Central & Northern IL Black Cutworm by Memorial Day

The black cutworm may do damage in central and northern Illinois corn fields over the Memorial Day weekend. Farmers should begin scouting soon because not all Bt corn hybrids offer adequate protection.

University of Illinois entomologist are estimating, based on black cutworm moth flights, that farmers might find the overnight work of the moth’s larval stage offspring beginning in late May. The larvae can cut a corn plant off. Farmers should scout for early feeding damage this week and next says University of Illinois Extension Entomologist Mike Gray.

Quote Summary - Growers should look for early signs of black cutworm activity. There will be small pin hole sized areas on leaves. These have been removed by very small caterpillars in the one to three instar stage. Once the caterpillars reach the fourth larval instar stage they can begin to cut plants.

Based on some heat unit calculations U of I entomologists project cutting dates will begin in Ford County (May 24), Mercer County (May 25), Lee County (May 31), Whiteside County (June 1), and Henry County (June 3) Illinois. Plants in the one to four leaf stage are most susceptible to cutting. It is important to note that not all Bt corn hybrids adequately protect against the black cutworm.

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