Evidence for Decreasing Corn Earworm Susceptibility to Pyrethroids: Impact & IPM Recommendations for 2007 W. Hutchison, E. Burkness, B. Jensen, R. Leonard, J. Temple, R. Weinzierl, R. Foster, T. Rabaey, B. Flood, S. Fleischer, P. Pietrantonio, R. Parker, M. Sandstrom, D. Changnon, B. Bishop, C. Welty, E. Roddy, E. Cullen -University, Industry, Agency Partnership -N. American Zea-Map Working Group Great Lakes Expo 2006 Jim Jasinski - Ohio State University Extension

Presentation Overview Background on growing pyrethroid resistance Testing & Results Summary and Recommendations

Why is this Important in the Great Lakes Region? H. zea that infest our late season sweet corn, tomatoes, peppers, and snap beans come from southern source regions. Primary host crops in those source regions are cotton, sorghum, soybean, and corn. These crops receive numerous applications of pyrethroid insecticides. Pyrethroid resistance that evolves in southern crops may present a problem in the northern destinations of migrating H. zea

Crops at Risk: Midwest Values (2004) CropAcres (harvested)Value ($) Sweet Corn -Processing214, M -Fresh Market42, M Snap Beans -Processing107, M -Fresh Market4, M Tomatoes -Processing18, M -Fresh Market10, M Bell Peppers -Proc/Fresh Market3, M Total400, M *USDA-NASS Quick Stats ( (RAW roduct) CEW TFW CEW

Implications for Zea Resistance in the Midwest Few to zero alternatives for many crops $400 Million at Risk in Midwest $ Impact does not yet include potential damage to Seed Corn Production Possible return migration in Fall conserves resistance genes? (Johnson 1995) –A function of midwest latitude?

CEW Migration: Classic Summer Scenario CEW Source Region L H Insect Pump DROP ZONE

CEW Reverse Migration Example: Fall CEW Source Region H L Insect Pump DROP ZONE

ZEA-MAP: Multi-state Network Connecting Collaborators- first year

ZEA-MAP: Daily Migration Forecasts Northern Illinois University (Mike Sandstrom, Dave Changnon, Dept. of Geography)

Types of Resistance Evaluation Adult Vial Tests (AVT) –Lab based –Single Dose (x micro grams ai) –Multiple Doses (5-30 micro grams ai) Larval Tests –Lab based Larval Tests –Field trials (small plots)

Measuring Insecticide Resistance with a Discriminating Dose in Adult Vial Tests Adult vial tests (AVT) use a discriminating dosage of insecticide (based on earlier log- dose / probit-mortality analyses) The discriminating or diagnostic dose is just high enough to kill 100 percent of a susceptible population, so … If a population is susceptible, we would expect 100% mortality (or at least percent)

Trend for Resistance in the Southern States Louisiana: CEW Adult Vial Test (AVT): Cypermethrin (5 µg/vial) Roger Leonard, D. Cook, et al. (LSU) -- Southern U.S. -- AVT Survival (%)

MeanYear Pyrethroid Efficacy in WI, MN Declines: % Larval Control (all instars) Sweet corn (Capture/Warrior pooled)

2005 CEW Pyrethroid Efficacy Multi-state Midwest Summary (Foster, Hutchison, Jensen, Rabaey, Weinzierl) *Univ. of MN = Percent control is for all CEW instars; approximately 90% of larvae were late instar *MN Green Giant = all percent control values are for 3-6 th instar CEW only *Univ. of WI = Percent control is for all CEW instars; approximately 75% of larvae were late instar *IN Purdue = Percent control is for all CEW instars; approximately 80-90% of larvae were late instar *Univ. of IL = Percent control is for all CEW instars NOTE: Slightly better results in 2006; Overall Mean of ca % control Insecticide Rate (oz/ac) Overall efficacy (% control) (mean ± SD; range)n Warrior 1CS oz19.3 ± 29.8 (0-71.4)6 Capture 2EC oz37.3 ± 30.0 ( )4 Mustang Max 0.8 EC3.4-4 oz33.4 ± 33.9 (0-75.0)5 Baythroid 2EC oz19.8 ± 29.6 (0-53.8)3 Untreated check - CEW/ear – 1.41

Multi-state Insecticide Trial Results

ColonynLD 50 95% CLSlopeX2X2 RR SC-ESTILL – ± 0.46n/a31 Champaign – ± Wisconsin – ± Ontario – ± St. Joseph – ± LD 50 Response of CEW Larvae to λ-Cyhalothrin Resistance response higher with Warrior (R. Leonard, LSU) Resistance Ratio (RR) calculated from LD 50 data (0.002 μg/larva) derived from SC Lab Conclusions to date: The more elevated resistance ratios for Warrior may be due to response to a more “refined” pyrethroid isomer; also supports previous work of cross-resistance among pyrethroids. (Results with larvae may be deemed more conclusive than adult assays.)

LD 50 Response of CEW Larvae to Cypermethrin 2006 – (J. Temple, R. Leonard; LSU) LocationNLD5095% CLSlopeX2RR Wisconsin ± Minnesota ± Winnsboro LA ± Pennsylvania ± Illinois ± Indiana ± Resistance Ratio (RR) calculated from LD50 data (0.013 – μg) derived from MO and LA 1988; Cooperators: Jensen; T. Rabaey; S. Fleischer; Weinzierl; Foster. Conclusions to date: Response of field-collected larvae for MN, WI locations show significant level of resistance; RRs > 5 generally reflect a significant genetic shift in resistance to an insecticide.

Assessing Midwest Level of CEW Resistance Currently, resistance remains variable, but trend is major concern… “Range of susceptibility” Within a colony (R. Leonard): –a) some show avg. resistance, –b) some high susceptibility, –c) some express very high resistance (e.g., 50% survival at 20 ug/vial)

Assessing Midwest Level of CEW Resistance (cont.) So far, few major control failures, Processing Sweet Corn, (Snap Beans ?) “Process Out” CEW; but how much? Lack of problem in Commercial fields? –Unique mortality effects in big fields? (vs. small plot trials) Commercial Fields: allow for adult control Adult control helps; but adults are not fully susceptible

Crops at Risk-Example: Sweet corn Kernel Damage– by Larval Size (Rosemount, MN) Quality, Economic Impacts : –Fresh-market: Direct larval contamination, reduces “marketable ears”; major impact for $3.50/doz sweet corn –Processing: Feeding damage to kernels (brown kernels), kernels lost, and larval contaminants (can be “processed out”, but still incur an average loss of 14 kernels/ear) –Economics: ca. $6 million in Midwest, plus added $850,000 in insecticide / applic. costs –(Rabaey, General Mills; personal comm., 2006) –Similar scenarios may apply to seed corn (in progress)

Adult Vial Test

CEW Moth Flight Cooperators: Hartstack Trap sites--2006

Pheromone Trap Study: Midwest US, 2006 Hartstack vs. Scentry trap Hartstack (# of moths) Scentry (# of moths) LocationTrapping interval TotalPer trap per night TotalPer trap per night Polk Co., IA6/8 – 9/ Dakota Co., MN 16/2 – 9/ Dakota Co., MN 26/2 – 9/ Le Sueur Co., MN6/2 – 9/ Clark Co., OH7/5 – 9/ Franklin Co., OH6/14 – 10/ Conclusions to date: Hartstack more consistent; better for resistance monitoring; provide necessary moth numbers

Pheromone Trap Study: Ohio, 2006 Hartstack vs. Scentry trap

CEW Adult Vial Test sites (Cypermethrin) 10 micro grams micro grams

Resistance Monitoring Results – 2006 ‘Standard AVT’ Method (moths from traps) (“results promising based on this method”) Mean % survival (ug cypermethrin) State*5ug (n)10ug (n) MN11 (170)6.5 (170) IN14 (151)2 (151) WI15 (100)3 (100) FMC, SD** (4,760) *Multi-dose AVT (0-30ug) **Single dose AVT (IA, IL, IN, MI, MN, NE, WI)

Response of Field-collected Larval Colonies to a Diagnostic Dose of Cypermethrin (5 μg/vial)

Response of Field-collected Larval Colonies to a Diagnostic Dose of Cypermethrin (10 μg/vial) *0*

Pyrethroid Analysis Protocol Multi-state Criteria for Trial Selection- Crop: - Sweet corn Design: - RCB, 4 reps Pest Pressure:- Ideally, min. 30% inf. ears (CEW) Spray Timing:** - 1 st spray = row tassel/1 st silk - usually 3 sprays (5-7 day interval) Location:- MN, WI, IL, IN, OH, PA Sample size:- 100 ears per treatment **Protocol prior for 2006 field research (and previous years). This will be revised in 2007 to reflect new recommended timing of 1 st spray at 50% silk; then 2 nd spray 3 days later.

CEW logistic model Results: Silk and Spray Interval between 1 st and 2 nd spray most critical variables Optimal timing: 50% silk Optimal timing: 3-4 days

Comparison of 2 and 4 spray program: Example: Capture (bifenthrin); MN prices ProcessingFresh Market 2-spray (0.10 lbs ai) 4-spray (0.04 lbs ai) 4-spray (0.04 lbs ai) Capture cost/ac $14.26$11.40$26.00 Application cost/ac-aerial $9.50$ Application cost/ac-ground -- $22.00 Total$23.76$30.40$48.00 **Capture 0.04 lbs ai = $2.85/ac (proc.); $6.50/ac (fresh mkt.) 0.10 lbs ai = $7.13/ac (proc.); $16.25/ac (fresh mkt.) **Aerial application cost = $4.75/ac; ground application cost = $5.50/ac (2006)

“Return” Fall Migration in CEW? Can migrants complete egg-adult up north? Degree day Calculations started on either Aug. 1 st or 15 th using a 55F lower and 92F upper threshold. Egg to adult = 760 DDs

Chance of CEW “Return-South” Migration? - by Latitude (conserving Rr genes) Arrival date 8/1Arrival date 8/15 LatitudeState % chance Emerg. Mean emerg. Date % chance Emerg. Mean Emerg. date 44 43’MN7010/ ’WI509/ ’NY5010/ ’IA1009/215010/ ’MI9010/31010/ ’IL1009/156010/ ’PA1009/173010/ ’OH1009/ / ’IN1009/910010/ ’VA1009/ / ’KY1009/ /4

To What Extent Should We Be Concerned? Not Advocating Panic Increasing Discussions with Southern U.S. Entomologists Resistance Monitoring Need new resistance management plans New chemistries?

NC IPM Guidelines: 2007 Cannot fully predict the CEW response in space or time Resistance depends on level of selection in the South: –a) continued level of pyrethroid use? –b) geographic extent of pyrethroid use? *Depends on continued “opportunity” for genetic mixing of moths each fall and spring in the south, prior to re- entry to the Midwest Numbers Game and Timing: Number of moths we receive each year; late-flight only vs. July + Aug. flights

NC IPM Guidelines: 2007 Use Pheromone Traps to Detect Flights –Base spray interval off of trap catch and temperature –Use State recommendations for spray thresholds Alternative (experimental) recommendation: –In conjunction with pheromone trapping… –1st spray applied at 50% silk –2nd spray applied 3-4 days later –Later 5-6 day intervals –Use Bifenthrin at max. rate (e.g, Capture; 0.10 lb ai / A) –Fresh-market, use Bt sweet corn for late plantings –Processors, “Process out” damage

Thanks to ALL Funding Agencies, Cooperators! NC IPM Regional Center (Michigan State and Univ. of Illinois) IRAC-U.S. University of Minnesota; Rapid Response Fund Midwest Food Processors Assoc. (MN, WI, IL) Minn. Dept. of Agric. IPM Fund DuPont, Dow AgroSciences, FMC In-Kind Support; Multiple Sources (FMC; General Mills-Green Giant; WI DTCP; Greg Payne-Univ. of W.Ga; Dept. of Geography, NIU; Great Lakes Veg. Working Group, NC IPM Center)