European Corn Borer Update: Early Sweet Corn

Bill Hutchison and Eric Burkness, Dept. of Entomology, University of Minnesota, St. Paul, MN 55108

The European corn borer (ECB) flight continues to be light this year for the first-generation of the “traditional” bivoltine (2-generations/yr.) strain in MN. Although we just exceeded 40 moths/night (6/26) at Rosemount, the maximum capture at several trap sites (east and south-central MN) have been <25/night. However, we do have a few “hot spots” in early-planted sweet corn near Rosemount, MN (Dakota Co.). Larval infestations (still mostly 1st and 2nd instars) were present in late-whorl sweet corn; 15% of plants infested with 2-4 larvae/plant. This corn was the tallest in the area during the first-generation flight. As of June 26, 2001, we are at 755 degree-days at Rosemount. As indicated by the figure below, the first generation flight should now be approximately 80% complete.

*The next ECB generation to watch for is the univoltine flight (late June to early August) in south-central, southwest, west-central, and northwest Minnesota.

Note: The ECB graph (below) applies only to growing regions where the dominant ECB strain is the bivoltine ecotype. In many areas of southwestern to south-central Minnesota (and as in northwestern MN), the univoltine (1 generation/yr) strain is dominant, or becoming more common. With the univoltine strain, the flight comes out 2-3 weeks later than the first flight of the bivoltine; the flight is also somewhat extended, occurring roughly from mid-June through July. In south-central MN, where both strains occur, this can create an insect management nightmare, where sweet corn and other crops can essentially be vulnerable to larval infestations throughout the summer. As the summer progresses, we will have more information about the current distribution of each strain in Minnesota. The WI/MN web site, noted below, is an excellent way to track the current Degree-day accumulations for ECB, for both MN, WI (and northern IA). The site is automatically updated daily! Please bookmark this site in your web browser, for rapid updates: http://bob.soils.wisc.edu/wimnext/corn/euroborer.html (The site also provides additional ECB biology, key events, etc. relative to DDs).

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, c-tong@tc.umn.edu
Production Editor:Suzanne Wold, Department of Entomology, University of Minnesota, woldx018@tc.umn.edu

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Last Revised June 27, 2001
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