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ONE HUNDRED TWENTY YEARS OF RESEARCH ON COTTON INSECTS IN THE UNITED STATES

.^>v UNITED STATES AGRICULTURE PREPARED BY %{àm} DEPARTMENT OF HANDBOOK AGRICULTURAL '' AGRICULTURE 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 agri- cultural 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.

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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 Agri- culture 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 Since the boll weevil entered Texas about 1892, insects did not begin in 1892 with the intro- it has been the most important pest of cotton, duction of the boll weevil, Anthonomus grandis receiving most of the attention focused on in- Boheman. The early colonists cultivated cotton sects attacking cotton. and had problems with cotton insects. T. Glover, Some results of boll weevil investigations, the first Government entomologist under the also, have been helpful in the development of Commissioner of Patents, mentions cotton in- control measures for other insects. Of particular sects in his first and second reports for 1854 importance have been the development of cal- and 1855. cium arsenate and organic insecticides, the im- Pursuant to an Act of Congress, Professor provements in ground application equipment, C. V. Riley, appointed entomologist of the De- and the development of applying calcium arse- partment of Agriculture in 1878, started a nate in a dust formulation and later other in- special investigation of cotton insects. Professor secticides in dust, as well as in spray formula- J. H. Comstock continued this investigation tions, by aircraft. and in 1879 published a large, practical volume With the advent of the organic insecticides on the cotton leafworm, Alabama argillacea in the mid-1940's, tremendous improvements (Hübner), and the bollworm, Heliothis zea were made in the control of all cotton insects. (Boddie), entitled **Report on Cotton Insects." However, as the boll weevil built up resistance The investigations on cotton insects were to the organochlorine insecticides in the mid- transferred to the U.S. Entomological Commis- 1950's and other species developed resistance sion under the Department of the Interior and to various insecticides, the need for alternate assigned to C. V. Riley. In 1885, Riley pub- methods of control became apparent. Budget lished another large volume on the cotton leaf- constraints, however, permitted research only worm and bollworm as the "Fourth Report of on solving immediate problems. As more money the U.S. Entomological Commission." Both became available for research, basic research Comstock's and Riley's reports had large edi- and development of alternatives to conventional tions and contained much useful information insecticides for control of insect pests that on the occurrence of outbreaks, methods of con- attack cotton were emphasized. trol, and spraying machines. In the 1960's research was expedited on the These two insects continued to be important boll weevil, resulting in a Pilot Boll Weevil pests of cotton until the boll weevil reached the Eradication Experiment in South Mississippi United States. Many references to the cotton and in adjoining areas of Louisiana and Ala- leafworm and other insects affecting cotton are bama, which began in July 1971 and terminated found in the early entomological publications. in August 1973. Results indicated that eliminat- ing the boll weevil from the continental United States was technologically and operationally ^ Bioenvironmental Insect Control Laboratory, U.S. Delta States Agricultural Research Center, Stoneville, feasible, and plans were submitted to the Sec- Miss. 38776. retary of Agriculture on December 12, 1973. AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Though much progress has been made, new thors of Federal and State agencies^ are sum- problems are continually arising and the need marized here, including some unpublished ob- for more effective and economical control of servations. most cotton insects continues. The author is indebted for much of the early This handbook consists of a brief discussion information to an unpublished manuscript, en- of progress made in research on the various titled ''Report on the Accomplishments of the cotton insects. The first section covers the period Work on Cotton Insects Investigations of the 1854 to 1940 and lists cotton insects and re- Bureau of Entomology and Plant Quarantine search achievements about each of them. The and Preceding Organizations of the United last section lists areas of research about all States Department of Agriculture from 1954 insects attacking cotton from 1941 to 1974. The to 1938.'' This manuscript v^as found in the outstanding research findings reported by au- Waco, Tex., Cotton Insects Laboratory files.

RESEARCH 1854 TO 1940

Boll Weevil noncotton zone to prevent further spread. The Department reported the seriousness of the pest The boll v^eevil {Anthonomus grandis Bo- to the Governor of Texas and urged immediate heman) v^as described by Boheman in 1843 legislation to permit quarantine and remedial from specimens received from Vera Cruz, Mex- work. These recommendations were not ico, and was recorded by Suffrian in 1871 as adopted, and in 1895 the boll weevil had spread occurring in Cuba. Its food plant was not as far north as San Antonio and as far east as known, and the first association of this species Wharton, Tex. with cotton was a note by C. V. Riley in 1885 The Division of Entomology continued its stating that the boll weevil had been reared investigations, and in 1896 and 1897 L. 0. from cotton bolls sent to the Department by Howard published the results. These publica- Dr. Edward Palmer from near Monclova, Mex- tions and many earlier ones on the boll weevil ico, where it was causing serious damage. In were published in English, Spanish, and Ger- the mid-1960's archeologists working in Oaxaca, man for the benefit of the large foreign popula- 150 miles south of Mexico City, found cotton tion of Texas. Townsend was stationed in Mex- bolls on the floor of a cave once inhabited by ico in 1897 to study the parasites and diseases Zapotee Indians. An adult boll weevil was dis- of the boll weevil, but he found none that ap- covered in a lock of one boll. The carbon-14 peared promising to control the insect. dating process established beyond doubt that The boll weevil was a newly introduced pest the weevil was alive about 900 A.D. making it at least 1,000 years old. causing almost total loss of the crops in the infested areas and rapidly spreading to new The first report of the occurrence of the boll territory. Therefore, to meet the demand for weevil in the United States was received in the immediate information, the Department issued Department of Agriculture in the fall of 1894 frequent publications on this subject matter. from Brownsville, Tex. The Division of Ento- L. 0. Howard in 1896 first suggested the im- mology immediately dispatched C. H. T. Town- portance of early planting and clean cultivation send to Texas. He found several counties in- as control measures. These recommendations fested with the boll weevil causing serious were based on his knowledge of the habits and damage to cotton since 1892. His report, pub- life history of the weevil. Marlatt and Town- lished in March 1895, dealt with the area in- send in 1896 experimented in poisoning the boll fested and the life history and habits of the weevil by spraying with paris green and sweet- boll weevil that were previously unknown. He ened poisons. Howard reported these results in concluded his report with recommendations for the destruction of cotton stalks to kill the over- wintering weevils and the establishment of a - See References, p. 70. RESEARCH ON COTTON INSECTS

1898. Because results indicated that the weevil and humidity result in faster development, while could not be controlled by poisons then available, low temperatures slow it down. As many as special emphasis in most of the early work was seven generations may develop in a year in the placed on other methods of control and on the extreme southern part of the Cotton Belt. The economic phases of the problem. adult boll weevil is one-eighth to one-third inch The year 1898 was important in the history long. It ranges in color from tan to dark gray, of the boll weevil in several ways. The season or sometimes to dark brown. was favorable for the development of the boll Starting in the spring, the female lays eggs weevil and it spread rapidly, causing serious singly in cotton squares (flower buds). When damage over a large area. the boll weevil population is high and a short- The first of a long series of boll weevil con- age of squares exists, two or more eggs may be ventions attended by many cottongrowers, laid in one square. Late in the season, eggs are merchants, and bankers was held on October 12, laid both in squares and in young bolls. 1898, in Victoria, Tex. The Legislature of Texas Eggs hatch in 3 to 5 days. The larvae feed appointed a State entomologist to investigate 7 to 12 days inside the squares or bolls. The means of controlling the pest. At the end of the pupal stage lasts 3 to 5 days. Adults cut their 1898 season, the Division of Entomology dis- way out of the squares or bolls. After feeding continued its work in Texas. 3 to 7 days and mating, females begin laying The boll weevil continued to spread, however. eggs. This cycle is repeated until the cotton In 1901 when it became evident that other plants are killed by cold weather (fig. 1). States were threatened, Congress appropriated Adult boll weevils hibernate in surface woods money for the first boll weevil investigations trash and along ditchbanks near cottonfields to discover means of preventing its spread. and in trash and litter around gins and farm From 1901 until his death in 1925, W. D. Hunter buildings. In the spring they return to the was in charge of this work. In addition to other cottonfields. work. Hunter inaugurated cooperative work on Jaws at the end of an adult weevil's snout eight farms in 1901 to demonstrate the cultural enable it to eat into a square or boll. Both males methods controlling the weevil that had been and females make feeding punctures. Females recommended by the Division of Entomology. make egg punctures, which are deeper than These farm demonstrations of boll weevil con- feeding punctures, in which they lay eggs. trol developed into the Farmers' Cooperative Both kinds of punctures cause damage. After Demonstration Work of the Bureau of Plant a square is egg punctured, the bracts around it Industry and, later, into the present Extension flare, the square turns yellow, and after a few Service of the Department. days, usually drops to the ground. The work was expanded in 1902, and a lab- Many punctured small bolls drop to the oratory was established at Victoria, Tex., to ground, but punctured large ones usually remain obtain much needed information on the life on the plants. If the large bolls have egg punc- history, habits, and hibernation of the boll tures, however, they will be damaged by the weevil. So much attention was devoted to the weevils developing in the locks where the eggs immediate economic phases of the problem that were laid. Weevil-infested locks produce little, detailed studies of the insect had not been possi- if any, cotton, and the quality of that produced ble up to that time. The results of the first 2 is inferior. years' work were published by Hunter and Early research,—Congress in 1904, after be- Hinds in 1904, and Howard in his letter of coming aware of the great damage inflicted by transmittal stated it was the most complete the boll weevil, appropriated $250,000 to enable treatise on the life history of a single insect the Secretary of Agriculture to meet the boll species published. weevil emergency. Of this amount, $100,000 Development,—The boll weevil has four was allotted to the then Bureau of Entomology stages in its life cycle—egg, larva, pupa, and and the rest to the then Bureau of Plant Indus- adult. Under favorable conditions, it completes try. Much of the money was used to expand the the cycle in 21/2 to 3 weeks. High temperatures demonstration work in newly infested areas. AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

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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 methods developed for reducing boll weevil scale, and experimenting with insecticides. The damage were the early maturity of the crop weevil had spread to Louisiana in the previous before the weevils become abundant by selecting year, and a special session of the Louisiana an early maturing variety, planting early, fer- Legislature, called in 1904, established the Crop tilizing and cultivating properly, and destroying Pest Commission of Louisiana. This commission stalks as early as possible in the fall. Early made many contributions toward controlling destruction of stalks in the fall prevented the the pest. large, late season increase in weevil populations, Early in 1905 the boll weevil laboratory was thus reducing the numbers that entered hiber- moved from Victoria to Dallas, Tex. Many nation sites and survived the winter. farmers' bulletins, circulars, and articles for Other investigations were also started. Stud- farm papers containing information of practical ies were made on the abundance and distribu- value to farmers were published in 1904 and tion of some 50 species of native parasites and 1905 and distributed in large numbers. A com- predators of the boll weevil, but efforts to prehensive publication by Hunter and Hinds in increase their usefulness were unsuccessful. 1906 brought together the more fundamental Estimates from many sources of the damage information that had been accumulated on life caused by the boll weevil during this period history, dissemination, and natural and artifi- varied greatly. The most reliable estimates cial control of the boll weevil. placed the losses in newly infested areas at The State of Texas offered a reward of about 50 percent of the crop, but after a few $50,000 for an effective control for the boll years growers were able to reduce this consid- weevil, and numerous remedies and devices erably by adopting the recommended cultural were proposed. The Bureau of Entomology test- control practices. About one-third of the acre- ed all remedies that were submitted and re- age planted to cotton in Texas was then infested, ported the results to the originator. Although and the loss to the 1904 crop was conservatively these tests required a great deal of time, they estimated by the cotton industry at $22 million. were of immense aid to farmers in reducing The boll weevil crossed the Mississippi River the amount of money spent for ineffective con- into Mississippi in 1907. All cotton-growing coctions and devices, as not a single new method States had previously enacted quarantines of any value resulted. against the introduction of infested material, Extensive tests with paris green showed that and the spread was almost entirely by natural some weevils could be killed, but under field dispersal. Only a few isolated infestations be- conditions the benefits were too slight to recom- came established at any distance ahead of the mend its use. A satisfactory method of fumi- general line of advance, with most of these gating cottonseed by vaporizing carbon bisul- being eradicated. It was then generally accepted phide was developed so that seed could be moved that the boll weevil would continue to spread from infested territory. Numerous machines over the Cotton Belt, and growers became con- and traps for controlling the weevils were cerned as the weevil entered the large planta- tested, also. Government entomologists studied tions in the Mississippi Delta. the relation of temperature and climate to The spread of the boll weevil year by year damage, dissemination, and areas where the was of paramount interest to the people in the weevil would become a pest. Results of biologi- line of advance. The most severe damage was cal studies indicated that the boll weevil could usually caused during the first few years before infest most of the Cotton Belt. the infestation became stabilized and growers With the apparent ineffectiveness of insecti- learned the best methods of growing cotton in cida! and other direct methods of control, em- the presence of weevils. One great service of phasis was placed by the Bureau of Entomology the Bureau of Entomology was in determining on ^'cultural methods," which included various the limits of infestation each season. Maps and modifications of the cropping system that articles giving this information were widely studies of the pest indicated might be useful in distributed each fall that greatly assisted farm- avoiding damage. The most important cultural ers, businessmen. State authorities, ginners, AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE and many others in planning for the next sea- because the boll weevil was found able to survive son. This service was rendered from the be- the winter above the caprock. By 1922 the boll ginning of the investigations in 1904 in south weevil had spread over North Carolina and into Texas until the weevils reached Virginia in Virginia, thus covering over 600,000 square 1922. miles of territory since its entry into the United The advance varied from 40 to 160 miles a States 30 years previously (fig. 2). About 85 year, although in several instances adverse percent of the cotton in the United States was winter conditions caused a reduction in the produced in the infested territory, and the rapid infested areas. Spread was more rapid to the expansion of cotton production to the West was north and northeast during the early years, partly due to the absence of the boll weevil in and then faster to the east as unfavorable that area. climatic conditions were reached in western Texas and Oklahoma. The semiarid areas with As the boll weevil continued to spread to new high summer and low winter temperatures are areas, it became more and more apparent that unfavorable for weevil development and survi- the ''boll weevil problem" was a series of prob- val, and infestation have never become estab- lems and that investigations should be con- lished in the High Plains of Texas, New Mexico, ducted under different climatic, ecological, and Arizona, and California. A suppression program agricultural conditions. Consequently, in 1909 to prevent the establishment of infestations on the laboratory moved from Dallas, Tex., to the High Plains has been underway, however, 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 although the breeding season at Tallulah was the southern edge of the Delta section where more than a month shorter. the boll weevil was expected to cause as much The discovery of the Thurberia weevil. An- damage as anywhere in the South. The soils thonomus grandis var. thurberia Pierce, a close were fertile and with the abundant rainfall relative of the boll weevil, in the ''wild cotton'' plants normally continued to produce cotton of Arizona led to further studies on the host until late in the season. Large areas of dense plants of the boll weevil. In experiments con- forests afforded good hibernation quarters, and ducted at Victoria, the boll weevil developed in with comparatively mild winters heavy infesta- Hibiscus syriacus, a common ornamental shrub, tions were the general rule. and fed and partially developed on two other The policy of investigating the boll weevil species of native Malvaceous plants under cage ''on the spot'' was followed throughout the work conditions. This was the first record of rearing and additional laboratories were established by the boll weevil on plants other than cotton. the Bureau of Entomology in Mississippi, A method of control consisting of collection Florida, South Carolina, Oklahoma, and of weevils and infested squares was thoroughly. Georgia. As the weevil spread to new areas, tested in the Mississippi Delta in 1915 and 1916. work also moved to these areas. Information on Considerable reduction in damage and fair in- creases in yield resulted from this practice, but habits, damage, and control measures best it was impractical because of the great amount adapted to different local conditions fully justi- of labor and expense involved. fied this procedure. The State agricultural ex- Research with insecticides.—Although the periment stations, particularly Texas, Okla- Bureau of Entomology had been concentrating homa, Alabama, Arkansas, Florida, and South its efforts on cultural control based on bio- Carolina, did a great deal of work on the boll logical data, research had also started on use of weevil, but the Tallulah laboratory was the insecticides as a control measure. In addition leader in these investigations. to the Bureau's work, the Louisiana Crop Pest The many phases of the boll weevil investi- Commission began conducting tests with paris gations and the interest in this insect are green in 1905. A certain amount of control was indicated by bibliographies compiled by Bishopp obtained, but paris green seemed to have some in 1911 (7), Dunn in 1964 {25), and Mitlin in adverse physiological effect on the plants and 1968 (7^), all of which contain titles or ab- increases in yield were not commensurate with stracts of important papers by both Federal the reduction in weevil infestation. Arsenate of and State entomologists. lead was coming into general use as a substitute Research for the first few years at the Tal- for paris green for use on fruit trees, but this lulah laboratory continued somewhat along the insecticide was then made only as a paste and same lines as the previous work in Texas. could be used only as a spray. Since spraying Whether the cultural methods that had given was considered impractical for cotton, Wilmon good results in Texas would be effective under Newell conceived the idea of making lead the ecological and farming conditions of the arsenate as a powder that could be dusted on cotton for boll weevil control. Delta had to be determined. Every phase of the The first powdered lead arsenate was pre- control methods then in use was based on bio- pared for Newell by the Grasselli Chemical logical facts, and life history studies had a Company in 1908 and was used in cage tests direct economic bearing on the boll weevil prob- against the weevil in that season. Field tests lem. Consequently, biological studies were made conducted in 1908 and 1909 showed consider- at Tallulah from 1910 to 1915. In 1913 another able increases in yield and profits from dusting series of biological studies, also, were made at with lead arsenate under some conditions. Em- Victoria, Tex., to check those made 10 years phasis was placed on the value of dusting early previously. Because of the shorter develop- in the season and forcing the dust inside the mental periods, the same number of generations bracts of the squares and into the terminal (7) were produced at Tallulah as at Victoria, 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 ing from 250 to 1,000 pounds of seed cotton tissues. Dusting was recommended as a useful per acre. A large-scale field test in Arkansas in supplementary measure to cultural methods. a heavily infested field of late cotton demon- The results were the most successful that had strated for the first time the value of a late been obtained to that date with insecticides, application of poison for protecting the bolls arousing considerable public interest as well from weevil damage. as stimulating renewed interest in insecticides Who first made calcium arsenate is not by the Bureau of Entomology. Results from known. Apparently, the first records of its use subsequent tests of dusting with lead arsenate as an insecticide were in 1907 by John B. Smith were erratic, and the method was neither of New Jersey and by Bedford and Pickering recommended nor used extensively by growers. of England, who tested it as a substitute for In 1916, however, tests with tri-plumbic arse- lead arsenate during the same year. Pickering nate of lead dust resulted in good gains in stated, however, that calcium arsenate had al- yield when applied late into the season. ready been used in the United States, and In 1916, the new insecticide, calcium arse- Smith reported that combinations of arsenic nate, was first compared in field tests against and lime were well known and easily prepared the boll weevil with di-plumbic arsenate of by farmers. Bedford and Pickering used a lead. Calcium arsenate in a dust formulation homemade product and gave the proportions was being made by a few manufacturers but of an arsenate and a calcium salt, with the was a comparatively unknown insecticide. Its recommendation that an excess of lime be used physical properties were poor, having a density to prevent an excess of soluble arsenic in the of about 40 cubic inches per pound, and when calicum arsenate. Smith used a calcium arse- applied it did not form a good dust cloud for nate sent him by Dr. Fred P. Dewey, a chemist plant coverage. Excessive quantities of water- of Washington, D.C., thought to have been con- soluble arsenic often made it phytotoxic. Con- nected with the U.S. Mint. siderable experimenting was done at Tallulah The next reports of calcium arsenate as an in cooperation with manufacturers to improve insecticide were by Scott and Siegler, of the its physical and chemical properties. Dusts, Division of Deciduous Fruit Insect Investiga- ranging in density from 80 to 160 cubic inches tions of the Bureau, who used it in laboratory per pound, were prepared. Those with densi- tests in comparison with many other arsenicals ties from 80 to 100 cubic inches per pound gave against the fall webworm, Hyphantria cunea better coverage and were better suited for cot- (Drury), and in orchard tests against the cod- ton. Some increases in yields were obtained ling moth, Laspeyresia pomonella (Linnaeus), from most of the treated plots in 1916, but the in 1912 at Benton Harbor, Mich. The calcium most striking results were obtained in a plot arsenate used in 1912 was a ''chemically pure" in a field of heavily weevil-infested cotton that powder, applied as a spray (0.5 pound to 50 was treated with calcium arsenate in August. gallons of water). Against the fall webworm The weevils were effectively controlled, and a the results were about equal to that obtained fair crop produced on cotton the owner had with lead arsenate, and against the codling abandoned as an absolute loss. The late season moth the results were somewhat below that poison applications resulted in good gains in obtained with lead arsenate. yield, whereas gains from the early season In 1913 further tests were made by Scott applications were slight. and Siegler with two homemade formulations Results of studies at Tallulah in 1917 to of calcium arsenate prepared in the laboratory obtain information on the efficacy of different from sodium arsenate and calcium acetate, and poisons, the time of day of applications, the a commercially prepared calcium arsenate paste. proper intervals between applications, and The commercial calcium arsenate paste was as other phases were inconclusive because of the effective as the lead arsenate paste against the light weevil infestation, but tests with calcium tent caterpillar (Malacosoma spp.). arsenate conducted in Mississippi and Arkan- An interesting account of the first commer- sas again gave good control, with gains rang- cial manufacture of calcium arsenate for insec- RESEARCH ON COTTON INSECTS ticidal use was furnished by E. H. Siegler. vision of Bureau personnel. As a result of the While the tests at Benton Harbor were in success of this work, over 3 million pounds of progress, Scott's brother, W. M. Scott, of the calcium arsenate were used for weevil control Thompson Chemical Company, Baltimore, Md., in 1919 and about 10 million pounds in 1920. became interested in the new insecticide. He The increase in the use of calcium arsenate for made a calcium arsenate paste to test as an control of the boll weevil was phenomenal, insecticide in 1913. In 1914, the Thompson probably the most rapid of any insect control Chemical Company also furnished a commercial measure ever developed up to that time. Em- calcium arsenate powder, which was as effective phasis in lines of work changed almost entirely as lead arsenate against the fall webworm in from cultural control to direct control by insec- laboratory tests at Benton Harbor. The pow- ticides and development of dusting machines. dered calcium arsenate was also furnished to Two new industries—the manufacture of cal- several investigators for use against the codling cium arsenate and of dusting machinery—were moth, and over 2,000 pounds were used against expanding simultaneously. Over 30 companies shade tree insects in 1914. were making calcium arsenate in 1920, and Although calcium arsenate was first used in many models of dusting machines were avail- experiments against fruit insects, it was still able. a comparatively unknown insecticide when With such rapid expansion in use, much of tested against the boll weevil. It gave better the calcium arsenate and machinery placed on control than the other arsenicals then in use. the market were not suitable. The physical The improvements in the physical and chemical quality of some early calcium arsenate was properties of calcium arsenate and the rapid poor and contained so much water-soluble ar- expansion in its use were due almost entirely senic that it was phytotoxic, or so little total to the work of the Bureau of Entolomogy on arsenic that it was not sufficiently toxic to kill the boll weevil. the weevils. The Tallulah laboratory tested all The results of the tests with calcium arsenate samples for growers or others, and in 1920 dust against the boll weevil in 1916 and 1917 had tested over 2,000 lots. It also tested new were so successful and aroused so much interest models of dusting machines and suggested and demand for information that USDA Bulle- improvements to the manufacturers before they tin 731, ''Recent Experimental Work on Poi- were placed on the market. soning Cotton Boll Weevils,'' was issued in July These services saved the growers much 1918, although it was felt that further details money that would have been expended for un- should be worked out before recommendations suitable insecticides and dusting machines. In were made to the public. addition, an educational campaign was urgently The machines then in use for applying dust needed to advise growers, county agents, and formulations were as crude as the insecticides. others on the use of the new methods of control. From the beginning of the dusting experiments Consequently, in 1921 most of the personnel at it was evident that improvements in machinery Tallulah were stationed at representative sec- were necessary before application of dust for- tions of several States to demonstrate dusting mulations of insecticides to cotton on a large with calcium arsenate and to obtain additional scale would be feasible. In 1916 Elmer Johnson, information on its use under different condi- an engineer with the Bureau of Public Roads, tions. Arrangements were made through the was detailed to the Bureau to improve and States Relations Service whereby the men develop dusting machines adapted to cotton. worked with the county agents and issued He was invaluable in improving the design and timely advice on local insect conditions and developing machines suitable for various dusting schedules. acreages and types of farms. These improve- Work on refinements in methods of applying ments were covered by Public Patents and were dust formulations to cotton were delayed as available for use by all manufacturers. every possible effort was made to help farmers In 1918 several thousand acres of cotton were in controlling the boll weevil. During this pe- dusted with calcium arsenate under the super- riod 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 vorably with that of ground equipment and its manufacture occurred. The Bureau of En- was much more convenient for the growers. At tomology surveyed available supplies and pro- least 1,000 acres to be treated in a community spective insect conditions to aid in the proper were needed for economical operation of air- distribution of calcium arsenate and dusting planes, and the dust companies contracted for machines to meet critical needs. This action led treating fields within a radius of several miles to the annual installation of a large series of of a landing field. This method of insect control hibernation cages in different States to study for cotton was used extensively in Texas, the emergence and abundance of weevils in Arkansas, Louisiana, Mississippi, and in other the new cotton-growing season. Such informa- States for truck crops and orchards. Expansion tion was valuable to manufacturers in planning in the use of airplanes was rapid, and many to meet the demand for calcium arsenate and commercial companies maintained fleets of air- dusting machines and to the farmers in sta- planes equipped for crop treating with as many bilizing prices and preventing scarcity of as 100 planes ready for instant call. Treating materials. with airplanes was spectacular, but at the The next important step in boll weevil con- same time entirely practical, economical, effec- trol occurred when the method of applying dust tive, and the most convenient method ever de- formulations of insecticides with airplanes vised for treating large acreages of cotton or was developed. The possibility of using air- other crops (fig. 3). In December 1931, the planes for this purpose was suggested by the Bureau of Entomology discontinued its work work of the Ohio Experiment Station in dis- and disposed of its airplanes after such method tributing lead arsenate for the catalpa sphinx of treatment was established commercially as Ceratomia catalpae (Boisduval) in 1921. The a result of the research done by the Division first tests for control of cotton insects were of Entomology. against the cotton leafworm in 1922, through Following the first successful demonstrations the cooperation of the Air Service of the with calcium arsenate for boll weevil control, United States Army that furnished planes and experiments on insecticidal control by the vari- personnel. ous State agencies renewed. Information on In the first flights, calcium arsenate was treatment schedules best adapted to each local- dropped by hand from the planes, but it was ity and on the profits that could be expected at soon evident that methods had to be developed different points was in great demand. Many to distribute the poison evenly at a controlled new remedies appeared on the market as a rate. After several years' work in cooperation result of this renewed interest. A large part with engineers of the Bureau of Agricultural of the Bureau of Entomology's work during the Engineering, U.S. Department of Agriculture, next several years consisted of demonstrations hoppers were developed that would evenly dis- in many areas to bring the results to growers tribute dust over a swath 150 to 200 feet wide, and State officials by seeing that control meth- and aerial applications were equally as effective ods were properly used and testing many as those applied by ground equipment for boll proprietary remedies that appeared on the weevil control. market. Treatment with airplane was much faster There was such a lack of uniformity in the than with ground equipment, as one airplane methods of experimentation and recommenda- could treat from 750 to 1,000 acres per day. tions by the various agencies that the Asso- This treatment was especially important when ciation of Southern Agricultural Workers the fields were too wet for use of ground equip- (ASAW) appointed a Cotton Council in 1922 ment or when large acreages had to be treated to review the boll weevil situation thoroughly quickly. Commercial airplane companies, under and to standardize the control recommenda- contract, did most of the aerial dusting. Grow- tions. The Council adopted the following resolu- ers did not need to purchase planes or other tions in 1924, which were slightly modified in dusting equipment. These costs compared fa- 1926: RESEARCH ON COTTON INSECTS 11

PN-4419 Figure 3.—Applying insecticides as dusts with aircraft.

For the bell weevil, one presquare poisoning may The boll weevil had spread over most of be applied if it appears there are numerous over- South Carolina by 1920 and, as usual in newly wintered weevils present. This should be given just infested territory, was causing serious damage. as squares begin to form. Then apply the regular The South Carolina Legislature made a special series of three or more dust applications of calcium arsenate at 4- or 5-day intervals, beginning when appropriation to conduct control investigations an average of approximately one-tenth of the in cooperation with the Bureau of Entomology. squares show weevil punctures. Dusting should be This was an excellent opportunity for the Bu- continued as needed to keep this infestation low reau of Entomology to obtain additional infor- until a full crop is set and matured beyond the mation on the weevil under the conditions in probability of further weevil injury (Proceedings, the Southeastern States, since most of the pre- ASAW, 1926). vious work had been done west of the Missis- sippi River. In 1922 a laboratory was estab- This action by the ASAW did much good in lished in Florence, S.C., which has operated gaining the cooperation and coordination of continuously. In the first few years of opera- the work of all agencies engaged in boll weevil tion, the work in the laboratory consisted control. largely of tests to determine the gains and 12 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE profits that could be obtained under local con- percentage of water-soluble arsenic by the Ge- ditions. neva method were more toxic to weevils in cage In 1925 a thorough study of the biology of tests than those medium or low in water-soluble the boll weevil in South Carolina began with arsenic but were no better than those medium the results published in 1929. Only four gener- or low in water-soluble arsenic in field tests. ations a year developed at Florence compared The three forms found in the commercial prod- with seven at Tallulah. Studies on dispersal ucts—mono-, di-, and tri-calcium arsenate— showed that the temperature and intensity of were separated and tested separately. Samples infestation were the principal factors causing were fractionated into different sizes of parti- the migration or flight of weevils from field to cles. The indicated results of the tests were that field and to new areas. After 1928 the attention if the most desirable physical and chemical of the Florence personnel was devoted largely properties could be determined they could be to such phases of control as the value of the incorporated into commercial practice by modi- mopping technique of reducing the amount of fying the manufacturing processes without in- calcium arsenate needed for control and the creasing the cost of production. effect of calcium arsenate used for boll weevil Parasites.—Parasites of the boll weevil were control on aphids and on the soil. Root aphids studied again from 1932 to 1935 to determine and other insects affecting cotton, also, were the change in native parasites during the 20 studied. years since the previous studies. About 20 From 1926 to 1940 several laboratories con- species of parasites were found, 3 of which ducted research on improving and refining were new. Findings from these studies indi- methods of boll weevil control to increase the cated little increase in the control of the boll efficiency of control and reduce the cost. Tests weevil by parasites since the previous investi- of applying insecticide dust formulations at gations. An average of 5.5 percent of the weevil various time intervals, at different times of the larvae collected in several States were para- day, and in reduced quantities were conducted. sitized, and there was little hope of increasing Special attention was given to developing com- the native parasites so that they would give binations of insecticides that would control some greater control. other insects that occurred simultaneously with Effects of calcmm arsenate on aphids, soils, the boll weevil. A mixture of calcium arsenate and crops following its use for boll weevil con- and sulphur was found to control combination trol.—The use of calcium arsenate dust at first infestations of the boll weevil and certain other appeared to have solved the problem of con- insects such as the cotton fleahopper Pseuda- trolling the boll weevil. However, soon after it tomoscelis seriatus (Reuter) and other mirids. came into extensive use, a conspicuous and Each year a large series of cage toxicity often injurious increase in infestations of the tests were conducted to compare other insecti- cotton aphid Aphis gossypii (Glover) occurred cides with calcium arsenate for effectiveness following its use on cotton. This was noted in against the boll weevil. The promising materi- 1920 in Texas and about the same time in als from these tests were then tested under field South Carolina and in other States. In some conditions. Many arsenical, rotenone, nicotine, instances where large amounts of calcium ar- fluorine, and other insecticides were tested, but senate were applied, the aphids increased to none were as effective and economical as cal- the extent that the gains from weevil control cium arsenate. Results of studies showed cal- were offset by the damage caused by them. cium arsenate was a complex material with Investigations conducted from 1922 to 1929 to varying physical and chemical qualities. This determine the reasons for the increase in aphids finding explains why some commercial calcium indicated that several factors were probably arsenates were more effective than others responsible for this complex problem. The against the boll weevil although they all met initial increase in aphid infestation was the required specifications. thought to be due to the attraction of the Commercial calcium arsenates with a high winged females to the white deposit of calcium RESEARCH ON COTTON INSECTS 13 arsenate or other white dusts on the plants. The rather tolerant to arsenic, and some growth aphid population then increased because the was even stimulated where considerable quan- hymenopterous parasites were killed when they tities had been applied. Injury from arsenic in emerged in the presence of the arsenical. Later South Carolina seemed to be correlated with tests with calcium arsenate colored with aniline soil deficiencies of iron and magnesium, and no dyes did not prevent the buildup of aphids. The injury was reported on dark or reddish soils. aphid problem on cotton became more serious, Also, all the reported injury in South Carolina especially in the Southeastern States. Rotenone were where larger quantities of calcium arse- dusts were not very effective against the cotton nate than recommended were used for boll aphid and control with nicotine sulphate, the weevil control, although there was no proof that most effective aphicide, was expensive and the recommended quantities might not also somewhat erratic unless weather conditions cause damage in the future. were ideal. In experiments to determine the types of Research on varietal resistance or tolerance soils that would be affected and methods of of cotton to aphids started in 1934 with the overcoming the injury, 500 pounds of calcium establishment of a Cotton Insects Research arsenate per acre were applied to the soil at Laboratory at Stoneville, Miss. The Bureau of Tallulah, La., for 4 successive years, or a total Plant Industry maintained a large collection of of 2,000 pounds, without decreasing the yield exotic and domestic species, varieties, and of cotton. However, after this quantity was crosses of cotton here. An endeavor to find applied there was some deleterious effect on strains of cotton or individual plants that were the germination and growth of vetch planted immune or resistant to aphid buildup showed as a winter cover crop. Of the principal soil that varieties with more pilose leaves retain types in Mississippi, 7 were treated with cal- the calcium arsenate for a greater time and cium arsenate at rates from 50 to 1,600 pounds that the aphids increased more rapidly than per acre and planted to cotton, corn, and soy- on the smoother leafed cottons. beans in the spring, and to vetch, Austrian The amount of damage actually caused was peas, and oats in the fall as winter cover crops* difficult to determine. Most farmers considered The germination and yields of some crops were the benefits from boll weevil control more im- reduced somewhat on the light sandy soils when portant than the aphid damage following use 100 pounds of calcium arsenate were applied of calcium arsenate. There were some, however, per acre, and when 200 pounds or^more were who were reluctant to use calcium arsenate applied per acre on some of the heavier soils. because of this factor. Analysis of the soils showed that large quan- About the same time that the effect of cal- tities of water-soluble arsenic were lost by cium arsenate on the increase in aphids was leaching or fixation in one year. Not more than observed, a few cases were reported on the 30 pounds of calicum arsenate per acre per reduction in yield of cotton and other crops year were estimated as needed to control the following its use on the light sandy soils of ordinary infestations of the boll weevil. With South Carolina. Later, similar reports were the rapid reduction in arsenic in the soils, there received regarding arsenical injury to soils on was little danger of soil injury to any of the the ricelands of Louisiana. The injury from soil types tested in Mississippi. No corrective arsenic in South Carolina was manifested by measures were found for arsenic injury to the poor stands of cotton and, more particularly, soil, but the damage naturally disappeared by by the adverse effect on the germination and fixation or leaching of the arsenic in a few growth of oats and legumes. Workers from the years. Louisiana Experiment Station found that cot- Progress was also made in avoiding soil in- ton treated with calcium arsenate was not af- jury by decreasing the amount of calcium arse- fected, but rice following treated cotton was nate dust used for boll weevil control by rather seriously injured. Other crops such as diluting it with sulphur, lime, or other inert rye, corn, sweet potatoes, and tobacco were materials. Injury was likely to occur only on 14 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

certain soil types found in comparatively small cause it was more generally used and recom- areas of the Cotton Belt, and while danger of mended by the South Carolina Extension Serv- soil injury was recognized as being serious ice. In tests at Florence, S.C., over an 9-year under certain conditions, the danger seemed period (1928-36), the average gain from to be overemphasized. mopping alone was 41.5 pounds of seed cotton The two disadvantages in the use of calcium per acre ; from mopping followed by later dust- arsenate were factors in preventing its wide ing with calcium arsenate, 294.3 pounds per acceptance for boll weevil control. acre; and from dusting with calcium arsenate Sweetened poison.—Besides dusting with after 10 percent of the squares were infested, calcium arsenate, the only other material gen- 270 pounds per acre. In tests in other States, erally used for weevil control was a mixture the results were similar to those in South of calcium arsenate, molasses or syrup, and Carolina. On the basis of these results, the water—"sweetened poison^' or ''mopping'' as it Bureau of Entomology did not recommend was usually called because the mixture was sweetened poison alone as a satisfactory control applied to the tops of the plants with a mop. but did recommend presquare mopping to be The advantage of the mopping method was that followed by later dustings with calcium arsenate the overwintered female weevils feeding in the in the South Atlantic States. Later demonstra- terminal buds of the plants before the squares tions showed that effective control of over- were present could be killed by ingesting the wintered boll weevils could not be obtained in poisoned mixture before they oviposited. small-plot experiments, which no doubt influ- Sweetened arsenicals were tested in the early enced the poor results obtained. investigations at Victoria, Tex., but were neither Hibernation and survival.—Hibernation was found to attract the weevils nor to give satis- considered to be the most critical period in the factory control and were not recommended. life history of the boll weevil and was studied After the weevil reached South Carolina, the under a great variety of conditions. In the ex- use of sweetened poison was revived and was treme southern part of the Cotton Belt, cotton more extensively used in that State and in continued to fruit and weevils bred continu- Florida than elsewhere. This method was advo- ously all the year, but in most areas they passed cated by some growers and State officials who the winter as adults in the old cotton bolls, claimed that it was a cheap method of control weeds, and surface trash in fields and surround- requiring no expensive application equipment. ing woods. Weevils entered hibernation in the A great many of the early emerging weevils fall when the mean temperature dropped to were killed by the presquare applications of 40° to 50° F and emerged in the spring when sweetened poison, but enough weevils usually the mean temperature averaged about 60°. emerged from hibernation sites after squares Some activity occurred during warm days in the formed, and sweetened poison was no longer winter—weevils left hibernation sites, became effective to cause serious damage. active, and entered hibernation sites again when Mopping was extensively tested in Texas, the temperature dropped. The hibernation and Oklahoma, Louisiana, South Carolina, Georgia, survival studies were of value in determining and Florida. Its effectiveness varied somewhat when boll weevils emerged from hibernation in different localities, apparently depending on sites in the spring and early summer to enter the time weevils entered the fields from hiber- cottonfields. nation shelter and climatic conditions. The more In 15 years of studies at Tallulah with various open type woods of the Southeast appeared to types of shelter material and dates of installa- warm up earlier in the spring than the denser tion, survival ranged from 0.01 to 6.14 percent, woods of the Middle Cotton Belt, and caused with an average of 1.22 percent. The minimum the weevils to emerge earlier over a shorter temperature was the most important winter period. Under these conditions the sweetened weather condition affecting survival, the lower poison seemed to be somewhat more effective. the temperatures or the greater number of times More extensive tests with mopping were con- the temperature was below freezing, the lower ducted in South Carolina than elsewhere be- the survival. Hibernation experiments also RESEARCH ON COTTON INSECTS 15 were conducted at several other places to obtain vestigations of such characters as the thickness information on survival, especially at Florence, of boll walls, the toughness of the carpel lining, S.C, Stoneville, Miss., and College Station and pilosity of leaves, amount of leaf area (shade), Waco, Tex., representative of the different sec- and early shedding of leaves were started at the tions of the Cotton Belt. Stoneville, Miss., laboratory in 1934. Many boll weevils hibernated in Spanish moss No resistant varieties were found and special although it is not very favorable for weevil attention was given to the characters most likely survival because it is open and subject to sudden to increase the difficulty of oviposition. Thick- changes in temperature. Examinations were ness of boll walls and toughness of carpel linings made of moss collected near cottonfields in the resisted oviposition, but as a strong negative fall and again in the spring for many years as correlation existed between the two characters, an index of weevil abundance at time of enter- both were not present in any one variety. ing hibernation and spring survival and for Toughness of the carpel lining without the predicting weevil abundance. protection of boll wall thickness was of little In 1957 Brazzel and Newsom of Louisiana value in resisting weevil damage, and the least State University found that the boll weevils damage was caused to varieties with walls inter- developed diapause to survive the winter in mediate in thickness and toughness. This work hibernation sites. Much of the survival data was continued in cooperation with plant geneti- developed in cage studies before that time be- cists, as the development of a variety with only came suspect since there was no way of knowing a slight degree in weevil resistance would mean whether the weevils were reproducing or dia- a great saving to growers. The work on resist- pausing when they were installed in the cages. ant varieties received increased emphasis in the The diapause finding did not adversely affect 1960's and 1970's and is discussed under that results of surface woods trash examinations section in this report. because most of the weevils that entered hiber- Attractants.—Considerable attention was nation sites had developed diapause, enabling given to studies of the chemical constituents of them to survive the winter. the cotton plant that attract boll weevils with the Since about 1935 examinations had also been hope of isolating and using them as baits. Chem- made of surface woods trash collected near ists assigned to this work at Tallulah in 1923 cottonfields at Tallulah, La., and Florence, S.C, distilled large quantities of cotton plants and and in later years at Stoneville, Miss., and Waco, separated the distillate into a number of con- Tex. Machines have been developed that sep- stituents. As ammonia and trimethylamine were arate most of the trash and greatly reduce the in greatest abundance, they were considered to labor involved in examining surface woods be the most likely materials to attract weevils trash. These examinations have also shown that to cottonfields. Extensive tests with these mate- most of the weevils occurred in trash within 50 rials in a chemotropometer and a specially feet of the edge, and no weevils were found designed apparatus for exposure in the field did more than 300 feet from the edge of the woods. not indicate that they would be of any practical Weevils have emerged from hibernation, fed value in attracting weevils though a few weevils throughout the summer in the insectary, and were attracted. Recent work is discussed in the entered hiberation again the second winter, but attractants section of this publication. no survival over two winters was recorded. Boll weevils and Sea Island cotton,—The boll Varietal resistance to boll weevil.—Another weevil caused more serious damage to Sea line of investigation was the study of immunity Island cotton than to short-staple and upland or resistance of cotton varieties to the boll cotton for the following reasons: Sea Island weevil. The reduction in damage by the boll cotton fruits over a much longer period; the weevil through the development of improved boll walls are thinner and softer, bolls require varieties was due to the shorter fruiting periods longer to mature, and bolls are subject to attack and earlier maturity of the plants, and the almost until they open. Very little work was morphological characters that might offer re- done on the boll weevil on Sea Island cotton, as sistance were studied very little previously. In- production was discontinued shortly after the 16 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE boll weevil reached the areas in Florida and time from buds of H. syriacus growing in a field Georgia where this cotton was grown. A move- of infested cotton and adults fed, and some ment was started in 1934 to revive the once oviposited, on several other species of Hibiscus prosperous Sea Island cotton industry, and one although no larvae reached maturity. It was felt of the most important problems to be solved that in an eradication program other host plants was the control of the boll weevil. The biology could not be overlooked. Althea is an orna- and habits of the weevil on Sea Island cotton mental shrub that is generally distributed had previously been studied in 1918, and experi- throughout the South. ments on control were undertaken at Tifton, In 1956 at Brownsville, Tex., M. J. Lukefahr Ga., in 1936 and in 1937 at Gainesville, Fla. The noticed that several flower buds of Thespesia results indicated that the same methods that populnea (L.) Soland were turning yellow and were successful on short-staple cotton could be shedding from the tree. He found that these used, although control was more difficult and buds were infested with boll weevil larvae and expensive because of the longer growing season. four adults were on the foliage. All the flower Spraying instead of dusting calcium arsenate buds and seed pods eventually became infested. also appeared to be more effective on the Several infested buds were collected, and 14 smoother leafed Sea Island than on upland adult boll weevils emerged from them. Nine of cottons. Most of the Sea Island cotton was them were placed in a cage containing potted produced in light sandy soils of low productiv- cotton plants, and in a short time all the fruit- ity, and despite the higher price per pound for ing forms showed evidence of feeding or egg Sea Island cotton, weevils could not be con- punctures. Thespesia populnea belongs to the trolled profitably. Pima, long-staple varieties, family Malvaceae and is commonly called portia are now grown only in western areas where the tree. Locally, it is referred to as the tulip tree. boll weevil does not occur. J. K. Walker of the Texas Agricultural Ex- Host plants other than cotton,—The boll periment Station in 1957 found that boll weevil weevil develops on the cultivated and wild cotton eggs removed from cotton squares and im- of the genus Gossypium and closely related planted individually in buds of the wine cup, genera. Fortunately, these are the only plants Callirrhoe involucrata (Nutt.) A. Gray, pro- on which the weevil breeds in sufficient numbers duced adults. The wine cup is a common mal- to be of importance under normal conditions. vaceous plant in central Texas and blooms in However, plans proposed for eradication of the April and May. Although boll weevils were boll weevil with noncotton zones in the early forced to feed and oviposit on this plant, they days raised the question whether the elimina- produced no adults in this manner. It is doubt- tion of cotton would force the weevils to other ful that the wine cup is a significant host of the hosts and enable them to maintain populations boll weevil. in the absence of cotton. In the early investiga- After finding that boll weevils developed on a tions weevils were noted to feed and to deposit caged Cienfugosia drummondi (St. Hil.) Garcke eggs on several malvaceous plants of the genus plant, Lukefahr and Martin reported that four Hibiscus, but the larvae did not reach maturity. adults developed from 182 capsules of this plant In 1913 weevils were bred for the first time on collected on July 14, 1961, on the Welder Wild- plants other than cotton when two completed life Refuge near Sinton, Tex. The nearest cot- development on althea. Hibiscus syriacus L., and tonfield was approximately 10 miles away and others partially developed on two species of was fruiting at the time the seed capsules were Callirrhoe under laboratory conditions. Weevils collected. are also known to breed in G. thurberia, but it On July 31, capsules and flower buds were occurs only in New Mexico and Arizona and is collected from six locations in Nueces County, infested with the thurberia weevil. Tex., and plants from three of the locations In 1932 when several States were considering were infested. Thirty-flve weevils were reared legislation to eradicate the weevil, host plants from 104 fruiting forms that were collected studies were again started to determine changes from plants growing about 500 feet from a in their status. Weevils were reared for the first heavily infested cottonfield located near Port- RESEARCH ON COTTON INSECTS 17 land, Tex. Twenty-eight adult weevils were mary host of the boll weevil. Large numbers can collected with an insect sweep net in an area 30 develop on one male tree. by 50 feet, containing approximately 100 plants, In reviewing the hosts of the boll weevil at this location. Another area near Gregory, other than cotton it seems that only Althea, Tex,, yielded 15 adults from 61 fruiting forms, (Hibiscus syriacus), Thespesia populnea, and and the third infested collection made near Cienfugosia would pose much of a problem in Corpus Christi, Tex., yielded 16 adults from an effort to eliminate the boll weevil as an 133 capsules. The plants in the three noninfested economic pest from the United States. Insofar locations were widely scattered and were not in as Althea is concerned, it could be handled with close proximity to cotton. regulatory procedures. Though homeowners C. drummondi belongs to the family Malva- may be reluctant to give up this ornamental, ceae and occurs primarily in the Coastal Bend of hopefully through education and information Texas. It is a perennial, low-growing plant, they could be persuaded to do so. Inspection of about 8 inches high with runners as long as 2 the many properties could be quite difficult. feet. It is found in poorly drained places that Thespesia populnea would be handled in the have been undisturbed by cultivation. This plant same way in the Lower Rio Grande Valley of has been observed blooming from April to Oc- Texas. Cienfugosia would pose some problem in tober in Nueces County and in February at a boll weevil elimination program. All colonies Brownsville, Tex. Its flowering cycle seems to would have to be located and delimited. How- be dependent on rains, but the plant is very ever, since infestations usually are light, they drought resistant. Twenty immature fruiting might be eliminated with release of sterile males forms and four mature capsules have been ob- or with pheromone traps or with a combination served on one plant. A fully developed capsule of the two techniques. has five locules ^^âth seven or eight seeds per locule. Each seed is covered with light-brown fibers that are closely appressed to it. Thurberia Weevil How long the boll weevil has been associated The Thurberia weevil {Anthonomus grandis with Cienfugosia is unknown, but it seems prob- var. thurberiae Pierce) was discovered by Dr. able that this insect may be able to maintain 0. F. Cook of the Bureau of Plant Industry and itself on some species of this genus and be the novelist, Harold Bell Wright, on Thurberia entirely independent of cotton. The weevil in- or ''wild cotton" in the Arizona mountains in festation on C drummondi plants growing on 1912. At first the boll weevil was thought to be the Welder Wildlife Refuge may be an example breeding on a new host plant under climatic of such a population. These plants were sur- conditions where it had not previously been rounded by mesquite trees and brush in a range- able to exist, and it was feared the weevils land widely separated from cultivated land; would spread to the large noninfested cotton however, they were found to be infested when areas of the West. Subsequent studies showed examined during midseason. Collections of the Thurberia weevil was a variety or biological weevils in pheromone traps in the spring in race of the boll weevil, difficult to distinguish these areas indicate that weevils can survive from the true boll weevil. from one year to the next on hosts other than Explorations were made to determine the cotton. distribution of the weevil and its host plant, and Five additional species were found to be hosts research on the biology, habits, and economic of the boll weevil by Lukefahr and Martin. importance of the species was undertaken in These were Cienfugosia argentinia Garcke and 1913. These studies showed that the Thurberia C sulphurea (A. Gray), C. hildebrandtii Garcke weevil would readily attack cotton and would of Africa, Thespesia lampas Cav. of Asia, and interbreed with the boll weevil. No commercial Hampea sp. of Mexico. Fryxell and Lukefahr plantings of cotton were made at that time near postulate that the geography and ecology of the the mountains where the weevils occurred, and infested Hampea sp. trees in Veracruz, Mexico, the infestation was confined to Thurberia suggest that they may be the long-sought pri- plants. However, an experimental planting of 18 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE cotton became infested in 1914, indicating that weevil also extended into Mexico, although the the weevils would infest commercial cotton in limits of distribution are not known. the future. Following the development of irri- Biological studies on the Thurberia weevil gation, commercial planting of cotton was ex- bred continuously on cotton for 10 years indi- tended in the Santa Cruz Valley nearer the cated that it was not likely to become a major mountains, and in 1920 Thurberia weevils were pest of cotton in the irrigated sections of the found infesting cotton north of Tucson, Ariz. Southwest. The weevils hibernate as adults In 1924 the State of Arizona attempted to within the pupal cells in old cotton bolls, and establish a noncotton zone in the infested areas, the necessary preplanting irrigation causes the but farmers took this matter to the courts and weevils to emerge and die before cotton begins were granted a permanent injunction against it. to fruit. Experiments extending over 4 years The trial attracted much attention and disclosed showed that agricultural practices used to pro- the lack of entomological information on many duce the crop could eradicate the weevil in one of the issues involved. Since about 2 million year from cotton in the irrigated section not bales of cotton, or about 15 percent of the U.S. subject to reinfestation from Thurberia plants. crop was grown in the West where the boll Damage to commercial cotton plantings never weevil does not occur, the Bureau decided to was severe and occurred only where infestations obtain the much needed information on the occurred from Thurberia plants. Dispersal by importance of the Thurberia weevil. A labora- flight is limited and the removal of infested tory was established in Tucson in 1925 to (1) Thurberia plants for 1 mile or more from cotton delineate more thoroughly the range of the fields greatly reduces the infestation. Research, Thurberia plants and weevils in the United also, showed that the Thurberia weevil can be States, and (2) determine if the Thurberia controlled with calcium arsenate. weevil could maintain itself on cultivated cotton A flareup in infestations in the 1960's caused in the absence of Thurberia plants, and the renewed interest in research on the boll weevil. damage it would cause to cotton. Results of the research substantiated much of An experiment was planned to rear the Thur- the early data. It was determined that if ''soca" beria weevil exclusively on cotton for at least or stub cotton was not grown in Arizona the 10 years to study any changes in its biology problem would be eliminated or greatly mini- and habits. The study was to be made on a mized. State regulations now ^forbid growing ranch isolated about 25 miles from any cotton stub cotton. or Thurberia plants. The work was delayed, however, as most of the weevils from the 1925 Bollworms crop were used in working out fumigation and The bollworm is very generally distributed sterilization methods for use in movement of throughout the world and has been recorded as cotton products from the area to be quarantined. a cotton pest in the United States since 1820. A Federal quarantine was promulgated in 1926, Entomologists have devoted considerable atten- and the farmers filed suit to restrain the De- tion to it since about 1854, and many early pub- partment from enforcing it in the Maraña dis- lications of the Patent Office and the Depart- trict of Arizona. The case, which was finally ment deal with the bollworm. won by the Department in 1928, was an im- The bollworm feeds also on corn, tomatoes, portant step in establishing the legality of Fed- grain sorghums, peas, alfalfa, lespedeza, beans, eral quarantines. soybeans, flax, peanuts, and many other plants. Detailed surveys in 1926 and 1927 and later It is called the corn earworm on corn and the studies showed that the Thurberia plants were tomato fruitworm on tomatoes. found only in the mountains of eight counties Development.—The bollworm has four stages in southeastern Arizona and Hidalgo County of in its development : Egg, larva, pupa, and adult. southwestern New Mexico, while the weevil was Only the larvae are destructive. Between spring limited to portions of the plant range in five and early fall, this insect produces 4 to 6 gen- counties in Arizona. Both the plants and the erations. The last generation remains in the RESEARCH ON COTTON INSECTS 19 pupal stage and passes the winter in the soil. the laboratory closed. Work on the bollworm For about a month in the spring, moths emerge continued at other locations, however. from overwintered pupae. Moths are yellowish The bollworm is difficult to control because of or brownish and have a wingspread of 1 to IV2 the large number of wild and cultivated host inches. plants and its habit of feeding within the Female moths of the season's first generation squares and bolls, and because the damage lay eggs on clover, alfalfa, bluebonnets, winter extends over a long period. The larvae often peas, young corn, and other plants. Second- are not sufficiently numerous at any one time generation moths lay eggs on silks of young on cotton to justify the expense of control yet ears of corn, if they are available. If corn silks the accumulative damage may be severe. Cot- are not available, the second-generation moths ton is not the preferred host, and the abundance lay eggs on other plants—on cotton in some and succession of other crops such as corn, areas. Third and later generations of moths grain sorghum, cowpeas, vetch, alfalfa, and (which often overlap) lay eggs on cotton. others from which the moths migrate to cotton On cotton, moths usually lay eggs on the are important factors in the damage caused tender, growing tips of plants and on the top to cotton. sides of leaves. Sometimes they lay eggs on The use of trap crops, especially corn, to squares, bolls, and stems. Eggs, which are white, prevent the early infestation on cotton was ribbed, and dome shaped, are about half the recommended but was not successful in actual size of a pinhead. Larvae hatch from the eggs use because of the reluctance of growers to in 3 to 5 days. destroy the crops sufficiently early to prevent Color of the larvae varies. It may be pale maturity of the larvae. Studies of the factors green, rose, brown, or almost black. Full-grown attracting moths to cotton for oviposition have larvae are 1 to II/2 inches long. For a day or shown that the more succulent plants are fa- two after hatching, larvae feed on the nearest vored for oviposition. Consequently, cotton on tender growth. Then, larvae on terminal buds river bottom land that had been overflowed or of the cotton plant move downward; those on had abundant moisture was usually the most fruiting branches move toward the center of the seriously damaged. In control experiments with plant. The larvae eat out the squares and tunnel insecticides, the most important factor was the into and eat the contents of the bolls. Mature timing of applications so that the plants would be larvae enter the ground and change into mahog- covered with insecticides when the larvae were any-brown pupae, from which moths emerge hatching so as to kill them while they are small. (fig. 4). The best early criterion for timing applica- Research.—In connection with the boll weevil tions was egg deposition on plants. Treatments investigations, work on the bollworm started in for control were recommended to begin when 1903 at the Victoria, Tex., laboratory. This 25 to 30 eggs are found per 100 terminal buds. work was expanded in 1904 with headquarters Unfortunately, egg counts are difficult to make at Paris, Tex. and growers usually did not recognize the Fortunately, most methods of control devel- presence of injurious infestations until the boll- oped for the boll weevil were of value, also, worms were too large for successful control. against the bollworm. In the early investiga- Tests were made with most of the common tions special attention was given to cultural insecticides including arsenicals, pyrethrum, methods, trap crops, and poisoning with paris rotenone, sulphur, fluorine compounds, and green, the arsenical then in general use. Fall others. Calcium arsenate or a mixture of cal- plowing of the land to destroy overwintering cium arsenate and paris green gave the best pupae and early maturity of the crop reduced results. Cyrolite dust was not as effective for infestations considerably. Investigations on the bollworm control on cotton as it was on lima bollworm as a cotton pest were resumed in 1928 beans. The most economical control on cotton with headquarters at College Station, Tex. In was obtained by treating with 10 to 12 pounds 1939 the headquarters moved to Waco, Tex., and of calcium arsenate per acre. Treating with the work continued until June 30, 1973, when 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 growth, the aphids are dark green to almost plants gave better results than aerial dusting, black, and about the same size as the spring although thousands of acres were successfully- aphids (fig. 5). treated by aerial dusting in the Brazos River The cotton aphid multiplies rapidly under bottom of Texas each year. favorable conditions. Enormous populations Naturally occurring predators and parasites may build up in a short time. New generations often keep infestations of the bollworm at sub- may occur every 5 days during summer months. economic levels. However, insecticides applied Reproduction is slower and the lifespan longer for the control of other insects, such as the during cold weather. cotton fleahopper and boll weevil, kill off the Only female cotton aphids occur in the Cot- beneficial insects. Thus, continued use of pro- ton Belt. They give birth to living young. As tective measures is necessary until the crop reproduction is continuous, generations are not matures and is no longer attractive to boll- distinct. These insects may spend part of the worms and tobacco budworms even though the winter as winged adults, hibernating in field target insect has been controlled. debris or in cracks in the soil. When warm pe- In the 1940's organic insecticides such as riods occur, they fly to weed hosts on which DDT, toxaphene, endrin, methyl parathion, they feed and continue to reproduce. and carbaryl, and later monocrotophos were In the spring, winged adults develop on the very effective. At the end of 1972, however, use weed hosts. They fly to cotton and melon plants, of DDT on cotton was banned. where they give birth to living young that The tobacco budworm, Heliothis virescens develop into wingless females. Winged forms (F.), which is even more difficult to control are produced on any host when crowding occurs than the bollworm, did not become a serious or when food becomes scarce. pest of cotton until the 1960's. It developed Males and females occur in the Northern resistance to available effective insecticides, States, where they feed on melons, cucumbers, creating a serious problem in several areas of and many other plants, both wild and cultivated. Texas and Louisiana. The problem superim- Females lay eggs that survive the winter and posed on other adverse factors resulted in hatch in the spring. abandoning cotton production in several locali- This insect damages cotton by sucking juices from the plants, reducing both yield and qual- ties in Mexico. ity, and often causes severe losses to growers. When heavy infestations occur on seedling cot- Cotton Aphid ton, the leaves curl or crinkle; plants become The cotton aphid. Aphis gossypii Glover, oc- stunted and may die. This often happens in curs wherever cotton is grown. It was described early spring, before natural enemies of the by Glover in 1877 although he made previous aphid become active. references to an aphid observed on cotton in When heavy infestations occur during the South Carolina, Florida, Georgia, and Missis- main fruiting period (from early bloom to full sippi in 1855 and in subsequent years. It bloom), the older leaves turn yellow and shed, attacks many plants in addition to cotton and causing premature opening of bolls and imma- is sometimes called the melon aphid because it ture development of fiber. Also, honeydew se- is a serious melon pest. cretions from the aphids drop on the fiber, Development—The adult cotton aphid is a making it sticky. Often, a fungus develops in soft-bodied, sucking insect that ranges in color the honeydew deposits, causing the plants to from light yellow to dark green or almost black. appear black or sooty. Fiber picked from such In the spring, it is dark green on the tender, plants is stained and sticky and of low quality ; growing leaves and terminal buds of cotton and seeds are low in viability and lightweight. about i/i4-inch long. Later in the summer, it The cotton aphid often is controlled by its is usually found on the undersides of mature natural enemies. It seldom increases to damag- leaves and is light yellow and much smaller. In ing numbers unless its natural enemies are the fall, when plants often put on new terminal 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 weeds, such as evening primrose and horsemint. spring, the cool weather prevents natural ene- As the weeds mature and become less juicy, mies from becoming active and numerous adults fly to cotton plants, which are usually enough to control the aphids. When warm in the presquaring or early fruiting stage. The weather arrives, the natural enemies if left un- pests stay on cotton as long as the plants are disturbed, increase sufficiently to bring the succulent. When cotton becomes tough, the flea- aphids under control. However, severe damage hoppers generally leave it and go to crotón and may occur before natural enemies take over. other weeds to feed and lay eggs. This insect Research.—Use of calcium arsenate for boll may produce six to eight generations in a sea- weevil control was limited because of the build- son. Cold weather kills both adults and nymphs. up of cotton aphid populations following its use The cotton fleahopper injures the entire cot- over wide areas (see p. 1). The only aphicide ton plant by feeding on juices from the tender available was nicotine sulfate, which was expen- parts. Leaves become ragged and deformed. sive, difficult to apply, and effective only under Squares turn brown or black and are shed when ideal conditions. The new organic insecticides they are the size of a pinhead. Heavy infesta- replaced calcium arsenate for boll weevil con- tions of fleahoppers restrict the growth of trol; most organophosphorus compounds effec- fruiting branches. Vegetative branches may de- tively control the cotton aphid. velop abnormally in length or in number. Af- fected plants often grow tall and whiplike (fig. Cotton Fleahopper 6). If the cotton fleahopper is not controlled early The cotton fleahopper, Pseudatomoscelis seri- in the season, fruiting is delayed. Cotton plants atus (Reuter), was known as a cotton pest in then may be attacked for a longer time later in local areas in southern Texas since about 1900, the season by other insects, particularly by the but its importance was not recognized until a boll weevil, bollworm, and pink bollworm. serious general outbreak occurred in 1923 over Research.—Investigations started in south a rather large area. The fleahopper is generally Texas on the biology, host plants, and control distributed over the Cotton Belt but causes the measures soon after the outbreak in 1923. These most serious damage in the Blacklands of Texas were followed by more detailed studies at Tallu- where it is often more injurious than the boll lah, La., of the habits of this and other species weevil. of mirids and their effect on the plani^ tissues. Development.—The cotton fleahopper has In 1933 a laboratory was established at Port three life stages—egg, nymph, and adult. In the Lavaca, Tex., to develop control measures for fall, adult females lay eggs in weeds, usually the cotton fleahopper. In the earlier Texas work in stems of crotón. This plant, known as goat- sulphur had been used with fairly good results, weed, is common throughout the Cotton Belt. but the details of application had not been The cotton fleahopper overwinters in the weeds, worked out. in the egg stage. Extensive cage and fleld tests with many in- The eggs hatch in early spring. Newly secticides showed that sulphur was the most hatched nymphs, which are about one twenty- effective insecticide against the nymphs, but fifth of an inch long, are white and translucent. that a mixture of sulphur and an arsenical was After feeding they become pale green. They more effective and gave quicker kill of the have prominent, scarlet-colored eyes. Nymphs adults. Mixtures of paris green and sulphur (1 progress through five instars before becoming part to 13 parts) or calcium arsenate and sul- adults. The last nymphal stage resembles the phur (1 part to 2 parts) were almost equal in adult but does not have fully developed wings. effectiveness against the fleahopper, but the cal- Adult cotton fleahoppers are about one- cium arsenate-sulphur mixture was recom- seventh of an inch long and are winged. They mended because it was somewhat cheaper and are pale green with small, dark spots on the was also effective against other insects such as body and- four black marks near the wingtips. the boll weevil and cotton leaf worm that usually These insects feed and reproduce on tender occurred at the same time. Calcium arsenate 24 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

PN-4422 Figure 6.—Cotton fleahopper and damage (a) blasted square (b) whiplike plant and lack of fruit resulting from blasted square; (c) injured leaf. ((A) and (c) actual size (b) about ^ne-fourth actual size; adult and nymphs 15 times natural size.) RESEARCH ON COTTON INSECTS 25 and paris green alone killed a high percentage the early fruiting stages of the cotton plants. of fleahopper adults, although it was not deter- Treating in the early fruiting stages permits mined how arsenicals kill these sucking insects. the reestablishment of beneficial insect popula- Results of field tests over a number of years tions before injurious bollworm complex infes- showed that from 2 to 3 applications of 15 tations occur. This can only be done if horse- pounds per acre of the calcium arsenate-sulphur mint matures early enough to result in migra- mixture gave good increases in yield in the Port tion of cotton fleahoppers to cotton by that Lavaca, Tex., area. The development of the time. arsenical-sulphur mixtures was the most popu- lar control used for cotton insects since the Cotton Leofperforator discovery of calcium arsenate for the boll wee- vil. Large quantities of the mixtures were ap- As a result of the severe cotton losses in the plied both with ground-dusting machines and Yuma and Imperial Valleys in 1925 from the airplanes. In Calhoun County, where most of cotton leafperforator (Bucculatrix thurberiella the experiments were conducted, over two- Busck), a substation of the Tucson, Ariz., labo- thirds of the cotton acreage was treated with ratory was established at Calexico, Calif., in power dusters, primarily for ñeahopper control. 1926 to investigate this insect. Very little in- Attention was also given to cultural methods formation was available, and the work during of controlling the ñeahopper since the insect 1926 and 1927 was devoted largely to life his- overwinters in the egg stage in the stems of tory studies reported but not published. plants with approximately 99 percent over- Work was resumed in 1930 to 1932 with par- wintering in the stems of crotón or ^'goatweed.'' ticular attention to practical control methods, In the winter of 1933, crotón on 10,000 acres of and while control measures were not satisfac- ranchland in Calhoun County, Tex., was de- torily worked out, considerable information was stroyed through a Civil Work Administration available. Barium fluosilicate was the most sat- grant. The following spring practically no flea- isfactory insecticide used, and eliminating soca hoppers were found on cotton until a heavy or stub cotton was valuable in reducing the migration of adults occurred. Results showed overwintering populations. that fleahoppers migrated for at least 20 miles Development.—Eggs of the perforator are and that destroying crotón would not be a laid on both the upper and lower leaf surfaces, feasible method of control. with an occasional one being placed on a peti- In the spring of 1939, the Cotton Fleahopper ole. The extremely small, whitish, elliptical egg Laboratory was moved from Port Lavaca to is attached to the leaf by one end with the Waco, Tex., where this work was combined longitudinal axis then being perpendicular to with that conducted at College Station, Tex., the leaf surface. The incubation period aver- for the bollworm. A sublaboratory was main- ages about 2.25 days under greenhouse condi- tained in Port Lavaca, however, until 1942. tions of 70° to 90° F. The first instar larva The cotton fleahopper continues to be consid- emerges directly through the attached end of ered a key pest of cotton in many areas of the egg and into the leaf, thus becoming a leaf Texas because treatment for control in the early miner. The first three instars are spent mining fruiting stage often results in increased sub- through the leaf, feeding primarily on the pali- sequent infestations of the bollworm and to- sade tissue. A larva seldom crosses a main leaf bacco budworm. Beneficial insects that often vein, and avoids gossypol glands. The feeding keep the bollworm complex infestations below channels are most readily visible on the upper economic levels are killed off by the treatment surface of the leaf, becoming progressively for control of cotton fleahoppers, necessitating wider with each of the two subsequent mining the continued use of protective measures until the crop matures and no longer is attractive to instars. The duration of the first three instars bollworms and tobacco budworms. The boll- (mining stages) averages 3.45 days (fig. 7). worm complex problem often can be avoided if After completing the third instar, the larva treatment for cotton fleahoppers is needed in emerges from within the leaf and begins the 26 AGRICULTURE HANDBOOK 515, U.S. DEPT. OP AGRICULTURE

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 whit- ish 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 'H'¿, leaf vein. The egg is white but darkens before hatching. The newly hatched larva (leaf miner) usually feeds in a tight circle before initiating '#7-' 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 PN-4423 Figure 7.—Third-stage larva of the cotton leafper- feeding in a single spot, thus creating larger forator, almost full grown, feeding upon a cotton "windows" in the leaf. As this stage completes leaf (natural size). Two mines, one large and one development, it usually becomes restless and small, can be seen in the leaf. The large mine is leaves the leaf in search of a suitable place to empty; the small one contains a miner, or first-stage spin its cocoon. larva, which is busily extending the large end of the mine. One difficulty in controlling this insect with insecticides appears to be related to the dis- proportionate amount of time that the insect spends in protected areas. For example, the fourth stage, feeding on the leaf surface. Dur- life cycle (egg to egg) in the greenhouse re- ing the feeding of the fourth and fifth instars, quired 21.5 days. Only 3.6 days were spent as the larva eats only to the opposite epidermis. an exposed, feeding larva. Feeding occurs on either upper or lower sur- Research.—With the advent of the organo- faces, but during daylight hours the larvae chlorine insecticides, the cotton leafperforator generally feed on the lower surface of the leaf. rarely became a problem. However, when these When disturbed, both fourth and fifth instar insecticides were replaced by the organophos- larvae wriggle vigorously, usually dropping phorus insecticides because of resistance, the from the leaf on a silken thread and returning problem intensified and occurred, also, in far when the disturbance is over. west Texas and in the Lower Rio Grande Val- ley. Research on the pest was resumed by the At completion of the feeding stage of the Arizona Agricultural Experiment Statin and fourth instar, the larvae spins a weblike cell the ARS Western Cotton Insects Laboratory on the leaf surface and assumes a "horseshoe" in the 1970's. Field tests for the evaluation of shape during this resting stage. The duration insecticides for its control were conducted, also, of the fourth instar is 2.1 days, 1.0 day in in the Lower Rio Grande Valley by the Texas the feeding stage and 1.1 days in the resting Agricultural Experiment Station land the ARS •stage. After molting, the fifth instar larvae Southwestern Cotton Insect Investigations emerges from the cell and feeds on the leaf Laboratory. surface, as in the fourth instar, until mature. This requires about 2.6 days. The fully grown fifth instar larva then spins Cotton Leafworm an elongate silken cocoon. This may be on the Though the cotton leafworm, Alabama ar- leaf but is usually elsewhere such as on a main gillacea (Hübner), is now considered to be a RESEARCH ON COTTON INSECTS 27 pest of little or no economic importance, it was the pest. It was of utmost importance that in- a major pest in the early days and received dustry be prepared to make sufficient quantities equal billing with the bollworm in Professor of insecticides available to meet the growers' J. H. Comstock's report in 1879 (18), Re stated : needs. Development,—The cotton leafworm has four The first appearance of the cotton worm in this country now on record was in 1793 in Georgia and stages in its life cycle—egg, larva, pupa, and South Carolina after cotton had been grown for adult. 150 years. The female moth lays bluish-green eggs, It was recognized as the first serious pest of singly, on the undersides of cotton leaves. They cotton. hatch in 3 or 4 days. Newly hatched larvae are pale, dingy yellow. They feed only on the under- The cotton leafworm is a tropical species sides of leaves. that does not overwinter in the United States. There are five larval instars. In the summer Every year the moths migrate into this country the larvae usually become full grown in about from Central or South America or from Mex- 2 weeks and are about II/2 inches long. Their ico. Each year since 1922 cotton leafworm lar- color varies with some being yellowish green, vae first have been found in southern Texas, without prominent stripes, while others have a usually in May but in some years in April, broad, black stripe and a fine central yellow June, or July. stripe down their backs. All cotton leafworm The cotton leafworms spread out from south- larvae have a distinguishing characteristic—on ern Texas. Usually by the end of a cotton grow- the top of each segment are four black dots ing season, they are present in every cotton- that form a square. producing State from Arizona eastward. Larvae When a larva has completed its feeding, it never have been reported in California or *Vebs up" in the fold of a leaf and becomes a Nevada. pupa. Other larvae may eat away the leaf, Before the organic insecticides came into leaving the pupa hanging by a thread from the general use in the late 1940's, the cotton leaf- leaf vein or stem (fig. 8). worm often was one of the most destructive The pupal stage lasts about 1 week in mid- cotton pests. In outbreak years, supplies of summer, but it may last up to 4 weeks in the insecticides, largely calcium arsenate, used in fall. The moth, which is olive tan, has a wing- control were usually exhausted before the end spread of about IV2 inches. It is a strong flier of the season. Since then, the widespread use and, frequently, is found in the northernmost of organic insecticides for the control of other States and in Canada. In these areas, it feeds cotton insects in southern Texas usually delays on ripe fruits, such as peaches, grapes, and population buildup so that migration to other cantaloups. areas occurs too late to be of much importance. The life cycle of the cotton leafworm is com- In the years before and through World War pleted in about a month with two to eight II, first findings of the pest in the United States generations in a year. were of considerable significance. Usually eco- Female cotton leafworm moths lay their eggs nomic damage and migration to other areas only on cotton in this country. However, in the could be expected from later generations. The mid-1960's Hampea sp. was discovered as a planting period of the cotton crop in Texas host in Mexico. ranges from February 1 in the Lower Rio Damage is first evident when the leaves start Grande Valley in the extreme southern tip into to appear ragged. Larvae feed between the main June on the High Plains. Thus, population veins and often skeletonize the leaves. When buildups in southern areas often resulted in leaves become scarce, the larvae eat the bracts injurious infestations in all other areas of the surrounding the squares and bolls. Finally, they State as well as in Oklahoma and other States may gnaw into the bolls. There is a charac- as the cotton-growing season progressed. Tre- teristic, pungent odor in infested fields. Early mendous amounts of insecticides were often infestations, if not controlled, prevent bolls required to prevent defoliation of the crop by 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 Other species of lygus bugs damage cotton, but crop is mature. Then some young bolls shed; usually they are of minor importance. older bolls open prematurely; and the quality Lygus bugs develop in three stages—egg, of both fiber and seed is lowered. Lint often is nymph, and adult. Female adults use their stained by excrement from the larvae. Leaf swordlike ovipositors to lay eggs in plant tis- skeletons become entwined in the lint and are sues, particularly in stems and leaf petioles. difficult to remove. Eggs are tiny, elongate, and slightly curved. The cotton leafworm has many natural ene- Nymphs develop through five instars before mies that help control it. Birds, wasps, ants, becoming adults. The life cycle is completed in spiders, beetles, robber flies, mantids, and aphis about 4 weeks in summer with a longer time lions are among the predatory enemies. in other seasons. It has an egg parasite and several pupal par- Adults are flat and about one-fourth inch asites. Hot, dry weather causes many leafworm long. They range in color from straw green to eggs to dry up, and the unhatched larvae die. dark brown and have a conspicuous lighter col- Diseases often destroy leafworm larvae. ored triangle between the wings (fig. 9). When disturbed by the cutting of a host crop Research.—In the early years materials used such as alfalfa, or when the plants are no for the control of this pest were mixtures of longer attractive as food, adults fly to another paris green or london purple with lime or flour host crop. They hide in plant foliage during applied primarily with the pole and bag meth- the day when the weather is hot. od. The author as a small boy in Texas in the Lygus bugs feed by inserting their long, early 1920's observed his father controlling needlelike mouthparts into plant tissues and cotton leafworm infestations many times with sucking out the juices. On cotton, they attack paris green applied with the pole and bag the tender terminal growth, squares, flowers, method from his best saddle horse. This was and young bolls. Injured squares and small usually done early in the morning or late in bolls usually shed. Injured bolls that do not the afternoon with a slight cross breeze, if possible. Lead arsenate applied as a high vol- ume spray was popular and effective. When calcium arsenate was developed in the 1920's, it was also found effective against cotton leaf- worms 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 exten- sive 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 legu- minous crops and may mov,e to nearby cotton and cause severe damage. Development.—Lygus hésperas Knight is the predominant species in western areas ; L. line-

olaris (Palisat de Beauvois), known as the PN-1425 tarnished plant bug, is prevalent in the South. Figure 9.—Adult lygus bug. 30 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE shed may open abnormally and produce inferior tion for cotton. An alfalfa seed crop requires lint that clings to the warty carpels that result at least 60 days before the seeds are mature from lygus feeding. and ready to harvest. This allows time for two Lygus damage reduces the yield. It causes or more generations of lygus bugs to develop the lint to be spotted and lower in grade. In- in very large numbers. If uncontrolled, they jured plants develop abnormally, becoming tall may destroy the entire seed crop. and whiplike, with fewer fruiting branches Lygus adults leave alfalfa soon after a seed (fig. 10). crop matures or a hay crop is cut. If cotton is In western areas of the United States, lygus growing nearby, the pests may move to it in bugs may develop on weeds such as wild mus- large numbers and gradually disperse over the tard. They develop large populations on alfalfa, entire cottonfield. If other alfaljfa is growing especially when the alfalfa is grown for seed. in the vicinity, they may move into it in pref- When lygus bugs infest an alfalfa hay crop, erence to remaining in the cotton. they have time to produce one generation be- In southern areas, alfalfa and other legumes tween cuttings. The crop is cut several times may serve as hosts for lygus bugs. Weed hosts, in a season and is a constant source of infesta- 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 effec- tive control but were replaced by the new or- ganic insecticides in the 1940's. Lygus bugs are key insect pests as insecticides applied for their control often result in subsequent injurious in- festations of the bollworm complex necessitat- ing 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 speci- men 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. Poten- tially, it is a serious pest of cotton in the United States. Quarantine regulations and cultural and PN-4426 chemical controls have reduced economic dam- Figure 10.—Damage to cotton plant exposed to lygus bugs for 7 weeks in a ñeld cage. age in most years in the infested areas of this RESEARCH ON COTTON INSECTS 31 country and have retarded the spread of this and 1954 to 1962, respectively. In 1965 a new insect to new areas. laboratory was established at Phoenix, Ariz., The pink bollworm was introduced into Mex- to conduct research on the pink bollworm. ico in 1911 through importing infested cotton- Although the infestation at Hearne, Tex., seed from Egypt for planting and into the was eradicated, the insect later crossed the Rio United States in 1916 in cottonseed from Mex- Grande from Mexico into Texas, and its occur- ico for milling. The pink bollworm was first rence has been general throughout the State. found in Texas at Hearne near an oil mill that Since 1952, this pest has caused considerable had received seed from Mexico. damage to cotton periodically in southern, cen- Research on the pink bollworm first started tral, and parts of western Texas. In 1958 and in Hawaii. In February 1918, the Department 1959 it caused heavy damage on some acreages established a laboratory for pink bollworm re- in the El Paso Valley of Texas. search at Lerdo, Durango, Mexico, where the The pink bollworm soon spread to other insect populations were sufficient for such States. General infestations have occurred studies. The work in Mexico was interrupted throughout Oklahoma and New Mexico. Infes- late in 1919 until early 1921 and then resumed tations in some parts of Louisiana and Ar- at Tlahualilo, Durango, until April 1925. At kansas have been light. that time the Tlahualilo laboratory closed be- Since 1940, the pink bollworm has caused cause infestations in southwestern Texas had heavy cotton losses in some areas of Arizona. built up to the extent that work on the pest In 1958 and 1959, severe outbreaks of the pest could be conducted there. occurred in the Gila Valley and in the Salt In July 1927, headquarters for research on River Valley of that State, and extended into the pink bollworm by the Department was Pima County. In these same years—1958 and established at El Paso, Tex. Since that time, 1959—this insect caused serious cotton losses other Federal laboratories in Texas have con- in some parts of the Mesilla Valley of New ducted research in cooperation with the Texas Mexico. In the 1960's, it became a serious pest Agricultural Experiment Station. in the Imperial and Coachella Valleys of Cali- The first experiment conducted with the in- fornia. sect in this country began in the fall of 1927 Development,—The pink bollworm has four at Castalon, now in the Big Bend National stages of development: Egg, larva, pupa, and Park. A laboratory staffed by both Texas adult (fig. 11). Adults are small, grayish-brown and Federal personnel was established at Pre- moths with a wingspread of about one-half sidio in April 1928, and it became headquarters inch. The average life of the adult is about 2 for this work in 1933. In August 1928, a sub- weeks. laboratory of the Presidio laboratory resumed Early in the cotton season, females lay eggs work at Tlahualilo, Mexico, where it was oper- on cotton stems, squares, and terminal buds. ated until 1936. A sublaboratory established at When green bolls are present, they usually lay Brownsville in 1939 became the headquarters most of their eggs in masses beneath the glove- laboratory in 1941. Then, the Presidio station like calyx at the base of the bolls. A moth lays became a sublaboratory and was operated as 100 to 200 eggs, which are white and oval. In such until it closed in 1947. A sublaboratory 4 to 5 days, the eggs hatch into larvae. Newly w^as operated at Ysleta, El Paso Valley, from hatched larvae are glossy white and have light- the fall of 1944 until the spring of 1952 and brown heads. They eat their way into squares another at San Benito from 1944 to 1951. or bolls, where they feed 10 to 14 days. At the Later sublaboratories were operated at Lub- end of this period they are light cream, and bock and Port Lavaca, both from 1953 to 1956. about one-half inch long. They have fairly well- Some phases of the work, coordinated by the defined, transverse bands of mottled pink on Brownsville laboratory, were carried out by the dorsal side. personnel of the cotton insect laboratories at Larvae feeding in squares usually complete College Station and Waco from 1954 to 1957 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 only at night. In the daytime they stay under produce the typical rosette bloom that is read- trash or clods of dirt or in cracks in the soil. ily recognized. Many of these larvae drop to In midsummer the pink bollworm completes the ground and pupate in cracks in the soil or its life cycle in 25 to 30 days. As many as six in surface trash. A few remain in the bloom generations may occur in a year. until it sheds. Occasionally, a square or young Pink bollworm damage to cotton is caused by boll may shed as a result of feeding injury. feeding of the larvae (fig. 11, left). Only minor Larvae in bolls feed on the seeds. When a damage results when larvae feed in squares, larva has finished feeding in a green boll, it since blossoming is not hindered and the re- either cuts a small hole through the carpel wall sulting young bolls usually are not damaged. and drops to the ground to pupate or remains Severe damage occurs when larvae feed in the seed in which it completed feeding. within the bolls, moving from one seed to an- A larva that remains in the seed may hiber- other and eating out the kernel of each. This nate in a single seed, or it may pull two hol- causes a loss of seed viability, and a reduction lowed-out seeds together and unite them by in the volume and quality of oil. Some bolls— spinning a continuous cocoon within the two often a high percentage of late-produced bolls cavities. Seeds thus united are called double —are damaged so severely that they are unpick- seeds. They become apparent after ginning and able and therefore are a total loss. usually are an indication of the presence of When larvae feed within the bolls, they cut the pink bollworm. and stain the fibers resulting in low-grade lint. The larvae change to pupae, and the pupae Fibers so damaged, when mixed with undam- transform to moths. In 3 or 4 days the female aged lint in the harvesting and ginning proc- moths begin laying eggs. The moths are active esses, reduce the average grade of the crop. RESEARCH ON COTTON INSECTS 33

Some larvae may leave the bolls to pupate or Cotton should be produced in the shortest hibernate by cutting exit holes in the carpels. time possible and harvested promptly and com- This increases damage because a single hole pletely. Most larvae in cotton taken to gins permits entrance of moisture and disease orga- are destroyed in the ginning process, but ap- nisms that cause boll rot. In fields heavily proved sanitation practices should be followed infested by the pink bollworm, boll damage may to prevent carryover in waste cotton on the gin be so severe that the cotton may not be worth premises. Clean harvesting reduces the number harvesting. of larvae left in the field. Control with cultural practices.—The pink Stalks should be cut promptly after harvest bollworm is the only major cotton insect that with a power-operated shredder (fig. 12). The passes the winter in cotton or okra residues flail-type shredder is preferred. It is quite ef- left in the field after harvest, or in cottonseed fective in killing pink boUworms, and it spreads and seed cotton taken from the field. the residue evenly on the ground, thus aiding Many larvae left in the field in crop residue plow-under efficiency (fig. 13). can be destroyed by using recommended cul- Crop residue, including infested material tural practices. To be more effective, cultural knocked to the ground at harvest, should be practices should be used as a community, plowed under promptly to a depth of at least county, State, or regional program and fol- 6 inches—^the deeper, the better. lowed by every grower in the control area. Prefrost stalk destruction increases winter Control of the pink bollworm can be made mortality of the pink bollworm. It reduces the more effective if other insects are controlled pest's reproduction in the fall, sometimes by and if other sound production practices that two or three generations. promote rapid, early setting, and maturity of Fields left fallow or unplowed in fall or fruiting forms are used. Early bolls escape winter should be plowed early in the spring. severe damage because they mature before the Survival of the pest is highest in bolls lying pink bollworm infestation builds up to its sea- on the ground. In areas that have sustained low sonal maximum intensity. temperatures, high mortality occurs in bolls on A thick, vigorous stand will hasten maturity standing stalks. and increase the efficiency of mechanical har- Soil moisture helps to kill pink bollworms. vesting. Seed should be treated with fungicide, So in cold, arid climates, fall or early winter the variety of cotton recommended for an area plowing of the dry soil may not be as effective should be planted, and a suitable fertilizer against pink bollworms as it is in other cli- should be used. In a generally infested area, mates. Under arid conditions, irrigation after the insecticide-control practices recommended winter plowing increases mortality of the pest. for that area in the State guide should be Many pink bollworm moths from overwin- followed. At the proper time, chemical defoli- tered larvae emerge early in the spring and die ants or desiccants to speed up harvest should before cotton squares become available for their be used. reproduction. Thus, the degree of infestation Cotton should not be irrigated late in the can be influenced by the date of planting. Ex- season to prevent late-season generations of tremely early, scattered plantings attract moths pink boll worms (and boll weevils, if they are emerging from hibernating larvae in surround- present) from going into winter hibernation. ing fields; therefore, heavy infestations occur The possibility of a high winter carryover of in these early plantings. When early plantings the pest, plus the cost of additional insecticide mature, the moths emerging in them migrate applications, usually makes the production of to later fruiting, more attractive cotton. a late top crop unprofitable to the cotton Usually, late plantings are severely damaged grower. The production of a top crop of bolls because moths migrate into them in large num- with resultant fall breeding of the pest seri- bers. The potential overwintering population is ously jeopardizes the efforts to suppress or increased because an abundance of green bolls eliminate the pink bollworm, and may greatly are available for pink bollworm development increase damage the following year. after the early and intermediate plantings have 34 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

FN-4429 Fignire 12.—Horizontal blade stalk destruction machines.

matured. An increase in the number of pink Spider Mites bollworm generations results when cotton is Spider mites attack many plants. A number planted over a long planting period. Then, the of species of these pests attack cotton, and increased population of the pest causes in- often cause serious damage. The most impor- creased crop damage. Because of this, cotton tant ones are carmine spider mite, Teranychus should be planted within a short, uniform cinnabarinus (Boisdval) ; desert spider mite, T. planting season for a given area. Planting desertorum Banks, T. ZO&OSîîS Boudreaux; pa- should not be started until near the time when cific spider mite, T. pacificvs McGregor ; schoene soil temperature becomes favorable for rapid spider mite, T. schoenei McGregor; strawberry seed germination and seedling growth. This is spider mite, T. turkestani Ugarov and Nikol- considered the best planting time whether or ski ; tumid spider mite, T. tunddiis Banks ; and not an insect problem is present. two-spotted spider mite, T. urticae Koch and Control with insecticide.—For many years T. ludeni Zacker. after it first appeared as a cotton pest, nothing The mites, which are barely visible, are red, was known of how to control effectively or green, orange, or straw colored. Usually, they eliminate the pink bollworm. Today, cultural are kept under control by weather, beneficial methods of control can be effectively supple- insects that kill the mites, other species of mented in either control or eradication pro- mites that prey on them, and disease (fig. 14). grams by properly timed and adequate appli- Outbreaks of spider mites are most likely to cations of insecticide. Effective insecticides did occur following application of a pesticide that not become available until the organic insecti- destroys the beneficial insects and mites. cides were developed in the 1940's. Development.—Spider mites develop in five Research.—^A detailed discussion of the re- stages—eggs, larva, two nymphal stages, and search on the pink bollworm is given in "Fifty adult. Females are able to reproduce without Years of Research on the Pink Bollworm in the mating and when they do, the offspring always United States" (78). are males. RESEARCH ON COTTON INSECTS 35

'^^^i^

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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 cotton- growing regions of the United States, spider mites may remain active and reproduce throughout the year. Under favorable condi- tions, 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 in- jurious from about July 1 until early Septem- ber. 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 PN-4431 areas that were infested in previous years. Figure 14.—Microphotograph of female twospotted Severe infestations may be recognized by spider mite. Note conidia of fungus Entomophthora dust collecting in webs that the pests spin over attached to legs. 36 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE leaf surfaces for protection as they feed and ganophosphorus compounds were effective. lay eggs. Such infestations may enclose plant Some species, however, have developed resist- terminals in the webbing. ance to these compounds. Spider mites damage cotton in all active stages of their life cycle.. Larvae, nymphs, and Stink Bugs adults suck the juices from leaves, stems, and Stink bugs that are sometimes serious pests fruits of the plants. Their feeding causes plant of cotton are Brown stink bug, Euschistus ser- parts to become blotched or stippled and leaves vus (Say) ; the onespot stink bug, E. variolarius to become discolored and drop prematurely (fig. (Polisat de Beauvois) ; conchuela, Chlorochroa 15). When plants are severely attacked, they ligata (Say) ; dusky stink bug, E. tristigmus may become defoliated and devitalized. (Say), and E. conspersus (Uhler) ; green stink Research.—Before the advent of the organic bug, Acrosternum hilare (Say), T. pallidovirens insecticides, spider mites were minor pests of spinosa (Ruckers) ; Say stink bug, Chlorochroa cotton. Infestations, when they did occur, often sayi Stal; southern green stink bug, Nezara were confined to a small area within fields. viridula (L.) ; and western brown stink bug, Sulphur dust was an effective acaricide. Ap- Euschistus impictiventris Stal. plication of the organic insecticides for other The importance of these pests and the species cotton insects often resulted in subsequent in- involved vary from year to year and from area festations of spider mites. However, several or- to area. The damage is confined principally to

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PN-4482 Figure IB.—Damage to cotton foliage by spider mite. RESEARCH ON COTTON INSECTS 37 the bolls and results in reduced yields and ing several thousand acres under the super- lower quality of both lint and seed. vision of the Bureau of Entomology. Several Research,—Lint staining, causing serious organic insecticides give effective control of loss in reduced grades and values, was found stink bugs, but stink bugs have not been a in much of Arizona cotton in the 1920's and major problem in recent years. 1930*s. Several species of hemipterous insects were responsible for the reduction in yield Thrips through the shedding of squares and bolls and Thrips are small winged insects that injure the production of nonpickable lint. The brown plants by feeding on their juices. The following stink bug, the conchuela, and the redshouldered species of thrips attack cotton plants : Frank- plant bug caused most of the staining. Surveys liniella exigua Hood; tobacco thrips, F. fusca over a 4-year period showed an average of 25 (Hinds) ; F. gossypiana Hood; F, occidentallis percent of the bolls of short-staple cotton pro- (Pergande) ; flower thrips, F, tritici (Fitch) ; duced in Arizona were punctured. This group onion thrips, Thrips tabaci Lindeman, and Se- of insects are general feeders and frequently ricothrips variabilis (Beach). Most common of caused considerable damage to sugar beets, al- these are the flower thrips and their closely falfa, grain sorghums, and tomatoes. related species, tobacco and onion thrips. Two Population buildup occurred in desert vege- or more species may be found in the same tation. Seasonal intercrop migrations of insects cottonfield, often on the same plant, although occurred, and the proportion of other crops, the one species usually predominates in a popula- time of harvest, and the effect of rain on desert tion. vegetation all influenced the amount of damage Thrips are found on cotton in all the major to cotton. Indications were that migrations oc- cotton-producing States. Some species, such as curred for considerable distances from wild onion thrips and F, exigua, occur across the host plants. Staining of lint, which caused re- entire Cotton Belt. Tobacco thrips are confined duction in grade and, thus, the value of the to approximately the eastern half of the United crop, was caused by several micro-organisms States with F. occidentalis occurring in the that entered through the punctures made by western half. The latter two species overlap in the insects. occurrence in western Oklahoma and in slightly Plants caged with insects and field surveys more than the central third of Texas. of the seasonal abundance gave much informa- Tobacco thrips usually are predominant on tion on the nature and extent of damage caused seedling plants, but other species may become by the several species in different localities of more numerous on plants beyond the seedling the State. stage of growth. Onion thrips rarely cause se- Research on methods of control started in rious injury to cotton in the eastern part of the 1933 in cage tests and later in small plot and Cotton Belt, except where onions are grown large-scale field experiments. Evaluation of a near cotton. large number of insecticides showed that sul- The duration and intensity of thrips infesta- phur and mixtures of sulphur and arsenicals tions vary greatly in different seasons and gave the best results and, in some cases, more locations. Experience is the best guide in pre- than doubled the yield where the infestations dicting damage to cotton in an area. were high. Mixtures of calcium arsenate and Development.—Thrips develop in four life sulphur or paris green and sulphur applied at stages—egg, larva, pupa, and adult. Female the rate of 15 to 18 pounds of dust per acre adults lay their eggs in the tender tissues of were about equal in effectiveness. The work on plants. Eggs are creamy white and minute— hemipterous insects aroused a great deal of about i/ioo-inch long. In about 4 days, the eggs popular interest among cottongrowers of Ari- hatch into tiny, white larvae. The larvae feed zona. One company in 1939 cooperated in a for about 6 days, shedding their skins twice large-scale experiment of airplane dusting by during that time. Then, they burrow into the furnishing the planes and insecticides for dust- soil and transform into pupae. The pupae 38 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE transform into adults and emerge from the soil The abundance of thrips, extent of their dam- in about 4 days. age, and need for their control vary greatly in Adult thrips may be yellow, brown, or black, different years and areas. Thrips may retard depending on the species. They are slender and seedling growth and delay fruiting. They may about i/i 6-inch long. They have two pairs of be responsible for reduction in yield where fringed wings and fly from plant to plant and droughts in late summer limit production or from field to field. where boll weevils, boUworms, or pink boll- Thrips complete a generation in about 2 worms are prevalent. weeks and produce many generations in a year. Research,—Considerable information on the In southern areas, they breed all year on vari- species, host relationships, and factors causing ous host plants. In other areas, they pass the outbreaks of thrips on cotton was accumulated winter in plant residues and resume the life at various research locations. Effective control cycle when hosts become available in the spring. measures were not developed, however, until Both thrips larvae and adults damage cotton organic insecticides were developed in the plants. They pierce the leaf tissues with their 194œs (fig. 16). sharp mouth parts and suck out the juices. These insects injure cotton seedlings and some- times older plants. They attack leaves and ter- Miscellaneous Cotton Insects minal buds. Severely infested young plants may All parts of the cotton plant are attacked by die, and the stand may be destroyed or reduced insects. In addition, the sweet liquid secreted to the point where the crop must be replanted. by the nectaries of the leaves and bracts at- This condition may occur when heavily infested tracts a great variety of harmless and beneficial onions, growing near cotton, are harvested. insects that are often mistaken for pests. The Heavy feeding on cotyledons gives the plants Department over the years has studied many a silvery appearance. A field of severely injured minor pests. Some outbreaks are sporadic in young cotton may appear to have been scorched local areas, and in others the species are gen- by fire. Thrips injury to leaf tissue in terminal erally distributed but are usually present in such buds results in ragged, crinkled leaves that curl limited numbers that their damage is not seri- upward. (Aphid injury would cause leaves to ous. Because of the great diversityy of species turn downward.) The terminal buds may be that attack cotton, the total damage caused by killed. When this occurs, new buds develop and the minor insect pests is considerable. About 50 the plant becomes distorted and excessively species of miscellaneous cotton insects were branched. studied in connection with the early boll weevil Infestations usually abate after cotton plants investigations. are 4 to 6 weeks old. The plants recover from the Research.—Damage to cotton by the field injury, but those that are severely injured may cricket led to studies of the biology and methods continue to shed squares for a week or more of controlling this common species. The salt- after recovery seems apparent. marsh caterpillar, beet armyworm, cutworms, If an infestation occurs on seedling cotton blister beetles. Fuller's rose beetle, and many and does not destroy the stand, it may retard other insects that attack cotton have been plant growth and delay fruiting and maturing of studied to some extent. The nature of the dam- the crop. The same is true if an infestation at- age caused by about 40 species of Coleóptera tacks cotton that has progressed beyond the and Lepidoptera that occur on cotton in Louisi- seedling stage. In some western cotton-growing ana was studied at the Tallulah laboratory as areas, cotton in the late-season stage of growth late as 1934 and 1935. Many of these had not is sometimes severely attacked by thrips. been recorded previously on cotton. Thrips attack many wild and cultivated host The brown cotton leaf worm, Acontia dacia plants. Large numbers of adults migrate to Druce, was collected on cotton from three coun- cottonfields in spring and early summer after ties in Texas in 1953. Damaging infestations other host plants begin to mature. have occurred through the 1950's over wide RESEARCH ON COTTON INSECTS 39

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_. 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 weed host plants, and the use of insecticides. In have been reported from Arkansas. western areas, irrigation forces the subter- Several Anomis leafworms are known to ranean forms to the surface, where they may occur in the cotton-growing regions of Africa, be treated with insecticides or destroyed by Asia, all of the America's, and the East and natural factors. If the vegetation in an infested West Indies. Three species—A. erosa Hübner, A. area is plowed under 3 to 6 weeks before the flava fimbriago (Stephens), and A. texana Riley cotton crop is seeded, insecticides may not be —occasionally damage cotton in the United needed. States. They are often mistaken for the cotton Root aphids known to attack cotton are the leafworm and are sometimes found on the same corn root aphid. Aphis maidiracidis (Forbes), plants with it. Smynthurodes betae (Westwood), and Rhopal- Several species of cutworms, including the osiphum rufiabdominalis (Sasaki). So far as is following, may develop in weeds or crops, es- known, injury before 1956 was confined to the specially legumes, and then attack adjacent cot- eastern seaboard. S. betae destroyed spots of ton or cotton planted on land previously in cotton up to 1^ acres in fields in Pemiscot weeds or legumes : Black cutworm, Agrotis Íp- County, Mo., in 1956. In 1961, root aphids caused silon (Hufnagel) ; palesided cutworm, A. male- some damage to cotton in the northeastern fida Guenée; variegated cutworm, Peridroma counties of North Carolina and Arkansas. Sev- saucia (Hübner) ; granulate cutworm, Feltia eral species of ants are known to be associated subterránea (F.) ; rough-skinned cutworm, with root aphids, the principal one being the Proxerms mindara, Barnes and McDunnough; cornfield ant, Lasius alienus (Foerster). Root and army cutworm, Euxoa auxilUaris (Grote). aphids injure cotton chiefly in the seedling Recommended control measures include thor- stage. Since cotton in this stage shows injury ough preparation of seedbed, elimination of without any evidence of insects being present, 40 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE the underground parts should be examined dons of seedling cotton in New Mexico in 1967 carefully. Ant mounds at the base of these and 1972. plants indicate the presence of root aphids. The cotton stainer, Dysdercus suturellus The cowpea aphid, Aphis craccivora Koch, (Herrich-Schaifer), is found within the United the green peach aphid, Myzus persicae (Sul- States in Florida only. However, probably ow- zer), and the potato aphid, Macrosiphum ing to mistaken identity, the literature also euphorbiae (Thomas), are common on seedling records it from Alabama, Georgia, and South cotton. Cotton is not believed to be a true host Carolina. of these species. However, in 1963, A, cracci- Several leafhoppers of the genus Empoasca vora caused severe and permanent stunting of are often abundant on cotton in many sections cotton plants in the San Joaquin Valley of of the Cotton Belt. Serious injury has been California. reported only in California, however, and this Darkling beetles, Blapstimus spp. and Ulus was caused by two species, southern garden spp., the adults of false v^ireworms, occasionally leafhopper, E, solana DeLong, and potato leaf- adversely affect the stand of young cotton in hopper, E. fabae (Harris). These species are western areas. known to be phloem feeders on some crops and The garden springtail, Bourletiella hor- cause damage typical of this type of feeding on tensis (Fitch), has caused injury to cotton cotton. locally in Hertford County, N.C. Another The saltmarsh caterpillar, Estigmene aerea springtail, Entomobrya unostrigata Stach, has (Drury), is a late-season pest of cotton prin- occasionally damaged seedling cotton over a cipally in western irrigated areas. Occasionally, wide area of the southern high plains of Texas the yellow woollybear, Diacrisia virginica (F.) and New Mexico. and the hairy larvae of several other tiger Leaf beetles of the genus Colaspis are wide- moths, Arctiidae, including Callarctia phyllira spread and often found on cotton, frequently (Drury), C. arge (Drury), and C, oithona Strk., on the foliage or near the base of squares and cause serious damage to cotton. bolls where they usually feed on the bracts The striped blister beetle, Epicauta vittata surrounding them. (F.), sometimes causes severe foliage damage The corn silk beetle, Calomicrus brunneus in small localized areas. Damage usually re- (Crotch), has been reported as a pest of sults when weeds, which are preferred host cotton in localized areas in South Carolina, plants, are cleaned out of cotton. Total loss of Georgia, Alabama, Mississippi, and Louisiana, foliage may result in small areas before the but little is known about it. insects move out of the field. The cowpea curculio, Chalcodermus aeneus Field crickets, Gryllus spp., occasionally feed Boheman, sometimes causes damage to seed- on cotton bolls and seedling plants in the Im- ling cotton. perial Valley of California and in Arizona. A curculionid, Compsus auricephalus (Say), During periods of drought late in the season, damaged young cotton plants and foliage in they may feed on the seed of open bolls, espe- Grady County, Okla., in 1961. It also appeared cially in the Delta sections of Arkansas, Loui- in large numbers in cottonfields in Pope County, siana, and Mississippi. This feeding is usually Ark. In 1963, heavy populations caused con- done at night as the crickets hide during the siderable foliage damage to young plants in day in deep cracks in the soil. localized areas of Grimes, Robertson, and Whitefringed beetles, Graphognathus spp., Brazos Counties in Texas and in Obion and are pests of cotton and many other farm crops Lake Counties in Tennessee. A curculionid, in limited areas of Alabama, Florida, Georgia, Conotrachelus erinaceus (LeConte) caused Louisiana, Mississippi, North Carolina, South damage to stems of seedling cotton in isolated Carolina, and Tennessee. Infestations in recent instances in Marion County, Ala. in 1962. A years have been discovered in Maryland, Vir- curculionid, Otiorhynchus cribricollis (Gyllen- ginia, and Texas. The larvae feed on the roots hal), caused spotted heavy damage to cotyle- of young plants. RESEARCH ON COTTON INSECTS 41 The seedcorn maggot, Hylemya platura fascialis (Stephens), a pyraustid larva, is re- Meigen, may seriously affect the stand of cot- ported occasionally attacking cotton bolls in ton, particularly when planting closely follows Imperial and San Joaquin Valley of California. the turning under of a green manure crop or It also has been reported from Ariozna, Okla- other heavy growth. homa, and Texas. The whitelined sphinx, Hyles lineata (F.), Bugs of the genus Nysiics, N. ericae (Schill- occasionally occurs in large numbers in uncul- ing), N, californicus Stal, and A^. raphanus tivated areas and migrates to cotton. Howard, commonly called false chinch bugs, Several species of wireworms are associated frequently migrate to cotton from adjacent with cotton. Damage is caused by the sand wire- weed hosts. Stands of seedling cotton may be worms, Horistonatus uhlerii Horn, in South destroyed by adults and nymphs. Carolina and Louisiana and by the Pacific Coast Snowy tree crickets, Oecanthus spp., infesta- wireworm Limonius canus Leconte, in Cali- tions caused alarm to some southwestern Okla- fornia. Adults of the tobacco wireworm, Con- homa cottongrowers in mid-July 1958. Ap- oderus vespertinus F., are frequently found on proximately 3-percent lodging of plants oc- the cotton plant, and the larvae may cause curred in the Blair area. There is evidence that damage to cotton. Wireworms, together with this group of insects may be predaceous on false wireworms and the seedcorn maggot, aphids. sometimes prevent the establishment of a stand. The European corn borer, Ostrinia nubilalis Approved crop-rotation practices, increased soil (Hübner), was first reported on cotton in the fertility, and added humus help to reduce United States on July 3, 1955, in Franklin damage to cotton by the sand wireworm. County, Tenn., in a 3-acre field adjacent to one Serpentine leaf miners, Liriomyza spp., and that was in corn the previous year. A few plants L. pictella (Thomson), in California have been near the edge of a field were severely damaged. present in large numbers in some areas during The cotton plants were only 8 to 10 inches high, the last few years. Drought conditions favor and the larvae had entered the stems 2 to 6 infestations of these pests. Heavy infestations inches from the ground and burrowed up may result in considerable leaf shed. Infesta- through their centers. In August light infesta- tions often are brought under control by rain tions were reported in cotton in Dunklin, New or irrigations. Madrid, Pemiscot, Butler, Stoddard, and Mis- Damage to cotton by periodical cicadas, sissippi Counties, Mo., and in Madison County, Magicicada spp., in the United States was first Tenn. The insect had bored into the upper third reported in 1905. Damage is caused by the of the stems, and second- and third-instar lar- deposition of eggs in the stems of young plants, vae were attacking small bolls. These records branches of older plants, and occasionally in were of special interest because the European leaf petioles. The parts of the plant above the corn borer was apparently spreading in the oviposition puncture usually die. Growth below Cotton Belt. No reports of this insect on cotton the puncture results in low bushy plants. Severe were received in 1956 and 1957. local damage to cotton by Diceroprocta vitri- In 1958, the European corn borer was found pennis (Say) occurred in the river bottoms of in cotton stalks in Autauga and Madison Coun- nine counties in Arkansas in 1937. An unde- ties, Ala., and in Washington County, Miss., in termined cicada caused light damage to cotton late July. In 1959, as many as 10 percent of the in some areas in Maricopa County, Ariz, in plants were infested in a 10-acre field of cotton 1961. in Etowah County, Ala. This field had been The harlequin bug, Murgantia histrionica planted to corn in 1958. The borer was found, (Hahn), heavily infested a few cottonfields in also, in Madison Parish, La., in 1959. Damage Graham County, Ariz., in August 1959. Feed- was confined to the terminal 6 to 8 inches of ing was similar to that of other stink bugs. No the plant. Other infestations were found in immature stages were noted. cottonfields in Autauga County, Ala. In 1961, The barberpole caterpillar, Mimoschima rufo- larvae were found in cotton in Hardeman, Lin- 42 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE coin, and Fayette Counties in southern Tennes- in that area. Moderate damage was caused to see. In 1966, larvae were found in cotton in young cotton plants in the Arkansas Delta area Florence, S.C. In other parts of the world, par- in 1962 by larvae of P. implícita (Horn). ticularly in Russia, Turkestan, and Hungary, The cotton stem moth, Platyedra subcinerea it has been reported as a serious pest of cotton. (Haworth), a close relative of the pink boll- One reference, Annual Conference Report on worm, was first discovered in the United States Cotton Insect Research and Control (100), in 1951, when larvae were found feeding in states, ''In Turkestan it is principally cotton hollyhock seed in Mineóla, Long Island, N.Y. which is attacked by the larvae and in which It is recorded as a pest of cotton in Iran, Iraq, they bore long tunnels in the upper part of the Morocco, Transcaucasia, Turkestan, and the stems.'' U.S.S.R., and as feeding on hollyhock and other The Fuller rose weevil, Pantomorus cervinus malvaceous plants in England, France, and cen- (Boheman), occasionally is a pest of cotton. tral and southern Europe. Collections made in It is a leaf feeder and usually attacks cotton in 1953 extended its known distribution in this the early season, causing ragging of the leaves country to a large part of Long Island and lim- and partial defoliation. It overwinters as an ited areas in Connecticut and Massachusetts. adult in about the same habitat as the boll Extensive scouting during 1954 disclosed that weevil. Examinations of surface woods trash it had reached 11 counties in four States as for hibernating boll weevils often reveal speci- follows: Hartford and New Haven, Conn.; men of the Fuller rose beetle. It has been re- Essex and Plymouth, Mass. ; Monmouth, Ocean, ported from cotton in Georgia more frequently and Union, N.J.; Westchester and all counties than from any other area. of Long Island (Nassau, Queens, and Suffolk), The stalk borer, Papaipema nebris (Guenée), N.Y. There has been no reported spread since is widely distributed east of the Rocky Moun- 1954 until 1965 when it was reported from tains. It attacks many kinds of plants, including Rockingham County, N.H. Although this species cotton, and is so destructive that one borer in a has not been found in the Cotton Belt in the field may attract attention. The borers are most United States, it is desirable to keep on the likely to be found near the edges of cottonfields. lookout for it on cotton, hollyhock, and other Light marginal injury occurred in scattered malvaceous plants. In 1956 it was collected from fields in Missouri during June 1957. It was also a natural infestation on cotton growing on the reported as causing some injury to cotton in laboratory grounds at Farmingdale, N.Y. Mississippi and Tennessee in 1956. In 1961 it Several of the leaf rollers, Tortricidae, occa- caused some damage along the edges of many sionally damage cotton. Platynota stultana cottonfields in western and southern counties in (Williamson) and P. rostrana (Wilkerson) are Tennessee. It is sometimes mistaken for the the species most commonly recorded, but P. European corn borer. Clean cultivation and flavedana (Clemens), P. idaeusalis (Wilkerson), keeping down weed growth help to hold them and Sparganothis nigrocervina (Williamson) in check. The use of stalk shredders early in the have also been reported. These species are wide- fall should reduce their numbers. ly distributed and have many host plants. P. A white grub, Phyllophaga ephilida (Say), stultana has at times been a serious pest of was reported to have destroyed 5 acres of cotton cotton in the Imperial Valley of California and in Union County, N.C., in 1956. As many as 20 part of Arizona and New Mexico. larvae per square foot were found. P. zavalana Heavy feeding on cotton by the Japanese Reinhard is also reported to be a pest of cotton beetle, Popillia japónica Newman, was reported in the Matamoras area of Mexico, where the in Sampson County, N.C., in 1961. Adults of the adults feed on foliage, particularly in the seed- Japanese beetle caused 30- to 35-percent de- ling stage. It is known to occur in Zavala and foliation of cotton plants in fields in the more Dimmit Counties, Tex. P. cribrosa (LeConte), heavily infested areas in North Carolina in sometimes known as the '% o'clock bug" in west 1970. Texas, has also been feeding on young cotton A giant appletree borer, Prionus sp., caused RESEARCH ON COTTON INSECTS 43 isolated root damage to cotton in one county in striped armyworm, S. praefica Grote, sometimes Arkansas in 1962. cause considerable damage to cotton. Adults of a buprestid beetle, Psiloptera druTri^ The cotton square borer, Strymon melinus mondi Lap., occasionally cause damage to cotton. (Hübner), occurs throughout the Cotton Belt, The damage consists of partly girdled terminals but rarely causes economic damage. The injury that break over and die. it causes to squares is often attributed to the The pink scavenger caterpillar, Sathrobrota bollworm. rileyi (Walsingham), is one of several insects The palestriped flea beetle, Systena blanda that resemble the pink bollworm and is some- Melscheimer, the elongated flea beetle, S. elon- times mistaken for it by laymen. The larvae is gata (F.) and S. frontalis (F.), sometimes cause primarily a scavenger in cotton bolls and corn serious damage to seedling cotton in some areas. husks that have been injured by other causes. The sweetpotato flea beetle, Chaetocnema con- Several species of grasshopper, including the finis Crotch, injured seedling cotton in the Pied- follov^ing, sometimes attack cotton: American mont section of South Carolina in May 1954. grasshopper, Schistocerca americana (Drury) ; The striped flea beetle, Phyllotreta striolata Trimerotropis pallidipennis pallidipennis (Bur- (Fabricius), caused damage to cotton in Ala- meister) ; differential grasshopper, Melanoplus bama in 1959. Other species of flea beetles have differentialis (Thomas) ; lubber grasshopper, been reported from cotton, but records regard- Brachystola magna (Girard) ; migratory grass- ing the injury they cause are.lacking. hopper, M. sanguinipes (F.) ; redlegged grass- Whiteflies, the bandedwing whitefly, Trialeu- hopper, M. fermurrubrum (De Geer) ; and two- rodes abutilonea (Haldeman), the greenhouse striped grasshopper, M, bivittatus (Say). whitefly, T. vaporariorum (Westwood), and the The American grasshopper overv^inters as an sweetpotato whitefly, Bemisia tabaci (Genna- adult and in the spring deposits eggs in the dius), are usually kept in check by parasites fields. Other species of grasshoppers overwinter and diseases, but occasionally may be serious as eggs in untilled soil, fence rows, sod water- pests late in season. Bemisia tabaci is reported ways, around stumps, and similar locations. The to be a vector of the leaf crumple virus of cotton. species overwintering in the egg stage can be Whiteflies have caused damage to cotton in best controlled with early treatment of hatching northwest Louisiana since 1964. Infestations beds before the grasshoppers migrate into the have increased in Alabama and IVKssissippi in fields. Sprays or dusts have largely replaced the early 1970's. poison baits, particularly where grasshoppers The cabbage looper, Trichoplusia ni (Hüb- must be controlled on lush or dense vegetation. ner), is a pest of cotton in many areas. It is The beet armyworm, Spodoptera exigua difficult to control with insecticides. It is fre- (Hbn.), is often a pest of seedling cotton, but quently controlled by virus and fungus orga- it may also attack older plants. Squares and nisms. When diseased loopers are commonly blooms may be destroyed, and feeding on the found, chemical control may be delayed or omit- bracts may cause small bolls to shed. Although ted. The cabbage looper became more of a prob- the beet armyworm has been a pest in the West lem in cotton in the 1950's and less so since and Southwest for many years, it was reported then. in Louisiana and Mississippi in 1962. Injurious The greenhouse leaftier, Udea rubigalis infestations occurred in some localities in Ala- (Guenee), also known as the celery leaftier, has bama and Georgia in 1963, and in Alabama, Ar- occasionally been abundant on cotton in the kansas, and Mississippi in 1969. It was a serious San Joaquin Valley of California. Despite the pest of cotton in Georgia in 1973 and 1974. heavy populations, damage was generally slight The fall armyworm, Spodoptera frugiperda and restricted to foliage on the lower third of (J. E. Smith), occasionally occurs in sufficient the plants in lush stands. This pest caused con- numbers to damage cotton. siderable damage in three fields near Yuma, The yellowstriped armyworm, Spodoptera Ariz., in 1964. ornithogalli (Guenee), and western yellow- The false celery leaftier, Udea profundalis 44 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

(Packard), caused considerable defoliation of products in which insects that attack stored cotton in some fields in Tulare, Kings, and products are likely to develop. Among the in- Fresno Counties, Calif., in 1962. Control was sects that cause damage to stored cottonseed or difficult because of the insect's feeding habits to cottonseed meal are the cigarette beetle, on the lower part of plants within a web. Lasioderma serricorne (F.), the Mediterranean Damage to cotton stalks by termites, unde- flour moth, Anagasta kuehniella (Zeller), the termined species, was reported in western almond moth, Cadra cautella (Walker), and the Tennessee in 1961, and in previous years in Indian-meal moth, Plodia interpunctella (Hüb- Texas. Termites, Reticulitermes sp. (Rhino- ner). Other insects commonly found in cotton- termitidae), partly destroyed a stand of cotton seed are the flat grain beetle, Crytolestes in Little River County, Ark., in 1961. Insects in or among cottonseed in storage,— pusillus (Schönherr), the red flour beetle, Tri- Insect infestations in cottonseed during storage bolium castaneum (Herbst), and the sawtoothed can be minimized if proper precautions are grain beetle, Oryzaephiltts surinamensis (L.). followed. Cottonseed, or seed cotton, should be The pink bollworm may be found in stored stored only in a bin or room thoroughly cleaned cottonseed, but such infestations would be pres- of all old cottonseed, grain, hay, or other similar ent in the seed before they were stored.

RESEARCH 1941 TO 1974

Attractants 1971-73, traps baited with grandlure at the rate of two per acre were used as one of the Boll Weevil suppression measures in the core or eradication area. Trap crops consisting of cotton planted In the 1950's an observation was made at the some 2 weeks earlier than that of the grower Stoneville, Miss., Cotton Insects Laboratory that cotton were baited with grandlure at 100-foot the female weevil sought the male rather than intervals. Plants in the trap crops were treated the usual procedure, most male insects seeking in-furrow at planting with aldicarb and side- the female. This was verified in laboratory stud- dressed with it at early squaring to kill over- ies at the Boll Weevil Research Laboratory in the wintered weevils attracted to them. The trap mid-1960's, and the attractant named grand- crops were treated with methyl parathion dur- lure was identified and synthesized. Now com- ing periods when the aldicarb treatment was mercially available, grandlure is widely used in considered not to be effective. Very few weevils migration, survey, and detection procedures. were found in the grower cotton before it began Hopefully, it will be registered in the future for to fruit. Even after grower cotton began to use in population management and eradication square, weevils continued to be attracted to the programs. A trap baited with grandlure was trap crops as evidenced by the collection of developed to capture female boll weevils. Grand- sterile males released in the grower cotton being lure is also an aggregant as early in the year collected in the trap crops. The development of males as well as females are attracted to it. infield traps, those that can be used within fields As cotton plants begin to square, however, re- without interfering with cultivation, baited sponse to the pheromone is predominately by with grandlure has great potential as a tool in female boll weevils. Traps baited with grand- population suppression or elimination pro- lure placed along the edges of cottonfields cap- grams. ture tremendous numbers of overwintered boll In the previous discussion of the boll weevil, weevils. efforts to develop attractants from cotton plants In the Pilot Boll Weevil Eradication Experi- to control the pest were unsuccessful. Interest in ment conducted in south Mississippi and in ad- boll weevil attractants from the cotton plant joining areas of Louisiana and Alabama in was revived by researchers in the 1960's. RESEARCH ON COTTON INSECTS 45

Water and chloroform extracts of cotton plant extract of the pheromone from females had very parts were attractive. A powerful arrestant and short activity, and a similar problem has been feeding stimulant was found in water extracts found with the synthetic material. Research is of all cotton parts and square components currently directed toward development of a tested. A feeding deterrent was found in the stable formulation of the synthetic pheromone calyx of an alternate host, Hibiscus syriacus. to give long-term activity in the field. However, the chemistry of the arrestant and A similar attractant has recently been dis- attractant compounds in the cotton plant is so covered for the bollworm ; however, it is as yet complex that chemists have been unable to iden- uncertain whether the synthesized compound is tify and synthesize all of them for use in con- the natural sex pheromone. trol, suppression, or survey programs. Once stable formulations of the pheromones of the two species are devised, the possibility Pink Bollworm for developing population suppression schemes In the mid-1960's research on the female pink will be opened. Among the methods suggested bollworm moth showed that the female emitted for use of these materials are elimination of a substance attractive to males. The chemists males by trapping or dispensing the attractant identified and synthesized the substance and on an insecticide-treated substance, luring the named it propylure. Unfortunately, propylure, males to substrate treated with chemosterilants, though attractive ^o males in the laboratory, or saturating an environment with the phero- failed to perform in the field. Apparently, some- mone, thus, interfering with the mating orien- thing was missing in the synthesized compound. tation of the males. However, it will be several A somewhat structurally related compound, years before these systems can be put to prac- called hexalure, was found to be attractive to tical use. Development of methods of using the males and was widely used in the West in pheromones in traps to anticipate outbreaks of survey and detection operations. Though not the pests for timing of insecticide applications as attractive as the natural pheromone, hexalure is apparently more immediately promising. was sufficiently attractive to be used to bait A related approach has been the search for traps so that use of live females was obviated. chemicals that will disrupt the chemical com- An intensive effort was made by ARS chemists munication between sexes. Researchers have to identify and synthesize the pheromone. How- shown that the attractiveness of female tobacco ever, progress was slow and in late 1973 re- budworms is greatly reduced if certain organic searchers at the University of California, Riv- chemicals are released into the environment. erside, identified and synthesized the compound. However, these studies are in the preliminary ARS chemists verified the finding. Named gossy- stages. plure, it has considerable potential for use in Researchers have reported that the male survey detection and population suppression pro- tobacco budworm, when preparing to mate with grams and has been used in a large-field experi- a female, produces a substance that suppresses ment as a confusant. When applied to a field of the emission of the female sex pheromone, but cotton, the male then cannot locate the female. no work has been done on isolating the active agent. Possibly such a substance would be use- Tobacco Budworm and Bollworm ful in combination with some of the previously noted techniques. Females of the tobacco budworm and boll- Results of recent research have shown that worm produce powerful sex pheromones or sex certain egg and larval parasites of Heliothis attractants to call males of the respective spe- spp. are attracted to the host by host-seeking cies for mating. Research has continued since stimulants named kairomones. 1963 on these pheromones with the ultimate goal of producing synthetic materials that could be used for population survey and suppression. Tarnished Plant Bug The pheromone of the female tobacco bud- In the early 1970's a researcher at the Stone- worm was identified and synthesized. A crude ville. Miss., laboratory found that the female 46 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE tarnished plant bug produced a substance at- tonfield, but knowledge is lacking on the habits tractive to males. Research is underway to and factors affecting abundance of the many identify the substance. species. Lady beetles (Coccinellidae) are com- mon predators in cottonfields. The large species, Biological Control including Coleomegilla macúlala, Hippodamia convergens, and Coccinella novemnotata, feed Predators, parasites, and diseases play an on eggs and small larvae of bollworms, other important role in the control of insect pests of Lepidoptera, and on aphids. Some smaller spe- cotton. The role of natural enemies in cotton cies in the genus Scymnus and all Stethorus insect control programs should be maximized spp. are primarily predators of mites. Collops by utilizing insecticides, cultural practices, and beetles (Malachinnae in the family Malyridae) other agents and techniques in supportive ways. are often abundant in cotton. They reportedly The role of beneficial insects in the field should feed on the eggs and small larvae of the boll- be evaluated when possible. Some predaceous worm and other lepidopterous species. and parasitic insects of prime importance are discussed in this section. Díptera

Predators Many families contain species predaceous as adults or larvae. Best known as predators in Hemiptera the cottonfields are the larvae of syrphid flies Orius insidiosiis and 0. tristicolor, often that prey primarily on aphids. called minute pirate bugs or fiower bugs, are Hymenoptera predators of eggs and first instar larvae of the bollworm, thrips, and other small insects. Popu- Ants (Formicidae) include many predaceous lations often build up in such crops as corn and species ; Iridomyrmex pruinosus is a predator grain sorghum. Big-eyed bugs, Geocoris pallens of bollworm eggs. Paper-nest wasps, Polistes and G, uliginosus, are common predators of spp., and solitary wasps of the genera Zethus, eggs and small larvae of the bollworm as well EumeneSy Rygchium, and Stenodynerus provide as of other Lepidoptera, mirids, and aphids. their young in the nests with Lepidopterous Damsel bugs of the genus Nabis are efficient larvae. Wasps of the genus Sphex nest in the predators of a wide range of prey including ground and provide their young with grass- mirids, leafhoppers, aphids, and eggs and lar- hoppers and related insects. vae of Lepidoptera. They attack bollworms as large as the second instar. Assassin bugs, par- Spiders ticularly the genus Zelus, feed freely on eggs All spiders are predaceous and many species and larvae of the bollworm, tobacco bollworm, are common in cottonfields. Orb weavers cap- and cabbage looper. However, these insects are ture many moths in their webs. Wolf spiders usually less abundant in cottonfields than those and lynx spiders capture moths and other in- discussed previously. Podisus maculiventris is sects. Larvae and adults of the bollworm and a common stink bug that preys on large boll- boll weevil adults are among the prey of jump- worms and other caterpillars in the West. ing spiders.

Neuroptera Parasites Larvae of green lacewings, Chrysopa spp., are important predators of eggs and small lar- Hymenoptera vae of bollworm and other Lepidoptera and of Numerous hymenopterous parasite species of many soft-bodied insects. several families are of great value in the bio- logical control of most cotton pests. These Coleóptera parasites vary tremendously in size, behavior, Ground beetles of the family Carabidae have ecology, and host preference. Within their considerable potential as predators in the cot- ranks, however, effective or potentially effective RESEARCH ON COTTON INSECTS 47 parasites of nearly every developmental stage, be necessary to insure that adequate numbers of egg through adult, of the majority of cotton these entomophagous insects will be available pests may be found. Many of them occur natu- to prevent the pests from causing economic rally in great numbers in certain geographical damage. areas. Some are nov^^ and many will eventually Recent experiments have demonstrated that have to be augmented in the field by means of augmentation of entomophagous insects through habitat management or mass release techniques mass rearing and release holds promise as so as to concentrate their populations at the an effective means of controlling Heliothis. time and in the place required for most effective Releasing large numbers (100,000) per acre control. of the predator, Chrysopa carnea Stephens, controlled Heliothis in field cages, which was confirmed in small field plots. Similar results Díptera were obtained with large releases of the egg Flies of the family Tachinidae are parasites parasite Trichogramma. A large-scale pilot primarily of larvae of Lepidoptera and Coleóp- test of augmentation was, therefore, under- tera. Several species are of value as parasites taken. A mass-rearing facility was developed of cotton pests and should be examined with the for producing Chrysopa and Trichogramma by same goals of augmentation through laboratory using Sitotroga eggs as host material. In addi- or field practices. tion, development of an encapsulated artificial diet was undertaken. Control with Predators and Parasites In 1972-73, Chrysopa and Trichogramma were produced for a large-scale test of the Native predators and parasites are often augmentative release method in Frio Co., Tex. highly effective against aphids, the bollworm, Methods of shipping and releasing the insects beet armyworm, tobacco budworm, cabbage were devised, and releases were made on about looper, cotton leafworm, cotton leafperforator, 1,700 acres. However, failure of a diapause boll cutworm, lygus bugs, saltmarsh caterpillar, weevil control program to reduce populations spider mites, whiteflies, and certain other pests. necessitated insecticidal treatment for the boll Diversified crops and uncultivated areas serve weevil and negated much of the effect of the as refuge and reservoir areas for predators and releases of the entomophagous species. parasites, and unfortunately for some pests. Results of this pilot test brought out several The need for controlling such insects as the points to be considered in using this technique. boll weevil, lygus bugs, and the cotton flea- Effective and economical use of this method hopper with insecticides often results in in- will require the design and operation of a pest creased subsequent infestations of the bollworm control system which makes possible the man- and tobacco budworm because beneficial insects agement of pests over large areas. Production that might hold such infestations below eco- practices on all farms in the area must be nomic levels are killed off by the insecticides. compatible with the- management of parasites The continued use of an insecticide then is and predators. Releases of beneficial insects in necessary even though infestations of the pri- cotton cannot be effective if conventional in- mary insect have been reduced below injurious secticides are applied at the same time to con- levels. If insecticidal control was not needed trol other pests such as the boll weevil. Methods for these insects, the control problem with the of determining and anticipating the numbers bollworm complex would be eased considerably. of pests and entomophagous species needed for Augmentation of food for lacewings has release must be improved. shown promise in field experiments in Cali- Two hymenopterous parasites, Bracon kirk- fornia. patricki (Wilkinson) and Chelonus blackburni Naturally occurring parasitic and predaceous (Cameron), were tested as control organisms insects frequently destroy sufficient Heliothis for the pink bollworm in approximately 100 to prevent outbreaks of these pests on cotton. acres of irrigated cotton near Tucson, Ariz., in However, supplementing natural control may 1971 and 1972. The parasites were reared on 48 AGEICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE the pink bollworm at the Biological Control at an average rate of about 50 miles per year. Investigations Laboratory in Tucson. The pink In Georgia in 1959, boll weevils infested a cot- bollworm populations were suppressed in the tonfield 25.5 miles from other cottonfields. In early season with releases of B, Kirkpatricki, 1968 boll weevils were captured in male-baited but C. blackburni was somewhat less effective wing traps along the highway from Juarez to later in the season. These parasites were reared Chihuahua in Mexico though the traps were in the Animal and Plant Health Inspection Serv- located 25 to 45 miles from .otton. During mid- ice, Methods Development Laboratory, Phoe- season in South Carolina, Fi and succeeding nix, Ariz., in 1973 and were released in the generations of the weevil dispersed at least 19 wild cotton in the southern most area of Flor- miles to find new cotton. In south Mississippi, ida. A few pink bollworm larvae infested with genetically marked weevils were collected in a the parasites were recovered. Though the para- pheromone-baited trap 25 and 35 miles from a sites show promise against low-level popula- release site. tions of the pink bollworm, the technique can- Pink bollworms have long been known to not be exploited until techniques for rearing move long distances when food supply became them artificially are developed. An effective egg scarce late in the season. The collection of pink parasite is needed. bollworm moths in traps operated from an air- Additional research is needed to reduce the plane at 3,000 feet over cottonfields in Mexico cost of rearing and to improve the quality of indicated that moths could migrate several hun- the released insects in various ways. More dred miles from Mexico to the United States. engineering research is needed to improve Though in small numbers pink bollworm moths mechanization of the systems. It is anticipated were collected in light traps early in the season, it will be a number of years before all of the almost none were caught after cotton plants necessary components can be developed to the began to fruit, an indication that early-season extent that this method can be used effectively movement was a search for oviposition sites in by cottongrowers. fruiting cotton. Collections in light traps in- creased as cotton plants began to mature and oviposition sites became scarce. Large numbers Biology and Ecology were captured when late season infestations were heavy. Results of teiçts conducted in Much of the biological work conducted on Riverside County, Calif., in 1970 showed that the boll weevil, bollworm, and pink bollworm moths from overwintering larvae were capable in the early days continues to have validity. of migrating at least 35 miles to infest cotton Progress has been considerable, however, in in areas not previously infested. This finding ecological studies as more sophisticated tech- will be of considerable value if any elimination niques became available. Sex attractants, light program for the pest is ever undertaken. traps, and marking techniques, genetic as well Though the bollworm is known to migrate as physical, have been invaluable in the fur- for considerable distances, definitive data have therance of ecological studies. been difficult to obtain. Hibernation and sur- vival studies in the early 1940's in central Texas Migration showed that a generation developed in the field before moth emergence from hibernating Migration of the boll weevil usually occurred pupae occurred in the cages. It was assumed that late in the season when populations developed the field generation resulted from migrants in extremely large numbers and new sources from the South where earlier emergence oc- of food and oviposition sites were needed. With curred. Use of black light traps to which the the advent of the more effective insecticides moths are attracted has been most helpful in and their widespread use, migration as oc- such studies. Results of studies in the Missis- curred previously was not so pronounced. Sur- sippi Delta area in the 1960's were similar. veys in the early days showed that the boll Moths were collected in the light traps some 30 weevil moved eastward across the Cotton Belt days before moths emerged from hibernating RESEARCH ON COTTON INSECTS 49

pupae. In 1968 moths from larvae developing were made during the day and night at all sea- on a plot of radiolabeled sv^eet corn on St. sons of the year at elevations of from 200 to Croix, U.S. Virgin Islands, dispersed in a non- 15,000 feet, during which 30,033 specimens of random pattern for distances up to 10 miles insects, spiders, and mites were collected. The to locate suitable hosts. In the same year, data weaker fliers were taken in greater numbers for released marked moths at Tifton, Ga., indi- at the higher elevations than the stronger fliers, cated that moths dispersed over an extended and numbers of wingless adults, nymphs, and distance, at least 16 miles in one night and at larvae were collected at elevations up to 14,000 least 45 miles over a period of 1 to 4 days. Col- feet. A spider was taken at 15,000 feet, the lections of moths in light traps at different highest elevation at which flights were made. heights indicated that bollworms are capable Temperature, surface vapor pressure, intensity of obtaining controlled flight altitude in excess of air currents, direction of the wind, and con- of 1,000 feet. A moth was collected in traps vection were the most important factors in from aircraft at 500 feet. In the fall of 1973 determining the abundance of the insects in the three moths v^ere captured in light traps on upper air. These flights were the most extensive unmanned oil platforms in the Gulf of Mexico ever undertaken for studying insect abundance 100 miles from land. and distribution in the upper air. Additional In 1971 laboratory-reared adult tobacco bud- flights were made over the Lower Rio Grande v^orms marked with dyes fed in the larval diet Valley and King Ranch areas of Texas in 1954. and sterilized with CO^^ irradiation were re- Late in the cotton season of 1956, flights were leased in northeastern Mexico and southern made over central Texas and in the Tri-State Texas and recovered in sex-lure traps at known areas of Texas, Arkansas, and Mississippi. distances at cardinal compass directions. In Much information of scientific interest and Mexico, male moths dispersed 10 miles north in practical value was obtain'^d. The collection of 24 hours, and a distance-dilution effect was pink bollworm moths at 3,000 feet in the air indicated. In southern Texas, moths dispersed over the cottonfields of Mexico, for example, as much as 70 miles from the release point confirmed evidence that the moths were migrat- within an estimated 4 to 5 days. ing several hundred miles from Mexico to the United States and were responsible for the failure of the eradication measures and the Collections of Insects in the Upper Air increase in infestation in the Big Bend area of Texas. Later flights over Texas resulted in In addition to being used for applying insec- captures of pink bollworm moths, which ticides, the airplane equipment of the Depart- showed that they could disperse into Arkansas ment, also, was used for collecting insects in on wind currents from infested fields in central the upper air to obtain information on the flight Texas. A boll weevil was taken at 2,000 feet in or carriage of insects by air currents. Special Louisiana and at 200 and 500 feet in the Lower traps were designed based on the principle of Rio Grande Valley of Texas. camera plat holders with screen-covered frames coated with adhesives carried in compartments for protecting the screens before and after ex- Genetic Control posure. The traps were mounted on the wings of the planes and controlled by wires to the Research on genetic control of cotton insects cockpit so that exposures could be made for a has centered on the sterile insect release ap- specified time at known elevations. proach that was so successful against the screw- Systematic flights were made during the 5 worm fly, Cochliomyia hominivorax (Coquerel). years, 1926-31, in which over 150,000 miles In this approach large numbers of insects are were flown and 1,007 hours spent in actual reared and exposed to ionizing irradiation or exposure of the traps. Most of the 1,385 sepa- to chemosterilants to induce sterility; then, rate flights were in Louisiana, but 44 were they are released among native populations at made in the Laguna section of Mexico. Flights sufficient ratios to insure a high proportion of 50 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

sterile matings. Developing this technique in- on various aspects of sexual competitiveness. cludes devising methods for rearing and steril- Gamma irradiation has been pursued most ex- izing large numbers of insects with minimum tensively because it is relatively easy to use effect on their competitiveness in securing and presents minimum environmental hazards mates, for shipping them from the rearing when proper equipment is used. facility to release sites and releasing them so A limited field test of this method against that they disperse among the native population, the bollworm conducted on St. Croix, U.S. and for monitoring the effectiveness of the Virgin Islands, was a partial success, but prob- program. Frequently, preliminary application lems with rearing interfered. of other population reduction measures, such as More extensive tests were carried out on insecticides, are needed to reduce native popula- the same island in 1972-74. The results of these tions to levels low enough so that an effective overflooding ratio can be achieved. tests indicated that released mass-reared in- sects, whether irradiated or not, competed poorly for native mates, especially the males. Boll Weevil However, populations of the bollworm were Much research has been conducted on steriliz- reduced to low levels because the sterile females ing the boll weevil. Effective doses of gamma mated earlier in the night than the native fe- irradiation reduce competitiveness and result males. Since the sterile males were essentially in high mortality. Similar results were obtained noncompetitive with the native males and since with some chemosterilants. Finally, workers at both types of males were ready to mate at any several laboratories found that busulfan could time of night, the native males mated with achieve sterility in the male when incorporated sterile females when these females were ready. in the adult diet for a 6-day feeding period. When the native females began mating at Two disadvantages of busulfan were the long the later hour, the available native males had feeding period and not sterilizing the female. already mated and, as a result, the sterile males Thus, in the Pilot Boll Weevil Eradication mated with these females >vith little competi- Experiment, the weevils had to be sexed for use tion. Since populations of the bollworms were of the sterile male component. Sexing has to limited to a few small plantings of corn on the be done manually and is, therefore, laborious island, relatively high ratios of sterile to native and costly. In an elimination program, the cost insect were achieved, and the population could of sexing would be prohibitive. An intensive be manipulated easily. Whether this procedure effort, then, was made to find a chemosterilant could be used on a large scale is questionable. effective against both sexes. A combination of The test with the tobacco budworms showed a 4-day feeding of busulfan-treated diet to that the sterile males were about 25 percent as adults plus a few hours of fumigation with competitive for mates as native ones. This re- hempa appeared to sterilize both sexes satis- sulted from the mass-rearing conditions and factorily. However, research continued because irradiation. A lack of synchrony in mating the long holding and feeding period needed to times of sterile and native insects of both sexes be reduced or eliminated. Thompson-Hayward's was noted, thus making the system used against TH 6040 N-(4-chlorophenyl)-Ni-(2.6-difluro- the bollworm ineffective in this case. Also, benzoyl)urea has exciting possibilities. Use of populations of the tobacco budworm were much fractioned doses of gamma irradiation applied larger and more widely distributed than those at 4-hour intervals also appears promising. of the bollworm, with the result that the sterile Chances are good that the problem will be to native insect ratios were generally too low solved before an elimination program is under- (5 to 1) to have much impact on the native taken. populations when the competitiveness problem was considered. Bollworm and Tobacco Budworm Research is continuing on development of A great deal of research has been done on this method for use against the tobacco bud- methods of sterilizing Heliothis and the effects worm with emphasis on defining and overcom- RESEARCH ON COTTON INSECTS 51

ing problems related to the poor competitive- Host Plant Resistance ness of the sterile insects. It will probably be a number of years before this method can be In the early days of the boll weevil when considered feasible for practical use. effective insecticides were not available, em- phasis was given to cultural controls and early maturing cotton varieties which made possible Pink Bollworm the production of a crop before the boll weevil could build up extremely high populations. With Gamma irradiation for sterilizing pink boll- the advent of better insecticides and needs for worms has been under study for some time. higher yields, varieties of indeterminate growth Research continues, and doses have been re- were developed for the rain belt and the irri- duced to 20 kr, which has improved competitive- gated areas of the West. Such varieties and ness of treated males with nonsterile males for production practices favored the boll weevil females. The pink bollworm has been mass rear- and pink bollworm. Though good yields were ed at the Methods Development Laboratory, Ani- produced with the intensive use of insecticides, mal and Plant Health Inspection Service large populations diapaused in the fall, enhanc- (APHIS), USDA, Phoenix, Ariz., since 1967. ing survival for infesting the subsequent crops Migrants from the Imperial and Coachella and necessitating repetition of the control cycle Valleys have been detected in relatively low year after year. numbers in certain localities of the San Joaquin

Valley in California each year since 1967. Ster- Boll Weevil ile moths have been released in these localities annually beginning in 1968. Approximately 100 When resistance to the organochlorine in- million were released annually from 1970 secticides developed in the boll weevil in the through 1973, but rearing problems reduced the mid-1950's, research turned to alternative meth- numbers released in 1974. The releases appar- ods of controlling the boll weevil and other ently have prevented establishment of infesta- cotton insects. Though considerable effort was tions in this important cotton producing valley. expended, progress in the development of vari- Such treatment must continue until the pest is eties resistant to the boll weevil was slow. In eliminated or populations are reduced to low the 1970's Frego bract cottons, the bracts are levels in the Coachella and Imperial Valleys so distorted and do not envelop a square as is done that they no longer will provide migrants to with normal bract cottons, reduced boll weevil the San Joaquin Valley. oviposition by 50 percent or more when com- Beginning in November 1972, sterile moths pared with normal bract varieties. However, the have been released in the off-cotton seasons in reduction in oviposition has been considerably the extreme southern tip of Florida to suppress less than that when the variety was grown pink bollworm populations in wild cotton grow- under '*no choice" situations. Frego bract varie- ing in the area. For many years, population sup- ties with acceptable agronomic characters might pression was attained by manual destruction of have a place in boll weevil control when field wild cotton plants, which was both costly and plantings are interspersed with trap crop plant- difficult as the cotton was impossible to eradi- ings of normal bract cottons to attract over- wintered weevils which could then be killed with cate with'this procedure. The sterile male re- insecticides. Unfortunately, Frego bract cottons lease technique hopefully will suppress popula- are more susceptible to lygus bugs. tions to the extent that the pink bollworm cannot migrate to the northern part of the State Some short-season determinate cotton varie- where cotton is grown. ties are now grown extensively in Texas and show promise in reducing late-season insect If elimination of the pink bollworm is under- damage, especially by the boll weevil. They also taken in the future, the sterile male release may help alleviate some damage caused by Heli- technique will no doubt be a major component othis by maturing before the damaging late- in the program. season peak of population occurs. 52 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

Bollworms pressed Heliothis spp. larval population 68 per- cent compared with the population on com- The development of cotton varieties resistant mercial cotton, and cottons with both the gla- to the tobacco budworm and bollv^orm has brous and high-gossypol characters reduced centered on three morphological characters of larval populations 60 to 80 percent. In field tests the cotton plant and on the development of with advanced strains, one strain with the early-maturing, determinate types of cotton glabrous-high gossypol combination yielded 700 that set the bulk of their fruit 2 to 3 v^eeks pounds per acre more seed cotton than a com- earlier than the nondeterminate cottons usually mercial variety. The nectariless cotton could not grov^n commercially. Research is in progress, be properly evaluated in the field because the also, to develop cotton varieties resistant to the size of the plots was too small to prevent moths cotton fleahopper, plant bugs, and the boll from obtaining food outside the plots. weevil, v^hich would help alleviate the Heliothis In 1974 a nectariless cotton strain was re- spp. problem by reducing the insecticide appli- leased to commercial seed companies and may cations for these pests, thus, conserving the soon be available to growers for large-scale natural enemies of Heliothis spp. planting. However, unless this cotton is planted The first morphological character is lack of on a community-wide basis and alternative nectaries. Normal cottons have extrafloral nec- sources of food are not available for moths, its taries on leaves and fruiting forms. The ab- effectiveness against Heliothis could be limited. sence of these structures deprives Heliothis adults of an important source of food when and Cotton Fleahopper where alternate food sources are not available. In controlled tests, the absence of extrafloral Cottons with the glabrous character are well nectaries (nectariless cotton) resulted in at advanced and could be expected to have con- least a 40-percent reduction in egg deposition siderable impact on Heliothis when available to and reduced longevity of adults. growers. There is a complication with these The second character measurably reducing cottons, however. Although these cottons have a populations of Heliothis spp. is a smooth (gla- significant impact on infestations of the cotton brous) plant surface. Commercial cottons have fleahopper as well as on infestations of Helio- 2,000 to 5,000 trichomes per square inch on the this spp., these cottons are actually more sensi- small terminal leaves and buds, which are the tive to fleahopper attack than more hirsute preferred oviposition sites of Heliothis spp. strains and, despite lower infestation levels, Glabrous stocks with less than 200 trichomes suffer greater damage. This damage, however, per square inch have reduced egg deposition by may result from infestations of leafhoppers 50 percent. rather than cotton fleahoppers. Until these The third character showing impact on Helio- problems are resolved and overcome, the use of this spp. populations is a high level of gossypol glabrous cotton may be questionable. in the flower buds (squares). Gossypol content Cottons with the high-gossypol character or in buds of commercial cotton is about 0.5 per- those with this character combined with other cent, which affects larvae very little. However, resistant characters also show a great deal of larval mortality of 50 percent occurs when the promise against Heliothis spp. In the late 1960*s gossypol level is 1.2 percent or higher. these cottons showed some resistance against the cotton fleahopper ; they have produced yields Studies in field cages with cotton strains in above those of current commercial varieties. which all three morphological characters have These varieties will probably not be available to been combined showed that populations of the the grower in any quantity, however, for several tobacco budworm increased 1.1-fold in two gen- years. erations, and those on glabrous plus high- gossypol cotton or nectariless cotton plus high- Tarnished Plant Bug gossypol cotton increased 2-fold; meanwhile populations on commercial cotton increased 10- The nectariless character in cotton has re- to 12-fold. In field tests a glabrous cotton sup- duced reproduction of the tarnished plant bug, RESEARCH ON COTTON INSECTS 53

Lygiis lineolaris (Palisat de Beauvois), with Insecticides considerably fewer nymphs developing on nec- tariless plants than on plants with nectaries. For many years before 1945, arsenicals and Apparently, the leaf nectaries are an important sulfur were the principal insecticides used for food source for the developing nymphs. cotton insect control. Calcium arsenate was the main weapon against the boll weevil, bollworm, Other Insects and cotton leafworm, but its application usually resulted in injurious infestations of cotton Research on the development of varieties re- aphids. sistant to the pink bollworm, cotton leafperfor- Nicotine, the only available aphicide, was ator, and spider mites is in progress ; some suc- mixed with calcium arsenate or was used alone cess has been attained against spider mites. for aphid control although expensive and not very effective under certain conditions. Mix- tures of sulphur and calcium arsenate were Gossypol and Gossypol-Free Cotton widely used for control of combination infesta- Generally, varieties having a high-gossypol tions of boll weevils and cotton fleahoppers. content are more tolerant to insect attack than Paris green and sulphur became popular in those with a low-gossypol content. Cottonseed the Far West for control of hemipterous insects. from commercially grown cottons could not be Sulphur suppressed aphid populations but, in used as a source of protein in food for nian and combination with arsenicals, did not always pre- in feed for nonruminant animals because of vent injurious infestations. In the early part gossypol content. Removing gossypol from the of the century, or before the advent of calcium meal was too costly. A new process, however, arsenate about 1916 to 1920, paris green and has been developed for extracting gossypol from lead arsenate were the principal insecticides cottonseed meal that may have considerable im- used to control outbreaks of the cotton leaf- pact as a source of protein for man. A mill in worm. the High Plains of Texas is producing gossypol- free cottonseed flour and another mill is planned Organic Insecticides for South Carolina. Before this new process was In the mid-1940's, the new organochjorine in- developed for removing gossypol, breeders spent secticides were developed and resulted in the considerable effort to develop gossypol-free ñrst major change in insecticides used on cotton varieties. These varieties had acceptable agro- since the development of calcium arsenate. Fed- nomic characters, but they were more susceptible eral and State research workers rapidly ex- to attacks of bollworms and certain species of plored their possibilities. Their general effec- insects that do not attack commercial varieties. tiveness against most of the injurious insects Though the protein source for human food was resulted in wide acceptance by growers so that by needed, the need for additional applications of the late 1940's considerably more cotton acreage insecticides to control these insects offset any was being treated than ever before. Much of gain in gossypol-free varieties. With the new this development was accomplished at Cotton gossypol-removal process, the need for gossy- Insect Research Laboratories in Florence, B.C. ; pol-free cotton varieties is less critical. Stoneville, Miss.; Tallulah, La.; Waco and Brownsville, Tex. ; Tucson, Ariz. ; and at many of the State agricultural experiment stations. Appraisal of Cotton Varieties Resistant to Insects The organochlorine compounds largely re- Although only modest success has been placed calcium arsenate though it continued to achieved in developing resistant varieties to be used for some years to some extent in local- cotton insects, this effort is important. Varieties ized areas. Some of them, BHC, aldrin, dieldrin, with comparatively low levels of resistance to chlordane, and heptachlor, were effective certain insects could be an essential factor in an against boll weevils but were ineffective against insect population management system. bollworms. Mixtures of these materials with 54 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

DDT gave effective control of combination in- insects were a menace. In the 1950's and 1960's festations of these two important pests. Toxa- as much as 80 percent of the cotton acreage phene, and later endrin, were effective against received such treatment in the Blacklands of both pests. central Texas. These experiments were the fore- Application equipment available at first was runners of the total insect population suppres- that used for applying calcium arsenate, and for sion and integrated control concepts that at- several years the new insecticides were applied tained much popularity in the 1970's. only as dusts. One limiting factor for wider Spray applications of insecticides for late- acceptance was the critical weather conditions season insect control were readily accepted by needed for effective dust applications. Dusts growers because of several advantages over had to be applied during late afternoon, at dusts. They fitted well into a daytime farm night, or early morning when the air was calm operation since they could be applied under more or nearly so. In many areas satisfactory dusting adverse weather conditions than dusts (fig. 17). conditions were of short duration and often The spider mite problem, which became some- nonexistent. Consequently, only limited acre- what more serious with spray applications of ages could be treated in a day's operation. the organochlorine insecticides, was solved With the advent of organochlorine insecti- when organophosphorus insecticides such as cides, entomologists at the Waco, Tex., Cotton parathion, methyl parathion, and demeton be- Insects Laboratory took a new look at ''pre- came available as sprays. square" boll weevil control with the idea of also In the 1960's the ultra-low volume spray ap- controlling other early-season injurious insects. pication of technical materials (less than 0.5 Previously no insecticides were available that gallon of total spray per acre) was developed. would control combination infestations of such Research results showed that most materials early-season pests as thrips, cotton aphids, over- are at least equally effective when they are ap- wintered boll weevils, and cotton ñeahoppers. plied as ultra-low volume sprays compared with The organochlorine insecticides filled this the same dose applied as low-volume (conven- need. Small plot and large-scale experiments tional) sprays. Only malathion, azinphosmethyl, (plots ranging in size from 1 to 5 acres) were endosulfan, methyl parathion, and a mixture of not too successful in 1946 and 1947. Community- malathion plus methyl parathion, however, are wide experiments in early-season cotton insect approved for ultra-low volume aerial applica- control experiments conducted in Wharton tions to control certain cotton insects. This County, Tex., in 1948 proved conclusively that application technique has the advantage of in- an early-season insect control program was creased pay load over conventional sprays, profitable and simplified the farmer's control which reduces application costs. It is used problem. Dusts were used in these experiments, especially in USDA-sponsored programs of in- and again it was realized that critical applica- sect suppression. tion requirements would limit the effectiveness of the program. Resistance to Insecticides The boll weevil developed resistance to the Insecticide Sprays organochlorine insecticides in the mid-1950's During the same year the new insecticides in Louisiana, Arkansas, and Mississippi, and in were found effective when formulated as emul- the other boll weevil infested States in subse- sifiable concentrates and applied as emulsion quent years. Fortunately, an organophosphorus sprays in low-pressure, low-volume spray equip- compound, methyl parathion, was effective and ment. Community-wide, early-season insect con- available. Azinphosmethyl, EPN, and mala- trol experiments with sprays conducted in cen- thion became available later. Azinphosmethyl tral Texas in 1949 and 1950 gave outstanding was believed to be the most effective weevilcide results, and the bottleneck was broken. The available. The carbamate, carbaryl, was used as early-season control program was practiced by a control but never gained full grower accept- growers over wide areas where early season ance because it could be formulated only as a RESEARCH ON>COTTON INSECTS 55

PN-4434 Figure 17.—Eight-row, low-volume, low-pressure spraying machine in operation. wettable powder and was more difficult to apply oped, may be of help in this respect. Unfortu- than an emulsifiable concentrate. The toxa- nately, methomyl is phytotoxic and cannot be phene plus DDT mixture, though both are or- used to a regular schedule of applications, and ganochlorines, continued to be effective against researchers are studying how chlordimeform resistant boll weevils. But DDT was banned should be used for greatest effectiveness. The for use on cotton by the Environmental Protec- synthetic pyrethroid compounds showed con- tion Agency (EPA) on December 31, 1972. siderable promise for the control of these pests Cotton insects rapidly have developed resist- in preliminary tests. ance to insecticides in recent years. Since 1947 when organic chemicals began to have wide Systemic Insecticides usage on cotton, 25 species of insects and spider mites that attack the crop have developed resist- Systemic insecticides such as phorate and ance and several other species are strongly disulfoton developed in the mid-1950's applied suspected of having developed resistance. At to cottonseed protect plants for several weeks least one of these resistant species occur in after plant emergence from such pests as thrips, localized areas in most cotton-producing States the cotton aphid, and spider mites. This method from California to North Carolina. Most of of control, however, has not been widely ac- these pests are resistant to the organochlorine cepted because the insecticides are expensive, insecticide, but four species of spider mites, the do not give protection as long as desired early armyworm, banded wing whitefly, bollworm, in the season, often reduce plant emergence, and tobacco budworm, are known to be resistant and may delay fruiting. Granular formulations to the organophosphorus compounds. of systemic insecticides are applied, also, in the Resistance in the tobacco budworm and boll- seed furrow at planting and as side dressings to worm is serious as few effective insecticides are established plants. Aldicarb developed in the available. However, the insecticides, methomyl 1960's applied in the seed furrow at planting and chlordimeform, which were recently devel- killed overwintered boll weevils and controlled 56 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE cotton fleahoppers 8 weeks after planting. It how much of the loss in yield was due to a kills boll weevils developing in cotton squares particular insect. Insects involved at all loca- when applied to plants as a side dressing in the tions were boll weevils, bollworms, cotton early squaring stage. The application of this aphids, and spider mites. In addition, lygus bugs compound, especially aS a side dressing in the were involved at Tallulah and the cotton flea- early squaring stage, often results in increased hopper and thrips at Waco. subsequent infestations of the bollworm. Re- Insect infestations and weather conditions search in the early 1970's showed that aldicarb vary from year to year. Thus, comparative may be useful in boll weevil eradication or sup- records over a period of years are more mean- pression programs when about 2 percent of each ingful than those of selected years. The average field is planted to a trap crop (cotton planted increase in yield in treated over untreated plots at least 2 weeks before the rest of the field is at Florence for the 31-year period, 1928 to 1958, planted) treated with it. was 40.6 percent with a range from 5.3 percent in 1942 to 217.9 percent in 1950. At Tallulah Appraisal of Insect Control with Insecticides for the 37-year period, 1920 to 1956, it was 31.2 Three ARS laboratories, Florence, S.C., in percent with a range of 1.1 percent in 1924 to the Southeast ; Tallulah, La., in the South ; and 112.8 percent in 1950; and at Waco for the 32- Waco, Tex., in the Southwest, kept annual com- year period, 1939 to 1970, it was 54.3 percent parative records of yields in treated and un- with a range of 9.9 percent in 1939 to 426.0 treated plots for periods of 31, 37, and 32 years, percent in 1961. respectively. These results are indicative of the Considerable improvement has been made in crop losses to insects when insecticides are not cotton insect control since 1945 with the advent applied for their control in those areas. The use of the organochlorine and later organophosphor- of the best insecticides, however, does not pre- us and carbamate insecticides. Before that time vent all insect damage, and a certain amount of growers depended primarily on such inorganic damage can be tolerated before the use of an insecticides as the arsenicals and sulphur for insecticide is economically feasible. Because insect control. The following tabulation illus- more than one insect was usually involved in the trates improvement in insect control since the experiments, no attempt was made to show new insecticides have been used :

Increase in yield in treated over untreated plots Study Location period Average Before 1945 After 1945

Percent Percent Percent Florence, S.C. 1928-58 40.6 23.6 53.9 Tallulah, La. 1920-56 31.2 26.4 41.3 Waco, Tex. 1939-70 54.3 34.0 77.6

Total reliance on the control of cotton insects 18). Much concern has arisen because compara- >vith insecticides is no longer acceptable because tively few candidate insecticides have been re- of adverse effects of insecticides on the environ- searched in recent years. Only chlordimeform. ment. However, development of alternatives to Chevron Ortho 9006, (Monitor), (0,S-dimethyl control insects is difficult and costly. Though phosphoromidothioate), methomyl, and methi- development of such alternatives has received dathion have recently been developed and show much emphasis, insecticides will continue in im- promise in control of cotton insects and spider portance in the control of cotton insects (fig. mites. A new class of insecticides, however, the RESEARCH ON COTTON INSECTS 57

PN-443Í Figure 18.—Cotton untreated (left) and treated (ri^fct)with insecticide. synthetic pyrethroids, showed promise in pre- Recommendations in the use of insecticides liminary tests toward the end of the reporting to control the various cotton insects are subject period. to change from year to year so they are not The cost of developing and registering a com- included in this publication. For such sugges- pound is expensive. Industry, therefore, is hav- tions on control, please consult the respective ing to take an extremely hard look at compounds State Guides for Controlling Cotton Insects. after the initial screening to see whether con- tinuing their development is justified. Conse- quently, few compounds are being made avail- Juvenile Hormones able in the testing program and even fewer of those make the grade insofar as registration and The effects of juvenile hormones on several ultimate use by growers are concerned. The situ- cotton insects have been studied at several lab- ation is serious in the control of the bollworm oratories. Though some activity was noted in complex with development of resistance to the the boll weevil, lygus bug, cotton aphid, and comparatively few available effective insecti- bollworm, it was not great enough to justify cides. Hopefully, some of the alternatives to field tests. Activity in the boll weevil was in the insecticide may be used with insecticides in a larval and pupal stages with no means available pest management system so that crises in insect to introduce the hormone under field conditions control may not occur because fewer effective since immature stages develop within the square insecticides are available. (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 Before 1973 B.t, was assumed to be a dis- affected some of the predaceous insects, such as ease-producing organism, and the potency of the green lacewing. Studies are continuing with preparations could not be judged by the quan- the bollworm. tity of spores present. The presence of a toxic For several years chemists at the Boll Weevil crystal associated with the B.t. spore, later Research Laboratory have attempted to identify named the S-endotoxin, was demonstrated in a compound from the boll v^eevil v^ith juvenile the 1950's. However, it was not until the early hormone activity, and also, to determine 1970's that the entire activity of the organism v^hether the Cecropia juvenile hormone is the was shown to result from the 8-endotoxin. This juvenile hormone in the boll weevil. They were work showed that toxicity varied from B.t. iso- unable to isolate a fraction from the boll weevil lates, regardless of serotype, and depending on that was active at less than one microgram the medium used for bacterial fermentation. though several methyl esters of fatty acids were These findings opened the way for development active at 15 to 30 micrograms. They were un- of a bioassay standardization procedure that able to isolate the Cecropia juvenile hormone could be used to gage the potency of prepara- from the boll weevil with gas Chromatographie tions and ultimately to provide more potent and mass spectral procedures on larvae, adults, preparations. An isolate 15 to 20 times more and adult frass. active against the tobacco budworm and some other insects than commercial materials avail- able at the time was then developed. This de- Pathogens velopment 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 In the need for developing alternatives to vegetable insects such as the cabbage looper conventional control of insects with insecticides, and against Heliothis on tobacco. attention was given to pathogens for the control of such cotton insects as the boll weevil and Tests with B.t. against Heliothis in the labo- the bollworm complex. Evidence of the occur- ratory and in the field on cotton have shown it rence of pathogens had been known for many to be effective. The rates, however, required to achieve control on cotton in the field (2 to 12 years. For instance, infestations of the cabbage looper, Trichoplusia ni (Hübner), were often pounds per acre) are not economical. The pri- decimated by a nuclear polyhedrosis virus. mary reason why large amounts'^of B.t. are Cultures of bollworms being reared under in- needed to achieve control of Heliothis on cotton sectary conditions often were wiped out by a is that the material must be ingested by the larvae to be effective, and most of the feeding virus, and large larvae killed by the virus were observed in the field though the disease never by Heliothis on cotton is within the fruit where reached epizootic proportions as with the cab- little B.t. is present. bage looper. Research is continuing to increase the po- tency of B.t. preparations against Heliothis spp. by selection of new isolates. Improvement Bacillus fhuringiensis of fermentation media has achieved a 15-fold The (delta) S-endotoxin of Bacillus thurin- increase in the yield of S-endotoxin, thus, re- giensis (B.t,) has insecticidal activity against ducing the amount of material needed to control several species of Lepidoptera including the the pests. Also, the use of various baits con- tobacco budworm and bollworm. It has been taining cornmeal or cottonseed oil to increase shown to be entirely safe to other groups of the amount of larval feeding on the B.t. has animals including man, wildlife, beneficial in- shown promise of reducing the quantity of B.t. sects, and plants. On this basis, EPA has needed for control of Heliothis. Despite this granted the formulations an exemption from continuing research, an effective and econom- tolerance ; however, it is not registered for use ical formulation will probably not be available against Heliothis spp. on cotton. for commercial use on cotton for a few years. RESEARCH ON COTTON INSECTS 59

Heliothis Nuclear Polyhedrosis Virus result from the rapid deactivation of the virus by sunlight and the feeding behavior of Helio- The nuclear polyhedrosis virus of Heliothis this noted in the section on B.t. is an obligate parasite that multiplies within Studies by several workers indicated that the the cells of larvae of Heliothis spp. and causes unprotected virus on foliage was deactivated a fatal disease. The virus was found first in by exposure to sunlight, with most of the activ- this country in larvae collected from cotton ity gone after 24 hours. Some progress has near San Benito, Tex. (fig. 19). Since then, the been made in overcoming tnis problem by add- material has been developed through labora- ing various ultraviolet-screening agents to for- tory, pilot-plant, and commercial stages. mulations of the virus. The activity has been The virus has received a temporary exemp- extended at least 25 hours by this means, but tion from tolerance by EPA with annual re- apparenty none of the preparations was con- newals and has been registered for sale in sidered adequate for further development. Spain. It is completely harmless to all animals Research to overcome the problem relating (including man) except Heliothis spp. Before to the feeding behavior of Heliothis spp. by this product can be registered, however, its obtaining better coverage of the plants, in- efficacy must be more fully demonstrated. creasing the amount of virus applied, and using Since the virus is an obligate parasite, it baits has been partially successful. Better con- must be produced in living Heliothis spp. larvae trol was obtained by reducing the size of the or on tissue cultures. Two companies are cur- spray particle and by increasing the volume of rently producing it in living Heliothis larvae. spray applied per acre. Some workers reported An estimated 2,000 to 4,000 pounds of the the effectiveness was substantially improved by product were produced in 1974. increasing the rate of application from the Results of field tests of this virus against suggested 40 diseased larval-equivalents to Heliothis spp. on cotton have been variable, 5,000 per acre. Baits containing such ingre- control equal to or better than that produced dients as water extract of corn silks, cotton- by standard insecticides has been achieved in seed oil, and sugars have improved efficacy. some instances, and inadequate control has re- Apparently, the formulations of the Heliothis sulted in others. These differences appear to virus that have been studied do not give the

PN-44S6 Fig:ure 19.—Diseased bollworm larva on leaf. 60 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE desired degree of control on cotton, especially adult diet, and diapause. Neutral glyceride and when heavy infestations occur. Effective eco- free fatty acid fractions account for as much nomical formulations, however, may be pro- as 90 percent of extractable lipids of diapäusing duced in the next few years. adults. Newly emerged weevils have 2 to 6 The alfalfa looper, Autographa californica, percent body fat (about 2 percent triglycéride). nuclear polyhedrosis virus has shown activity After 2 to 3 weeks of feeding, nondiapausing against several lepidopterous pests of cotton adults have 6 to 10 percent body fat (40 to 60 and may have potential in their control. percent triglycéride), but diapausing adults have 18 to 25 percent body fat (75 to 85 percent Other Pathogens triglycéride). The triglycéride level drops dur- ing the winter when the insects are not feeding. At the Boll Weevil Research Laboratory re- Several guanine analogs were tested as in- sults of biological control tests showed that hibitors of reproduction. Two, 8-bromoguanine Beauveria bassiana can infect larvae, pupae, and 9 methyl, 2 butyl guanine were effective and adult boll weevils in the laboratory, but it ovarial growth inhibitors in the boll weevil. cannot be cultured for practical use in the Larvae reared in a radioactive medium were field. Laboratory cultures of the boll weevil be- inhibited in their development and only a small came infected with a new species of neogregar- percentage developed to adulthood. The purine ine that subsequently was named Mattesia guanine was identified in the excreta of the boll grandis McLaughlin. The ensuing epizootic weevil. The effects of nitrogenous-elid products resulted in destruction of the boll weevil colony. of the metabolism of the boll weevil fed on To be effective, the neogregarine had to be artificial diet, cotton squares, or bolls were ingested by the adult boll weevils. A cotton- determined. Fecal analyses for amino acids, seed oil bait was developed to enhance inges- nitrogen, ammonia, creatines, creatinine, tion of the pathogen. Production and applica- guanine, urea, and uric acid showed that pres- tion problems have prevented the pathogen ence of these materials varied with the type of from becoming a practical tool in the control diet fed the insects. The purine guanine was of the boll weevil. found in relatively large quantities in the feces of weevils fed all three diets. The feces of the Physiology and Morphology boll weevil were examined for nonprotein amino acids. A total of 20 amino acids were Boll Weevil detected in ethanalic extract with Chromato- graphie techniques, and 23 acids were detected In the late 1950's a study was made of the by acid hydrolysis. The free and bound non- reproductive system of the boll weevil. The protein amino acids and ammonia accounted genitalia and reproductive organs of the re- for 3.23 percent of total feces nitrogen. producing male and female were described and No striking effects of DDT, toxaphene, or a illustrated. The musculature associated with combination of these two insecticides on the the reproductive systems of both sexes were activity of succinic dehydrogenase were shown. described. Results of studies at the same time In a study of the activity of ATPase in homog- showed that the spermatheca of the female enates of the boll weevil, sufficient magnesium may provide a useful basis for identification of occurred to activate the enzyme. Additional Thurberia weevils. magnesium did not increase activity of the Dehydrogenases were studied in the brain enzyme. A higher level of ATPase occurred in and in the related neural and secretory struc- a laboratory-reared than in a field-cultured tures in the boll weevil. The fatty acid fraction population. of the boll weevil is a complex mixture of 23 fatty acids ranging in chain length from 6 to Bollworm 20 carbon atoms. Total body fat of the boll weevil and relative distribution in major lipid Differences in percentages of phospholipids, classes are dependent on adult age, larval and partial glycerides, and triglycérides were RESEARCH ON COTTON INSECTS 61 found between large and small larvae of the search could only come with ability to mass tobacco budworm and the bollworm and, also, rear the various insects on artificial diets. between the two species. The difference may explain the greater tolerance of the tobacco Pink Bollworm budworm to insecticides. High percentages of fatty acids in bollworm larvae may have a role The first phytophagous insect to be reared on in the naturally greater tolerance of the tobacco an artificial diet was the pink bollworm so budworm to insecticides because they could reared in the early 1950's at the College Sta- affect the solubility of insecticides in lipids or tion, Tex., ARS Cotton Insects Laboratory. The the characteristics of cell membrane. artificial diet developed for this insect served as The bollworm moth vibrates its wings dur- the basic diet for many phytophagous insects ing courtship, and the male wipes the scales of now being mass reared in the laboratory as a his claspers on a supporting surface between result of this research. The pink bollworm was periods of vibration. Receptive females extend mass reared in tremendous numbers in the the terminal abdominal segments and vibrate late 1960's and 1970's in the USDA, of the now their wings. Then, the receptive female, whose Animal and Plant Health Inspection Service terminal abdominal wings are extended, is Laboratory in Phoenix, Ariz. (See section on approached from behind by the male who taps Genetic Control in this publication.) the ovipositor of the female with his antennae, crawls to a position at the side of and about 2 Boll Weevil cm from and parallel to her, and snaps his In the early 1960's boll weevils were reared claspers around her genitalia to complete the on artificial diets at the College Station, Tex., copulatory connection. Mated pairs remain in Cotton Insects Research Laboratory. Progress copula from % to li/^ hours. in mass rearing the insect was made with the Histological studies of the structure of the establishment of the Boll Weevil Research La- compound eyes of the tobacco budworm and boratory on the Mississippi State University bollworm indicated that the major structural Campus in 1962. After it became apparent difference between the eyes of the two species that the insect could be reared in sufficient is the relatively shorter ommatidia in the eye numbers, it was deemed that a Pilot Boll of the tobacco budworm. Whether this morpho- Weevil Eradication Experiment should be con- logical difference affects the sensitivity of the ducted to determine whether it was technolog- eye to wavelength or intensity of light stimuli ically and operationally feasible to eradicate is not known. Results of behavioral and electro- the boll weevil. Through a more than a half physiological studies on the visual sensitivity million dollar appropriation by the Mississippi of the bollworm and tobacco budworm indicate Legislature, the Gast Insect Rearing Labora- that these moths detect the radiant energy from tory was built on the campus of Mississippi 15-W ultraviolet lamps from a limited distance State University. Though problems with the only and that the 15-W BL lamp would be use- facility and with rearing procedures were such ful only for surveying the activity of the boll- that numbers of boll weevils needed for sterile worm and tobacco budworm moth population male releases in the experiment were not in a limited area near the trap. reached, the facility made a significant contri- bution to the success of the experiment. It is expected to make an even greater contribution Rearing if elimination of the insect from the United States is undertaken. Research on cotton insects was hampered for many years because of difficulties encountered in rearing them in the laboratory. Rearing in- Bollworm sects on their hosts was difficult from the Nutrition and techniques for rearing the standpoint of needed numbers as well as being bollworm, also, were developed at the College quite expensive. Major breakthrough in re- Station laboratory. Though small cultures have 62 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE been reared at several laboratories, the major strengthen cotton's ability to compete for thrust in mass rearing has been done at the markets. Scientists and industry leaders agreed ARS Southern Grain Insect Laboratory at that the boll weevil represented one of the most Tifton, Ga. A prototype machine for mass rear- costly problems confronting the cotton industry ing the insect has been developed at this and, therefore, was one of cotton's major prob- laboratory. lems in urgent need of research support. In the Agricultural Appropriation Reports for Fiscal Tobacco Budworm Year 1959, both the House and Senate Com- Techniques for mass rearing the tobacco bud- mittees requested the Secretary of Agriculture worm were developed at the Brownsville, Tex., to review the boll weevil problem and to submit laboratory in the late 1960's and early 1970's. a report on research and facility needs to meet Production was stabilized at about 60,000 the problem to the next appropriations com- pupae per day. Pupae were furnished from nlittees. this laboratory for the sterile male release The Office of the Secretary appointed a work- study conducted on St. Croix, U.S. Virgin Is- ing group consisting of E. R. McGovran, Co- lands, in the early 1970's. In addition, moths operative State Research Service (CSRS), were reared for several years for the identifi- USDA; H. G. Johnston, National Cotton Coun- cation of the sex pheromone emitted by the cil of America, and E. F. Knipling (chairman) female. Chromatographie analysis indicated the and C. R. Parencia (secretary), ARS, USDA, to pheromone to be a multiple component system. study the problem. In addition the group was The sex pheromone was isolated, purified, iden- to ( 1 ) develop information on current research tified, and synthesized early in 1974. programs devoted to boll weevil investigations by State, Federal, and private industry; (2) Lygus Bugs determine the needs for an overall comprehen- Lygus bugs, Lygus hesperus and L. Lineo- sive research program; and (3) determine the lavis, have been reared on artificial diets. Tech- broad areas of research that would be appro- niques for mass rearing them on these diets, priate for Federal attention and support in an however, have not yet been developed. effort to help meet the overall needs. The group's report was submitted to the Secretary Saltmorsh Caterpillar on December 30, 1958. This report culminated The saltmarsh caterpillar, Estigmene aerea in appropriations by Congress to establish the (Drury) has been reared on the wheat-germ Boll Weevil Research Laboratory at State Col- diet at the Cotton Insects Research Laboratory, lege (now Mississippi State), Miss., and to College Station, Tex., and has been mass reared strengthen ongoing research programs at the at the Biological Cotton Insect Control Labora- Cotton Insect Research Laboratories at College tory, Tucson, Ariz. Station, Tex.; Baton Rouge, La.; and Flor- ence, S.C. The new research facility at Missis- Beneficial Insects sippi State was dedicated in a formal cere- The green lacewing has been reared on an mony in March 1962. Research on the boll artificial diet, and some progress has been made weevil was simultaneously strengthened in in mass rearing it on this diet. Some progress several State agricultural experiment stations. has been made in rearing Campoletis perdis- Significant research findings resulting from tinctiis and Micropletis senorensis, parasites of the expedited research on the boll weevil were : Heliothis spp., on artificial diets. (1) Techniques for mass rearing the boll weevil; (2) development of the reproduction- diapause control program; (3) development of Pilot Boll Weevil Eradication Experiment ultra-low volume spray applications of insec- ticides; (4) development of the systemic insec- Cotton leaders have repeatedly emphasizea ticide, aldicarb, that controls the boll weevil; that the economic survival of the industry de- (5) finding that the male boll weevil emits a pends on adequate research necessary to pheromone that attracts females and, also, acts RESEARCH ON COTTON INSECTS 63 as an aggregant; (6) identification and syn- financed by $1 million from ARS (later with thesis of the attractant, grandlure, and devel- APHIS), $500,000 from CSRS, and $500,000 opment of traps baited with it for capturing from industry. Cotton Incorporated, for each of boll weevils; (7) progress in development of a 2 years. Mississippi was to provide a rearing chemosterilant making the male-sterile release facility. A detailed study of the area was made, technique feasible ; (8) use of trap crops treated and the cost of the experiment was estimated with aldicarb in furrow and as a side dressing at $2.5 million. Since only $2 million was avail- together with grandlure bait in reducing over- able, the experiment was delayed for a year or wintered boll weevil populations; and (9) prog- until the needed additional funds could be ress in the development of a frego bract strain obtained. In 1971, however, the new cotton pro- of cotton with considerable resistance to the gram resulted in a considerable reduction in boll weevil. the cotton acreage to be planted, making it In recognition of the importance and urgency possible to start the experiment with available of eliminating the boll weevil problem as soon funds. The Director of Science and Education as it became technically and operationally fea- of the Department appointed a Technical Guid- sible, the National Cotton Council of America ance Committee for the Pilot Boll Weevil Eradi- in its 1969 annual meeting established a Special cation Experiment. Study Committee on Boll Weevil Eradication. The experiment got under way in July 1971 The Special Study Committee met in Memphis, (fig. 20). It was conducted cooperatively with Tenn., on May 6, 1969, to review the status of the Departments of Agriculture, Experiment current knowledge of boll weevil suppressive Stations, and Extension Services of Mississippi, measures and to consider actions that should Louisiana, Alabama, and Texas; with Cotton be taken in efforts toward the elimination of Incorporated and the National Cotton Council the boll weevil as a pest of cotton. The chairman representing the industry; and with USDA's of the Special Study Committee appointed a APHIS, ARS, CSRS, ASCS, and ES. The repro- Subcommittee of P. L. Adkisson, Texas A&M duction-diapause phase of the experiment was University; J. R. Brazzel, APHIS, USD A; H. carried out in the fall of 1971. Unfortunately G. Johnston, National Cotton Council; D. F. boll weevil populations were very heavy, and Young, Mississippi State University; and C. as a result of the mild winter, survival of boll R. Parencia (secretary) and E. F. Knipling weevils was high. A trap crop treated with (chairman), ARS, USD A, to select areas repre- aldicarb was planted in each field iA the eradi- sentative of boll weevil conditions in the south- cation and first buffer areas, and pheromone east,, south, and southwest areas of the Cotton traps at the rate of 2 per acre were placed Belt that would be suitable for undertaking around each field in 1972. An insecticide appli- large-scale experiments to determine if boll cation was made when plants began to square. weevil eradication is feasible with currently A period of dry weather resulted in late emer- available suppression techniques. The Subcom- gence of weevils from hibernation sites, leaving mittee prepared a report dated August 15, too many weevils in the fields for the sterile 1969, that was presented to the Special Study male releases to be effective. Committee on Boll Weevil Eradication in Mem- Five in-season applications of azinphos- phis, Tenn., on September 16, 1969. It recom- methyl were made followed with 13 applications mended that a Pilot Boll Weevil Eradication for reproduction-diapause control. By October Experiment be conducted beginning in calendar adults were too scarce to be detected. Phero- year 1970 in an area centered in South Missis- mone trap catches in the spring of 1973 indi- sippi and including adjacent cotton acreages cated very low surviving populations in the in Alabama and Louisiana. eradication and first buffer areas. Release of The Special Study Committee accepted the sterile males began in early June, but rearing recommendations of the Subcommittee and its problems necessitated reducing releases to 50 representatives met with USDA officials to dis- per acre instead of the hoped for 100 in the cuss ways of financing the experiment. A deci- eradication area and extending only 5 miles sion was made that the project would be 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 last week of the experiment so that time did not acre per week. Fields with infestations in the permit total elimination of reproduction in it. remaining first buffer fields were to be treated The experiment was terminated on August with insecticides. 10, 1973, and the Technical Guidance Com- Only 33 of the 236 fields were infested in the mittee met on August 30 to evaluate the re- eradication area, and they were in the northern sults. The committee concluded **that it is zones nearest the first buffer. Indications were technically and operationally feasible to elimi- that the problem was caused by migration from nate the boll weevil as an economic pest in the the second buffer where overwintering popu- United States by the use of techniques that are lations were considerably higher. Infested fields ecologically acceptable." were treated at 3-day intervals with azinphos- Members of the committee were as follows : methyl. As a result of these treatments, repro- P. L. Adkisson, Texas A&M Univ. ; F. S. Arant, duction could not be detected in 32 of the 33 Auburn Univ.; Richard Carleton, La. Dept. fields at the end of the experiment. The infes- Agr.; T. B. Davich, E. F. Knipling (co-chair- tation in the one field was not detected until the man), 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. Braz- in the Department of Agriculture's budget but zel, and D. R. Shepherd, APHIS, USDA; C. C. was not included in the budg-ot presented to Fancher and O. T. Guice, Miss. Dept. Agr. and the President by the Office of Management Com.; F. G. Maxwell and David Young, Miss. and Budget. Initiation of the trail is awaiting State Univ. ; J. S. Roussel, La. Agr. Expt. Sta. ; funding. W. A. Ruffin, Ala. Dept. Agr.; George Slater, Cotton, Inc.; and Ritchie Smith, National Cotton Council. Field Laboratories The National Cotton Council's Special Study- Committee for Boll Weevil Eradication met in Tallulah, La. Memphis, Tennessee, on January 10, 1972, to The Tallulah laboratory was established in reviev^ the progress and status of the experi- 1909 and was in continuous operation until it ment. The Committee expressed a need for a closed at the end of June 1973. The laboratory comprehensive, overall eradication plan that was the oldest continuously operated insect re- would outline areas for initiation and subse- search laboratory in ARS. It was selected as quent target zones, timetables, probable costs, an ideal location to do research on the boll program requirements, operational arrange- weevil, and it developed the first practical ments, and the like. The chairman appointed a method of controlling the boll weevil with Technical Committee to Develop a Plan for calcium arsenate. Its acknowledged leadership Overall Boll Weevil Eradication. in research on the new cotton pest was dis- Members of the Technical Committee were cussed in the section of the boll weevil. It con- P. L. Adkisson, Texas A&M Univ. ; C. R. Jor- tinued to be an ideal location to do practical dan of Univ., Ga. ; D. F. Young, Miss State field research on the boll weevil because winter Univ.; H. L. Breur, Tenn. Dept. of Agrie; survival was usually high and climatic condi- George Slater, Cotton Incorporated; James tions were favorable for rapid population Brown, the National Cotton Council; H. M. buildup. It was in a remote location, and the Taft, ARS; C. R. Parencia, ARS, Secretary; facilities were poor with no opportunities for J. R. Brazzel, APHIS, Vice Chairman; and E. laboratory personnel to associate with other F. Knipling, ARS, Chairman. research scientists. For these reasons and for Though two preliminary meetings were held economy, the laboratory was closed and the in November 1972 and early January 1973, equipment and personnel transferred to the the work of the Committee did not gain impetus Stoneville, Miss., laboratory. The program of until results of the experiment became avail- research in recent years was centered around able at the end of August. An overall Plan for the biology and control of the boll weevil with a National Program to Eliminate the Boll some emphasis on the bollworm, lygus bugs, Weevil From the United States was presented and thrips. Large plot field tests were conducted by the Technical Committee to the Special to evaluate promising new insecticides and Study Committee on December 4, 1973. It was formulations against these insects. accepted and, in turn, presented to the Secre- tary of Agriculture on December 12. In the Florence, S.C. Agricultural Act of 1973, the Secretary had The Southeastern Cotton Insects Investiga- been instructed to carry out elimination pro- tions Laboratory was established in 1921 in grams for the boll weevil, pink bollworm, and cooperation with the South Carolina Agricul- other cotton insects if he determined that it tural Experiment Station and thereafter has was feasible to do so. been in continuous operation. The program in- After much discussion with various agencies, volves (1) electrophysiological research to dis- it was decided that a 3-year Boll Weevil Eradi- cover and develop practical methods of using cation Trail be conducted in northeast North electromagnetic energy to control the bollworm, Carolina and adjacent cotton growing areas of tobacco budworm, and boll weevil; (2) eco- Virginia. Funding for the trail was included logical research on the boll weevil, bollworm. 66 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

and tobacco budworm; (3) physiological and Waco, Tex. nutritional research on the boll weevil and The Blacklands Cotton Insects Investigations bollworm; (4) evaluation of insecticides against Laboratory was established in Waco, Tex., in cotton insect pests indigenous to the South- March 1939 by consolidating the work of the eastern States; and (5) development of ma- two laboratories located at Port Lavaca and chinery for applying insecticides (in coopera- College Station. The laboratory continued in tion with agricultural engineers). operation until it was closed at the end of June 1973. The program was concerned with re- Tucson, Ariz. search on (1) biology and ecology of the boll weevil, bollworm, tobacco budworm, cotton flea- The Cotton Insects Biological Control Inves- hopper, and thrips; (2) comparative field plot tigations Laboratory was established in the evaluation of promising new insecticides and spring of 1925 (Tucson, Ariz., Cotton Insects formulations; (3) large-scale evaluation of sea- Laboratory) to study the life history and habits sonal control programs; and (4) development of the Thurberia weevil. After these investiga- of a practical insect population management tions showed that this insect would not likely program for the Blacklands area. become a serious cotton pest, research was turned to hemipterous insect pests and later Baton Rouge, La. to lepidopterous insect pests of cotton. Primary emphasis now is on the biological control of The Cotton Insects Physiology Investigations cotton insects. The program consists of re- Laboratory was established on July 15, 1956, search on (1) population dynamics of cotton in cooperation with the Louisiana Agricultural insects, (2) bioclimatology, and (3) biological Experiment Station. It was first designated as control agents, particularly parasites and pred- Cotton Insects Insecticide Resistance Investiga- ators of cotton's lepidopterous insect pests, tions and was specifically set up to study factors including the development of mass-rearing influencing resistance of the boll weevil to techniques and field evaluations. insecticides and to develop methods of over- coming this resistance. Much of the work was physiological and biochemical. After more than Stoneville, Miss. 12 years of work on the resistance problem, it became evident that this line of research would The Delta Cotton Insects Investigations Lab- not attain its objective. Many other investiga- oratory was established in Stoneville, Miss., in tors working simultaneously on other insect 1934 in cooperation with the Mississippi Agri- resistant problems came to the same conclusion. cultural Experiment Station. It has recently Since the staff members were trained in insect been made a part of the Bioenvironmental In- physiology and biochemistry and since it was sect Control Laboratory in Stoneville. The re- actually contributing much to physiological re- search program at Stoneville involves (1) search, the laboratory was redesignated as the biological and ecological research on the boll Cotton Insects Physiology Investigations Labo- weevil under Mississippi Delta conditions; (2) ratory on July 17, 1969. The program is cen- small field plot and entire field evaluations of tered around research on (1) chemosterilants, insecticides for control of boll weevil, bollworm, (2) hormones and other essential metabolites tobacco budworm, plant bugs, thrips, spider and biological regulators, and (3) carbohydrate mites, and cotton aphids; (3) biological, nutri- metabolism in the boll weevil. tional, and physiological research on the boll- worm, tobacco budworm, plant bugs, and spider mites; (4) development of cotton varieties Brownsville, Tex. resistant to or tolerant of attack by lygus bugs The Southwestern Cotton Insect Investiga- and spider mites; (5) biological control involv- tions Laboratory was established in 1941 spe- ing parasites and predators; and (6) insect cifically to conduct research on the pink boll- population management programs. worm. It had operated as a sublaboratory of the RESEARCH ON COTTON INSECTS 67

Presidio, Tex., laboratory in 1939 and 1940. tion products in the breakdown of insecticides, Research was primarily concentrated on the and (6) development of slow release formula- pink bollworm until findings showed that the tions of systemic insecticides and synthetic insect could be controlled with cultural meth- pheromones. ods. Gradually, the pink bollworm became less of a problem, while the bollworm-tobacco bud- Mississippi State, Miss. worm problem intensified. The program now is largely concerned with research on lepidopter- The Boll Weevil Research Laboratory was ous insect pests of cotton. The program consists established in 1961, resulting from recommen- of research on (1) developing practical ways of dations made by The Secretary's Working sterilizing the pink bollworm and the tobacco Group on Boll Weevil Research Programs in budworm, (2) developing practical and econom- 1958. Its primary objective is "the elimination ical ways of mass rearing the tobacco bud- of the boll weevil as an economic factor in cotton worm, (3) studying the biology and ecology production,'' with the ultimate objective of erad- of the boll weevil, bollworm, and tobacco bud- icating it. The research program is multidis- worm, (4) isolating, identifying, and synthesiz- cipline involving entomologists, chemists, plant ing the sex pheromone of the tobacco budworm, geneticists, plant physiologists, agricultural en- (5) evaluating promising new insecticides and gineers, and soil and water research scientists. formulations against Southwestern insect pests A comprehensive program of research is cur- of cotton in laboratory and field tests, (6) de- rently underway involving (1) biology and ecol- veloping practical ways of using Bacilhts thur- ogy of the boll weevil, (2) development of an ingiensis and other pathogens for control of attractant bait containing pathogens to control cotton insect pests, (7) evaluating parasites and the boll weevil and bollworm, (3) mechanical predators as biological control agents of cotton control of the boll weevil, (4) research on the insect pests, (8) developing cotton varieties male pheromone (grandlure) as a survey, con- resistant to or tolerant of attack by insect pests trol, and possible eradication tool, (4) chemo- of cotton, (9) studying alternate host plants sterilant research on the boll weevil, (6) breed- of the boll weevil, bollworm, tobacco budworm, ing cotton varieties resistant to or tolerant of and cotton fleahopper, and (10) studying, both attacks of the boll weevil, (7) integrated control biochemically and nutritionally, lepidopterous of cotton pests, (8) physiological and nutri- insect pests of cotton. tional research including mass rearing of the boll weevil, and (9) large-scale evaluations of College Station, Tex. promising leads in the suppression or eradica- tion of the boll weevil. The Cotton Insects Systemic Chemical and Nutritional Investigations Laboratory was es- Phoenix, Ariz. tablished in 1948 in accordance with the terms of the Research and Marketing Act of 1946 in The Western Cotton Insects Investigations cooperation with the Texas Agricultural Ex- Laboratory was established in October 1965. periment Station. The program is concerned Previously, a sublaboratory of the Tucson lab- with research on (1) the nutritional require- oratory had been operated at Mesa. The Depart- ments for several cotton insects including pre- ment's 1965 Appropriation Act (78 Stat. 862), daceous and parasitic insects, (2) the develop- approved September 2, 1964, authorized and ment of nutritionally adequate artificial diets on provided planning money only for a Western which these insects may be reared, (3) the dis- Cotton Insects and Cotton Physiology Labora- covery and development of systemic chemicals tory. The 1966 Appropriation Act (79 Stat. that may be useful in cotton insect control, (4) 1165), approved November 2, 1965, authorized the development of practical methods of utiliz- and provided funds. The laboratory was com- ing predators and parasites for the control of pleted in 1970 and was fully staffed in 1972. lepidopterous insect pests of cotton, (5) deter- The program is concerned with (1) ecological mination of the metabolites and other degrada- investigations of the pink bollworm, (2) evalu- 68 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE ation of sex pheromones and different trap cal for control of Western cotton insects includ- designs for luring and trapping the pink boll- ing breeding cotton varieties resistant to or worm, (3) genetic investigations of the pink tolerant of attack by insects and pathogens, and bollworm and other Western cotton insect pests, (5) development of insect population and man- (4) development of methods other than chemi- agement programs.

ANNUAL CONFERENCE ON COTTON INSECT RESEARCH AND CONTROL, 1947-74 Each year research and extension entomolo- A. S. Hoyt, F. C. Bishopp, R. L. Haller, E. R. gists and associate technical v^orkers from 14 McGovran, and M. P. Jones. Others from the cotton-grov^ing States, the United States De- States supporting the conference were Dwight partment of Agriculture, the National Cotton Isely and Charles Lincoln, Arkansas; F S. Council of America, and Cotton Incorporated Arant and Jerry Ruffin, Alabama; C. E. Smith meet to reviev^ research and experiences of and W. S. McGregor, Louisiana ; Clay Lyle and the previous year and to formulate guiding L. C. Murphree, Mississippi ; Walter Kulash and statements for control recommendations in the Jim Conner, North Carolina ; M. D. Farrar and subsequent year. W. C. Nettles, South Carolina; H. G. Johnston The advent of the organic insecticides for and C. A. King, Texas; and F. A. Fenton and cotton insect control in the mid-1940's was C. F. Stiles, Oklahoma. responsible for the origin of the conference. ARS and its predecessor, ARA, have always DDT was used experimentally in 1944 and 1945, had the major responsibility for the manage- BHC, the BHC plus DDT mixture, and toxa- ment and coordination of the conference. R. W. phene in 1946. Others, such as aldrin, dieldrin, Harned served as general chairman for the first endrin, heptachlor, and parathion, followed six conferences, K. P. Ewing for the next four, shortly thereafter. These new insecticides were C. F. Rainwater for the next eight, and C. R. such an improvement over those previously Parencia for the next nine. The structure has available that their evaluation as quickly as not been changed because it has worked well. possible was imperative. Equally important was Also, it was essential that the revised confer- that all concerned with cotton insect control ence report be made available at an early date have the latest information on the performance and ARS had the mechanism for its publication. of the various insecticides available to them. With the help of many people, the report has R. W. Harned, who was in charge of cotton been published by the end of February each insect research for the Department from 1931 year after the January conference. The general to 1953, is credited with being the '^father'' of chairman serves as chairman of the program the conference. In the fall of 1946, he called a committee that develops the program for each conference of employees of his Division's lab- conference and, also, has the responbility for oratories at Tallullah, La. Appropriate agricul- the annual revision, publication, and distribu- tural experiment station and extension service tion of the conference report. The report is personnel of Louisiana and Texas were invited generally considered to be the cotton insect to participate. That conference was a fore- control bible of the world. It is distributed runner of the First Annual Conference on Cot- throughout the world where cotton is grown. ton Insect Research and Control held in Stone- As a result of the annual conferences, there ville. Miss., November 17-19, 1947. Others in is no other agricultural area with as much com- the Agricultural Research Administration patibility among State, ARS, and industry per- (ARA) who supported Professor Harned in sonnel in the research, extension, and control initiating the conference in addition to labora- efforts for insects than those that attack cotton. tory leaders F. F. Bondy, E. W. Dunnam, R. C. The Twenty-Seventh Annual Conference was Gaines, K. P. Ewing, and A. J. Chapman were 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 develop- other pest. Presently known procedures for ment of procedures for the control of cotton reducing boil weevil populations permit effec- insects, and growers are doing a better job of tive management of bollworm populations, but controlling them than they have ever done be- this would be much easier to accomplish if the fore. However, much continues to need to be boll weevil did not have to be considered. done, especially since growers face resistance to In the Imperial and Coachella Valleys of insecticides in more and more insects and more California, insecticidal control for the pink boll- and more restrictions are being placed on in- worm precludes management of bollworm pop- secticides used to control various pests. These ulations. In areas of the Southwest where restrictions may result in reduced development cultural and other controls keep pink bollworm and availability of new insecticides in the fu- populations at low levels, the pink bollworm is ture. Thus, future procedures for controlling not considered a key insect and thus does not insects will have to be even more sophisticated. contribute to the disruption of management of Research has progressed to the extent that insect populations. it is operationally and technologically feasible The cotton fleahopper in the Southwest, to eradicate the boll weevil as an economic pest Texas and Oklahoma, is a key insect. Unless a of cotton from the United States with environ- way, such as a resistant variety, is developed mentally acceptable techniques. Various known to eliminate the need for its control with insec- components need to be put together and tested ticides, it will, just as was discussed for the in a large field trial to determine whether the boll weevil, continue to interfere with manage- pink bollworm, too, can be eradicated. Both ment of bollworm populations. Lygus bugs have pests are host specific to cotton for all practical similar status in the Far West, Arizona and considerations. Unfortunately, this is not true California. with the other injurious pests. The changing status of the bandedwing white- Much progress has been made in developing fly, the cotton leafperforator, and the beet procedures for managing cotton insect popula- armyworm as pests of cotton must be con- tions. However, it would be much easier to sidered. The bandedwing whitefly is becoming manage populations of the bollworm and to- a problem in areas other than in northeast bacco budworm if the boll weevil were eradi- Louisiana. The cotton leafperforator, though cated. Insecticides used for the boll weevil a pest commonly associated with the Far West, destroy beneficial insects, which often in the is becoming more prevalent in certain areas in absence of insecticides keep bollworm popula- Texas. The beet armyworm, also, considered tions below economic levels. As a result subse- to be a pest of cotton in the Far West, has in- quent injurious infestations of bollworms occur, creased in importance in the Midsouth and necessitating treatment for these insects until Southeast. the crop matures even though boll weevil popu- Though much progress has been made in lations have been reduced below injurious lev- cotton insect control, improvements continue els. The mass release of predators or parasites to be needed, and judging from progress made cannot be used for control of bollworms when in the last two decades they will be developed insecticides are applied for the control of an- in the future. 70 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

REFERENCES

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(62) Lukefahr, M. J., C. B. Cowan, and J. E. (73) and M. R. Bell. 1970. Mass pro- Houghtaling. 1970. Field evaluation of duction in vivo of two protozoans. Mat- improved cotton strains resistant to cot- tesia grandis and Glugea gasti, of the ton fleahopper. Journal of Economic En- boll weevil. Journal of Insect Pathology tomology 63: 1101-1103. 16:84-88. (63) and J. E. Houghtaling. 1969. Re- (74) Mitlin, L. L., and N. Mitlin. 1968. Boll sistance of cotton strains with high pig- weevil Anthonomus grandis Boheman. ment content to Heliothis spp. Journal of Abstracts of Research Publications 1961- Economic Entomology 62: 588-591. 65. United States Department of Agri- (64) J. E. Houghtaling, and H. M. culture Miscellaneous Publication No. Graham. 1971. Suppression of Heliothis 1092, 32 pp. populations with glabrous cotton strains. (75) Moore, R. F., Jr., and H. M. Taft. 1969. Journal of Economic Entomology 69: The relationship of insecticide tolerance 486-488. and the lipids of early and late instar (65) D. F. Martin, and J. R. Meyer. larvae and pupae of the bollworm and 1965. Plant resistance to 5 lepidopterous tobacco budworm. Journal of Economic insects attacking cotton. Journal of Eco- Entomology 62: 1397-1400. nomic Entomology 58: 516-518. (76) and H. M. Taft. 1970. Fatty acids (66) L. W. Noble, and J. E. Hough- in lipid fractions from early and late taling. 1966. Growth and infestation of instar larvae of Heliothis virescens. An- bollworms and other insects on glanded nals of the Entomological Society of and glandless strains of cotton. Journal America 63: 1275-1279. of Entomology 59: 817-820. (77) and H. M. Taft. 1971. Difference (67) and T. N. Shaver. 1972. The in f at*y acid contents of triglycérides and potential of resistant cottons in the sup- phospholipids from Heliothis zea (Bod- pression of Heliothis populations. South- die) and H. virescens F. larvae as a fac- ern Cooperative Bulletin No. 169, pp. tor in their tolerance to insecticides. 27-32. Journal of Economics Entomology 64: (68) Mally, F. W. 1891. The bollworm of cot- 1060-1062. ton. United States Department of Agri- (78) Noble, L. W. 1969. Fifty years of re- culture, Division of Entomology Bulle- search on the pink bollworm in the tin No. 24 (old ser.), 50 pp. United States. United States Department of Agriculture, Agriculture Handbook (69) 1893. The bollworm of cotton. No. 357, 62 pp. United States Department of Agricul- (79) Ouye, M. T., R. S. Garcia, and D. F. ture, Division of Entomology Bulletin Martin. 1964. Determination of the opti- No. 29 (old ser.), 73 pp. mum sterilizing dosages for pink boll- (70) McGarr, R. L., and C. M. Ignoffo. 1966. worms treated as pupae with gamma Control of Heliothis spp. with a nuclear radiation. Journal of Economic Ento- polythedrosis virus, EPN, and two newer mology 57: 387-390. insecticides. Journal of Economic Ento- (80) Parencia, C. R., Jr., J. W. Davis, and mology 59: 1284-1285. C. B. Cowan, Jr. 1957. Control of early- (71) McHafFey, D. G., M. H. Flint, J. W. season cotton insects with systemic in- Haynes, and others. 1972. Sterility in- secticides employed as seed treatments. duced in boll weevils by alkylating agents Journal of Economic Entomology 1: administered in an adult diet. Journal of 31-36. Entomology 65: 13-19. (81) Parencia, C. R., Jr., J. W. Davis, and (72) McLaughlin, R. E. Glugea gasti sp. m. C. B. Cowan, Jr. 1957. Further field tests 1969. A microsporidian pathogen of the with systemic insecticides employed as boll weevil. Journal of Protozology 16: seed treatments. Journal of Economic 84-92. Entomology 5: 614-617. 74 AGRICULTURE HANDBOOK 515, U.S. DEPT. OF AGRICULTURE

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GPO 924-374