Soybean Aphid Wisconsin 2003 Recap Latitude Bridge Illinois – Iowa – Minnesota - Wisconsin February 5th, 2004 Eileen Cullen University of Wisconsin Extension Entomology Department

Wisconsin Recap 2003 State Soybean Aphid Survey Dynamic Threshold Concept Role of Insecticides Treatment Decision Dynamics Additional (Evolving) Tactics Eileen Cullen – UW Extension, Entomology

Summary   19% of sites with aphids/plant  20% of sites with aphids/plant  16% of sites with aphids/plant  11% of sites with aphids/plant Courtesy of Krista Lambrecht, WI DATCP

Statewide Average Statewide Average  770 aphids/plant Northwest West Central Northeast Southwest Southeast 994 East Central South Central Central North Central District Averages District Averages Number of Soybean Aphids per Plant Courtesy of Krista Lambrecht, WI DATCP

Direct and Indirect Effects on Yield Reduced # flowers Reduces # beans per pod Reduces bean size Changes bean quality Virus Transmission Soybean aphids feed on plant sap Photo © Iowa State University

Soybean Aphid Threshold Potassium Levels Drought Stress! Soybean Varietal Tolerance to SBA? Indirect Yield Loss Direct Yield Loss Crop Stage Soybean Yield Response to Insecticide Treatment Biological Control & Abiotic Factors Economic Injury Level = Pest density which causes loss equal to the cost of control. Economic Threshold = Pest density at which control action is taken to PREVENT pest population from reaching or exceeding the EIL Cost of Control Expected price of crop Soybean aphid Exponential Growth Eileen Cullen – UW Extension, Entomology

Yield Response by Spray Date 31 on-farm strip trials from WI 2003 July 23 – August 11 Applications Avg. Yield Advantage = 7.1 Bu/A Eileen Cullen – UW Extension, Entomology

Trade Name Active Ingredient Rate/Acre (fl. oz.) REI (Hours) PHI (Days) Asana * esfenvalerate5.8 to Baythroid ** cyfluthrin2.8 fl. oz (15 green forage) Mustang Max zeta- cypermethrin 2.8 to Warrior lambda- cyhalothrin 1.92 to Pounce * permethrin4.0 to * 2(ee) Label ** Labeled for soybean aphid Suppression Pyrethroid Labels for Soybean Aphid Eileen Cullen – UW Extension, Entomology

Trade Name Active Ingredient Rate/Acre (pint/A) REIPHI (Days) Dimate 4EC * Dimethoate 4E * dimethoate ½ to ¾48 hrs21 Lorsban 4E chlorpyrifos1 to 2 24 hrs28 Penncap-Mmethyl-parathion1 to 34 days * 5 days ** 20 Organophosphate Labels for Soybean Aphid * 2(ee) Label * avg. annual rainfall = or > than 25” ** avg. annual rainfall < 25” Eileen Cullen – UW Extension, Entomology

Trade Name Active Ingredient Rate/Acre (pint/A) REIPHI (Days) Furadan 4F carbofuran ¼ to ½ 4821 Carbamate Label for Soybean Aphid Eileen Cullen – UW Extension, Entomology

Product Performance & Canopy Distribution Lorsban Furadan Pyrethroids Volatile distribution through canopy. May “fume” into untreated check strips Systemic, a.i. activity within plant in addition to contact activity Cannot work its way through canopy beyond contact activity. Coverage in closed canopy critical for efficacy against aphids at lower and inner locations on plant. Eileen Cullen – UW Extension, Entomology

Product Performance & Temperature Lorsban Furadan Pyrethroids Optimal performance at higher temps. (may increase “fuming” action) Also relatively better at higher temp Exhibits a Negative Temp Relationship: Works better under cool conditions below 90 o F. Eileen Cullen – UW Extension, Entomology

Product Performance & Residual Lorsban Furadan Pyrethroids Short residual, measured in days. Longer residual than organophosphates. Some additional feeding exposure, due to systemic activity Longest residual, 2 weeks or more Eileen Cullen – UW Extension, Entomology

Data Courtesy of Craig Grau, UW Plant Pathology Watch Late-Planted Fields  Plants relatively younger, more nitrogen (?)  Soybeans in critical bloom/reproductive stages at aphid build

Relatively Cool Summer 2003 Optimal temperature for soybean aphid development: 68 to 77 °F Soybean aphid predators function better at high temperatures Fungal disease: prolonged hot and humid conditions Eileen Cullen – UW Extension, Entomology Biological Control Weather Biotic and Abiotic Dynamics! Drought, Scattered Rainfall Heavy rainfall can temporarily reduce aphid populations – depending on canopy density.

Natural Enemy “Lag” Time Spray Timing Critical – Aphid Resurgence Factor Bob Ellingson and David Hogg, UW Entomology

Winged Aphids Efficient Virus Vectors Alfalfa Mosaic Virus Soybean Mosaic Virus Cucumber Mosaic Virus Snap Beans Foliar symptoms of virus Yellow chlorotic leaf patterns Crinkled, “drawstring” leaflets No Thresholds for Virus Eileen Cullen – UW Extension, Entomology Photo Courtesy of Lisa Behnken U of MN, Extension

Soybean Aphid – Interaction with other Stresses Drought Stress Potassium Deficiency Multiple Pest complex -Bean Leaf Beetle -BLB transmitted virus BPMV -Planting Dates: late plant against BLB/BPMV early plant less aphid trouble Eileen Cullen – UW Extension, Entomology

Craig Grau et al.– UW Extension, Plant Pathology Soybean Genetics Breeding lines differ for population density and symptom severity

Craig Grau et al.– UW Extension, Plant Pathology Soybean Genetics Yield Response to Insecticide – Breeding Line Differences

Role of Insecticides: Insecticides timed properly on the basis of scouting Reduce aphid populations and plant stress quickly Scouting Threshold Optimal Timing Evolving Approaches and Correlations: Varietal Resistance/Tolerance Biological Control Nicotinoid Insecticide Seed Treatment Moisture Stress Potassium Level Eileen Cullen – UW Extension, Entomology

Soybean Aphid Efficacy Data & Threshold Guidelines Latitude Bridge Illinois – Iowa – Minnesota - Wisconsin February 5th, 2004 Eileen Cullen University of Wisconsin Extension Entomology Department

Efficacy Data & Management Guidelines Eileen Cullen – UW Extension, Entomology Nicotinoid Seed Applied Insecticides on Soybean WI 2003 Efficacy Data:  Foliar Residual Activity  Seed Treatments 2004 Scouting &Threshold Guidelines

a.i. ~ clothianidin [Poncho] a.i. ~ imidacloprid [Gaucho] a.i. ~ thiamethoxam [Cruiser] Systemic. As the seed imbibes water and germinates, a.i. on the seed is taken up into plant through the xylem. Nicotinoid Insecticide Seed Treatment How does it work in the plant? Graphic courtesy of Karen Arthur, Gustafson LLC Nicotinoid Class: Eileen Cullen – UW Extension, Entomology

Sodium Channel: Pyrethroids Acetylcholine esterase: OP’s,Carbamates Acetylcholine receptor: Neonicotinoids Pre-synapse Post-synapse Synaptic Cleft Nicotinoid Insecticide Seed Treatment How does it work in the insect? Graphic courtesy of Karen Arthur, Gustafson LLC

Nicotinoid Seed Treatment Soybean – In Trial Phase Eileen Cullen – UW Extension, Entomology  Soybeans treated on a grams a.i. per 100 Kg seed basis. “Poncho 62.5” = 62.5 g a.i. / 100 Kg seed  Early season protection. Interest in how long into season activity persists. (4 – 6 + weeks depending on a.i., crop, and pest)

 Nicotinoid Resistance Concerns Imidacloprid – clothianidin - thiamethoxam  Selective activity against piercing-sucking insect feeding and virus transmission.  Reduced non-target effects  Field Corn corn rootworm  Field Corn 2° soil pests  YieldGard Rootworm Bt Field Corn seed protectant  Seed and Food Grade Soybeans  Grain Soybeans (registration in development phase) Eileen Cullen – UW Extension, Entomology

Soybean Aphid Insecticide Trials Arlington, WI 2003  Foliar Trial (pyrethroids,organophospates)  Nicotinoid Seed Treatment Trials ~ clothianidin [Poncho] ~ imidacloprid [Gaucho] ~ thiamethoxam [Cruiser] Eileen Cullen – UW Extension, Entomology

Soybean aphid FOLIAR trial. Arlington, WI Mean Aphids/Plant 4d, 1wk and 2 wks post treat. Treated 7/31 at R2 (500+ aphids/plant) Mean yields (bu/A) within a column followed by a different letter are significantly different at  = 0.05 (Fishers exact test) Treatment4 days1 week2 weeks Untreated996.5 a a a Warrior 1CS 3.84 oz f 22.2 e 72.6 e dimethoate 1 pt e 45.5 d c Baythroid 2.8 oz d b b Mustang Max 4.0 oz d c c Mustang Max + NIS b b b Asana 6.4 oz b b b Asana 9.6 oz c b c Lorsban 4E 2.0 pt. 0.5 g 15.3 e 91.9 d Eileen Cullen – UW Extension, Entomology

Seed Treatment Trial Soybean Aphid Trial 1 Planted: June 9 Harvest: Oct 16 Cultivar: NK S19-V2 Plots: 10’ w x 25’ l CRBD: 4 replicates Poncho 62.5 Poncho 125 Gaucho 62.5 Cruiser 62.5 CHECK Trial 2 Planted: June 9 Harvest: Oct 16 Cultivar: NK S24-K4 Plots: 10’ x 25’ l CRBD: 4 replicates Cruiser 30 Cruiser 50 Gaucho 62.5 CHECK Eileen Cullen – UW Extension, Entomology

Soybean Aphid Seed Treatment Trial 1, Arlington WI 2003 Mean Aphids/Plant by sampling date Aphids/ plant Sample Date Aphids/Plant Eileen Cullen – UW Extension, Entomology

TreatmentYield (bu/A) Untreated38.1 b Poncho ab Poncho ab Gaucho ab Cruiser a Soybean [aphid] seed treatment trial 1, Arlington WI 2003 Yield (bu/A) by Treatment. (P = ; F = 2.33; df, 4) Means followed a different letter are significantly different at  = 0.05 Eileen Cullen – UW Extension, Entomology

Soybean Aphid Seed Treatment Trial 2, Arlington WI 2003 Mean Aphids/Plant by sampling date Aphids/ plant Sample Date Aphids/Plant Eileen Cullen – UW Extension, Entomology

TreatmentYield (bu/A) Untreated 38.1 c Cruiser bc Cruiser ab Gaucho bc Soybean [aphid] seed treatment trial 2, Arlington WI 2003 Yield (bu/A) by Treatment. (P = 0.002; F = 6.59; df, 5) Means followed a different letter are significantly different at  = 0.05 Eileen Cullen – UW Extension, Entomology

Seed Treatment Summary  Seed treatment trials were LATE planted (June 9).  Seed treatment for soybean aphid will need to take planting date into account to ensure systemic activity during aphid impact. Eileen Cullen – UW Extension, Entomology

EPA Section 18 Emergency Exemption Registration in WI and IA (March 28 to June 1, 2003) for Gaucho on seed and food grade soybean only. Labeled for early season Bean Leaf Beetle and Bean Pod Mottle Virus control. Gustafson has been contacted by the state of IA with plans to request another Section 18 for Gaucho seed treatment Early season Bean Leaf Beetle control and Soybean Aphid. May cover all soybeans. Soybeans are treated by the manufacturer or seed dealer, NOT on-farm by producer. Soybeans may only be treated in state(s) with the Section 18 registration. [2003: 400,000 Acres worth of seed/food-grade beans could be treated in IA and WI, then planted in other states]. Eileen Cullen – UW Extension, Entomology

Cooperating Entomologists/ Universities Ragsdale, Ostlie, et al. U of Minn Eileen Cullen U of WI Phil Glogoza ND State Chris DiFonzo MSU Hammond, Eisley OSU Doug Johnson Univ of Kentucky Marlin Rice Iowa State Tom Hunt Univ of Nebraska Tracey Baute OMAF Voegtlin Steffey Gray U of IL Larry Bledsoe Purdue Wayne Bailey U of MO Consensus Recommendations for 2004 Chris DiFonzo, Michigan State University

Threshold aphids per plant increase - assumes aphid numbers are on the increase - provides a 7-day lead time (call in equipment, deal with weather delays) - use through R4 (full-pod stage) Cannot overemphasize DROUGHT Chris DiFonzo, Michigan State University

How fast can a soybean aphid reproduce? [data generated in the lab by Ragsdale et al., Univ. of Minnesota] Temp 68 o F 77 o F 86 o F 95 o F Lifespan(days) (die)Doublingtime(days) deadTotal#babies Firstbabies (# days) Chris DiFonzo, Michigan State University

[Based on data from University of Minnesota plots in 2003] Price$/bu $5.00 $6.00 $7.00 How much yield (# bushels) must be lost from aphid damage to equal a control cost of $12.00/ acre? #bu % 3.3% 2.8%50 4.8% 4.0% 3.4%40 6.0% 5.0% 4.2% % of Yield potential, bu/acre % of Yield potential, bu/acre Chris DiFonzo, Michigan State University

How many aphids per plant cause that much yield loss….. + a 7-day lead time? [Based on data from University of Minnesota plots in 2003] Price$/bu $5.00 $6.00 $ % 3.3% 2.8%50 4.8% 4.0% 3.4%40 6.0% 5.0% 4.2% % of Yield potential, bu/acre % of Yield potential, bu/acre#bu Chris DiFonzo, Michigan State University

Scouting When: When: begin late June/ early July (may vary by region) What: What: Whole plant counts - 20 to 30 plants per field - no apparent edge effects (winged aphids colonize uniformly) - increasing populations even out across plants Pay special attention to: - areas w/ buckthorn (colonized early) - late-planted fields - double-cropped beans - beans under stress, particularly DROUGHT STRESS How many times? How many times? Fields have to be visited multiple times How Long? How Long? 2003, up to third week of August in many locations. Chris DiFonzo, Michigan State University

Timing of Application R1 – R2 bloom R8 mature R7 matur- ing R6 full seed R5 seeds forming’ filling R3-R4 pods forming, growing Do Not treat Late Veg stages 250 aphids per plant - Increase threshold. - Yield benefit may be less. Chris DiFonzo, Michigan State University Continue to scout and work from 250/plant as a reference threshold

Prepare with Guidelines Presented Here: Scouting Use of Threshold Optimal Spray Timing Will 2004 be a repeat of 2003? What is the Soybean Aphid “Norm”?

Watch for state-specific information in your summer newsletters. Wisconsin Crop Manager: