MN Fruit & Vegetable IPM News - Vol. 2, No. 4

The first generation flight of the European corn borer (ECB) should begin soon for much of southern Minnesota. Because of variable and cool weather, emergence is typically erratic during the 1^st flight. For example, a bi-modal pattern of emergence will be observed when periods of cold or rainy nights occurs between warm, favorable nights for moth flight. We are currently at 350 degree-days (degree-days > 50F), which is near the beginning of the first flight, based on several years of data from the Rosemount Experiment Station (see Figure, below ). This past week, we caught the 1^st moth at Rosemount. With some warmer nights in the next week (hopefully), moths should get active, and corn might start growing. Peak flight occurs at 50% "Cumulative Moth Capture" (see 0.5; see Figure), which is approximately 600 degree-days. Please review the ECB forecast graph, for expected emergence, and follow upcoming issues of the newsletter for ECB and degree-day updates. All early-planted sweet corn, with extended leaf height at least 17" and/or corn in the early green tassel stage will be most attractive for egg-lay. These fields should be watched closely. Because relatively few fields of field or sweet corn will likely be attractive for egg-lay, the early planted sweet corn is often a major magnet for early infestations.

Reminder: View and save the Moth Flight web page to track the 2005 ECB and Corn Earworm flights this summer.

Beware of the "UCB" (Univoltine Corn Borer): The model presented in this article applies only to growing regions where the dominant ECB strain is the "bivoltine" (2-generation/year) ecotype. However, during the past 10 years, we have also observed a continued increase in univoltine activity (same ECB species, but single generation/year) in southern Minnesota, and eastward spread across southern Minnesota. In 2002, we observed a significant univoltine flight at Rosemount. In many areas of southern Minnesota (as in northwestern MN), the univoltine (1 gen/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 (i.e., late June to late 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 keep you abreast of significant flights of the Univoltine strain of ECB.

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ACKNOWLEDGEMENTS

Co-Editors: Bill Hutchison ( hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness ( woldx018@umn.edu), Department of Entomology, University of Minnesota

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jeanne Ciborowski, 651-297-3217, jeanne.ciborowski@state.mn.us , MDA, 90 W. Plato Blvd., St. Paul, MN 55107-2094. You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: www.mda.state.mn.us/biocon/fruitreports/

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture – Risk Management Agency (RMA). These institutions are equal opportunity providers.

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