Stalk Borers Are Active in Some Areas June 7, 2002 Degree-day accumulations (base 41 deg F, Figure 6) suggest that stalk borers have moved into cornfields in central Illinois and are beginning to move into cornfields in northern Illinois. According to reports from the field, such is the case. Some of the movement into corn has been premature because burndown herbicides have killed early-season host plants (such as quackgrass and ragweed). Initial movement of stalk borers from weed hosts into corn (~1,100 degree-days) may have begun as far north as the Quad Cities in northwestern Illinois, Streator in north-central Illinois, and Kankakee in eastern Illinois. We recommend scouting when 1,300 to 1,400 degree-days have accumulated, and a decision to treat with an insecticide should be made when 1,400 to 1,700 degree-days have accumulated. However, if movement of stalk borer larvae has been forced by burndown herbicides, use your best judgment for when to apply an insecticide. Thresholds and insecticides for stalk borers in corn were presented in issue no. 10 (May 31, 2002) of the Bulletin. Please follow all label directions and precautions.--Kevin Steffey Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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