Soybean Aphid: Critical Info for Clone Warfare Ken Ostlie Department of Entomology - University of Minnesota email@example.com (612) 624-7436 office (612) 750-0993 cell www.soybeans.umn.edu
Wanted Information Leading to the Successful Management Soybean aphid (Aphis glycines Mats.) The Challenges of Clone Warfare: • The soybean aphid is unlike typical corn or soybean pests. • Population female in summer • Females give birth to live young • Young mature in ca. 5 days • Populations double in 2-3 days • In response to crowding, poor host quality or seasonal cues, females produce young that will become winged. • Winged aphids spread within fields, colonize nearby fields or disperse long distance, avg. 7-10 miles/day. • Aphids suck soybean sap; damage photosynthetic capacity of soybean plant.
Where is it now?Spread of Soybean Aphid in the US, 2000-2003 • Spread to S & W continues • Outbreaks in 2003 primarily in western half of NC states • Treatment occurred in DE & MD in 2003 R. Venette, unpublished data
Status of Soybean Aphid In Minnesota • First found in SE corner in scattered fields in 2000. • Spread across the state in 2001 with ca. 50K acres sprayed and extensive losses in SE Minnesota. • Anticipated severe problems in 2002, but only scattered pockets developed. <15K acres sprayed. • Widespread, severe infestations in 2003 with 3-3.5 million acres sprayed, losses exceeded $120 million (25% insecticide and application, 55% unprotected yield loss, 20% loss despite control), value of crop saved by spraying $135-205 million. • Timely scouting an issue in 2003. • Application delays up to 5 days. • Localized depletion of product. • Difficulty in deciding when to quit spraying.
July 23 Aug. 8 July 30 July 9 July 16 Seasonal Dispersal of Soybean Aphid:M.Abrahamson, MDA Plant Pest Survey Program
Factors Influencing Population Dynamics of Soybean Aphid • Duration and intensity of colonization • Proximity and density of buckthorn • Fall and spring predation on buckthorn • Winter mortality • Survival and reproductive success on soybean • Host quality / resistance • Natural enemies (lady beetles, minute pirate bugs, lacewings, parasitic wasps, fungi) • Rainfall (direct mortality, fungal outbreaks) • Temperature • Optimal temperature ca. 82oF Each year has seen different dynamics!
Soybean Aphid Impacts on Yield & Yield Components:5 MN Fields in 2001
Soybean Aphid Impacts on Soybean Growth, Yield & Quality Soybean Growth • Early infestations reduce stem nodes (up to 3 nodes) and height (up to 25%). Yield(84 fields) • Insecticide sprays produced yield increases averaging 8.8 bu/A; range (0-27 bu/A) • Primary effects on pod number with later infestations having more affect on seed size. Seed Quality (25 fields) • Oil reduced 0.5% • Protein increased 0.8%.
Yield Response (bu/A) to Insecticide Application for Soybean Aphid: 2001 vs 2003 On-farm Trials Potential Yield Benefit Typical Yield Benefit: 8.8 bu/acre
Sprayed 8/8 None 8/13 7/31 Yield (bu/A) 42 36 42 55 Yield Response to Insecticide TimingTim Steier – Blue Earth Aviation Insecticides – Warrior @ 3.2 oz/A (7/31, 8/8), Lorsban @ 1 pt/A (8/13) in 4 gpa by air
Minnesota Research on Soybean Aphid • Biology • Overwintering survival • Development, Reproduction and Temperature • Dispersal • Sampling • Within field distribution • Within plant distribution • Thresholds • Insecticide Management • Understanding efficacy • Air vs. Ground • Tankmixing with RoundUp • Foliars vs seed treatments • Cultural control • Natural control
2002 2003 Can it survive here?Winter & soybean aphid Winter conditions do affect the overwintering range!
Soybean Aphid and Temperatures:Survival and Reproductive RateMcCornack, Venette and Ragsdale - 2003 Optimal Temperature ca. 82oF Doubling Time ~ 1.5-2 days in greenhouse!
Optimal Temperature Upper Temperature F Soybean Aphid Developmental Rateand Temperature
Alate Production in MN Soybean: 2003Hodgson, McCornack & Ragsdale Spring Colonization Mid-Summer Dispersal Late-summer Dispersal Samples collected by MDA Plant Pest Survey Program
15 June, V1 26 June, V3 27 July, R1 11 July, V5 2002 % Plants Infested Colonization of Soybean Fields: 2001 vs 2002 July 19 July 26 July 12 2001 Aphids per plant
Insecticide Decisions for Soybean Aphid: Key Concepts • Goal: A reliable and accurate scouting and decision process that maximizes economic benefit with minimal scouting input. • Economic damage = Yield loss equal to the cost of control…about 3 bu/acre • Economic Injury Level (EIL) = pest population that causes economic damage • Economic Threshold (ET) = point at which an increasing pest population needs to be controlled to keep it from reaching the EIL…considers pest population dynamics and logistics of insecticide application.
Plot Yield * All Minnesota data to date *
Calculating the Economic Injury Level Assumes: Cost of Control = $12.00/acre, doubling time 1.4d Sampling every 7 days. EIL = Average over 7 days = (AD/7)
Insecticides Labeled for Soybean Aphid Insecticide*Rate (fl oz/A)REIPHIClass** ***Asana XL 5.8 - 9.6 fl oz 12h 21d Pyr ***Baythroid 2E 2.8 fl oz. 12h 45d Pyr dimethoate (see label) 48h 21d OP ***Furadan 4F 0.5 pt/acre 48h 21d Carb ***Lorsban 4E 1.0 - 2.0 pt 24h 28d OP ***Mustang Max 3.4 - 4.3 oz/acre 12h 21d Pyr ***Penncap-M 2.0 - 3.0 pt 4d 20d OP ***Pounce 3.2EC 4.0 - 8.0 fl oz 12h 60d Pyr ***Warrior T 1.92 - 3.84 fl oz 24h 45d Pyr * Note Bee Precautions on Label ** Classes: Pyr = pyrethriod, OP = Organophosphate, Carb = carbamate ** Restricted-Use Pesticide
Insecticide Performance Depends on Several Factors • Soybean Aphid • Density, canopy distribution, colonization • Soybean Crop • Canopy development, crop phenology, density • Weather • Rainfall, temperature (reproductive rate, effects on insecticides), wind • Application logistics • Air vs ground; carrier volume; nozzle type, pressure and speed; adjuvents. • Insecticide Properties • Toxicity, residual protection, repellency, natural enemies
Insecticides Against Soybean AphidMacRae & Noetzel – Underwood, MN Application July 31, 2003
2003 Insecticide Performance: Soybeans after PeasOstlie and Price – Rosemount, MN
^ * * * * * * * * Alate Frequency After Insecticide Application*Suspected Repellency / Toxicity ^ Enhanced Colonization
Soybean Aphid Insecticides:Aerial vs. Ground Holen, Holen, Holder & Noetzel – Fergus FallsWarrior applied at 3 oz/A in 12 gpa ground and 5 gpa air on July 30.
Soybean Aphid Insecticides:Alone or Tankmixed with Herbicides? Ostlie and Price – Rosemount RoundUp Max & tank mix applied with Turbo T nozzles in 10 gpa. Warrior T alone applied with Extended Range flat fan nozzles in 20 gpa.
2003 Seed Applied vs Foliar InsecticidesPotter - SWROC B. Potter University of MN 2003
Areas with Overwintering SBA Earlier onset of aphid infestations, wider range of population densities Most likely near buckthorn concentrations Potentially higher yield loss; affects both growth & yield Treatments begin earlier in season but may occur as late => longer scouting window May need second insecticide application Serve as source for mid and late summer colonizing aphids Areas Colonized by Summer Immigrants Later onset of aphid infestations, more uniform infestations among fields Likely where conditions marginal, buckthorn sparse Lower yield loss if arrive later (less time for aphid buildup); canopy development OK Uncertain need for scouting and insecticides, but need intense if outbreaks occur Preemptive strikes unlikely to be economical (treat too early) Unlikely to need second application Soybean Aphid Management Strategies
Data generated by: Soybean Aphid Team – U of M and Minnesota Department of Agriculture Funding from Minnesota Rapid Agricultural Response Fund, Minnesota Soybean Research & Promotion Council North Central Soybean Research Program