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Stalk Borers Could Attack Corn in Southern Illinois Soon

May 8, 2003

As with European corn borers, degree-day accumulations can provide a heads-up for the occurrence of stalk borers in corn. Figure 4 shows actual degree-day accumulations (base 41°F, the minimum developmental temperature for stalk borers), from January 1 through May 5, 2003. 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 4 suggests that movement of stalk borers from weedy hosts into corn has not begun anywhere in Illinois. However, a warm spell will speed up accumulation of degree-days quite a bit, so cornfields in southern Illinois could be at risk soon. Farmers in central and northern Illinois probably won't see stalk borers for a couple of weeks. We'll continue to generate these maps until we are certain of the presence of stalk borers throughout the state.--Kevin Steffey

Author: Kevin Steffey

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

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