced to low

levels in the Coachella and Imperial Valleys so

that they no longer will provide migrants to

the San Joaquin Valley.

Beginning in November 1972, sterile moths

have been released in the off-cotton seasons in

the extreme southern tip of Florida to suppress

pink bollworm populations in wild cotton growing in the area. For many years, population suppression was attained by manual destruction of

wild cotton plants, which was both costly and

difficult as the cotton was impossible to eradicate with'this procedure. The sterile male release technique hopefully will suppress populations to the extent that the pink bollworm

cannot migrate to the northern part of the State

where cotton is grown.

If elimination of the pink bollworm is undertaken in the future, the sterile male release

technique will no doubt be a major component

in the program.

Host Plant Resistance

In the early days of the boll weevil when

effective insecticides were not available, emphasis was given to cultural controls and early

maturing cotton varieties which made possible

the production of a crop before the boll weevil

could build up extremely high populations. With

the advent of better insecticides and needs for

higher yields, varieties of indeterminate growth

were developed for the rain belt and the irrigated areas of the West. Such varieties and

production practices favored the boll weevil

and pink bollworm. Though good yields were

produced with the intensive use of insecticides,

large populations diapaused in the fall, enhancing survival for infesting the subsequent crops

and necessitating repetition of the control cycle

year after year.

Boll Weevil

When resistance to the organochlorine insecticides developed in the boll weevil in the

mid-1950's, research turned to alternative methods of controlling the boll weevil and other

cotton insects. Though considerable effort was

expended, progress in the development of varieties resistant to the boll weevil was slow. In

the 1970's Frego bract cottons, the bracts are

distorted and do not envelop a square as is done

with normal bract cottons, reduced boll weevil

oviposition by 50 percent or more when compared with normal bract varieties. However, the

reduction in oviposition has been considerably

less than that when the variety was grown

under '*no choice" situations. Frego bract varieties with acceptable agronomic characters might

have a place in boll weevil control when field

plantings are interspersed with trap crop plantings of normal bract cottons to attract overwintered weevils which could then be killed with

insecticides. Unfortunately, Frego bract cottons

are more susceptible to lygus bugs.

Some short-season determinate cotton varieties are now grown extensively in Texas and

show promise in reducing late-season insect

damage, especially by the boll weevil. They also

may help alleviate some damage caused by Heliothis by maturing before the damaging lateseason peak of population occurs.
52 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Bollworms

The development of cotton varieties resistant

to the tobacco budworm and bollv^orm has

centered on three morphological characters of

the cotton plant and on the development of

early-maturing, determinate types of cotton

that set the bulk of their fruit 2 to 3 v^eeks

earlier than the nondeterminate cottons usually

grov^n commercially. Research is in progress,

also, to develop cotton varieties resistant to the

cotton fleahopper, plant bugs, and the boll

weevil, v^hich would help alleviate the Heliothis

spp. problem by reducing the insecticide applications for these pests, thus, conserving the

natural enemies of Heliothis spp.

The first morphological character is lack of

nectaries. Normal cottons have extrafloral nectaries on leaves and fruiting forms. The absence of these structures deprives Heliothis

adults of an important source of food when and

where alternate food sources are not available.

In controlled tests, the absence of extrafloral

nectaries (nectariless cotton) resulted in at

least a 40-percent reduction in egg deposition

and reduced longevity of adults.

The second character measurably reducing

populations of Heliothis spp. is a smooth (glabrous) plant surface. Commercial cottons have

2,000 to 5,000 trichomes per square inch on the

small terminal leaves and buds, which are the

preferred oviposition sites of Heliothis spp.

Glabrous stocks with less than 200 trichomes

per square inch have reduced egg deposition by

50 percent.

The third character showing impact on Heliothis spp. populations is a high level of gossypol

in the flower buds (squares). Gossypol content

in buds of commercial cotton is about 0.5 percent, which affects larvae very little. However,

larval mortality of 50 percent occurs when the

gossypol level is 1.2 percent or higher.

Studies in field cages with cotton strains in

which all three morphological characters have

been combined showed that populations of the

tobacco budworm increased 1.1-fold in two generations, and those on glabrous plus highgossypol cotton or nectariless cotton plus highgossypol cotton increased 2-fold; meanwhile

populations on commercial cotton increased 10-

to 12-fold. In field tests a glabrous cotton suppressed Heliothis spp. larval population 68 percent compared with the population on commercial cotton, and cottons with both the glabrous and high-gossypol characters reduced

larval populations 60 to 80 percent. In field tests

with advanced strains, one strain with the

glabrous-high gossypol combination yielded 700

pounds per acre more seed cotton than a commercial variety. The nectariless cotton could not

be properly evaluated in the field because the

size of the plots was too small to prevent moths

from obtaining food outside the plots.

In 1974 a nectariless cotton strain was released to commercial seed companies and may

soon be available to growers for large-scale

planting. However, unless this cotton is planted

on a community-wide basis and alternative

sources of food are not available for moths, its

effectiveness against Heliothis could be limited.

Cotton Fleahopper

Cottons with the glabrous character are well

advanced and could be expected to have considerable impact on Heliothis when available to

growers. There is a complication with these

cottons, however. Although these cottons have a

significant impact on infestations of the cotton

fleahopper as well as on infestations of Heliothis spp., these cottons are actually more sensitive to fleahopper attack than more hirsute

strains and, despite lower infestation levels,

suffer greater damage. This damage, however,

may result from infestations of leafhoppers

rather than cotton fleahoppers. Until these

problems are resolved and overcome, the use of

glabrous cotton may be questionable.

Cottons with the high-gossypol character or

those with this character combined with other

resistant characters also show a great deal of

promise against Heliothis spp. In the late 1960*s

these cottons showed some resistance against

the cotton fleahopper ; they have produced yields

above those of current commercial varieties.

These varieties will probably not be available to

the grower in any quantity, however, for several

years.

Tarnished Plant Bug

The nectariless character in cotton has reduced reproduction of the tarnished plant bug,
RESEARCH ON COTTON INSECTS 53

Lygiis lineolaris (Palisat de Beauvois), with

considerably fewer nymphs developing on nectariless plants than on plants with nectaries.

Apparently, the leaf nectaries are an important

food source for the developing nymphs.

Other Insects

Research on the development of varieties resistant to the pink bollworm, cotton leafperforator, and spider mites is in progress ; some success has been attained against spider mites.

Gossypol and Gossypol-Free Cotton

Generally, varieties having a high-gossypol

content are more tolerant to insect attack than

those with a low-gossypol content. Cottonseed

from commercially grown cottons could not be

used as a source of protein in food for nian and

in feed for nonruminant animals because of

gossypol content. Removing gossypol from the

meal was too costly. A new process, however,

has been developed for extracting gossypol from

cottonseed meal that may have considerable impact as a source of protein for man. A mill in

the High Plains of Texas is producing gossypolfree cottonseed flour and another mill is planned

for South Carolina. Before this new process was

developed for removing gossypol, breeders spent

considerable effort to develop gossypol-free

varieties. These varieties had acceptable agronomic characters, but they were more susceptible

to attacks of bollworms and certain species of

insects that do not attack commercial varieties.

Though the protein source for human food was

needed, the need for additional applications of

insecticides to control these insects offset any

gain in gossypol-free varieties. With the new

gossypol-removal process, the need for gossypol-free cotton varieties is less critical.

Appraisal of Cotton Varieties Resistant to Insects

Although only modest success has been

achieved in developing resistant varieties to

cotton insects, this effort is important. Varieties

with comparatively low levels of resistance to

certain insects could be an essential factor in an

insect population management system.

Insecticides

For many years before 1945, arsenicals and

sulfur were the principal insecticides used for

cotton insect control. Calcium arsenate was the

main weapon against the boll weevil, bollworm,

and cotton leafworm, but its application usually

resulted in injurious infestations of cotton

aphids.

Nicotine, the only available aphicide, was

mixed with calcium arsenate or was used alone

for aphid control although expensive and not

very effective under certain conditions. Mixtures of sulphur and calcium arsenate were

widely used for control of combination infestations of boll weevils and cotton fleahoppers.

Paris green and sulphur became popular in

the Far West for control of hemipterous insects.

Sulphur suppressed aphid populations but, in

combination with arsenicals, did not always prevent injurious infestations. In the early part

of the century, or before the advent of calcium

arsenate about 1916 to 1920, paris green and

lead arsenate were the principal insecticides

used to control outbreaks of the cotton leafworm.

Organic Insecticides

In the mid-1940's, the new organochjorine insecticides were developed and resulted in the

ñrst major change in insecticides used on cotton

since the development of calcium arsenate. Federal and State research workers rapidly explored their possibilities. Their general effectiveness against most of the injurious insects

resulted in wide acceptance by growers so that by

the late 1940's considerably more cotton acreage

was being treated than ever before. Much of

this development was accomplished at Cotton

Insect Research Laboratories in Florence, B.C. ;

Stoneville, Miss.; Tallulah, La.; Waco and

Brownsville, Tex. ; Tucson, Ariz. ; and at many

of the State agricultural experiment stations.

The organochlorine compounds largely replaced calcium arsenate though it continued to

be used for some years to some extent in localized areas. Some of them, BHC, aldrin, dieldrin,

chlordane, and heptachlor, were effective

against boll weevils but were ineffective against

bollworms. Mixtures of these materials with
54 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

DDT gave effective control of combination infestations of these two important pests. Toxaphene, and later endrin, were effective against

both pests.

Application equipment available at first was

that used for applying calcium arsenate, and for

several years the new insecticides were applied

only as dusts. One limiting factor for wider

acceptance was the critical weather conditions

needed for effective dust applications. Dusts

had to be applied during late afternoon, at

night, or early morning when the air was calm

or nearly so. In many areas satisfactory dusting

conditions were of short duration and often

nonexistent. Consequently, only limited acreages could be treated in a day's operation.

With the advent of organochlorine insecticides, entomologists at the Waco, Tex., Cotton

Insects Laboratory took a new look at ''presquare" boll weevil control with the idea of also

controlling other early-season injurious insects.

Previously no insecticides were available that

would control combination infestations of such

early-season pests as thrips, cotton aphids, overwintered boll weevils, and cotton ñeahoppers.

The organochlorine insecticides filled this

need. Small plot and large-scale experiments

(plots ranging in size from 1 to 5 acres) were

not too successful in 1946 and 1947. Communitywide experiments in early-season cotton insect

control experiments conducted in Wharton

County, Tex., in 1948 proved conclusively that

an early-season insect control program was

profitable and simplified the farmer's control

problem. Dusts were used in these experiments,

and again it was realized that critical application requirements would limit the effectiveness

of the program.

Insecticide Sprays

During the same year the new insecticides

were found effective when formulated as emulsifiable concentrates and applied as emulsion

sprays in low-pressure, low-volume spray equipment. Community-wide, early-season insect control experiments with sprays conducted in central Texas in 1949 and 1950 gave outstanding

results, and the bottleneck was broken. The

early-season control program was practiced by

growers over wide areas where early season

insects were a menace. In the 1950's and 1960's

as much as 80 percent of the cotton acreage

received such treatment in the Blacklands of

central Texas. These experiments were the forerunners of the total insect population suppression and integrated control concepts that attained much popularity in the 1970's.

Spray applications of insecticides for lateseason insect control were readily accepted by

growers because of several advantages over

dusts. They fitted well into a daytime farm

operation since they could be applied under more

adverse weather conditions than dusts (fig. 17).

The spider mite problem, which became somewhat more serious with spray applications of

the organochlorine insecticides, was solved

when organophosphorus insecticides such as

parathion, methyl parathion, and demeton became available as sprays.

In the 1960's the ultra-low volume spray appication of technical materials (less than 0.5

gallon of total spray per acre) was developed.

Research results showed that most materials

are at least equally effective when they are applied as ultra-low volume sprays compared with

the same dose applied as low-volume (conventional) sprays. Only malathion, azinphosmethyl,

endosulfan, methyl parathion, and a mixture of

malathion plus methyl parathion, however, are

approved for ultra-low volume aerial applications to control certain cotton insects. This

application technique has the advantage of increased pay load over conventional sprays,

which reduces application costs. It is used

especially in USDA-sponsored programs of insect suppression.

Resistance to Insecticides

The boll weevil developed resistance to the

organochlorine insecticides in the mid-1950's

in Louisiana, Arkansas, and Mississippi, and in

the other boll weevil infested States in subsequent years. Fortunately, an organophosphorus

compound, methyl parathion, was effective and

available. Azinphosmethyl, EPN, and malathion became available later. Azinphosmethyl

was believed to be the most effective weevilcide

available. The carbamate, carbaryl, was used as

a control but never gained full grower acceptance because it could be formulated only as a
RESEARCH ON>COTTON INSECTS 55

Figure 17.—Eight-row, low-volume, low-pressure spraying machine in operation.

PN-4434

wettable powder and was more difficult to apply

than an emulsifiable concentrate. The toxaphene plus DDT mixture, though both are organochlorines, continued to be effective against

resistant boll weevils. But DDT was banned

for use on cotton by the Environmental Protection Agency (EPA) on December 31, 1972.

Cotton insects rapidly have developed resistance to insecticides in recent years. Since 1947

when organic chemicals began to have wide

usage on cotton, 25 species of insects and spider

mites that attack the crop have developed resistance and several other species are strongly

suspected of having developed resistance. At

least one of these resistant species occur in

localized areas in most cotton-producing States

from California to North Carolina. Most of

these pests are resistant to the organochlorine

insecticide, but four species of spider mites, the

armyworm, banded wing whitefly, bollworm,

and tobacco budworm, are known to be resistant

to the organophosphorus compounds.

Resistance in the tobacco budworm and bollworm is serious as few effective insecticides are

available. However, the insecticides, methomyl

and chlordimeform, which were recently developed, may be of help in this respect. Unfortunately, methomyl is phytotoxic and cannot be

used to a regular schedule of applications, and

researchers are studying how chlordimeform

should be used for greatest effectiveness. The

synthetic pyrethroid compounds showed considerable promise for the control of these pests

in preliminary tests.

Systemic Insecticides

Systemic insecticides such as phorate and

disulfoton developed in the mid-1950's applied

to cottonseed protect plants for several weeks

after plant emergence from such pests as thrips,

the cotton aphid, and spider mites. This method

of control, however, has not been widely accepted because the insecticides are expensive,

do not give protection as long as desired early

in the season, often reduce plant emergence,

and may delay fruiting. Granular formulations

of systemic insecticides are applied, also, in the

seed furrow at planting and as side dressings to

established plants. Aldicarb developed in the

1960's applied in the seed furrow at planting

killed overwintered boll weevils and controlled
56 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

cotton fleahoppers 8 weeks after planting. It

kills boll weevils developing in cotton squares

when applied to plants as a side dressing in the

early squaring stage. The application of this

compound, especially aS a side dressing in the

early squaring stage, often results in increased

subsequent infestations of the bollworm. Research in the early 1970's showed that aldicarb

may be useful in boll weevil eradication or suppression programs when about 2 percent of each

field is planted to a trap crop (cotton planted

at least 2 weeks before the rest of the field is

planted) treated with it.

Appraisal of Insect Control with Insecticides

Three ARS laboratories, Florence, S.C., in

the Southeast ; Tallulah, La., in the South ; and

Waco, Tex., in the Southwest, kept annual comparative records of yields in treated and untreated plots for periods of 31, 37, and 32 years,

respectively. These results are indicative of the

crop losses to insects when insecticides are not

applied for their control in those areas. The use

of the best insecticides, however, does not prevent all insect damage, and a certain amount of

damage can be tolerated before the use of an

insecticide is economically feasible. Because

more than one insect was usually involved in the

experiments, no attempt was made to show

how much of the loss in yield was due to a

particular insect. Insects involved at all locations were boll weevils, bollworms, cotton

aphids, and spider mites. In addition, lygus bugs

were involved at Tallulah and the cotton fleahopper and thrips at Waco.

Insect infestations and weather conditions

vary from year to year. Thus, comparative

records over a period of years are more meaningful than those of selected years. The average

increase in yield in treated over untreated plots

at Florence for the 31-year period, 1928 to 1958,

was 40.6 percent with a range from 5.3 percent

in 1942 to 217.9 percent in 1950. At Tallulah

for the 37-year period, 1920 to 1956, it was 31.2

percent with a range of 1.1 percent in 1924 to

112.8 percent in 1950; and at Waco for the 32-

year period, 1939 to 1970, it was 54.3 percent

with a range of 9.9 percent in 1939 to 426.0

percent in 1961.

Considerable improvement has been made in

cotton insect control since 1945 with the advent

of the organochlorine and later organophosphorus and carbamate insecticides. Before that time

growers depended primarily on such inorganic

insecticides as the arsenicals and sulphur for

insect control. The following tabulation illustrates improvement in insect control since the

new insecticides have been used :

Location

Study

period

Increase in yield in treated over

untreated plots

Average Before 1945 After 1945

Florence, S.C.

Tallulah, La.

Waco, Tex.

1928-58

1920-56

1939-70

Percent

40.6

31.2

54.3

Percent Percent

23.6 53.9

26.4 41.3

34.0 77.6

Total reliance on the control of cotton insects

>vith insecticides is no longer acceptable because

of adverse effects of insecticides on the environment. However, development of alternatives to

control insects is difficult and costly. Though

development of such alternatives has received

much emphasis, insecticides will continue in importance in the control of cotton insects (fig.

18). Much concern has arisen because comparatively few candidate insecticides have been researched in recent years. Only chlordimeform.

Chevron Ortho 9006, (Monitor), (0,S-dimethyl

phosphoromidothioate), methomyl, and methidathion have recently been developed and show

promise in control of cotton insects and spider

mites. A new class of insecticides, however, the
RESEARCH ON COTTON INSECTS 57

Figure 18.—Cotton untreated (left) and treated (ri^fct)with insecticide.

PN-443Í

synthetic pyrethroids, showed promise in preliminary tests toward the end of the reporting

period.

The cost of developing and registering a compound is expensive. Industry, therefore, is having to take an extremely hard look at compounds

after the initial screening to see whether continuing their development is justified. Consequently, few compounds are being made available in the testing program and even fewer of

those make the grade insofar as registration and

ultimate use by growers are concerned. The situation is serious in the control of the bollworm

complex with development of resistance to the

comparatively few available effective insecticides. Hopefully, some of the alternatives to

insecticide may be used with insecticides in a

pest management system so that crises in insect

control may not occur because fewer effective

insecticides are available.

Recommendations in the use of insecticides

to control the various cotton insects are subject

to change from year to year so they are not

included in this publication. For such suggestions on control, please consult the respective

State Guides for Controlling Cotton Insects.

Juvenile Hormones

The effects of juvenile hormones on several

cotton insects have been studied at several laboratories. Though some activity was noted in

the boll weevil, lygus bug, cotton aphid, and

bollworm, it was not great enough to justify

field tests. Activity in the boll weevil was in the

larval and pupal stages with no means available

to introduce the hormone under field conditions

since immature stages develop within the square

(fruiting buds) and bolls. In addition, the hor-
58 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

mones affecting lygus bugs and the cotton aphid

affected some of the predaceous insects, such as

the green lacewing. Studies are continuing with

the bollworm.

For several years chemists at the Boll Weevil

Research Laboratory have attempted to identify

a compound from the boll v^eevil v^ith juvenile

hormone activity, and also, to determine

v^hether the Cecropia juvenile hormone is the

juvenile hormone in the boll weevil. They were

unable to isolate a fraction from the boll weevil

that was active at less than one microgram

though several methyl esters of fatty acids were

active at 15 to 30 micrograms. They were unable to isolate the Cecropia juvenile hormone

from the boll weevil with gas Chromatographie

and mass spectral procedures on larvae, adults,

and adult frass.

Pathogens

In the need for developing alternatives to

conventional control of insects with insecticides,

attention was given to pathogens for the control

of such cotton insects as the boll weevil and

the bollworm complex. Evidence of the occurrence of pathogens had been known for many

years. For instance, infestations of the cabbage

looper, Trichoplusia ni (Hübner), were often

decimated by a nuclear polyhedrosis virus.

Cultures of bollworms being reared under insectary conditions often were wiped out by a

virus, and large larvae killed by the virus were

observed in the field though the disease never

reached epizootic proportions as with the cabbage looper.

Bacillus fhuringiensis

The (delta) S-endotoxin of Bacillus thuringiensis (B.t,) has insecticidal activity against

several species of Lepidoptera including the

tobacco budworm and bollworm. It has been

shown to be entirely safe to other groups of

animals including man, wildlife, beneficial insects, and plants. On this basis, EPA has

granted the formulations an exemption from

tolerance ; however, it is not registered for use

against Heliothis spp. on cotton.

Before 1973 B.t, was assumed to be a disease-producing organism, and the potency of

preparations could not be judged by the quantity of spores present. The presence of a toxic

crystal associated with the B.t. spore, later

named the S-endotoxin, was demonstrated in

the 1950's. However, it was not until the early

1970's that the entire activity of the organism

was shown to result from the 8-endotoxin. This

work showed that toxicity varied from B.t. isolates, regardless of serotype, and depending on

the medium used for bacterial fermentation.

These findings opened the way for development

of a bioassay standardization procedure that

could be used to gage the potency of preparations and ultimately to provide more potent

preparations. An isolate 15 to 20 times more

active against the tobacco budworm and some

other insects than commercial materials available at the time was then developed. This development was rapidly put to use by commercial

producers of B.t., which led to a great increase

in the use of the product, chiefly against certain

vegetable insects such as the cabbage looper

and against Heliothis on tobacco.

Tests with B.t. against Heliothis in the laboratory and in the field on cotton have shown it

to be effective. The rates, however, required to

achieve control on cotton in the field (2 to 12

pounds per acre) are not economical. The primary reason why large amounts'^of B.t. are

needed to achieve control of Heliothis on cotton

is that the material must be ingested by the

larvae to be effective, and most of the feeding

by Heliothis on cotton is within the fruit where

little B.t. is present.

Research is continuing to increase the potency of B.t. preparations against Heliothis

spp. by selection of new isolates. Improvement

of fermentation media has achieved a 15-fold

increase in the yield of S-endotoxin, thus, reducing the amount of material needed to control

the pests. Also, the use of various baits containing cornmeal or cottonseed oil to increase

the amount of larval feeding on the B.t. has

shown promise of reducing the quantity of B.t.

needed for control of Heliothis. Despite this

continuing research, an effective and economical formulation will probably not be available

for commercial use on cotton for a few years.
RESEARCH ON COTTON INSECTS 59

Heliothis Nuclear Polyhedrosis Virus

The nuclear polyhedrosis virus of Heliothis

is an obligate parasite that multiplies within

the cells of larvae of Heliothis spp. and causes

a fatal disease. The virus was found first in

this country in larvae collected from cotton

near San Benito, Tex. (fig. 19). Since then, the

material has been developed through laboratory, pilot-plant, and commercial stages.

The virus has received a temporary exemption from tolerance by EPA with annual renewals and has been registered for sale in

Spain. It is completely harmless to all animals

(including man) except Heliothis spp. Before

this product can be registered, however, its

efficacy must be more fully demonstrated.

Since the virus is an obligate parasite, it

must be produced in living Heliothis spp. larvae

or on tissue cultures. Two companies are currently producing it in living Heliothis larvae.

An estimated 2,000 to 4,000 pounds of the

product were produced in 1974.

Results of field tests of this virus against

Heliothis spp. on cotton have been variable,

control equal to or better than that produced

by standard insecticides has been achieved in

some instances, and inadequate control has resulted in others. These differences appear to

result from the rapid deactivation of the virus

by sunlight and the feeding behavior of Heliothis noted in the section on B.t.

Studies by several workers indicated that the

unprotected virus on foliage was deactivated

by exposure to sunlight, with most of the activity gone after 24 hours. Some progress has

been made in overcoming tnis problem by adding various ultraviolet-screening agents to formulations of the virus. The activity has been

extended at least 25 hours by this means, but

apparenty none of the preparations was considered adequate for further development.

Research to overcome the problem relating

to the feeding behavior of Heliothis spp. by

obtaining better coverage of the plants, increasing the amount of virus applied, and using

baits has been partially successful. Better control was obtained by reducing the size of the

spray particle and by increasing the volume of

spray applied per acre. Some workers reported

the effectiveness was substantially improved by

increasing the rate of application from the

suggested 40 diseased larval-equivalents to

5,000 per acre. Baits containing such ingredients as water extract of corn silks, cottonseed oil, and sugars have improved efficacy.

Apparently, the formulations of the Heliothis

virus that have been studied do not give the

Fig:ure 19.—Diseased bollworm larva on leaf.

PN-44S6
60 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

desired degree of control on cotton, especially

when heavy infestations occur. Effective economical formulations, however, may be produced in the next few years.

The alfalfa looper, Autographa californica,

nuclear polyhedrosis virus has shown activity

against several lepidopterous pests of cotton

and may have potential in their control.

Other Pathogens

At the Boll Weevil Research Laboratory results of biological control tests showed that

Beauveria bassiana can infect larvae, pupae,

and adult boll weevils in the laboratory, but it

cannot be cultured for practical use in the

field. Laboratory cultures of the boll weevil became infected with a new species of neogregarine that subsequently was named Mattesia

grandis McLaughlin. The ensuing epizootic

resulted in destruction of the boll weevil colony.

To be effective, the neogregarine had to be

ingested by the adult boll weevils. A cottonseed oil bait was developed to enhance ingestion of the pathogen. Production and application problems have prevented the pathogen

from becoming a practical tool in the control

of the boll weevil.

Physiology and Morphology

Boll Weevil

In the late 1950's a study was made of the

reproductive system of the boll weevil. The

genitalia and reproductive organs of the reproducing male and female were described and

illustrated. The musculature associated with

the reproductive systems of both sexes were

described. Results of studies at the same time

showed that the spermatheca of the female

may provide a useful basis for identification of

Thurberia weevils.

Dehydrogenases were studied in the brain

and in the related neural and secretory structures in the boll weevil. The fatty acid fraction

of the boll weevil is a complex mixture of 23

fatty acids ranging in chain length from 6 to

20 carbon atoms. Total body fat of the boll

weevil and relative distribution in major lipid

classes are dependent on adult age, larval and

adult diet, and diapause. Neutral glyceride and

free fatty acid fractions account for as much

as 90 percent of extractable lipids of diapäusing

adults. Newly emerged weevils have 2 to 6

percent body fat (about 2 percent triglycéride).

After 2 to 3 weeks of feeding, nondiapausing

adults have 6 to 10 percent body fat (40 to 60

percent triglycéride), but diapausing adults

have 18 to 25 percent body fat (75 to 85 percent

triglycéride). The triglycéride level drops during the winter when the insects are not feeding.

Several guanine analogs were tested as inhibitors of reproduction. Two, 8-bromoguanine

and 9 methyl, 2 butyl guanine were effective

ovarial growth inhibitors in the boll weevil.

Larvae reared in a radioactive medium were

inhibited in their development and only a small

percentage developed to adulthood. The purine

guanine was identified in the excreta of the boll

weevil. The effects of nitrogenous-elid products

of the metabolism of the boll weevil fed on

artificial diet, cotton squares, or bolls were

determined. Fecal analyses for amino acids,

nitrogen, ammonia, creatines, creatinine,

guanine, urea, and uric acid showed that presence of these materials varied with the type of

diet fed the insects. The purine guanine was

found in relatively large quantities in the feces

of weevils fed all three diets. The feces of the

boll weevil were examined for nonprotein

amino acids. A total of 20 amino acids were

detected in ethanalic extract with Chromatographie techniques, and 23 acids were detected

by acid hydrolysis. The free and bound nonprotein amino acids and ammonia accounted

for 3.23 percent of total feces nitrogen.

No striking effects of DDT, toxaphene, or a

combination of these two insecticides on the

activity of succinic dehydrogenase were shown.

In a study of the activity of ATPase in homogenates of the boll weevil, sufficient magnesium

occurred to activate the enzyme. Additional

magnesium did not increase activity of the

enzyme. A higher level of ATPase occurred in

a laboratory-reared than in a field-cultured

population.

Bollworm

Differences in percentages of phospholipids,

partial glycerides, and triglycérides were
RESEARCH ON COTTON INSECTS 61

found between large and small larvae of the

tobacco budworm and the bollworm and, also,

between the two species. The difference may

explain the greater tolerance of the tobacco

budworm to insecticides. High percentages of

fatty acids in bollworm larvae may have a role

in the naturally greater tolerance of the tobacco

budworm to insecticides because they could

affect the solubility of insecticides in lipids or

the characteristics of cell membrane.

The bollworm moth vibrates its wings during courtship, and the male wipes the scales of

his claspers on a supporting surface between

periods of vibration. Receptive females extend

the terminal abdominal segments and vibrate

their wings. Then, the receptive female, whose

terminal abdominal wings are extended, is

approached from behind by the male who taps

the ovipositor of the female with his antennae,

crawls to a position at the side of and about 2

cm from and parallel to her, and snaps his

claspers around her genitalia to complete the

copulatory connection. Mated pairs remain in

copula from % to li/^ hours.

Histological studies of the structure of the

compound eyes of the tobacco budworm and

bollworm indicated that the major structural

difference between the eyes of the two species

is the relatively shorter ommatidia in the eye

of the tobacco budworm. Whether this morphological difference affects the sensitivity of the

eye to wavelength or intensity of light stimuli

is not known. Results of behavioral and electrophysiological studies on the visual sensitivity

of the bollworm and tobacco budworm indicate

that these moths detect the radiant energy from

15-W ultraviolet lamps from a limited distance

only and that the 15-W BL lamp would be useful only for surveying the activity of the bollworm and tobacco budworm moth population

in a limited area near the trap.

Rearing

Research on cotton insects was hampered for

many years because of difficulties encountered

in rearing them in the laboratory. Rearing insects on their hosts was difficult from the

standpoint of needed numbers as well as being

quite expensive. Major breakthrough in research could only come with ability to mass

rear the various insects on artificial diets.

Pink Bollworm

The first phytophagous insect to be reared on

an artificial diet was the pink bollworm so

reared in the early 1950's at the College Station, Tex., ARS Cotton Insects Laboratory. The

artificial diet developed for this insect served as

the basic diet for many phytophagous insects

now being mass reared in the laboratory as a

result of this research. The pink bollworm was

mass reared in tremendous numbers in the

late 1960's and 1970's in the USDA, of the now

Animal and Plant Health Inspection Service

Laboratory in Phoenix, Ariz. (See section on

Genetic Control in this publication.)

Boll Weevil

In the early 1960's boll weevils were reared

on artificial diets at the College Station, Tex.,

Cotton Insects Research Laboratory. Progress

in mass rearing the insect was made with the

establishment of the Boll Weevil Research Laboratory on the Mississippi State University

Campus in 1962. After it became apparent

that the insect could be reared in sufficient

numbers, it was deemed that a Pilot Boll

Weevil Eradication Experiment should be conducted to determine whether it was technologically and operationally feasible to eradicate

the boll weevil. Through a more than a half

million dollar appropriation by the Mississippi

Legislature, the Gast Insect Rearing Laboratory was built on the campus of Mississippi

State University. Though problems with the

facility and with rearing procedures were such

that numbers of boll weevils needed for sterile

male releases in the experiment were not

reached, the facility made a significant contribution to the success of the experiment. It is

expected to make an even greater contribution

if elimination of the insect from the United

States is undertaken.

Bollworm

Nutrition and techniques for rearing the

bollworm, also, were developed at the College

Station laboratory. Though small cultures have
62 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

been reared at several laboratories, the major

thrust in mass rearing has been done at the

ARS Southern Grain Insect Laboratory at

Tifton, Ga. A prototype machine for mass rearing the insect has been developed at this

laboratory.

Tobacco Budworm

Techniques for mass rearing the tobacco budworm were developed at the Brownsville, Tex.,

laboratory in the late 1960's and early 1970's.

Production was stabilized at about 60,000

pupae per day. Pupae were furnished from

this laboratory for the sterile male release

study conducted on St. Croix, U.S. Virgin Islands, in the early 1970's. In addition, moths

were reared for several years for the identification of the sex pheromone emitted by the

female. Chromatographie analysis indicated the

pheromone to be a multiple component system.

The sex pheromone was isolated, purified, identified, and synthesized early in 1974.

Lygus Bugs

Lygus bugs, Lygus hesperus and L. Lineolavis, have been reared on artificial diets. Techniques for mass rearing them on these diets,

however, have not yet been developed.

Saltmorsh Caterpillar

The saltmarsh caterpillar, Estigmene aerea

(Drury) has been reared on the wheat-germ

diet at the Cotton Insects Research Laboratory,

College Station, Tex., and has been mass reared

at the Biological Cotton Insect Control Laboratory, Tucson, Ariz.

Beneficial Insects

The green lacewing has been reared on an

artificial diet, and some progress has been made

in mass rearing it on this diet. Some progress

has been made in rearing Campoletis perdistinctiis and Micropletis senorensis, parasites of

Heliothis spp., on artificial diets.

Pilot Boll Weevil Eradication Experiment

Cotton leaders have repeatedly emphasizea

that the economic survival of the industry depends on adequate research necessary to

strengthen cotton's ability to compete for

markets. Scientists and industry leaders agreed

that the boll weevil represented one of the most

costly problems confronting the cotton industry

and, therefore, was one of cotton's major problems in urgent need of research support. In the

Agricultural Appropriation Reports for Fiscal

Year 1959, both the House and Senate Committees requested the Secretary of Agriculture

to review the boll weevil problem and to submit

a report on research and facility needs to meet

the problem to the next appropriations comnlittees.

The Office of the Secretary appointed a working group consisting of E. R. McGovran, Cooperative State Research Service (CSRS),

USDA; H. G. Johnston, National Cotton Council of America, and E. F. Knipling (chairman)

and C. R. Parencia (secretary), ARS, USDA, to

study the problem. In addition the group was

to ( 1 ) develop information on current research

programs devoted to boll weevil investigations

by State, Federal, and private industry; (2)

determine the needs for an overall comprehensive research program; and (3) determine the

broad areas of research that would be appropriate for Federal attention and support in an

effort to help meet the overall needs. The

group's report was submitted to the Secretary

on December 30, 1958. This report culminated

in appropriations by Congress to establish the

Boll Weevil Research Laboratory at State College (now Mississippi State), Miss., and to

strengthen ongoing research programs at the

Cotton Insect Research Laboratories at College

Station, Tex.; Baton Rouge, La.; and Florence, S.C. The new research facility at Mississippi State was dedicated in a formal ceremony in March 1962. Research on the boll

weevil was simultaneously strengthened in

several State agricultural experiment stations.

Significant research findings resulting from

the expedited research on the boll weevil were :

(1) Techniques for mass rearing the boll

weevil; (2) development of the reproductiondiapause control program; (3) development of

ultra-low volume spray applications of insecticides; (4) development of the systemic insecticide, aldicarb, that controls the boll weevil;

(5) finding that the male boll weevil emits a

pheromone that attracts females and, also, acts
RESEARCH ON COTTON INSECTS 63

as an aggregant; (6) identification and synthesis of the attractant, grandlure, and development of traps baited with it for capturing

boll weevils; (7) progress in development of a

chemosterilant making the male-sterile release

technique feasible ; (8) use of trap crops treated

with aldicarb in furrow and as a side dressing

together with grandlure bait in reducing overwintered boll weevil populations; and (9) progress in the development of a frego bract strain

of cotton with considerable resistance to the

boll weevil.

In recognition of the importance and urgency

of eliminating the boll weevil problem as soon

as it became technically and operationally feasible, the National Cotton Council of America

in its 1969 annual meeting established a Special

Study Committee on Boll Weevil Eradication.

The Special Study Committee met in Memphis,

Tenn., on May 6, 1969, to review the status of

current knowledge of boll weevil suppressive

measures and to consider actions that should

be taken in efforts toward the elimination of

the boll weevil as a pest of cotton. The chairman

of the Special Study Committee appointed a

Subcommittee of P. L. Adkisson, Texas A&M

University; J. R. Brazzel, APHIS, USDA; H.

G. Johnston, National Cotton Council; D. F.

Young, Mississippi State University; and C.

R. Parencia (secretary) and E. F. Knipling

(chairman), ARS, USDA, to select areas representative of boll weevil conditions in the southeast,, south, and southwest areas of the Cotton

Belt that would be suitable for undertaking

large-scale experiments to determine if boll

weevil eradication is feasible with currently

available suppression techniques. The Subcommittee prepared a report dated August 15,

1969, that was presented to the Special Study

Committee on Boll Weevil Eradication in Memphis, Tenn., on September 16, 1969. It recommended that a Pilot Boll Weevil Eradication

Experiment be conducted beginning in calendar

year 1970 in an area centered in South Mississippi and including adjacent cotton acreages

in Alabama and Louisiana.

The Special Study Committee accepted the

recommendations of the Subcommittee and its

representatives met with USDA officials to discuss ways of financing the experiment. A decision was made that the project would be

financed by $1 million from ARS (later with

APHIS), $500,000 from CSRS, and $500,000

from industry. Cotton Incorporated, for each of

2 years. Mississippi was to provide a rearing

facility. A detailed study of the area was made,

and the cost of the experiment was estimated

at $2.5 million. Since only $2 million was available, the experiment was delayed for a year or

until the needed additional funds could be

obtained. In 1971, however, the new cotton program resulted in a considerable reduction in

the cotton acreage to be planted, making it

possible to start the experiment with available

funds. The Director of Science and Education

of the Department appointed a Technical Guidance Committee for the Pilot Boll Weevil Eradication Experiment.

The experiment got under way in July 1971

(fig. 20). It was conducted cooperatively with

the Departments of Agriculture, Experiment

Stations, and Extension Services of Mississippi,

Louisiana, Alabama, and Texas; with Cotton

Incorporated and the National Cotton Council

representing the industry; and with USDA's

APHIS, ARS, CSRS, ASCS, and ES. The reproduction-diapause phase of the experiment was

carried out in the fall of 1971. Unfortunately

boll weevil populations were very heavy, and

as a result of the mild winter, survival of boll

weevils was high. A trap crop treated with

aldicarb was planted in each field iA the eradication and first buffer areas, and pheromone

traps at the rate of 2 per acre were placed

around each field in 1972. An insecticide application was made when plants began to square.

A period of dry weather resulted in late emergence of weevils from hibernation sites, leaving

too many weevils in the fields for the sterile

male releases to be effective.

Five in-season applications of azinphosmethyl were made followed with 13 applications

for reproduction-diapause control. By October

adults were too scarce to be detected. Pheromone trap catches in the spring of 1973 indicated very low surviving populations in the

eradication and first buffer areas. Release of

sterile males began in early June, but rearing

problems necessitated reducing releases to 50

per acre instead of the hoped for 100 in the

eradication area and extending only 5 miles

into the first buffer area. Both areas originally
64 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

were planned to receive 100 sterile males per

acre per week. Fields with infestations in the

remaining first buffer fields were to be treated

with insecticides.

Only 33 of the 236 fields were infested in the

eradication area, and they were in the northern

zones nearest the first buffer. Indications were

that the problem was caused by migration from

the second buffer where overwintering populations were considerably higher. Infested fields

were treated at 3-day intervals with azinphosmethyl. As a result of these treatments, reproduction could not be detected in 32 of the 33

fields at the end of the experiment. The infestation in the one field was not detected until the

last week of the experiment so that time did not

permit total elimination of reproduction in it.

The experiment was terminated on August

10, 1973, and the Technical Guidance Committee met on August 30 to evaluate the results. The committee concluded **that it is

technically and operationally feasible to eliminate the boll weevil as an economic pest in the

United States by the use of techniques that are

ecologically acceptable."

Members of the committee were as follows :

P. L. Adkisson, Texas A&M Univ. ; F. S. Arant,

Auburn Univ.; Richard Carleton, La. Dept.

Agr.; T. B. Davich, E. F. Knipling (co-chairman), and C. R. Parencia (secretary), ARS;

Figure 20.—Site of Pilot Boll Weevil Eradication Experiment, 1971-73.
RESEARCH ON COTTON INSECTS 65

R. C. Riley, CSRS, and W. F. Helm, J. R. Brazzel, and D. R. Shepherd, APHIS, USDA; C. C.

Fancher and O. T. Guice, Miss. Dept. Agr. and

Com.; F. G. Maxwell and David Young, Miss.

State Univ. ; J. S. Roussel, La. Agr. Expt. Sta. ;

W. A. Ruffin, Ala. Dept. Agr.; George Slater,

Cotton, Inc.; and Ritchie Smith, National

Cotton Council.

The National Cotton Council's Special StudyCommittee for Boll Weevil Eradication met in

Memphis, Tennessee, on January 10, 1972, to

reviev^ the progress and status of the experiment. The Committee expressed a need for a

comprehensive, overall eradication plan that

would outline areas for initiation and subsequent target zones, timetables, probable costs,

program requirements, operational arrangements, and the like. The chairman appointed a

Technical Committee to Develop a Plan for

Overall Boll Weevil Eradication.

Members of the Technical Committee were

P. L. Adkisson, Texas A&M Univ. ; C. R. Jordan of Univ., Ga. ; D. F. Young, Miss State

Univ.; H. L. Breur, Tenn. Dept. of Agrie;

George Slater, Cotton Incorporated; James

Brown, the National Cotton Council; H. M.

Taft, ARS; C. R. Parencia, ARS, Secretary;

J. R. Brazzel, APHIS, Vice Chairman; and E.

F. Knipling, ARS, Chairman.

Though two preliminary meetings were held

in November 1972 and early January 1973,

the work of the Committee did not gain impetus

until results of the experiment became available at the end of August. An overall Plan for

a National Program to Eliminate the Boll

Weevil From the United States was presented

by the Technical Committee to the Special

Study Committee on December 4, 1973. It was

accepted and, in turn, presented to the Secretary of Agriculture on December 12. In the

Agricultural Act of 1973, the Secretary had

been instructed to carry out elimination programs for the boll weevil, pink bollworm, and

other cotton insects if he determined that it

was feasible to do so.

After much discussion with various agencies,

it was decided that a 3-year Boll Weevil Eradication Trail be conducted in northeast North

Carolina and adjacent cotton growing areas of

Virginia. Funding for the trail was included

in the Department of Agriculture's budget but

was not included in the budg-ot presented to

the President by the Office of Management

and Budget. Initiation of the trail is awaiting

funding.

Field Laboratories

Tallulah, La.

The Tallulah laboratory was established in

1909 and was in continuous operation until it

closed at the end of June 1973. The laboratory

was the oldest continuously operated insect research laboratory in ARS. It was selected as

an ideal location to do research on the boll

weevil, and it developed the first practical

method of controlling the boll weevil with

calcium arsenate. Its acknowledged leadership

in research on the new cotton pest was discussed in the section of the boll weevil. It continued to be an ideal location to do practical

field research on the boll weevil because winter

survival was usually high and climatic conditions were favorable for rapid population

buildup. It was in a remote location, and the

facilities were poor with no opportunities for

laboratory personnel to associate with other

research scientists. For these reasons and for

economy, the laboratory was closed and the

equipment and personnel transferred to the

Stoneville, Miss., laboratory. The program of

research in recent years was centered around

the biology and control of the boll weevil with

some emphasis on the bollworm, lygus bugs,

and thrips. Large plot field tests were conducted

to evaluate promising new insecticides and

formulations against these insects.

Florence, S.C.

The Southeastern Cotton Insects Investigations Laboratory was established in 1921 in

cooperation with the South Carolina Agricultural Experiment Station and thereafter has

been in continuous operation. The program involves (1) electrophysiological research to discover and develop practical methods of using

electromagnetic energy to control the bollworm,

tobacco budworm, and boll weevil; (2) ecological research on the boll weevil, bollworm.
66 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

and tobacco budworm; (3) physiological and

nutritional research on the boll weevil and

bollworm; (4) evaluation of insecticides against

cotton insect pests indigenous to the Southeastern States; and (5) development of machinery for applying insecticides (in cooperation with agricultural engineers).

Tucson, Ariz.

The Cotton Insects Biological Control Investigations Laboratory was established in the

spring of 1925 (Tucson, Ariz., Cotton Insects

Laboratory) to study the life history and habits

of the Thurberia weevil. After these investigations showed that this insect would not likely

become a serious cotton pest, research was

turned to hemipterous insect pests and later

to lepidopterous insect pests of cotton. Primary

emphasis now is on the biological control of

cotton insects. The program consists of research on (1) population dynamics of cotton

insects, (2) bioclimatology, and (3) biological

control agents, particularly parasites and predators of cotton's lepidopterous insect pests,

including the development of mass-rearing

techniques and field evaluations.

Stoneville, Miss.

The Delta Cotton Insects Investigations Laboratory was established in Stoneville, Miss., in

1934 in cooperation with the Mississippi Agricultural Experiment Station. It has recently

been made a part of the Bioenvironmental Insect Control Laboratory in Stoneville. The research program at Stoneville involves (1)

biological and ecological research on the boll

weevil under Mississippi Delta conditions; (2)

small field plot and entire field evaluations of

insecticides for control of boll weevil, bollworm,

tobacco budworm, plant bugs, thrips, spider

mites, and cotton aphids; (3) biological, nutritional, and physiological research on the bollworm, tobacco budworm, plant bugs, and spider

mites; (4) development of cotton varieties

resistant to or tolerant of attack by lygus bugs

and spider mites; (5) biological control involving parasites and predators; and (6) insect

population management programs.

Waco, Tex.

The Blacklands Cotton Insects Investigations

Laboratory was established in Waco, Tex., in

March 1939 by consolidating the work of the

two laboratories located at Port Lavaca and

College Station. The laboratory continued in

operation until it was closed at the end of June

1973. The program was concerned with research on (1) biology and ecology of the boll

weevil, bollworm, tobacco budworm, cotton fleahopper, and thrips; (2) comparative field plot

evaluation of promising new insecticides and

formulations; (3) large-scale evaluation of seasonal control programs; and (4) development

of a practical insect population management

program for the Blacklands area.

Baton Rouge, La.

The Cotton Insects Physiology Investigations

Laboratory was established on July 15, 1956,

in cooperation with the Louisiana Agricultural

Experiment Station. It was first designated as

Cotton Insects Insecticide Resistance Investigations and was specifically set up to study factors

influencing resistance of the boll weevil to

insecticides and to develop methods of overcoming this resistance. Much of the work was

physiological and biochemical. After more than

12 years of work on the resistance problem, it

became evident that this line of research would

not attain its objective. Many other investigators working simultaneously on other insect

resistant problems came to the same conclusion.

Since the staff members were trained in insect

physiology and biochemistry and since it was

actually contributing much to physiological research, the laboratory was redesignated as the

Cotton Insects Physiology Investigations Laboratory on July 17, 1969. The program is centered around research on (1) chemosterilants,

(2) hormones and other essential metabolites

and biological regulators, and (3) carbohydrate

metabolism in the boll weevil.

Brownsville, Tex.

The Southwestern Cotton Insect Investigations Laboratory was established in 1941 specifically to conduct research on the pink bollworm. It had operated as a sublaboratory of the
RESEARCH ON COTTON INSECTS 67

Presidio, Tex., laboratory in 1939 and 1940.

Research was primarily concentrated on the

pink bollworm until findings showed that the

insect could be controlled with cultural methods. Gradually, the pink bollworm became less

of a problem, while the bollworm-tobacco budworm problem intensified. The program now is

largely concerned with research on lepidopterous insect pests of cotton. The program consists

of research on (1) developing practical ways of

sterilizing the pink bollworm and the tobacco

budworm, (2) developing practical and economical ways of mass rearing the tobacco budworm, (3) studying the biology and ecology

of the boll weevil, bollworm, and tobacco budworm, (4) isolating, identifying, and synthesizing the sex pheromone of the tobacco budworm,

(5) evaluating promising new insecticides and

formulations against Southwestern insect pests

of cotton in laboratory and field tests, (6) developing practical ways of using Bacilhts thuringiensis and other pathogens for control of

cotton insect pests, (7) evaluating parasites and

predators as biological control agents of cotton

insect pests, (8) developing cotton varieties

resistant to or tolerant of attack by insect pests

of cotton, (9) studying alternate host plants

of the boll weevil, bollworm, tobacco budworm,

and cotton fleahopper, and (10) studying, both

biochemically and nutritionally, lepidopterous

insect pests of cotton.

College Station, Tex.

The Cotton Insects Systemic Chemical and

Nutritional Investigations Laboratory was established in 1948 in accordance with the terms

of the Research and Marketing Act of 1946 in

cooperation with the Texas Agricultural Experiment Station. The program is concerned

with research on (1) the nutritional requirements for several cotton insects including predaceous and parasitic insects, (2) the development of nutritionally adequate artificial diets on

which these insects may be reared, (3) the discovery and development of systemic chemicals

that may be useful in cotton insect control, (4)

the development of practical methods of utilizing predators and parasites for the control of

lepidopterous insect pests of cotton, (5) determination of the metabolites and other degradation products in the breakdown of insecticides,

and (6) development of slow release formulations of systemic insecticides and synthetic

pheromones.

Mississippi State, Miss.

The Boll Weevil Research Laboratory was

established in 1961, resulting from recommendations made by The Secretary's Working

Group on Boll Weevil Research Programs in

1958. Its primary objective is "the elimination

of the boll weevil as an economic factor in cotton

production,'' with the ultimate objective of eradicating it. The research program is multidiscipline involving entomologists, chemists, plant

geneticists, plant physiologists, agricultural engineers, and soil and water research scientists.

A comprehensive program of research is currently underway involving (1) biology and ecology of the boll weevil, (2) development of an

attractant bait containing pathogens to control

the boll weevil and bollworm, (3) mechanical

control of the boll weevil, (4) research on the

male pheromone (grandlure) as a survey, control, and possible eradication tool, (4) chemosterilant research on the boll weevil, (6) breeding cotton varieties resistant to or tolerant of

attacks of the boll weevil, (7) integrated control

of cotton pests, (8) physiological and nutritional research including mass rearing of the

boll weevil, and (9) large-scale evaluations of

promising leads in the suppression or eradication of the boll weevil.

Phoenix, Ariz.

The Western Cotton Insects Investigations

Laboratory was established in October 1965.

Previously, a sublaboratory of the Tucson laboratory had been operated at Mesa. The Department's 1965 Appropriation Act (78 Stat. 862),

approved September 2, 1964, authorized and

provided planning money only for a Western

Cotton Insects and Cotton Physiology Laboratory. The 1966 Appropriation Act (79 Stat.

1165), approved November 2, 1965, authorized

and provided funds. The laboratory was completed in 1970 and was fully staffed in 1972.

The program is concerned with (1) ecological

investigations of the pink bollworm, (2) evalu-
68 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

ation of sex pheromones and different trap

designs for luring and trapping the pink bollworm, (3) genetic investigations of the pink

bollworm and other Western cotton insect pests,

(4) development of methods other than chemical for control of Western cotton insects including breeding cotton varieties resistant to or

tolerant of attack by insects and pathogens, and

(5) development of insect population and management programs.

ANNUAL CONFERENCE ON COTTON INSECT RESEARCH AND

CONTROL, 1947-74

Each year research and extension entomologists and associate technical v^orkers from 14

cotton-grov^ing States, the United States Department of Agriculture, the National Cotton

Council of America, and Cotton Incorporated

meet to reviev^ research and experiences of

the previous year and to formulate guiding

statements for control recommendations in the

subsequent year.

The advent of the organic insecticides for

cotton insect control in the mid-1940's was

responsible for the origin of the conference.

DDT was used experimentally in 1944 and 1945,

BHC, the BHC plus DDT mixture, and toxaphene in 1946. Others, such as aldrin, dieldrin,

endrin, heptachlor, and parathion, followed

shortly thereafter. These new insecticides were

such an improvement over those previously

available that their evaluation as quickly as

possible was imperative. Equally important was

that all concerned with cotton insect control

have the latest information on the performance

of the various insecticides available to them.

R. W. Harned, who was in charge of cotton

insect research for the Department from 1931

to 1953, is credited with being the '^father'' of

the conference. In the fall of 1946, he called a

conference of employees of his Division's laboratories at Tallullah, La. Appropriate agricultural experiment station and extension service

personnel of Louisiana and Texas were invited

to participate. That conference was a forerunner of the First Annual Conference on Cotton Insect Research and Control held in Stoneville. Miss., November 17-19, 1947. Others in

the Agricultural Research Administration

(ARA) who supported Professor Harned in

initiating the conference in addition to laboratory leaders F. F. Bondy, E. W. Dunnam, R. C.

Gaines, K. P. Ewing, and A. J. Chapman were

A. S. Hoyt, F. C. Bishopp, R. L. Haller, E. R.

McGovran, and M. P. Jones. Others from the

States supporting the conference were Dwight

Isely and Charles Lincoln, Arkansas; F S.

Arant and Jerry Ruffin, Alabama; C. E. Smith

and W. S. McGregor, Louisiana ; Clay Lyle and

L. C. Murphree, Mississippi ; Walter Kulash and

Jim Conner, North Carolina ; M. D. Farrar and

W. C. Nettles, South Carolina; H. G. Johnston

and C. A. King, Texas; and F. A. Fenton and

C. F. Stiles, Oklahoma.

ARS and its predecessor, ARA, have always

had the major responsibility for the management and coordination of the conference. R. W.

Harned served as general chairman for the first

six conferences, K. P. Ewing for the next four,

C. F. Rainwater for the next eight, and C. R.

Parencia for the next nine. The structure has

not been changed because it has worked well.

Also, it was essential that the revised conference report be made available at an early date

and ARS had the mechanism for its publication.

With the help of many people, the report has

been published by the end of February each

year after the January conference. The general

chairman serves as chairman of the program

committee that develops the program for each

conference and, also, has the responbility for

the annual revision, publication, and distribution of the conference report. The report is

generally considered to be the cotton insect

control bible of the world. It is distributed

throughout the world where cotton is grown.

As a result of the annual conferences, there

is no other agricultural area with as much compatibility among State, ARS, and industry personnel in the research, extension, and control

efforts for insects than those that attack cotton.

The Twenty-Seventh Annual Conference was

held in Dallas, Tex., on January 7-9, 1974.
RESEARCH ON COTTON INSECt'S 69

STATUS OF COTTON INSECT CONTROL

Much has been accomplished in the development of procedures for the control of cotton

insects, and growers are doing a better job of

controlling them than they have ever done before. However, much continues to need to be

done, especially since growers face resistance to

insecticides in more and more insects and more

and more restrictions are being placed on insecticides used to control various pests. These

restrictions may result in reduced development

and availability of new insecticides in the future. Thus, future procedures for controlling

insects will have to be even more sophisticated.

Research has progressed to the extent that

it is operationally and technologically feasible

to eradicate the boll weevil as an economic pest

of cotton from the United States with environmentally acceptable techniques. Various known

components need to be put together and tested

in a large field trial to determine whether the

pink bollworm, too, can be eradicated. Both

pests are host specific to cotton for all practical

considerations. Unfortunately, this is not true

with the other injurious pests.

Much progress has been made in developing

procedures for managing cotton insect populations. However, it would be much easier to

manage populations of the bollworm and tobacco budworm if the boll weevil were eradicated. Insecticides used for the boll weevil

destroy beneficial insects, which often in the

absence of insecticides keep bollworm populations below economic levels. As a result subsequent injurious infestations of bollworms occur,

necessitating treatment for these insects until

the crop matures even though boll weevil populations have been reduced below injurious levels. The mass release of predators or parasites

cannot be used for control of bollworms when

insecticides are applied for the control of another pest. Presently known procedures for

reducing boil weevil populations permit effective management of bollworm populations, but

this would be much easier to accomplish if the

boll weevil did not have to be considered.

In the Imperial and Coachella Valleys of

California, insecticidal control for the pink bollworm precludes management of bollworm populations. In areas of the Southwest where

cultural and other controls keep pink bollworm

populations at low levels, the pink bollworm is

not considered a key insect and thus does not

contribute to the disruption of management of

insect populations.

The cotton fleahopper in the Southwest,

Texas and Oklahoma, is a key insect. Unless a

way, such as a resistant variety, is developed

to eliminate the need for its control with insecticides, it will, just as was discussed for the

boll weevil, continue to interfere with management of bollworm populations. Lygus bugs have

similar status in the Far West, Arizona and

California.

The changing status of the bandedwing whitefly, the cotton leafperforator, and the beet

armyworm as pests of cotton must be considered. The bandedwing whitefly is becoming

a problem in areas other than in northeast

Louisiana. The cotton leafperforator, though

a pest commonly associated with the Far West,

is becoming more prevalent in certain areas in

Texas. The beet armyworm, also, considered

to be a pest of cotton in the Far West, has increased in importance in the Midsouth and

Southeast.

Though much progress has been made in

cotton insect control, improvements continue

to be needed, and judging from progress made

in the last two decades they will be developed

in the future.
70 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

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L. Bull, and W. E. Allison. 1960. A wheat

germ medium for rearing the pink bollworm. Journal of Economic Entomology

53:759-762.

(2) Agee, H. R. 1969. Mating behavior of

bollworm moths. Entomological Society

of America Annals 62: 1120-1122.

(3) 1972. Histology of the compound eye of Heliothis virescens (Lepidoptera: Noctuidae). Entomological Society of America Annals 65: 767-768.

(4) 1972. Sensory responses of the

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(5) Bariola, L. A., J. C. Keller, D. L. Turley,

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(7) Bishopp, F. C. 1911. An annotated bibliography of the Mexican cotton boll

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(9) and C. R. Jones. 1907. The cotton bollworm ; a summary of its life history and habits with some results of investigations in 1905 and 1906. United

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(10) Boheman, C. H. 1843. Genera et species

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(11) Byran, D. E., R. E. Fye, C. G. Jackson,

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blackburni Cameron for pink bollworm

control in Arizona. United States Department of Agriculture Production Research Report No. 150, 22 pp.

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suppression of pink bollworms in Arizona. United States Department of Agriculture, Agricultural Research Service,

ARS W-7, 8 pp.

(13) Bryan, D. E., C. G. Jackson, and Adair

Stoner. 1969. Rearing cotton insect parasites in the laboratory. United States

Department of Agriculture Production

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(14) Bullock, H. R., and H. T. Dulmage. 1969.

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of Economic Entomology 62: 994-995.

(15) Burton, R. L, 1969. Mass rearing the

corn earworm in the laboratory. United

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8 pp.

(16) Chapman, A. J., R. A. Bell, and C. M.

Ignoffo. 1967. Field tests with nuclear

polyhedrosis virus for control of Heliothis in the southern high plains of

Texas. Journal of Economic Entomology

60: 655-656.

(17) Goad, B. R. 1918. Recent experimental

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United States Department of Agriculture Bulletin 731, 15 p. 10 fig.

(18) Comstock, J. H. 1880. Report on cotton

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315 pp.

(19) Cook, 0. F. 1913. A wild host plant of

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GPO 924-374