In this issue:

Sweet Corn Insect Pest Update

Bayer to Phase out Guthion

National Organic Program

Corn Smut Hits Again

Rootworm Beetles Feeding on Silks

Squash Bug Populations Increasing

Sweet Corn Insect Pest Update

Bill Hutchison, Eric Burkness, Robert Koch & Patrick O’Rourke, Dept. of Entomology, University of Minnesota

The 2nd generation flight of the European corn borer (ECB), which peaked at 150-200/night, has slowed a bit this past week for much of southern Minnesota (see Fig. 1). The ECB flight has been high at St. James throughout the year. As noted by the ECB degree day map, as of August 20th, most of southern MN and WI have accumulated 2000 to 2200 degree-days, which is past the 1750 mark generally associated with the peak ECB flight (bivoltine strain). The ECB degree day map, which is updated daily for MN, WI and northern Iowa, can be accessed at: http://bob.soils.wisc.edu/wimnext/corn/euroborer.html Despite the reduced ECB moth flight, fresh egg masses continue to be found in both sweet and field corn (Rosemount area).

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Corn earworm (CEW) flights, as in 2001, have been high at Blue Earth and Owatonna (100-500/night) during the past 10 days. The flight continues to be much lighter at Rosemount (Fig. 2).

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Western bean cutworm (WBC) flights continue to be light at most of the trap locations in Minnesota, based on pheromone trap data (Fig. 3).

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However, the light trap at Fulda (SW MN; Murray Co), caught 100s of WBC moths, including a peak catch of 695/night, July 30th.The higher flight at this location is similar to the large flights observed this past summer at several sites in NW Iowa. Some NW Iowa locations exceeded 1000-2000 moths/night.

This is the 2nd year that significant WBC moths have been collected in SW Minnesota and NW Iowa. Significant larval damage has also been observed in MN and IA since 1999. The timing of the flight (peak in late July) is also in agreement with the degree-day models developed in Nebraska and Idaho. These results provide additional evidence for an established overwintering population in the NW Iowa, and southern Minnesota. More information about WBC will be presented in future articles. With regard to all three pests, all sweet corn still in the late tassel (spike or open tassel) to early silk stages will be attractive for egg-lay and should be protected (treated with insecticide). See earlier issues of the MN Vegetable IPM Newsletter for more information on treatment recommendations.

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
Cindy Tong, Department of Horticulture, University of Minnesota, ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Assistant, University of Minnesota, woldx018@tc.umn.edu

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Last Revised August 23, 2002.
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