University of Illinois

No. 12/June 11, 1998

More on Grape Colaspis Situation

In last week's issue of this Bulletin (issue no. 11, June 5, 1998), we explained in some detail about the ongoing problems with grape colaspis in many fields of corn throughout Illinois. Although the number of calls about this unique problem decreased during the past week, a few reports trickled in. Among the most noteworthy were the reports that pupae were beginning to appear in some affected fields. This is good news. We indicated that grape colaspis larvae usually complete their feeding by mid-June, and we hoped that pupation would begin soon. If the injury caused by grape colaspis larvae has not killed the plants and good growing conditions prevail for the next several days, many of the raggedy-looking plants will recover when the stress from grape colaspis is gone.

If you are in an area where grape colaspis has been causing significant damage and you still are diagnosing this problem, keep us informed about the progress of grape colaspis development. After about 1 week to 10 days as a pupa, the grape colaspis will emerge from the soil as an adult, usually in July. The tan adult is oval and about 1/6-inch long, with rows of tiny punctures on its wing covers, making them appear ridged. Colaspis adults sometimes are confused with newly emerged northern corn rootworm adults, which have smooth wing covers.

The problem will subside very soon. Hopefully, most growers have been able to grin and bear it without resorting to replanting.

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