BULLETIN 326 MARCH 1960 4 - CORN EARWORM CONTROL AGRICULTURAL EXPERIMENT STATION AUBURN UNIVERSITY E. Smith, Director V. Auburn, Alabama .4 r FIRST PRINTING 5M, MARCH 1960 HOW to CONTROL CORN EARWORM Alabama sweet corn growers are faced with the task of co,. trolling the corn earworm every year. Unless this pest is kept under control, almost all ears of sweet corn are badly damaged. Good control is possible, but it requires timely and thorough insecticide applications. What to Use. DDT emulsion sprays give best results. Two pounds of DDT (1 gallon of 25 per cent emulsifiable concentrate) in 20 to 25 gallons of water should be used per acre for each application. How to Apply. Spray application is recommended. It should be put on with ground equipment. The sprayer should be equipped with four flat fan nozzles per row, two on each side. The two nozzles on each side of the row should be at least 12 inches apart (vertically) and cover at least 24 inches of the plant in the ear region. Spray should be applied at 150 to 200 pounds pressure, with the highest pressure for heavy growth of corn. When to Spray. Spraying should be begun in time to make two applications (2 days apart) before first silks appear. Then spraying should be done every other day until silks are brown. Daily spraying during silking gives better worm control and is good insurance against delays in subsequent application caused by heavy rains or machinery breakdowns. Caution, Do not feed DDT-treated foliage to lactating dairy animals or to meat animals within 60 days of slaughter. CONTENTS Page DESCRIPTION, LIFE HISTORY, AND HABITS- CONTROL OF THE EARWORM 8 8 9 9 10 14 Insecticides Rates of DDT Sprays and Dusts Application of Insecticides Timing of Sprays Control of Earworms in the Whorl SUMMARY AND CONCLUSIONS -16 17 30 LITERATURE CITED- Corn Earworm Control on Sweet Corn in Alabama W. HAROLD YATES, G. EDEN, Entomologist Gulf Coast Substation Superintendent, I 1F ( (WIN earxx 1)110k is the miost ilnportalit insect pest of swccit co)rd in Alabama. Uni less control ineasuires are ised each Xear. alm ost ccl- cuXer is dhanmagedh andt the sXXect Con I growXer silH ers hlea\ losses. Until at few, \ ears ago. Sxx rrt corn growers made 11(1 effort to conitrol the earwormill colIi. Es snil 7 / so1 e the p)acker andi ship1asinfested, crocon ~ per Clipped the tip endts frol roatig crsto remus e the can wXoriii iarviae anid their damit 1 (:Clipp)Cd c'lit roastingi. ears wX (I aiit olin sighlt inl grot'(rX store ('r r throughout the tcounitry. LilectiX methodhs for (01ntro(lIill the con)l earXworml ill 555 (ct co)rni with insecticides hiae eciil ties elop)Cd ini the p)ast 20 5 ears Ihe il ijecton lijetlii iii'tiotl(2)I C Shown typical damage to ears The il ncthd (2 rc of sweethere iswhen the corn earworm corn polrtetd ill 1938 reneesd ('t terest is not controlled in Alabama. ill the problemn. Iii 1945 it wXas fot i dt that DDT wIXas ani ('i('tXe insecticide again st the carXX orni in swXeet corn (.3). Subsequient wXork (1, 4, .5, 6, 7, S, .9, 1M 11, 12, 13, 16, 17, 18', 19) wXith DD1T resulted in p)ractitcal mneasuires for wsormi control ini fresh market corn. i (' 1 lisolbis ZLa ( Boddis )rder It pRidot&Irt. I .nilx IIh itt'tdt. 6 ALABAMA AGRICULTURAL EXPERIMENT STATION When practical worm-control measures became a reality, consumers no longer accepted "clipped end" corn. The practice of clipping tips has been completely abandoned. The grower must strive through insect control measures to deliver worm-free corn to the packing shed. Research on earworm control in sweet corn was begun at the Gulf Coast Substation, Fairhope, in 1941 and continued through 1959. Life history studies were made at Auburn in 1948 (14). The early work on control involved application of insecticides to individual ears with a hand applicator. Dichloroethyl ether, oil, and pyrethrum extracts, as well as arsenate of lead, were included in these early experiments. Some earworm control was obtained with these materials, but no practical control measures resulted. Subsequent research (7, 8, 9, 10, 11, 12) conducted primarily at the Gulf Coast Substation resulted in practical and effective control measures. Results of this research and recommendations based on it are given in this publication. DESCRIPTION, LIFE HISTORY, and HABITS The corn earworm has been studied by many researchers, and reports on its description, life history, and habits have been published (7, 14, 15). The four stages in the life cycle of the corn earworm are the egg, larva (worm), pupa, and adult (moth). The eggs, which are deposited singly, are white and shiny at first but darken before hatching. They are somewhat smaller than a pin head but are visible to the naked eye. The eggs are hemispherical and are ridged along the sides. The moth prefers to deposit eggs on the corn silk; however, before silks appear the eggs are laid on leaves and stalks of young plants. One moth lays from 500 to more than 1,000 eggs. The eggs hatch in 2 to 3 days. The larvae are very small (1.5 mm.) when they emerge from the egg. The head and legs of newly-hatched larvae are shiny black and the body is pale and transparent. After some feeding, which begins soon after hatching, the body becomes opaque and creamy yellow. The larvae grow rapidly for about 3 weeks and reach a length of almost 2 inches. The older larvae vary in color from light green to brown or nearly black. Alternating light and dark stripes run lengthwise of the body. There is usually a double CORN EARWORM CONTROL 7 Stages in the life cycle of the corn earworm ore shown above. At top left are eggs (arrows) on corn silks; small larva is shown at top right. An older larva is at bottom left and the adult (math) is shown at bottom right. dark ilic the length of the hovaong the center of the back. The 1had is~ xe ow and the legs are nearly black. Lar\ ae from eggs deposited ont leav es and stalks migrate to the w~horl wxhere thex feed ai d( often cause dlamage. XNhen tassels emerge from the whorls, the larvxae migrate down the stalks to the cars. \iost sev ere dlamage caulsedl h\- the earworm is to ears, and most of this (lamage is 1 icn by larx ae that hatched from eggs deposited on the silks. Larxvae from eggs laid on silks start feeding oni the tend~er silks and migrate dowxn the silk chaninel to the tip of the ear where tlhex feed on the dcx eloping kernels, haidl damaghini1g tihe ear tip. In sexvere cases the entire ear iliax be dlestro ed. Although sexveral larxvae moax hatch on one silk mass, more than one mature larxva is seldom found in an ear since earxx ol arvxae are cannibalistic. The mnaturye larxvae cut holes ill the shucks. drop) to the grounod, and burrow into the soil to pupamte. The pupa is dlark brown amnd ab~out :j inch in len gth. It is formed in) an earthen cell 2 to 6 inches bloxw the soil surface. 8 ALABAMA AGRICULTURAL EXPERIMENT STATION Pupation requires 8 to 9 days during the summer months. The corn earworm passes the winter in the pupal stage. Corn earworm adults (moths) emerge from the pupae and make their way to the surface of the soil. The moths, which have a wing expanse of about 112 inches, vary in color from light brown to gray. The front wings are usually grayish brown marked with dark irregular lines and have dark areas near the tips. The hind wings are white with irregular dark spots. The first moths emerge from overwintering pupae at Fairhope in early April and at Auburn they appear about the middle of May. Moths feed on the nectar of flowers. Mating occurs soon after emergence and egg laying begins. The moths move about on warm, cloudy days but primarily in late afternoon and early evening. Total time from egg to adult is about 30 days during the summer. Several generations occur each year. CONTROL of the EARWORM Insecticides The following insecticides were used in experiments on earworm control in sweet corn since 1950: mineral oil, toxaphene, parathion, aldrin, dieldrin, TDE, Dilan, endrin, heptachlor, methoxychlor, CPR (a combination of piperonyl cyclonene, pyrethrins, and rotenone), DDT, Phosdrin, Thiodan, Chlorthion, Delnav, Sevin, and malathion. Various combinations of these insecticides, with and without mineral oil, were evaluated, Tables 1-6. Throughout the various experiments, the most consistent control was obtained with DDT. Thiodan and Sevin, two relatively new insecticidal compounds, compared favorably with DDT when used at the same rates as DDT. Mineral oil-DDT combinations for earworm control were thoroughly investigated. Various oils were tested, Table 6, as well as several proprietary formulations containing DDT and mineral oil. In these studies, Tables 2, 5, 6, 7, 8, 9, 13, as well as in nationally coordinated research (12), use of mineral oil resulted in increased earworm control over that obtained with DDT alone. However, mineral oil frequently caused foliage injury to corn and undesirable spots on shucks and flag leaves CORN EARWORM CONTROL 9 Effect of a good earworm control program is shown by these ears of sweet corn. Untreated corn, left, is badly damaged, but treated ears, right, are worm-free. I E-1 pL Rates of DDT se e diiriitg hot, (Ir\ wXeathter. of1 roastili (2ars. 1102lb)11-11 was~sc F'or this reasoni, minll'a oil is not gYelleralX ulsed in Alabamna. 201(1 lentI to deterine1t the SIX t'ral experimen(1ts XX't' of 1)1)1' to Il se in serla" s for miost e{fectix e t'aXXorin Sonie of the trials incltided comoparisonls XXitli ad( withiout oil. Hates from 0.5 to -1. pot 1ds1 ot 1)1)1 per acre per tion Xwere ulsed, 'Tables :3, 7, 8, 19, 2.9 atnot ilt conltrol. mlinleral appl ica- )DT (I gallon of (s Ini these e\1)erimlilts at least ?~ pound of I __5 per cenit ettisi fiable concenltrate) XXas nleedIed per acire per applicjation for Igood earXX'orlll control. Sprays and Dusts as An~ exp)trimlenlt XX conducltedl in 1952 to deteriniie the I ('atix t' t'hcieiicx of 1)1)TI dusts and spray s, Tab~le 9. Fou~r j)ounlds of I))T as sp)ray aid dulst Xwas appliedi per acre per application hy airplane. lix c applicationis wXere maide at .3-da interX als lie11illgn XXhenI 10 per cent of stalks Xwere ini silk:. The spra\ s reorm fr-et ears anld th' tdusts in sulitedl ill about :30 per cent XX Xere' superior to dutsts for wXormf abiout 15 per cent. Thus, sprays w Conitrol. 10 ALABAMA AGRICULTURAL EXPERIMENT STATION lDusts arc washed off b\ rains to a greater degree tban are spray residues. Ini fact, it is gencraliv heliev ed byx entoinologists that rain flhi) actitalix increase cilectix cess of emuilsioin sprays5 bx carrx jog the insecticidle into the silk: channels of ears. Application of Insecticides Airplanei ap~plication of insecticides for earxxorm control in sweet corn woul 0111le diesirable if good results couild he obtained. It xx ouild he particiduarlx diesirale lc xhc thc mro nid is mu ddx or Wxhen corn stalks haxe k een blowxn and twxisted bvxvxxnd. liesults ot ai cxpcriniernt in which airplane andl groun d equ ipinent were compared arc (riveni in Table 9. Althoumgh 4l ponds of DD)T per acre xxas applied bx airplanec and onix 2 pounlds byx grounid equiipment spray s applied bx ground e(Iuipmip cnt resulted in sign ificantix more x-worm-free ears. The sprax s we rc applied at :3-dax irate rxals in this experimnet. Iledinced interx als betxxeeci applications max havec resulted in less difference betxvcen thle twxo methods of applicatimi. Airplane application, of course. dloes not conlcentrate the insecticide in the ear region. Twxo ty pes of grounid eq~uipment for sprax ing sxxect corn haxve been used successfullxy. One is a high-clearance self-propelled . High-clearance sprayers like the one shown above have been used successfully for applying insecticide to sweet corn for controlling the corn earworm. CORN EARWORM CONTROL 11 A low-cleorance power sprayer drawn by a regular farm tractor can be used successfully for spraying sweet corn, but an alley far the tractor must be left unplanted for every eight rows. Nozzle arrangement is shown in the inset. seaX 11 laiellie that XX rill iliOX e oX er the cornt \v ithlout breakin g the stalks. ScX (ral such1 machincs are ctirrct t on tbc m arket and otliers hiay c llce fahricated ili mnachjine shops). F'or small acreagecs, a nudeii-dra t, high clcaratuec spraX (r tIna iW iisei. For hest results, high-clcarauicc (1pipmctit should liax at least 6 fect claaucc fronm the ground1(. The sccol d tX pc of sera. ((jtlintit is at lXX -clearance poxx (r SpraX cr (l11aXX1i bV a rcgutlar farmi tractor. 1(o usc this sprax cr in corn. ain arca the wXidthi of twXo roXX s is left tiI plal itd after ch e ight rowXs. lTe spraX cr is equiipped wXithlia hiorizon tal boo011 tiiotitcd high enlluh to clcar thc con istalks. (C0rn spraX ens shotuild hbe cylippcd Xwith horizonital that call he raisedi or IoXX crel XXithli atiiiiioif of labor. TlIc hooini sholdt lc lon g ctiollgli to c'OXei at least ciglut roXws. Dooms XXith flexible joints arc prclcrred lot. casc of turtig nicar feniccs or b)oons1 other obstacles or iill I[oiiig X aloung pubilic roads. Considerable recscarchi XXias doneti o[] no//ic typ pc. rcssuirc, 1 loniagc pci acrd, andI~ othier factors in ii ('arXX t cotitrol. Pressure. illwXormi Pressure ofl gal- tie spri is at itmfportai t con sidecratin cotntrol. lihi. pl('ssliiu []ilist lhc high enouigih tou atomizii thic spray aiitl to petnctrate thi( iage atnd silk mass. I low~c\ cr. fol Xhicn nozles wXitli stiiail orifices arc iiscel. pressure'( Caln le tooi 12 ALABAMA AGRICULTURAL EXPERIMENT STATION high for maximum effect. If the spray is divided into a very fine mist, it drifts or blows away and does not stick when it strikes the corn plant. Corn with heavy growth requires greater pressure than that with less growth. Amount of growth varies with variety, soil type, and moisture. An example of the result of using insufficient pressure when there was a heavy infestation of earworm in the whorls before tasselling is shown in Table 19. None of the spray treatments given in Table 19 resulted in satisfactory worm control, even though the rate of DDT and spray intervals were optimum in some of the treatments. Results of experiments in which pressure was a variable are shown in Tables 10 and 20. In Table 10, where vegetative growth was medium to light, 120 pounds of pressure was most effective of the three pressures tried. Where growth was heavy, 200 pounds pressure was much more effective than 100, Table 20. With nozzles that deliver 20 to 30 gallons of spray per acre, such as four No. 65067 per row, 200 pounds of pressure was considered an effective operating pressure. Gallonage. Investigations were made on varying the gallons per acre from 6 to 50. Results of two such studies are presented in Tables 11 and 12. There was no difference between treatments because of different gallonages of spray. Gallonages of less than 20 per acre require nozzles with very fine orifices. The fine orifices are difficult to keep from clogging. Thus, 20 to 25 gallons of spray per acre is about the minimum for efficient sprayer operation. The gallonage, of course, must contain the correct amount of insecticide. The same amount of DDT, 2 pounds per acre, should be used regardless of total gallons of spray per acre. In order to know the correct proportions of DDT concentrate to mix with water, it is essential to know the amount of spray (gallonage) delivered per acre. An excellent description of how to calibrate a sprayer is given in Auburn University Agricultural Experiment Station Circular 126. Nozzles. Studies were conducted on type and number of nozzles per row for the most effective spray for control of earworm. Comparisons were made of flat fan and hollow cone nozzles and of two and four nozzles per row. Results of these experiments are given in Tables 12 and 13. In 1951 excellent control was obtained with all nozzle arrange- CORN EARWORM CONTROL 13 (stuIts atnd there XX as ll ign5jf1ific~ant dliffe'renie ibetweX l r'' ne no11zz10les nor( WXitihA 0 01 four flat fan fild or liolIM o 1 nozzles gaX e better (titles per roxx- "Kalae 12. Itt 955, flat fati 0 resu lts than the hollow con e tX pe, Tale( 13. It is nte(d that t-xx hI lidigloi agre agricuttural nozzles2 (such as u sed for sprax ing funtogic ides on pt tatoes ) grar e('5(1 tiall \ tihe satmte conitroli as did( tour flat fll niozles. The cutrr('nt r(eotnnittdatioti is four flat fan nozles per roxx . iThe nozzle( mostt eottiitotii used'( is No. 65067. 1elcits WXitht flat (:ovXerage spra inig. of ear- region of the stalk is essei tial G;ood (OX eragt' ini earXormi thli nozle t\pe of Iiozlcs( inifluencte tihe ctcnett of (oX (rage ob tained 11( I(gardiless of t\ p)( or tit imbler of no'/zles, at ('rticai cove(rage oft at le'ast 24 itnides itt the car reg00i of the stalk is ne'essary . Position oft ('ars ott corn1 stalks carie's sotttexvltat Mudi(' ener ea' miiust b)'eO cored XXitli ('ach app~lication for is iiore impo)trtnt altihouigh t\ pe atil hnit tit) iT) obtaiti de(sired1 cove rage. tilis' are' piaced( ont dIrops fro01 i A nozzle arrangement like the one shown here gives good ear-region coverage. 14 ALABAMA AGRICULTURAL EXPERIMENT STATION a horizontal boom that passes over the top of the corn. Two nozzles are arranged on each side of each row so that the spray is directed into the ear region. The two nozzles on each side should be at least 12 inches apart vertically. The lower nozzle works satisfactorily by directing the spray directly toward the row. Center of the spray pattern from the lower nozzle should be as near the middle of the ears as can be determined. The upper nozzle should direct the spray slightly downward and forward (or backward) onto the silks. This arrangement gives an overlapping of the spray patterns from the two nozzles near the ear tips, and it provides at least 2 feet of vertical coverage. Speed. As indicated in Table 12, there was no difference in control between ground speeds of 4 or 8 miles per hour of the spraying machinery provided the sprayer was calibrated at the speed used. Speed of the machine affects the volume of spray inversely. The faster a machine moves over the ground, the less gallonage per acre it delivers at a constant pressure. A satisfactory operating speed, dependent on the machine and terrain, should be determined and the machine calibrated for that speed. It has been suggested that reversing the direction of the spray machinery with alternate applications would increase effectiveness of earworm control. However, in an experiment in 1956 where sufficient pressure was used, reversing direction of the sprayer with alternate applications had no effect on earworm control, Table 3. Timing of Sprays Considerable research in the past few years was devoted to determining when to begin spraying, how often to spray, and when to stop. The silk is the most desirable place for the earworm moth to lay eggs. Thus, protection of the silk is the most important consideration in earworm control. The longer the silking period, the longer the spray program must continue. Studies have been made on the time and rate that sweet corn produces silks. The rate of silking depends on moisture conditions, and within a specific field, on the homogenity of the soil. In 1955, Table 14, 1 week was required for a field of sweet corn on the Gulf Coast Substation to develop full silk (every stalk CORN EARWORM CONTROL 15 showing silk, not all silks full grown) after the first silks appeared. Soil moisture was low and the soil varied from one side of the field to the other. In 1958, Table 15, the corn was in full silk the fourth day after appearance of the first silks. In this field the first silks appeared about 2 weeks after the first ear shoots began to show on stalks. Tassels appeared about 1 day after ear shoots. When to Begin. When earworm infestations were light to medium and there were no ea,rworms in the whorls of sweet corn, there was no advantage in beginning the spray program before silks appeared, Tables 4 and 17. However, when earworm infestations were heavy and worms were present in the whorls, presilk sprays were advantageous, Table 3. A delay of 1 day in beginning the spray program may result in less control, Table 18. It is difficult to. determine in advance how severe worm infestation will be in the ears, even though no whorl injury may be evident. Therefore, the grower should attempt to apply at least two sprays before the first silks appear. Interval Between Sprays. Much of the early work was done with 3-day intervals between sprays, since it takes about 3 days for earworm eggs to hatch. Because the favorite part of the plant for egg laying is the green silk, it would appear that application of DDT to corn silks at 3-day intervals would give excellent control. Early recommendations for earworm control stated that spraying should begin when 10 per cent of stalks were in silk and continue at 3-day intervals until silks were brown (4). This program normally required four or five applications. When earworm infestations were not severe (10 to 20 per cent worm-free ears in unsprayed corn), this program usually resulted in over 90 per cent worm-free ears, Tables 16 and 17. However, in 1954 when infestation was heavy (no worm-free ears in unsprayed corn), seven sprays applied at 3-day intervals beginning before the first silks appeared resulted in only 80 to 85 per cent worm-free ears, Table 8. This experiment vividly illustrated that when earworm infestation was severe, a spray program with 3-day intervals between sprays gave only fair earworm control, even though it began before silks appeared. In 1955, a year of reasonably light earworm infestation (11 per cent worm-free ears in unsprayed corn), five or six sprays 16 ALABAMA AGRICULTURAL EXPERIMENT STATION applied at 2-day intervals during the silking period resulted in over 90 per cent worm-free ears, Table 18. Three-day interval spray programs in the same experiment gave poorer worm control. A delay of one day in beginning the spray program in this experiment caused a drop in control. In another experiment in the same field, 16 daily applications resulted in 93.5 per cent worm-free ears, Table 13. Experiments conducted in 1956 and 1957 (years of high and medium infestations, respectively) with 1- or 2-day intervals between sprays during the silking period resulted in good earworm control, Tables 3 and 4. In 1959, under conditions of severe earworm infestations, a 3-1-3 program (3-day interval until silking began; 1-day interval until full silk; and 3-day interval until silks were brown) was superior to a continuous 2-day interval program. When to Stop. The current recommendation is to continue spraying until silks turn brown. This recommendation is based on the premise that eggs may be laid on the corn silks as long as the silks are living. Normally such a spray program is discontinued about a week before harvest. There are some indications that sprays applied after the silks stop growing may be unnecessary, Tables 19 and 20. However, further research is needed to definitely establish this fact. Control of Earworms in the Whorl Corn earworms frequently damage corn by feeding in the whorls before the stalks tassel, especially in late plantings. Severe injury in the whorl will reduce yield. When tassels emerge, the larvae migrate down the stalk, attack the developing ear, and cause severe damage to green market sweet corn. Earworms in the whorl can be controlled with DDT sprays or granules. Treatment should be applied as soon as leaf-feeding injury becomes prevalent. Two pounds of technical DDT (1 gallon of 25 per cent emulsifiable concentrate or 40 pounds of 5 per cent granules) should be applied per acre to corn knee-high or larger. The spray or granules should be applied directly into the whorls. DDT sprays applied in the ear region will not successfully control earworm larvae that move down the stalks from tassel to ear. These worms are usually half-grown or larger and are CORN EARWORM CONTROL 17 difficult to kill. They usually reach the ear before they get enough DDT to kill them. SUMMARY and CONCLUSIONS The corn earworm attacks sweet corn in Alabama every year. Control measures must be applied every year to produce wormfree market sweet corn. DDT at 2 pounds per acre per application has consistently given the best earworm control of any insecticide tested. Use of mineral oil with DDT gave an increase in earworm control, but its use may cause foliage and ear injury during hot, dry weather. Emulsion sprays have resulted in better worm control than dusts. Applications of DDT sprays by airplane at 3-day intervals were not as effective as by ground equipment. Sprays must be applied at pressures sufficient to penetrate the foliage and silk mass. In corn with heavy foliage, spray should be applied at 200 pounds pressure. Effective earworm control was obtained with spray volumes of 6 to 50 gallons per acre. Twenty to 25 gallons per acre was most practical. Flat fan nozzles were slightly superior to hollow cone nozzles. The sprayer should be equipped with four flat fan nozzles per row, two on each side of the row that direct the spray into the ear region of the stalk. Reversing direction of the spray machinery with alternate applications failed to increase earworm control. For best earworm control, spraying should be started in time to make two applications before the first silks appear. At this time, about one-half of the stalks will be in tassel. Sprays should be applied at 2-day intervals. Daily applications during the silking period assure even more effective worm control. Continuing to spray until silks turn brown has given good earworm control. Indications are that spraying may be stopped sooner; however, further research is needed to establish this fact. 18 ALABAMA AGRICULTURAL EXPERIMENT STATION Earworms in the whorls of untasselled corn may reduce yield, and they move down the stalks to the ears when tassels emerge and do further damage. DDT granules or sprays should be applied when earworm injury appears in untasselled corn. CORN EARWORM CONTROL 19 CORN EARWORM CONTROL 19 TABLE 1. WORM-FREE EARS IN SWEET CORN FOLLOWING INSECTICIDAL EMULSION SPRAYS, TALLASSEE, 1951 TreatmentTreatent)Worm-free cent ears Angle Untreated check0--0----No insecticide, 10 lb. mineral oil------------Insecticide mixed with 10 lb. mineral oil 4 lb. toxaphene, 1 lb. parathion-----------------------------1 lb. aldrin ---- ---- ---- ---- ---- ---- ---- ----1 lb. dieldrin--- -2 lb. TDE-7057.0----------2 lb. toxaphene --------------------------------1 lb. D ilan ---- ---- --- ---- ---- --- ---- ---- --0.5 lb. endrin -------------- -------------- ----1 lb. heptachlor --------------------------------2 lb. methoxyc hlor--------------------LSD, .05--------------------------------.8 3 82 41 60 70 46 64 34 6.8 65.4 39.4 51.0 57.0 42.0 53.1 35.4 12.8 7 'Four sprays were applied at 3-day intervals beginning when 50 per cent of stalks were showing silk. Indicated rates are per acre per application. TABLE 2. WORM-FREE EARS IN SWEET CORN FOLLOWING VARIOUS INSECTICIDAL TREATMENTS, CLANTON, 1952 Treatment'Woi-reas Per cent Untreated check-----------------------------------------2 lb. toxaphene, 1 lb. D DT-------------------------------CP R , 1 Angle qt.-------------------------------------------- ,2 45 26 27.7 42.2 30.3 2 lb . D DT - -- - -- - -- -- - -- - -- -- - - - - - - - - - - - -- - -- - - - - -- - --2 lb. DDT, 2.8 gal. mineral oil ---------------------------L S D, .05.-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 56 53 -8 sprays were applied at 3-day intervals beginning when 34 per cent of stalks were showing silk. Indicated rates are per acre per application. 2 CPR was a commercial formulation containing 2 gin. piperonyl cyclonene, 0.2 gin. pyrethrins, and 1.0 gmn. rotenone per 100 ml. 'Four 4 8.2 46.5 .1 4 20 ALABAMA AGRICULTURAL EXPERIMENT STATION 20 TABLE 3. WORM-FREE ALABAMA AGRICULTURA XEIEN TTO EARS IN SWEET CORN FOLLOWING VARIOUS INSECTICIDAL TREATMENTS, FAIRHOPE, 1956 Treatment 1 No. of applications Worm-free ears Per cent Angle Untreated check----------------------2.5 lb. DDT, began spraying 1 day after first .silks appeared, intervals as indicated 1-day--------------------2-day--------- --------- ---3-day------- ------- -------1-day for 7 applications, 2-day thereafter 2-day for 4 applications, 1-day thereafter 3-day for 3 applications 1-day thereafter 1-day for 7 applications, 3-day thereafter 0 15 8 5 1.0 96.5 84.5 65.5 4.90 81.69 67.28 54.07 - 11 11 9 9 95.5 81.8 52.5 91.8 78.37 65.05 46.44 74.07 2.5 lb. DDT applied at 2-day intervals until 1 spray was applied to full silk, 3-day intervals thereafter, spray schedules started as indicated 3 days before silking began--------------------1 day before silking began--------------------1 day after silking began-------------------1 day after silking began, reversed directions of machinery with alternate applications----------1.5 lb. DDT and 1.75 gal. mineral oil, began spraying 1 day after first silks appeared, 2-day intervals throughout--------------------------Began spraying 1 day after first silks appeared, 2-day intervals until 1 spray was applied to full silk, 3-day intervals thereafter 0.25 lb. Phosdrin---------------------------,2.0 lb. Thiodan ----------------------------1.0 lb. Chlorthion ------------------- -------LSD, 9 8 7 7 8 89.8 84.0 81.0 80.0 71.73 67.00 64.43 63.61 91.0 74.20 7 7 7 8.8 81.3 12.3 -- 16.63 64.75 20.34 8.54 .05 ----------.01 -- - - - - - - - - -- - - - - - - - - - -- - - - - - - - - - -- - - - - - - 1 1 .41 1 Spraying was continued on all plots until silks turned brown. Indicated rates are per acre per application. CORN EARWORM CONTROL 21 CORN EARWIORM TABLE 4. CONSTROL 2 WORM-FREE EARS IN SWEET CORN FOLLOWING VARIOUS INSECTICIDAL SPRA~YS, FAIRHOPE, 1957 Treatments VLLU'~V~ - ~~--~~-V--~) -V No. of applications Worm-free ears Per cent 6.8 99.5 96.3 86.3 98.3 Angle 14.88 87.13 80.34 68.26 83.65 Untreated check--------------2.0 lb. DDT, began spraying when stalks were shooting freely, intervals as indicated 1-da y------- ------- ------ ---- ------ ---2-day-----------------3-day 3-day until silking began, 1-day until full silk, 3-day thereafter---Same as above less first spray 0 21 11 8 12 Same as above less first and second sprays 2.0 lb. DDT, began spraying day first silks ;appeared, 1-day intervals until 1 spray was applied to full silk, 3-day intervals thereafter----- 11 10 10 99.3 98.5 86.53 84.04 79.24 98.6 Began spraying when stalks shooting freely, 3-day intervals until silking began, 1-day intervals until thereafter, insecticide rate as indicated 1.0 lb . D DT - - - - - - - - - - - -- -- --- - - -- - - - - -- 1 spray was applied to fuli silk, 3-day intervals 12 12 12 12 12 12 12 12 95.5 32.5 74.5 0.25lb. Delnav----------lb. 0.5 LSD, 2.0 lb. toxaphene -------------------------endrin --------------------- ------- ----------------2.0 lb . S evin .- - - - - - - - -- - - -- - - -- - - - - -- - - -0.5 lb. heptachlor ----------------- -------0.51lb. malathion ------------------------0.25 Ilb. parathion L1I I I II II ------------------------ 1 I- LILLlu F. 55.0 96.5 60.0 51.0 58.0 78.62 34.74 59.79 47.88 79.51 50.94 45.53 .01-1 Spraying was continued on all plots until silks turned brown. .05 49.64 6.06 8.10 Indicated rates are per acre per application. TABLE 5. WORM-FREE EARS IN SWEET CORN FOLLOWING APPLICATION OF THREE MINERAL OIL EMULSION SPRAYS, FAIRHOPE, 1951 TreatmentPercentage worm-free ears Untreated check .-----------------------------------------------------------2 lb. DDT2 lb . TD E - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --- - - - - - - - - -2 -------------------------------4 lb . toxaphene - --------------LSD, .05 1 Each spray contained 10 pounds of mineral oil per acre. Tbree were made at 3-day intervals beginning when 90 per cent of the stalks ing silk. Indicated rates are per acre per application. 2 47--3 28 12--------applications were show- 22 22 ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 6. WORM-FREE EARS IN SWEET CORN FOLLOWING USE OF SEVERAL MINERAL OILS WITH DDT, FAIRHOPE, 1952 Treatment' Wor-free Per cent ears Angle Untreated check---- --- ---- --- ---- ------- ---1.5 2 70 73 76 59 75 65 52 65 5.7 57.1 59.1 60.6 50.1 59.8 53.8 46.2 53.7 7.06 lb. DDT plus 1.75 gallons of oil Sovaspray No. 1------------------------------Superla White No. 13-----------------------------Prem ier White----- -----------------M ineral Seal------ ------ ------ ------ ---Carnation Shell N o. 7------------- ------------- ------ 1.5 lb. DD T, no oil--------------------------------WE-5------------------L S D , .05 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- 'Four sprays were applied at 3-day intervals beginning when 42 per cent of stalks were showing silk. Indicated rates are per acre per application. WE-S is a proprietary product containing 0.8 lb. DDT and 4.32 lb. mineral oil per gallon. It was used at the rate of 2 gallons per acre. " TABLE 7. WORM-FREE EARS OF SWEET CORN FOLLOWING SPRAYS WITH VARYING RATES OF DDT IN DDT-MINERAL OIL EMULSIONS, CORTE FARM, 1951 Treatment' 1 Worni-free ears Per cent Angle Untreated check ---------------------------------------No DDT, 10 lb. mineral oil-------------------------------------------------------------------------- 19.0 32.5 53.3 77.5 89.0 25.1 34.5 47.0 61.7 70.7 Mixed with 10 lb. mineral oil 0.5 lb. D DT --------------------------------------------1.0 2.0 lb..D DT -------------------------------------------lb D D T 1 L S D, .05 -- - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -8 .0 Indicated rates are per acre per application for 4 applications at 3-day intervals beginning when 10 per cent of stalks were showing silk. CORN EARWORM CONTROL 23 CORN EARWORM CONTROL 2 TABLE 8. WORM-FREE EARS IN SWEET CORN FOLLOWING DDT SPRAYS WITH AND WITHOUT MINERAL OIL, FAIRHOPE, 1953-54 Worm-free ears Treatment' 1958' Per cent Angle 1954' Per cent Angle Untreated check----------------------------------13.5 21.3 0 0 1.0 lb. DDT with mineral oil 82.0 65.3 58.8 50.1 1.0 lb. D DT, no oil -----------------------------------51.8 46.0 17.5 24.5 1.5 lb. DDT with mineral oil--------------------------90.0 72.6 74.5 60.0 1.5 lb. DDT, no oil--------------------78.7 59.4 42.8 40.7 2.0 lb. DDT with mineral oil--------------------------88.0 70.0 81.0 64.3 2.0 lb. DD T, no oil ---------------------------------------80.3 63.7 53.3 46.9 2.5 lb. DDT with mineral oil------------------86.8 68.9 DDT, no oil.------------------------85.8 67.7 64.5 53.5 3.0 lb. DD T, no oil------------------------------54.0 47.3 4.0 lb. D DT, no oil------------------------------67.5 55.3 LSD , .05---------------- --9.5 ---6.0 1 Indicated amounts are per acre per application. Mineral oil was used at rate of 1.75 gallons. -Five sprays were applied at 3-day intervals beginning when 5 per cent of --------------------------- 2.5 lb. stalks were in silk. 'Seven sprays were applied at 3-day intervals beginning when corn was shoot- ing and tasseling. TABLE 9. WORM-FREE EARS IN SWEET CORN FOLLOWING VARYING METHODS OF APPLYING DDT, BON SECOUR, 1952 Treatment' Worm-free ears Per cent Angle Untreated check--------------------------------Applied by airplane ------- 5.5 30.3 27.3 14.8 73.3 73.8 13.3 33.0 31.2 22.5 58.9 59.3 6.8 4 lb. DDT spray, 300 4 lb. DDT spray, 50 microns-----------------------------4 lb. DD T dust-- - -------------------------------------Applied by ground equipment 2 lb. D DT spray--------------------------------- ------2 lb. DDT-mineral oil spray------------------------------L SD, microns----------------------------- .05 ------------------- ' Five applications were made at 3-day intervals beginning when 10 per cent of stalks were showing silk. Indicated amounts are per acre per. application. 24 ALABAMA AGRICULTURAL EXPERIMENT STATION 24 ALABAMA AGRICULTURLEPIMN STIO TABLE 10. WORM-FREE EARS IN SWEET CORN FOLLOWING APPLICATION OF DDT-MINERAL OIL SPRAYS AT DIFFERENT PRESSURES, FAIRHOPE, 1951 Per cent worm-free ears Spray pressure' First harvest, June 12 Second harvest, June 19 12 0 - - - - - -- - - - - -- - - - - -- - - - - -- - - --- 15 35 no difference 48 62 7.0 2405---------------5 LSD, .05------------------------------------1 Two nozzles per row were used in this experiment. Three sprays were applied at 3-day intervals when 90 per cent of stalks were showing silk. TABLE 11. WORM-FREE EARS IN SWEET CORN FOLLOWING APPLICATION OF DDTMINERAL OIL SPRAYS IN DIFFERENT GALLONAGES PER ACRE, FAIRHOPE, 1951 Per cent worm-free ears Gallons of spray per acre1 First harvest, June 12 Second harvest, June 19 6 9 ------12.5 --------------------------------_-------------------------- 164------------------------------------4 23 13-no difference 43 44------------------------no difference LSD, .05------------- 1 Three gallons per acre per application of a proprietary DDT-mineral oil concentrate was applied in each case. Three sprays were applied at 3-day intervals beginning when 90 per cent of stalks were in silk. TABLE 12. WORM-FREE EARS IN SWEET CORN FOLLOWING APPLICATION OF DDT-MINERAL OIL SPRAYS BY VARIOUS METHODS, CORTE FARM, 1951 Treatment' Worm-free ears Per cent Angle Untreated check--------------------------------- ------4 fan-type nozzles used per row 12.5 gal., low speed------------------------------------25 gal., low speed--------------------------------------50 gal., low speed ------------------------------- -------25 gal., high speed-------------------------------------4 cone-type nozzles used per row 25 gal., low speed ------------------------------- -------2 fan-type nozzles used per row 25 gal., low 37 95 98 37.3 77.6 82.2 99 98 98 98 83.9 84.4 83.0 83.6 LS D speed. ---------------- , .05 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -8 .2 ' Four sprays were applied at 3-day intervals beginning when 10 per cent of stalks were in silk. All plots received the same amount of DDT-mineral oil concentrate per acre per application. Indicated amounts are for volume of spray per acre. Low speed was approximately 4 mph. and high speed 8 mph. CORN EARWORM CONTROL 25 CORN EARW(ORM CONTROL TABLE 13. WORM-FREE EARS IN SWEET CORN FOLLOWING USE OF VARIOUS NOZZLE ARRANGEMENTS, SPRAY INTERVALS, AND RATES OF DDT, FAIRHOPE, 1955 2 Treatment Y )lllr ~r I III ~IYI1 ,1~111IIYI Total no. Worm-free ears of sprays Per cent Angle 0 16 8 6 8.5 93.5 75.5 67.3 72.8 73.3 51.8 14.7 Untreated check -- -- - --- -- -- - - - - -- Four flat fan nozzles per row 1-day interval, 2 lb. DDT 2-day interval, 2 lb. DDT 3-day interval, 2 lb. DDT 3-day interval, 2.5 lb. DDT 3-day interval, 3 lb. DDT 3-day interval, 2 lb. DDT with 1 gal. mineral oil in altermate applications 2 77.7 60.8 55.2 58.8 58.9 46.0 6 6 ----------. 6 Four hollow cone nozzles per row 2-day interval, 2 lb. DDT -------------- _ ----------63.8 8 53.0 3-day interval, 2 lb. DDT --------------- ---------6 41.3 39.9 Two hollow cone high-gallonage agricultural nozzles per row 61.3 51.5 6 3-day interval, 2 lb. DDT -------------------------------------------------- -9 .6 LS D , .05 --- - - - - - - - - - - - - - - - - - - - - - - - - - - -1 Spray program started on May 23 continued until June 8; delayed 1 day because heavy rain on May 29. Indicated rates are per acre per application. Received oil on May 23 and 30 and June 6. and TABLE 14. SILKING RATE OF GOLDEN CROSS BANTAM EVERGREEN SWEET CORN, 1955 FAIRHOPE, - ------------------- Date and time May 23, 4:00 p.m.__ May 24, 9:00 am. May 24, 5:00 May 25, 8:00 26, 10:00 Per cent of stalks showing silk - ---------------------------------------- - - - - 2.5 . May p.m. a.m.-- -- ---------------- -- ----- --------- -------- -- --- -- -- --- -- -17 -- -- -- ------ -- -- --- -- -- -- --- -- -- -3 -- -- -- --- 9.8 .7 19 .7 May 30, 8:00 am. a.m.__ 26 ALABAMA AGRICULTURAL EXPERIMENT STATION 26 ALABAMA AGRICULTURA XEIEN TTO TABLE 15. DEVELOPMENT OF EAR SHOOTS, TASSELS, AND SILKS IN GOLDEN SECURITY SWEET CORN, FAIRHOPE, 1958 Date and time May 14, 2:00 p.m .----------------------------- -19M ay 19, 2:00 p.m.---------------------------May 20, 7:00 am.52--4------M ay 20, 4:00 p.m .---------------------------M ay 21, 7:00 a.m .---------------------------M ay 21, 4:00 p.m .--------------------------------M ay 22, 7:00 a.m.------81----------- ---May 27, 7:00 a.m. ___________ May 28, 7:00 a.m. - -- -- -- -- -- -- -- -- -- -26-M ay 29, 7:00 am .---------------------------------M ay 30, 7:00 a.m . ---------------------------- Per cent of stalks showing Ear shoots 30 60 71 75 ----- 1526334649----_____5 82 ---- --- --- - -57 --- TABLE 16. EFFECT OF NUMBER OF APPLICATIONS OF DDT-MINERAL OIL EMULSION SPRAYS ON CONTROL OF CORN EARWORM IN SWEET CORN, CORTE FARM, 1951 1 Treatment' Treatent Worm-free ears Per cent Angle Untreated check---- --- --- --- --- ---- --- ---3 4 5 6 ---------applications--------applications --------------------- -------------applications---- - -- -- - -- -- --applications ------------- -------------- -----1All 19 77 95 97 96 - 25.2 61.6 76.7 81.0 80.5 7.2 L S D , .0 5 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- sprayed plots received 1.5 pounds of DDT and 16 pounds of mineral oil per acre per application. All sprays were applied at 3-day intervals beginning when 10 per cent of stalks were in silk except the plots receiving 6 applications; in that case, the first spray was applied when 1 per cent of stalks were in silk. TABLE 17. WORM-FREE EARS IN SWEET CORN FOLLOWING DIFFERENT TREATMENTS WITH DDT-MINERAL OIL SPRAYS, CORTE FARM, 1952 1 Treatent Worm-free ears Per cent Angle U ntreated check--------------------------------4 5 4 5 applications applications applications applications beginning beginning beginning beginning ------- 22.0 93.0 92.8 91.5 90.0 27.9 74.7 74.7 73.3 71.9 presilk---------------------------presilk 10% 10% silk -------------------------silk-------------------------- --------------------------- L SD , .05 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - were applied at 3-day intervals. 1Sprays -- 4.4 CORN EARWORM CONTROL 27 TABLE 18. RESULTS OF VARIOUS DDT-MINERAL OIL SPRAY TREATMENTS ON CONTROL OF THE CORN EARWORM IN SWEET CORN, FAIRIHOPE, 1955 Treatment Worm-free ears Per cent Angle Untreated check--------6 applications at 5 applications at 5 applications at 4 applications at 2-day 3-day 2-day 3-day ----- 11.0 90.5 81.0 91.8 77.8 76.8 19.1 72.4 64.3 73.4 62.0 61.4 Began spraying first day after first silk -------- intervals--------. intervals intervals--------_ intervals--------. Began spraying second day after first silk 6 applications at 2-day 4 applications at 3-day intervals--------. intervals--------.~-' ~~ il U 74.5 L S D, .0 5 -- - - - - - - - - - - - - - - - - - - - - - - - -- 59.7 ___ 5.4 28 TABLE 19. ALABAMA AGRICULTURAL EXPERIMENT STATION WORM-FREE EARS IN SWEET CORN FOLLOWING VARIOUS DDT 1 EMULSION SPRAY TREATMENTS , FAIRHOPE, 1958 Treatment DDT, lb./a. 2.0 2.0 2.0 2.0 1.5 1.0 0.5 1.5 1.0 0.5 2.0 2.0 2.0 2.0 2.0 Began spraying 25% ear shoots 50% tassel 50% tassel 50% tassel 50% 50% 50% 50% tassel tassel tassel tassel Stopped spraying silks brown silks brown silks brown silks brown silks brown silks brown silks brown silks brown silks brown silks brown silks grown silks grown + 1 appln. silks grown + 2 applns. silks grown silks grown + 1 appln. Interval between sprays (days) 2 2 3 to silking; 1 to full silk; 3 thereafter 3 to silking; 2 to full silk; 3 thereafter 2 2 2 3 to silking; 1 to full silk; 3 thereafter 3 to silking; 1 to full silk; 3 thereafter 3 to silking; I to full silk; 3 thereafter 2 2 2 3 to silking; 1 to full silk; 3 thereafter 3 to silking; 1 to full silk; 3 thereafter Worm-free ears Per cent er 0.0 41.8 44.3 38.5 28.5 29.5 18.0 2.5 25.8 13.8 1.3 41.83 41.8 42.8 33.5 42.0 S Angle 0.0 40.2 41.7 38.5 32.3 32.8 25.1 8.9 30.1 21.6 4.5 40.0 40.2 40.8 35.3 40.3 9.9 Untreated check 50% tassel 50% tassel 50% tassel 50% tassel 50% tassel 50% tassel 50% tassel LSD, .05 1 The poor worm control shown in this table resulted from a combination of insufficient pressure for the heavy vegetative growth and a heavy infestation of earworm in the whorls before tasselling. CORN EARWORM CONTROL 29 CRN EARWNORM CNTROL 2 TABLE 20. WORM-FREE EARS IN SWEET CORN FOLLOWING VARIOUS DDT EMULSION SPRAY TREATMENTS, GULF COAST SUBSTATION, 1959 Treatment' Worm-free ears Per cent Angle Untreated check -----2 lb. DDT interval until silks are brown 3-day interval to silking; 1-day to full silk; -3-day until silks are brownSame as above except 3-2-3 intervals 2-day interval until silks are brown 1.5 lb. DDT -------1.0 lb. DDT---------------------0.5 lb. DDT----3-1-3 intervals until silks are brown 1 .5 lb . D DT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -1.0 lb. D D T - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -.0 lb . D D T - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -.5 2 lb. DDT, 2-day interval until silks are grown ---Same as above plus 1 application at 2-day interval Same as above plus 2 applications at 2-day interval _ Same as above plus 3 applications at 2-day interval- 0.0 65.3 0.00 53.99 61.94 46.05 50.96 39.07 20.11 2day 77.8 51.8 60.3 40.3 12.3 72.8 45.5 16.3 64.8 62.5 61.0 66.5 35.0 58.67 42.41 23.48 53.69 52.37 51.36 54.80 36.76 1 lb. DDT, 2-day interval until silks are brown, plus sticker-----------------2 lb. DDT, 2-day interval until silks are brown, 100 psi.-------------------LS D , .0 5 -- --------------------- -- -- -- - 36.0 36.66 2 .3 6 ----------------------------- --- - 1'All sprays were applied at 200 psi. pressure unless otherwise indicated. Spraying began when corn was in full tassel but before silks began to show. Indicated amounts are per acre per application. 30 ALABAMA AGRICULTURAL EXPERIMENT STATION LITERATURE CITED (1) ANDERSON, on W. Control of Corn L. D. AND HASHE, Sweet Corn in Southern California. Jour. Econ. Ent. 42(6):933-41. J. Earworm 1949. (2) (3) BARBER, C. W. New Control Methods for the Corn Earworm. Jour. Econ. Ent. 31(3):459. 1938. R. A. Tests of DDT and Pyrethrum in Oil Solution and in Emulsion Against the Earworm in Sweet Corn. USDA, BEPQ E-665. 1945. C. P., AND WOOTEN, 0. B. W.A., WENE, (4) ------------------------------- , DOUGLAS, DDT Sprays for Control of the Corn Earworm and the Budworm in Sweet Corn. USDA, BEPQ E-780. 1951. (5) DITMAN, L. P. Control of the Corn Earworm and Other Pests of Corn. Jour. Econ. Ent. 43(2):191-3. 1950. TODD, (6) _______________________,H. S., AND HARRISON, F. P. Investigations on Insects Attacking the Sweet Corn Ear. U. of Md. Agr. Expt. Sta. Bull. A-82. 1955. (7) EDEN, W. C. Control of Corn Earworm in Sweet Corn. API. Agr. Expt. Sta. Leaflet 32. 1951. Econ.-Control of Corn Earworm in Sweet Corn in Alabama. (8) Jour. Eco. Ent. 45(1):105-8. 1952. DDT for Earworm Control in Sweet Corn. Jour. Econ. (9) Ent. 46(2):359-60. 1953. 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