University of Illinois

No. 7/May 9, 1997

Stalk Borer Information

A couple of folks have called asking for some information about stalk borers in corn. We can track their development by examining accumulated heat units above a base temperature of 41 degrees F. Unfortunately, I did not ask the climatologists to add this base temperature soon enough. Consequently, you'll have to wait a week to obtain this information. However, Steve Hollinger and Robert Scott, both with the Illinois State Water Survey, will provide us with a map next week showing heat-unit accumulations above 41 degrees F. Sorry for the delay.

If you happen to be tracking heat-unit accumulations on your own, you may find information related to stalk borer development useful. To coincide with egg hatch, an insecticide can be applied when 575 to 750 heat units have accumulated above a base temperature of 41 degrees F since January 1. However, this approach is preventive because the density of stalk borers is not known at the time of application. Insecticide application also can be timed to coincide with movement of the larvae from grass hosts to corn. Stalk borers first begin to move into corn when about 1,100 heat units have accumulated above a base temperature of 41 degrees F since January 1; 50% movement occurs when about 1,400 to 1,700 degree days have accumulated. When about 1,300 to 1,400 degrees days have accumulated, scout corn to verify the presence of stalk borers in the grasses (dead stems, larvae inside) or border rows of corn.

In next week's issue of the Bulletin, we'll offer more details about stalk borers and provide some information about heat-unit accumulations.

Kevin Steffey, Extension Entomology, (217)333-6652