MSU Weed Science - Department of Crop and Soil Sciences
Mar 27th, 2015

Field Crops Entomology Program
Michigan State University

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For regional field crops information, visit Purdue's Chat 'n Chew Cafe

Corn rootworm resistance to Bt: 
Update on field failures in Michigan &
recognizing and combating the problem

Rootworm resistance to Bt corn has been confirmed in western states like Iowa and Minnesota, and in 2012 suspicious field failures were sampled in Michigan and New York. Now is the time to become familiar with the risk factors and symptoms of field failures, and to learn what to do about it. Nine entomologists from universities in the eastern corn belt (Purdue, MSU, Ohio State, Penn State, Cornell, University of Guelph) cooperated to develop a consensus recommendation for our region, which focuses on CROP ROTATION. Our goal is to preserve the usefulness of Cry3Bb1 and other rootworm Bts for you and your customers for as long as possible.

As the season progresses, please report suspicious fields immediately to Chris DiFonzo (517-353-5328 or, an MSUE agent, and to your seedsman. The faster people can visit a field, the better diagnosis we can make.

Learn more about the causes, identification, and management of Cry3Bb1 resistance:
**Read the WHITE PAPER prepared and submitted to EPA by 9 entomologists in the eastern corn belt
**Download a four-page BULLETIN that summarizes our recommendation for producers
**View a SLIDE SET about the current state of CRW resistance in Michigan

For information on the types of Bt corn, efficacy, and refuge requriements, print off the HANDY Bt TRAIT TABLE by DiFonzo and Cullen.