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Issue No. 11, Article 4/June 3, 2005

Corn Rootworm Larval Hatch Confirmed

The corn rootworm "season" has begun. Larry Bledsoe, an entomologist with the Department of Entomology at Purdue University, detected first-instar larvae near West Lafayette on May 31. He suspects that some larvae hatched a few days earlier. In the Bulletin last week, we predicted that corn rootworm "larval hatch may not be well under way across central Illinois until June 7 (based on 2-week projections)." This prediction is based on research indicating that after 684 to 767 soil heat units (base 52°F, 4-inch soil profile) have accumulated, from January 1, approximately 50% of corn rootworm larvae should have hatched. So we anticipate over the next week to 10 days hearing many more reports of corn rootworm larvae feeding on tender corn roots.

First-instar corn rootworm (photo courtesy of Larry Bledsoe, Purdue University).

The continuing very dry conditions across much of central Illinois persist. Rainfall totals for the month of May were many inches below normal for the month. If this dry pattern lingers for the next several weeks, producers should expect marginal performance for soil insecticides. Let's hope for some rain.--Mike Gray

Mike Gray

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