Ken Ostlie

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Soybean Aphid Critical Info for Clone Warfare

• Ken Ostlie
• Department of Entomology - University of
  Minnesota
• ostli001_at_umn.edu
• [phone] office [phone] cell
• www.soybeans.umn.edu

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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.

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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R. Venette, unpublished data
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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. lt15K 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.

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Seasonal Dispersal of Soybean AphidM.
Abrahamson, MDA Plant Pest Survey Program
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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!

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Soybean Aphid Impacts on Yield Yield
Components5 MN Fields in 2001
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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.

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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
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Yield Response to Insecticide TimingTim Steier
Blue Earth Aviation
Insecticides Warrior _at_ 3.2 oz/A (7/31, 8/8),
Lorsban _at_ 1 pt/A (8/13) in 4 gpa by air
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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

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Can it survive here?Winter soybean aphid
Winter conditions do affect the overwintering
range!
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Soybean Aphid and TemperaturesSurvival and
Reproductive RateMcCornack, Venette and Ragsdale
- 2003
Optimal Temperature ca. 82oF Doubling Time
1.5-2 days in greenhouse!
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Soybean Aphid Developmental Rateand Temperature
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Alate Production in MN Soybean 2003Hodgson,
McCornack Ragsdale
Spring Colonization
Mid-Summer Dispersal
Late-summer Dispersal
Samples collected by MDA Plant Pest Survey Program
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Colonization of Soybean Fields 2001 vs 2002
2002 Plants Infested
July 26
July 19
July 12
2001 Aphids per plant
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Soybean Aphid Distribution on Vegetative Soybean
(V7-8)
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Soybean Aphid Shift Within the Plant
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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
  controlabout 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 EILconsiders pest
  population dynamics and logistics of insecticide
  application.

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Logistics and Timing Soybean Aphid Insecticides
EIL
ET
?
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(S15-B1)
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Plot Yield All Minnesota data to date
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Calculating the Economic Injury Level
Max Yield (bu/ac) Price (/bu) 60 50 40
5.00 254 305 381
6.00 210 254 317
7.00 178 216 270
Assumes Cost of Control 12.00/acre, doubling
time 1.4d Sampling every 7 days. EIL Average
over 7 days (AD/7)
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Insecticides Labeled for Soybean Aphid
Insecticide Rate (fl oz/A) REI PHI Class Asa
na 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
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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

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Insecticides Against Soybean AphidB. Potter
New Ulm
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Insecticides Against Soybean AphidMacRae
Noetzel Underwood, MN
Application July 31, 2003
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2003 Insecticide Performance Soybeans after
PeasOstlie and Price Rosemount, MN
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Alate Frequency After Insecticide
ApplicationSuspected Repellency / Toxicity
Enhanced Colonization
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Soybean Aphid InsecticidesAerial vs. Ground
Holen, Holen, Holder Noetzel Fergus Falls
Warrior applied at 3 oz/A in 12 gpa ground and 5
gpa air on July 30.
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Soybean Aphid InsecticidesAlone 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.
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2003 Seed Applied vs Foliar InsecticidesPotter -
SWROC
B. Potter University of MN 2003
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(No Transcript)
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B. Potter University of MN 2003
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Soybean Aphid Management Strategies

• 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 gt 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

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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