Heads Up for Stalk Borers May 17, 2002 It's probably a bit early for farmers in northern Illinois (where quite a bit of corn has been planted) to be concerned about stalk borers, but degree-day accumulations can provide a "heads up." Figure 2 shows actual degree-day accumulations (base 41 deg F, the minimum developmental temperature for stalk borers), from January 1 through May 13, 2002. Stalk borers first begin to move into corn when about 1,100 heat units have accumulated from January 1; 50% movement occurs when about 1,400 to 1,700 heat units have accumulated. We recommend scouting when 1,300 to 1,400 heat units have accumulated, and a decision to treat with an insecticide should be made between 1,400 and 1,700 heat units. The map in Figure 2 suggests that farmers in southern counties (where very little corn has been planted) should watch for stalk borers; however, farmers in central and northern Illinois probably won't see stalk borers right away. When (if) temperatures become more late spring-like, development of stalk borers will accelerate. I'll provide a more detailed article about stalk borers in next week's issue of the Bulletin.--Kevin Steffey Author: Kevin Steffey

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

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