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Parasitoids of Armyworms Have Been Common

June 29, 2001
In the aftermath of the significant outbreak of armyworms in Illinois and elsewhere in the Midwest, many keen observers have found white, cottony masses that appear to be either eggs or cocoons. Some people have feared that they had found armyworm eggs. However, we have learned from photographs and specimens sent to us that the white, cottony masses were cocoons of a parasitic wasp, tentatively identified by Rob Wiedenmann (Illinois Natural History Survey) as Glyptapanteles militaris in the family Braconidae. This parasitoid attacks armyworms as well as several other caterpillars.

Wasp parasitoids of the armyworm, Pseudaletia unipuncta. (Photo courtesy of Kevin Black, Growmark, Inc.)

Wasp parasitoids and cocoons. (Photo courtesy of Kevin Black, Growmark, Inc.)

This is a good sign. Many of us are waiting and watching for the second generation of armyworms to show up. Fair numbers of adult moths have been flying for some time now, so we know the females have begun to lay eggs. In fact, I suspect that young larvae are present in some areas, particularly in southern Illinois. However, G. militaris and other natural enemies could suppress armyworm populations and keep them well below economic levels. So, as we wait and watch, let's also root for the good guys!--Kevin Steffey

Author: Kevin Steffey

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

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