CIRCULAR No. 106 OCTOBER 1951 4 COTTON INSECTS andZc THEIR CONTROL INSECTICIDES AGRICULTURAL EXPERIMENT STATION of the ALABAMA POLYTECHNIC INSTITUTE E. V. Smith. Director Auburn, Alabama CONTENTS Page PRINCIPAL COTTON PESTS 3----------------------- Thrips3 Spider mites--------- 4 Cotton aphid 5 Bollworms 6 Boll weevil .----------------------------- 7 COTTON INSECTICIDES---------------------------11 Aldrin - 11 Benzene hexachloride ..------------------.- 11 Calcium arsenate 12 DDT 12 Dieldrin 13 Toxaphene 13 RESULTS OF CONTROL EXPERIMENTS WITH INSECTICIDES 1 Experiments with various insecticidal treatments 14 T iming of applications ............................... 18 Interval betw een applications .......................... 26 Four-year average results of experiments with ins e c tic id e s .. 2 7 Effectiveness of dusts and sprays ....................... 28 PROCEDURES IN CONTROL OF COTTON INSECTS 29 When to begin applications --------------------------- 29 Application intervals and number of treatments 30 R ate p er acre -- - - - -- - - - --- -- - -- -- -- - - - - - - -- - - - - - -- - - 30 How to app ly ---- -- --------- ------------------- ----- 31 Evaluation of dusts and sprays ------------------------ -33 P recau tion s - - - - ----- -- - - - - - - -- -- - - ---- -- --- - - - ---- 33 SUMMARY AND CONCLUSIONS- ---- --------- ............- 35 REFERENCES ----- 36------------------------86 FIRST PRINTING 10M, OCTOBER 1951 COTTON INSECTSad THEIR CONTROLd INSECTICIDES F. S. ARANT, Entomologist The boll weevil and other cotton insects have destroyed more than one bale of cotton for every three harvested during the past few years in Alabama. These losses occurred in spite of the fact that information is available for successful control of the pests, even during seasons of extreme insect abundance and heavy rainfall. Control measures properly applied can increase the cash income of Alabama farmers by many millions of dollars annually. This circular contains information on the important pests of cotton, results of experiments in the control of cotton insects, and insect control procedures for use in a program of profitable cotton production. PRINCIPAL COTTON PESTS The most important pests of cotton in Alabama are boll weevil, bollworms, cotton aphid, and spider mites and thrips. Thrips Several species of thrips feed in buds of seedling cotton, causing the leaves to become ragged and distorted in appearance. In rare in- stances, enough thrips may be present to seriously damage the stand of cotton. Species involved include onion thrips, Thrips tabaci Lind; tobacco thrips, Frankliniella fusca (Hinds); flower thrips, F. tritici (Fitch); and others. These tiny insects (Figure 1-A) may breed on weeds and wild plants, vegetables, grains, and many other crops. When the cotton emerges, they may move to the seedling plants. Much so-called early insect control is aimed at thrips control. However, there is some question as to benefits resulting from control of these insects. In some sections of the country where cotton is C A D FIGURE 1. Three of the important cotton pests: (A) thrips (about SOX enlarge- ment), (B) aphid, winged stage, and C) wingless (about IOX enlargement); (D) spider mite (1OOX enlargement). (B, C, and D courtesy of the USDA Bureau of Entomology and Plant Quarantine.) planitedl l)(twccu rows of onions, serious d~amagne to stands results f root the transfer of thtrips tron thte onions to the cottonl. In Alabama, seriotus (Li aa(e iuax occur locally dutringi some sea sons. Experiments inic~iate that thurips con1 trol usually does not increase' the \ jeld of cottoni uniless insects are nnicrous mioulth to dlamuage the stand. Cotrol of mouderat( to heasvy inestationis oil seedlingi cotton does con tribiute to solesshat earl ier mnatuurity of the co tton. At present thrips control is nuot generally- recommendled ill.1labl~aa iuless there is (lanlger of (lamuage to the staild 01 cotton. Spider Mites Scendra species f spiderimites. inel uuing (1 ron 1111 Is binlaldatnus l ars e y, itfest cotton iinAlabamna ( Figure 1-I) ) . These umites, also kinowsn as redl sp~iders. lbreedl oin numuerous w5ildl and cuiltisvatedl planlts, l41 including pokeweed, Caley pea, vetches, clovers, beans, weeds of many kinds, and other plants. Infestation is spread largely by mechani- cal means, such as by cultivation, from infested to uninfested plants. Different species respond in somewhat different ways to environ- mental conditions. In general, however, spider mites are most numerous during seasons of hot, dry weather. Heavy, washing rains usually reduce mite infestations. Gentle rains are less effective. Most of the new insecticides applied to cotton will not control spider mites. In fact, they tend to cause a build-up in the mite popu- lation, although under Alabama conditions this build-up is usually not very great. During 4 years of experimental work with new or- ganic compounds, it has not been necessary to control spider mites in any experiment.' However, if the infestation becomes extensive in a cotton field during the fruiting period, the yield of cotton may be reduced by this pest. Parathion is one of the most effective insecti- cides for eleminating spider mite infestations. This material is hazard- ous to use and is recommended only where adequate precautions will be taken. Two to three applications of a 1.5 per cent dust applied 8 days apart at the rate of 20 to 25 pounds per acre will usually control spider mite infestations. Two to three applications of sulphur applied in the same manner is also a standard treatment but is less effective than parathion for eliminating heavy infestations. Cotton Aphid The cotton aphid, Aphis gossypii Glov. (Figure 1, B and C), attacks cotton in the seedling as well as in later stages of growth. During cool weather, seedling cotton may be stunted by heavy aphid infestations. However, the most serious damage from this insect results when heavy infestations develop during the time the crop is being set and matured. Heavy infestations at that time may develop from applications of such insecticides as calcium arsenate and DDT for control of other pests. Aldrin and dieldrin may also create con- ditions favorable for development of aphid populations, although information on this point is limited. Serious reduction in yield of cotton results from heavy aphid in- festations during the fruiting period. Control of the insect with benzene hexachloride, nicotine, or other aphicides is highly profitable. 'Extensive infestations of strawberry spider mite, Tetranychus atlanticus McG., developed on cotton in northern Alabama in the late summer of 1951. However, the infestations were associated with extremely dry, hot weather rather than with repeated applications of organic insecticides. [5] Boll wo rm s III Nd.11ulli \ iIi ar i t l II i to iii ii l \\ iI ni Iii t lt)c in cottonill iiII till cai iIN h),rt if tilt sxiiiili c - a ithd titithe i s till ti hIiiii\I rII iir (ill , dl\r it ii) II. tI/ili i c It .!t I'i 41 iii '_ 11i nla h iahln t ii (I 4lti i xits11 liiii.l\\trn . Th I ssII c n e te II I tise li)II" til iiailxli i iixlli (attix i i li lx iii IS li l)ii )ix. li iiiit i iir iti li i iti ii xxi iuti iiirtnc asiix t ' f cottonii FIUR 2t. eft, s tilnc cston1 bl . j ia o .tw blwri nd e Tize);rig ll ts and back view of areIstwo, Ii cre nt! nu. i orh fur sc\Inilcs er~t] hch)1-e ell h~sit i- \ cu or tils o hue n Icae and\ bud oiiifli thie cotton l )aits. The (12j.,x hatchi ill 2 or 3 days aiid the xu<O liarx ae teed fiist oh the teniter Ica\ ex. I'atti tiIxN 1)ore into squiares and biolls. After ttttiii for i peiodi of 2 to :3 xxeeks, tie lii~a r eIach ita hi £ft of 1' incies dxtrop to the ,rioundo aind pup ate inltiie soil. I)( th)lop l it [1romIL to moth 1(11liles ia period of ap- 10 \iiateix )30 dax s. lloihx olrli can1 11(hIIC L(Velltix tihe \ ield of coltton, i.1)atiilliari\ if tilex ar1e Inmelous ini bolis. Bolixxolin dannei, max 1)1 iniereased b\ the aplicatlin of lbei/e Iie:aihorichc ildior I.(F Iieidriiin nliex DDTIY is addedc~ to tihe l01111 latioi. I3oilkxxoinfesn ttat ins are lrc jlcit \v ors MexI re111 application oflxiiinslxct icidiex ihayX, ibein nInlac wh)(ix too1 h lohlitlln il\a1) hc l lccn tratlcs ) als tend ixiiXtoI ildux Ilhcs( nialtcrilis airt lllwt (ifctkX OL,:lillt the inisect XX lc it i. smill. Ia(, "li4a terihll1 are difu(lft tol kili. 13011 Weevil Hibernation and Temperature Relationship. Boll x Aexill- FIGURE 3. Life stages of the boll weevil (about 3X enlargement). .4 y ayy1 - 4, 4 buildings, particularly under loose boards and shingles; along the edges of woods, in trash or under loose bark; and in other protected places. Temperature has an important bearing on winter survival. In general, many adults are killed by temperatures of 100 F. and be- low. This refers to the temperature of the insect and not of the atmos- phere. Adults hibernating in trash on the ground and protected by snow may survive, even though the air temperatures may be below 100 F. Intermittent cold periods and thaws will kill more weevils than continuous cold. Adults begin to emerge from hibernation as the weather becomes warm in the spring. The period of emergence may extend from March to the middle of July. The peak emergence usually occurs in June, although there is some variation from northern to southern Alabama. A hypothetical example of boll weevil emergence is illustrated in Figure 4. Longevity. Most of the adult weevils emerging from hiberna- tion before the plants begin squaring live for only 7 to 14 days. Those that emerge after squaring begins may live 8 to 4 weeks, although many of them die in a shorter time. Overwintering females usually No. weevils Squaring Squaring Per cent 210per.