In this Issue:

Sweet Corn Insecticide Trial Results

Corn Earworm Control in Minnesota Sweet Corn

Guthion Label Change

Farmers Urge Congress to Keep COOL

Corn Earworm Control in Minnesota Sweet Corn, 2003

W.D. Hutchison, E.C. Burkness, and R.L. Koch, Department of Entomology, University of Minnesota

Corn Earworm (CEW) Note: In three replicated trials this month in Minnesota and Wisconsin, we observed poor pyrethroid control of CEW larvae. We are refering to similar, replicated trials at Rosemount (University of Minnesota), Green Giant Agricultural Research Group (Tom Rabaey, Le Sueur, MN), and a Wisconsin study by Bryan Jensen (University of Wisconsin - Madison). For example, Capture and Warrior averaged 67 and 22% control, respectively, in our Rosemount trial. In the Wisconsin trial, Capture and Warrior averaged 23 and 45% control, respectively. All three trials also included a total of four sprays, from open tassel/first silk, to brown silk (5-7 days before harvest). We normally expect to see >90% control of CEW by these pyrethroids. With 40-50% of treated ears still harboring CEW larvae, this could be a concern, particularly for fresh-market growers. Because CEW migrate to the Midwest from the southern states, some individuals may be resistant or tolerant to selected pyrethroids. Fresh-market producers and processsors should check their sweet corn carefully as you approach harvest.

If you used pyrethroids this year, and find significant numbers of surviving larvae, contact us for more information; Eric Burkness: 612-624-3670, or email: burkn001@umn.edu. We have initiated a monitoring project to assay CEW populations for possible resistance/tolerance to pyrethroids.

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Production Editor: Suzanne Wold Burkness, Research Fellow, Department of Entomology, University of Minnesota, woldx018@tc.umn.edu

Last Revised September 11, 2003.
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