Sweet Corn Insect Pest Updates

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

European corn borer (ECB) second-generation flight, for the bivoltine strain, is now underway at several southern Minnesota locations (see trap catch figure below). We are now at approximately 1500 Degree-days (since Jan. 1) at most locations, which is indicative of the onset of the second flight and egg lay. It appears that the univoltine flight is ending. All sweet corn in the row tassel (28 days before harvest) to early silk stages (21 days before harvest) will be attractive for egg-lay. In addition to trap catch, the in-field action thresholds of 12% (row tassel stage) and 4%(first silk stage) of the plants infested with egg masses or early instars.

Corn earworm (CEW) moth catches remained low this past week, averaging 0.1/trap/night at the Rosemount Experiment Station. Reports from southeastern Minnesota indicate that early-planted fresh-market sweet corn has under 3% of the ears infested. The major migration of CEW typically arrives in most corn producing regions of central Minnesota on August 20 +/- 5 days.

Note: Corn leaf aphid -- Although corn leaf aphid is rarely a pest, relatively high corn leaf aphid populations have been detected in early-planted sweet corn at the Rosemount Experiment Station, with infestations approaching 50% of the plants. The corn leaf aphid has a dark grey-green appearance. Corn leaf aphid is most prevalent in the whorl or on the tassle and the leaves surrounding the tassle. By feeding on the tassle and silk, and coating them with honeydew, they may interfere with pollination. Treatment would be justified if the field is less than 50% pollinated and at least 50% of the plants are infested with at least 50 aphids/plant.

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 Specialist, University of Minnesota, woldx018@tc.umn.edu

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Last Revised August 2, 2000.
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