Corn Rootworm Situation in 2004 Distance Education Workshop February 4 and 11, 2005 Mike Gray and Kevin Steffey Department of Crop Sciences University of Illinois

Corn Rootworm Management Issues Illinois, 2004 Severe rootworm larval damage (northern half of Illinois) June Reports of poor performance of granular and liquid insecticides, insecticidal seed treatments July, August Corn rootworm control trials; numerous reports of lodging; reports of greater-than-expected damage in YieldGard Rootworm corn More widespread distribution of variant western corn rootworm—distribution extended west and south

Corn Rootworm Management Issues Illinois, 2004 Performance issues with corn rootworm control products Granules, liquids, seed treatments Planting time (~80% of corn planted in IL by 4/30/04) Windy conditions during planting Soil conditions Application and incorporation YieldGard Rootworm Corn Low dose Planting time (declining expression of Bt) Hybrid and environmental interactions

Numbers are average root ratings: 10 fields per county 5 roots per field Orange = confirmed variant WCR Yellow = “fringe” Survey for CRW larval injury Corn after soybeans 2004

Corn Rootworms: Lessons (re)learned in 2004 No corn rootworm control product is “bulletproof.” Despite our best expectations, environmental conditions can affect the performance of any rootworm-control product. Some products do not perform well when corn rootworm larval pressure is heavy. Accurate granular insecticide application and incorporation is particularly important in early planted fields.

Overheard “solutions” to CRW problems Control adults in soybeans, use rootworm control product in corn the following year Low-rate insecticidal seed treatment + soil insecticide YieldGard Rootworm corn + soil insecticide Control adults in soybeans + YieldGard Rootworm corn following year + High-rate insecticidal seed treatment

Corn Rootworm Situation 2004 Indiana Larry Bledsoe Purdue University

Western Corn Rootworm Hatch

Exceptionally wet during egg hatch and initial larval feeding period

Western Corn Rootworm Adults

Statewide WCRW Survey Late July-Early August About 70 of 92 Counties 1-3 Fields Per County 5 X 20 Sweeps/Field

Western Corn Rootworm Sweep Net Surveys in Soybean (#/100 Sweeps)

2004 Western Corn Rootworm Sweep Net Survey in Soybean (#/100 Sweeps)

Perceived First-Year Corn Rootworm Risk Areas

Western Corn Rootworm - Variant Management strategies: –recognize high risk areas –be observant of damage in unconfirmed areas –monitor for WCRW beetles in soybean fields – rootworm soil insecticides, treated seed, and Bt RW

Western Corn Rootworm In Indiana 2004 Questions?

Corn Rootworm Situation in Iowa Dr. Jon Tollefson Professor of Entomology Iowa State University

Corn Rootworm Situation in IA 2004 weather corn rootworm phenology rotation-resistant western corn rootworm extended diapause northern corn rootworm insecticide performance

Flooding in June

Flooded Corn; Drowned Larvae?

Adult Corn Rootworm Emergence, 2004 July August Sept.

Rotation-Resistant Western in IA? ☻ Durant

Corn Rootworm Situation in IA 2004 weather corn rootworm phenology rotation-resistant western corn rootworm extended diapause northern corn rootworm insecticide performance

Ostlie © 2005 Corn Rootworm Situation in Minnesota Ken Ostlie Department of Entomology - University of Minnesota (612) office(612) cell

Ostlie © 2005 Corn Rootworms in Minnesota u WCR reach the northern edge of their distribution in MN, SD and ND. WCR most common in areas with higher incidence of corn following corn (e.g., SE MN). u NCR distributed statewide, but are most common in areas with rotated corn. NCR also exhibit S →N gradient. u Severe, open winters have only slight impacts on NCR, but routinely knock back WCR populations. NCR typically comprise 90% or more of the corn rootworms in MN. u winter was fairly severe and open until late January u Heavy, repeated rains and cool weather dominated early summer. u The MDA Plant Pest Survey Program conducts an annual survey of corn rootworms (3 continuous and 3 rotated fields per county) in corn during the first two weeks of August.

Ostlie © 2005 What Happened with Corn Rootworms in 2004? ♦ Corn rootworm survival was better than expected, perhaps due to deeper egg laying during the drought of ♦ Widespread insecticide use in soybean for soybean aphid potentially reduced corn rootworm populations foraging in soybean. ♦Early season rainfall favored shallow root systems and enhanced leaching of insecticides. ♦ Later-season thunderstorms were common leading to greater lodging problems than observed in drought of 2003.

Ostlie © 2005 Corn Rootworm Dynamics: Continuous Corn in SE Minnesota Data supplied by MDA – Plant Pest Survey Program Mild Winters Favor WCR

Ostlie © 2005 Corn Rootworm Dynamics: Relative Species Success Data supplied by MDA – Plant Pest Survey Program Severe Winters ? Mild Winters

Ostlie © 2005 Western Corn Rootworm: Abundance and Distribution in MN WCR populations declined dramatically from levels. Probably reflects winter mortality and heavy early-season rains.

Ostlie © Crop Rotation 2-Crop Rotation Jim Boersma Picture taken south of Olivia Minnesota 2002 Crop Rotation and Extended Diapause: A Minnesota Problem Since Late 1970s

Ostlie © 2005 NCR Exhibit Similar Patterns Regardless of Crop Rotation Map supplied by MDA - Plant Pest Survey Program

Ostlie © 2005 Comparative Population Dynamics of Rootworms and Soybean Pests, 2003 Ostlie – Rosemount, MN Timing of Insecticide Application

Ostlie © 2005 Risk Management of Corn Rootworms is Becoming More Complicated Different Strategies to Succeed in Rotated Corn! Western corn rootworms have lost their fidelity to corn and now lay eggs in other crops. Northern corn rootworms have extended their overwintering diapause to 2 or even 3 years.

Rootworm Situation in Nebraska, 2004 Lance J. Meinke Robert Wright University of Nebraska