Corn Rootworm Situationin 2004

Distance Education Workshop

February 4 and 11, 2005

Mike Gray and Kevin SteffeyDepartment of Crop SciencesUniversity of Illinois

Corn Rootworm Management IssuesIllinois, 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 IssuesIllinois, 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

1.18 1.91

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2.042.06

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1.971.98

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1.74

Numbers areaverage root ratings:

10 fields per county5 roots per field

Orange = confirmed variant WCRYellow = “fringe”

Survey forCRW larval injuryCorn after soybeans2004

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 BledsoePurdue University

Western Corn Rootworm Hatch

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DATES CORN ROOTWORM LARVAE FIRSTOBSERVED IN CORN ROOTS, TIPPECANOECOUNTY, INDIANA, 1982-2004

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Exceptionally wet during egg hatch and initial larval feeding period

Western Corn Rootworm Adults

Statewide WCRW SurveyLate July-Early August

About 70 of 92 Counties

1-3 Fields Per County

5 X 20 Sweeps/Field

1997 1998 1999 2000

2001 2002

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

2003 2004

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. 2004

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

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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 OstlieDepartment of Entomology - University of Minnesota

ostli001@umn.edu(612) 624-7436 office (612) 750-0993 cell

Ostlie © 2005

Corn Rootworms in Minnesota 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).

NCR distributed statewide, but are most common in areas with rotated corn. NCR also exhibit S →N gradient.

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.

2003-4 winter was fairly severe and open until late January Heavy, repeated rains and cool weather dominated early

summer. 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 2003.♦ 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 MinnesotaData supplied by MDA – Plant Pest Survey Program

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Mild Winters Favor WCR

Ostlie © 2005

Corn Rootworm Dynamics:Relative Species Success

Data supplied by MDA – Plant Pest Survey Program

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Ostlie © 2005

Western Corn Rootworm: Abundance and Distribution in MN - 2004

WCR populations declined dramatically from 2002-3 levels. Probably reflects winter mortality and heavy early-season rains.

Ostlie © 2005

3-Crop Rotation

2-Crop Rotation

Jim BoersmaJim BoersmaPicture 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

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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 SituationRootworm Situationin Nebraska, 2004in Nebraska, 2004

Lance J. MeinkeLance J. Meinke

Robert WrightRobert Wright

University of NebraskaUniversity of Nebraska