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Corn Rootworm Management: Situation, Issues, and Options

Corn Rootworm Management: Situation, Issues, and Options. Distance Education Workshop February 4 and 11, 2005. Overview of the Program February 4, 2005. Corn rootworm fundamentals Biology Effects of weather on corn rootworm biology and performance of rootworm-control products

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Corn Rootworm Management: Situation, Issues, and Options

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  1. Corn Rootworm Management:Situation, Issues, and Options Distance Education Workshop February 4 and 11, 2005

  2. Overview of the ProgramFebruary 4, 2005 • Corn rootworm fundamentals • Biology • Effects of weather on corn rootworm biology and performance of rootworm-control products • Corn rootworm situation in 2004(alphabetically by state) • Questions and Answers, followed by a break • Results from 2004 corn rootworm control efficacy trials • Questions and Answers

  3. Overview of the ProgramFebruary 11, 2005 • Recap of February 4 program • Issues associated with corn rootworm management • Overview • Soil insecticides and seed treatments • YieldGard Rootworm corn • Adult corn rootworm suppression • Variant western corn rootworm • Extended diapause (northern corn rootworm) • Management of corn rootworms in 2005 • Questions and Answers

  4. Acknowledgments David Feltes Extension Educator, IPM Quad Cities Extension Center Susan Ratcliffe Facilitator, NC IPM Center Michael Greifenkamp Information Technologist NC IPM Center

  5. PresentersCorn Rootworm Management Workshop Mike Gray, University of Illinois Kevin Steffey, University of Illinois Jon Tollefson, Iowa State University Larry Bledsoe, Purdue University

  6. PresentersCorn Rootworm Management Workshop Ken Ostlie, University of Minnesota Lance Meinke, University of Nebraska Entomologists in other states may contribute comments during the course of the program. Robert Wright, University of Nebraska

  7. Corn RootwormFundamentalsBiology Dr. Jon Tollefson Professor of Entomology Iowa State University

  8. Adult Corn Rootworms northern corn rootworm D. barberii western corn rootworm Diabrotica virgifera

  9. Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec adult pupa larva egg Corn Rootworm Life Cycle

  10. Corn Rootworm Larvae www.ipmworld.umn.edu/chapters/maize/SoCRWA

  11. RootwormLarval Injury

  12. Symptoms of Larval Injury

  13. Planting Corn Rootworm Management Preventive Control crop rotation soil insecticides GM maize Decision Making

  14. Corn Corn Soybean Extended Diapause Year 1 Year 2 Year 3

  15. Extended Diapause Iowa

  16. Rotation Resistance Year 1 Female leaves corn, lays eggs in soybean Eggs hatch, damage 1st year corn Corn Corn Field B Field A Field A Field B Soybean Soybean X X Year 2

  17. Rotation Resistance Iowa

  18. Weather Effects on Corn Rootworm Population Dynamics and Management Ken Ostlie Department of Entomology - University of Minnesota ostli001@umn.edu (612) 624-7436 office (612) 750-0993 cell

  19. Why Talk about Weather Effects on Corn Rootworm Population Dynamics? • Direct Effects on Corn Rootworms: • Eggs • Larvae • Pupae • Adults • Indirect Effects: • Corn & Weedy Grass Hosts • Soil Environment

  20. Direct Effects of Weather on Corn Rootworms: Overwintering • Overwintering of corn rootworm eggs • Northerns more winter hardy than westerns! • WCR egg mortality begins ca. 19oF and increases dramatically with freeze units (Gustin 1981, Godfrey et al. 1995, Lawson 1986). Mortality exceeded 95% after 4 weeks at 14oF. • NCR egg hatching success actually increased during the first 8-10 weeks at temps of 23oF and only declined with prolonged exposure (4 to 6 weeks or more) at temps below 14oF. Mortality was only 42% after 4 weeks at 14oF. • Depends on egg distribution in soils, tillage / residue cover, snow depth and harshness of winter temps. Fluctuating temps are more detrimental.

  21. Corn Rootworm Development is based on Temperature • Egg development begins at ca. 52oF (similar to corn) and requires ca. 680 – 760 DD for 50% hatch. • Degree-days calculated from air temps and adjusted for minimum (52oF) and maximum (64oF) thresholds provided the best predictors of northern and western emergence [Davis et al. 1996]. Evidence of adaptation to local conditions. • Male WCR emerge 1-3 days earlier than female and develop faster at all stages. • NCR emergence relative to WCR varies, peaking earlier in northern sites and later in southern locations. NCR emergence is generally longer than WCR. • Predicted peak emergence for WCR for Minnesota has varied by 8-12 days over the last 4 years.

  22. Weather can Alter the Synchrony Between Rootworms and Root Development Strnad et al. 1987 Delays in root development or accelerated hatch = reduced food availability & increased larval competition

  23. Newly Hatched Larvae and Pupae can Drown in Saturated Soils • Impact depends on: • Timing of rainfall • Amount and intensity • Soil texture and drainage

  24. Adult Longevity and Reproductive Success Reduced by Heat & Drought Drought and heat reduce the availability of silks and pollen.

  25. What’s Changed with Corn Production? • Earlier planting dates • Higher plant populations • Narrower row spacing • Higher yielding hybrids • Reduced tillage These Changes Increase Corn Rootworm Survival or Damage! Higher yields with smaller root systems => Pushing the envelope on roots!

  26. Weather Effects on Corn Rootworm Management • Wind during application can displace insecticide bands • Rainfall is required to activate soil insecticides and move them into root zone. • Eroding rains before hatch may displace insecticides • Excessive leaching moves insecticides out of root zone • Soil moisture and temperature affect insecticide half-life

  27. Factors Affecting Performance of Corn Rootworm Management Options • Corn rootworm pressure • Site conditions (soil charcteristics) • Field history and cultural practices • crop rotation • tillage • planting date • fertility • hybrid • weed control • Insecticide & application • Application (placement, equipment, weather) • Weather • Soil moisture • Soil temperatures

  28. 30 ppm Range of insecticide bioavailability Normal residue levels at hatch 10 ppm 5 ppm Lower limit of control 2 ppm CRW hatch Larval feeding Planting Pupae Average year May 30 Jun 30 Jul 30 Jul 10 May 10 Jun 10 Soil Insecticide Degradation and Corn Rootworm Phenology

  29. Weather and Interpretation of • Management Trials • Application conditions • Rainfall (planting to hatch) • Temperatures (planting to hatch) • Occurrence, severity and timing of lodging events • Timing / severity of weather- related stresses on yield

  30. Weather and Yield Loss from Corn Rootworms • Impaired uptake of water and nutrients (worse during drought) • Increased incidence of stalk / root rots (worse under stress) • Reduced light interception by lodged canopy • Interference with pollination from lodging or silk feeding

  31. Lodging Affects Grower Perception of Management Success

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