Cooperative
Extension
Service


University of Illinois
at
Urbana-Champaign


No. 9/May 22, 1998

Status Report on European Corn Borers: First Report of Moths

Is it possible that the first flight of European corn borer moths is under way? Dave Feltes, IPM educator, Quad Cities Extension Center, reported that he observed European corn borer moths for the first time in Whiteside County on May 17. Kevin Black, Cargill, reported captures of European corn borer moths the evenings of May 18 and 19 in the Bloomington area. Figure 2 depicts the accumulation of heat units (base 50 degrees F) from January 1 to May 18. Entomologists often have attempted to predict European corn borer phenology based upon the number of heat units (base 50 degrees F) that have amassed from January 1. These attempts often have proved frustrating and inaccurate.

Figure 2. Actual heat-unit accumulation (base 50 degrees F), January 1 to May 18, 1998.

A better approach to predicting future corn borer development is to begin keeping track of heat units after the first flight of moths begins. Nonetheless, entomologists have observed the first spring flight of European corn borer moths as early as the accumulation of 374 heat units (base 50 degrees F) from January 1. Currently, even for northern Illinois, we are well beyond 374 accumulated heat units. Using the old system of monitoring corn borer phenology suggests that the peak flight of the first flush of moths can occur as early as the accumulation of 631 heat units. In future issues of this Bulletin, we will provide heat-unit projections based upon the accumulation of heat units after the initial flight has occurred. We believe the newer system of tracking the progress of European corn borer development is more accurate. However, with the first observations of moths under way, we thought a quick examination of the older system was worth a quick look. Please let us know if European corn borer moths are common in your area of the state.

Mike Gray, (m-gray4@uiuc.edu), Extension Entomology, (217)333-6652