Managing corn earworm using GMO varieties, conventional and OMRI listed insecticides in sweet corn

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1 Mnging corn erworm using GMO vrieties, conventionl nd OMRI listed insecticides in sweet corn Brin A. Nult 1, Dn Olmsted 2 nd Abby Semn 2, Deprtment of Entomology 1, New York Stte IPM Progrm 2, Cornell University, NYSAES, 630 W. North St., Genev, NY 14456; Emil: bn6@cornell.edu; Website: Corn erworm (CEW) is mjor thret to sweet corn production in New York s infesttions hve become chllenging to control when pressure is high. Mngement of CEW relies on properly timed folir pplictions of insecticides during the green silk stge. In sesons when CEW pressure is high, poor control my result becuse either the popultion is resistnt to the insecticides pplied (e.g., pyrethroids) ginst them, the pplictions re not well-timed, re not frequent enough, or ll three. Reserch is needed to identify effective insecticides nd proper timing of pplictions for CEW control. Moreover, there is incresing interest in growing sweet corn grown orgniclly, so informtion bout the efficcy of insecticide products listed by the Orgnic Mterils Review Institute (OMRI) is needed. There is lso gret interest in relying less on folir insecticide pplictions for mnging CEW nd tking dvntge of GM-sweet corn tht is resistnt to CEW. While GM-sweet corn is not currently vible option for the processing industry, it is n excellent option for the fresh-mrket industry. Below describes the objectives of reserch conducted in 2017 tht ddressed these questions for improving CEW control in sweet corn: OBJECTIVES (1) Evlute combintions of conventionl insecticide product nd ppliction timings (2) Evlute efficcy of selected OMRI-listed products (3) Evlute the performnce of single- nd multiple Bt-gene sweet corn vrieties I. Evlute vrious conventionl insecticide product by ppliction timing combintions for CEW control Tble 1. Vrious insecticide by ppliction timing strtegies evluted for control of corn erworm in sweet corn in Genev, NY in Trt # Product * Timing Strt time End time Rte 1 Corgen Stndrd IPM 50% silk Hrvest 5 fl oz/cre 2 Corgen One ppliction 50% tssel 50% tssel 5 fl oz/cre 3 Corgen 3d intervl 50% tssel 25% dry silk 5 fl oz/cre 4 Corgen 5d intervl 50% tssel 25% dry silk 5 fl oz/cre 5 Besiege Stndrd IPM 50% silk Hrvest 6 fl oz/cre 6 Besiege One ppliction 50% tssel 50% tssel 6 fl oz/cre 7 Besiege 3d intervl 50% tssel 25% dry silk 6 fl oz/cre 8 Besiege 5d intervl 50% tssel 25% dry silk 6 fl oz/cre 9 Wrrior II Stndrd IPM 50% silk Hrvest 1.92 fl oz/cre 10 Wrrior II One ppliction 50% tssel 50% tssel 1.92 fl oz/cre 11 Wrrior II 3d intervl 50% tssel 25% dry silk 1.92 fl oz/cre 12 Wrrior II 5d intervl 50% tssel 25% dry silk 1.92 fl oz/cre 13 Untreted New insecticide spry timings were evluted in which the initil ppliction ws pplied when 50% of the plnts were tsseling, rther thn 50% of the ers silking. Additionl pplictions were either not mde or mde following 3- or 5-dy intervl until mjority of the ers hd silks tht were 25% brown nd dry. Becuse dimide insecticides hve longer residul ctivity thn pyrethroids, Corgen (chlorntrniliprole), Besiege (chlorntrniliprole + lmbdcyhlothrin) nd Wrrior II w/zeon Technology (lmbd-cyhlothrin) were compred. Tretment structure ws 4 x 3 fctoril with ppliction timing s the first fctor (4 timings: stndrd ppliction timing, one single ppliction t 50% tssel, initil ppliction t

2 2 50% tssel followed by dditionl sprys every 3-d or 5-d) nd insecticide s the second fctor (3 insecticides: Corgen, Besiege nd Wrrior II w/zeon Technology) (Tble 1). These 12 tretments plus n untreted control were rrnged in rndomized complete block design nd replicted 5 times. Plots consisted of three 20-ft 30 in spcing; seeds of the processing cultivr, cv. 2390, were plnted t 8-inch spcing. Three weeks fter first silk, 50 primry ers from the middle two rows were rndomly hrvested nd evluted for CEW presence nd/or dmge s well s other cterpillr pests. CEW pressure ws very low in this tril. Consequently, it ws not possible to sttisticlly discern the best insecticide by ppliction timing tretment (Tble 2). However, ll insecticides pplied more thn one time, regrdless of when the initil ppliction ws mde reltive to the phenology of the crop, performed numericlly better thn tretments pplied single time t 50% tssel (Tble 2). Tble 2. Men percentge (± SEM) of undmged, mrket-sized ers in vrious insecticide by ppliction timing tretments mde in sweet corn in Genev, NY in Tretments re listed in descending order of performnce bsed on the percentge of non-dmged, mrket-sized ers. Trt # Tretment Mens followed by the sme letter re not significntly different (P>0.05). Number of pplictions Men undmged clen ers (%) 12 Wrrior II, 5d intervl from 50% tssel to 25% dry silk ± Wrrior II, 3d intervl from 50% tssel to 25% dry silk ± Corgen, 3d intervl from 50% tssel to 25% dry silk ± Corgen, 5d intervl from 50% tssel to 25% dry silk ± Besiege, 5d intervl from 50% tssel to 25% dry silk ± Corgen, 50% ers silking to hrvest ± Besiege, 50% ers silking to hrvest ± 2.0 b 7 Besiege, 3d intervl from 50% tssel to 25% dry silk ± 2.1 b 9 Wrrior II, 50% ers silking to hrvest ± 3.4 b 6 Besiege, 1 50% tssel ± 2.4 b 13 Untreted ± 2.1 b 10 Wrrior II, 1 50% tssel ± 3.6 b 2 Corgen, 1 50% tssel ± 4.2 b While there ws trend for multiple pplictions of insecticides to provide better control of CEW thn single ppliction t 50% tssel, dditionl reserch is needed before recommending n optiml strtegy for corn erworm mngement.

3 3 II. Evlute efficcy of selected OMRI-listed products for CEW control OMRI-listed insecticides were evluted for their efficcy ginst CEW nd other cterpillr pests in fresh-mrket sweet corn, cv. AP 426 F1, in Genev, NY in On 6 July, seeds were plnted in tworow, 25-ft long plots. This experiment included 10 tretments (including the untreted control) (Tble 3). Corgen SC (not listed by OMRI) ws included s conventionl stndrd. All tretments were rrnged in rndomized complete block design with ech tretment replicted 5 times. Tble 3. Insecticide products nd rtes evluted for control of CEW in sweet corn in Genev, NY in *Corgen is not listed by OMRI. Tretments were pplied using CO 2 Trt # Tretment Active ingredient Rte pressurized bckpck 1 Untreted control - - spryer nd boom 2 Azer pyrethrin+zdirchtin 40 fl oz/a equipped with two, fltfn nozzles (XR-Teejet 3 Entrust spinosd 5 fl oz/a 8002) clibrted to 4 Entrust spinosd 10 fl oz/a (not lbelled) deliver 25 gllons per 5 Agree WG B.t. izwi 2 lbs/a cre t 40 psi. Nozzles were seprted by 20 6 Jvelin B.t. kurstki 1.5 lbs/a inches nd directed 7 Gemstr OBs of NPV 10 fl oz/a horizontlly towrd the 8 Entrust + Agree spinosd + B.t. izwi 5 fl oz/a + 2 lbs/a primry er nd pplied to only one row t time. 9 Entrust + Jvelin spinosd + B.t. kurstki 5 fl oz/a lbs/a All tretments included 10 Corgen SC* chlorntrniliprole 5 fl oz/a the OMRI-listed surfctnt, NuFilm 8 fl oz/cre. All tretments were initilly spryed on 4 September when 49% of the ers hd produced fresh silk. Additionl pplictions were mde on 9 nd 15 September. All silks were brown nd dry shortly fter the lst ppliction. On 2 October, 40 primry, mrket-sized ers were hrvested within ech plot. Efficcy of tretments ws evluted by recording the number of ers dmged. Additionlly, the loction of dmge on ech er ws recorded s either tip only (the top inch or where developed kernels hd mde complete ring) or below the tip/bse of the er (ny dmge tht extended from below 1 inch of the er tip to the er bse). Ers with dmge to both the tip nd below the tip were ctegorized s below the tip/bse of the er. The CEW infesttion ws low nd cused only 15% er dmge in the untreted control (Tble 4). Entrust pplied t high rte (Tretment #4) significntly reduced the percentge of totl dmged ers compred with the percentge in the untreted control. None of the other tretments significntly reduced the percentge of dmge ers compred with dmge in the untreted control. Surprisingly, this included Corgen. However, Corgen nd ll tretments tht included Entrust (either lone or in mixes with Bt products) reduced the percentge of dmged ers compred with those treted only with Bt products (Agree nd Jvelin) or the nucler polyhedrosis virus of H. ze product (Gemstr) (Tble 4). There ws no pprent dvntge of co-pplying the Bt products with the lower rte of Entrust (5 fl oz rte) for reducing dmge. The high rte of Entrust (Tretment #4) ws pplied t rte of 10 fl oz/cre nd the totl mount of Entrust pplied to the crop ws 30 fl oz/cre; both of these mounts exceeded the mximum llowble per ppliction (6 fl oz/cre) nd mximum llowble per crop per seson (29 fl oz/cre). This tril should be repeted to determine if there is consistent dvntge of using 10 fl oz/cre rte versus 5 fl oz/cre rte. If so, informtion my help the registrnt modify the existing lbel.

4 4 Tble 4. Men percent of mrket-sized ers dmged primrily by corn erworm in fresh-mrket sweet corn plnted on 6 July 2017 in Genev, NY. Men percent dmged ers (%) Trt # Product b Totl Tip only Below tip/bse of the er 1 Untreted control 15.0 bc 8.5 -d Azer d 9.0 -d Entrust (5 fl oz) 4.0 cd 2.5 d Entrust (10 fl oz) 0.9 d 0.9 d Agree WG bc Jvelin Gemstr 18.0 b 13.0 b Entrust + Agree 5.0 bcd 3.5 cd Entrust + Jvelin 4.5 cd 4.0 bcd Corgen SC 1.5 cd 1.0 d 0.5 P Vlue < < Mens followed by the sme letter within column re not significntly different (P> 0.05; Tukey s Studentized Rnge [HSD] Test; n= 5). If the P vlue for the overll test ws not significnt (>0.05), no letters were included. Er dmge tended to be loclized more t the tip thn below the tip (Tble 4). Corgen nd Entrust pplied either lone or in combintion with the Bt products hd the lest mount of tip dmge compred with the other products, but overll tip dmge did not differ from tip dmge in the untreted control. Tip dmge levels in tretments tht received either Bt products lone or Gemstr tended to be greter thn dmge levels in tretments tht included either Entrust or Corgen (Tble 4). Er dmge locted below the tip/bsed of the er tended to be highest in the untreted control s well s tretments tht received either Azer, Bt products or Gemstr, but dmge levels were not significntly higher thn those in the other tretments. Entrust ws the best OMRI-listed product for protecting sweet corn from CEW. Entrust t 10 fl oz/cre impressively provided n equivlent level of control s tht provided by the conventionl product, Corgen. Future reserch is needed to determine the repetbility of Entrust s performnce ginst CEW, especilly t the highest lbelled rte.

5 5 III. Evlute the performnce of single- nd multiple Bt-gene sweet corn vrieties Two types of Bt sweet corn hybrids from Syngent Seeds were evluted for their efficcy ginst CEW nd other cterpillr pests in Genev, NY in Attribute hybrids (expressing Cry1Ab toxin cv. BC0805 ), Attribute II hybrids (expressing Cry1Ab nd Vip3A cv., Remedy ) nd the non-expressing isoline, cv. Providence, were evluted. On 6 July, seeds were plnted in four-row, 100-ft long plots. This experiment included 3 tretments tht were rrnged in rndomized complete block design with ech tretment replicted 4 times (Tble 5). On 27 September, 100 primry, mrket-sized ers were hrvested within the center rows of ech plot. Efficcy of tretments ws evluted s described in the study ddressed in Objective 2. In ddition to this tril, the sme protocol ws followed by collegues locted in seven sttes (NC, VA, WV, MD, DE, NJ, nd NY), for totl of trils in totl in The cterpillr pest infesttion in Genev ws moderte nd cused 19% er dmge (81% clen ers) in the non-bt isoline (Tble 5). In contrst, overll er dmge by cterpillr pests in trils in other sttes prticipting in the tril in 2017 ws much higher nd verged 87.4% (only 12.6% clen ers) (Tble 5). In Genev, CEW ws by fr the mjor pest, followed by ECB nd then FAW. Averged cross the other sttes, CEW ws lso the mjor pest, but followed by FAW nd then ECB. In Genev, the percentge of clen ers in Remedy ws significntly greter thn the percentges of clen ers in both BC0805 nd the non-bt isoline (Tble 5). The percentge of clen ers in BC0805 lso ws significntly greter thn those in the non-bt isoline. Unlike BC0805, there were significntly fewer ers dmged by CEW in Remedy thn in the non-bt isoline, indicting tht inclusion of the Vip3 gene is responsible for the enhnced control of CEW. Both Bt cultivrs provided excellent nd equivlent control of ECB (Tble 5). Too few FAW infested corn in our tril to compre the two Bt cultivrs. Of 18 field trils cross seven sttes in 2017 compring Attribute II hybrids (e.g., Remedy) with non-bt hybrids, less thn 1.5% of the ers were dmged, indicting ner 100% control efficcy of ll erinvding worms including CEW (Tble 5). In contrst, Attribute hybrids (e.g., BC0805) verged 21% dmge, primrily cused by CEW, which is not commercilly cceptble. Tble 5. Summry of insect control efficcy of different Bt sweet corn hybrids compred with the non-expressing isoline in Genev, NY in Dt in prentheses ws compiled from individul field trils conducted t 15 loctions cross seven sttes (NC, VA, WV, MD, DE, NJ, nd NY) in Hybrid Bt trits expressed % clen ers % ers dmged by CEW % ers dmged by ECB % ers dmged by FAW Remedy Cry1Ab+Vip3A 99.5 (98.7) 0.5 b ( 0.6) 0.0 b (0.0) 0.0 (0.1) BC0805 Cry1Ab 91.8 b (23.8) 7.8 (79.0) 0.3 b (0.1) 0.5 (1.9) Providence Non-Bt isoline 81.0 c (12.6) 12.3 (84.4) 6.3 (3.6) 0.8 (6.1) Mens followed by the sme letter within column re not significntly different (P> 0.05; Tukey s Studentized Rnge [HSD] Test; n= 4). If the P vlue for the overll test ws not significnt (>0.05), no letters were included. Attribute II sweet corn provides excellent control of ll folige feeding nd er-invding cterpillrs, thus no insecticidl sprys re required, except for secondry pests such s sp beetles, rootworm dults nd Jpnese beetles.