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White Grubs and Wireworms Can Injure Slow-Growing Corn

May 3, 2002
The report from the Illinois Agricultural Statistics Service (, issued for the week ending April 28, indicated that 25% of the corn crop in Illinois had been planted, and only 5% had emerged. Wet weather has delayed planting in many areas, and cool soils are not encouraging rapid corn growth. Consequently, subterranean insects such as white grubs and wireworms can ravage slow-growing corn seedlings.

I have reported that many people have observed large numbers of white grubs (primarily Japanese beetle grubs) this season, so it's only a matter of time before we start to receive more reports of injury to corn. Although I haven't said much thus far about wireworms, they are causing a few problems as well. Entomologists at the University of Kentucky have received reports of serious wireworm activity. Not surprisingly, our first report of wireworm activity in Illinois came from a southern county. Dale Burmester, crop specialist with Gateway FS in Redbud, found a lot of wireworms in a field near Sparta (Randolph County).

As folks wait anxiously to resume planting corn, don't forget the corn already in the ground. Check fields for wilted and/or missing plants, signs of injury by underground insects. Keep in mind that other factors can cause similar injury, so you have to find the culprits to blame the problem on white grubs or wireworms. Considering the numbers of these pests that have been reported thus far, finding them shouldn't be too difficult.

Unfortunately, because there are no rescue treatments of insecticides that will control white grubs or wireworms, fields that are heavily infested may have to be replanted. Both types of pests will remain a threat into mid-May, after which concern about their feeding will diminish.--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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