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A Few "Thumbnail" Reports of Insects in Field Crops

June 28, 2002
Following are some brief reports of occurrences of insects and mites in Illinois.

· For issue no. 12 (June 14, 2002) of the Bulletin, I wrote an article regarding insects interfering with the activity of some postapplied herbicides. One of the insects was identified as a beetle larva, but at the time we were not certain what type of beetle it was. Mark Hoard, Extension IPM educator in Mt. Vernon, has identified the specimens I sent him as members of the family Anthribidae (fungus beetles). As the common name implies, many of these species are associated with fungus, so it's possible that the larvae we found were secondary invaders that came in after some other insect had excavated the marestail stems. However, some species of Anthribidae are known to feed inside weed stems, and they may have been responsible for the tunneling. As we learn more, we will share the information with you.

· Although grape colaspis injury did not seem to be widespread in 2002, this pest caused significant stunting and some stand reduction in some fields in western Illinois. In some instances, the symptoms of injury had been masked by the poor condition of the corn related to crummy growing conditions. After the corn began to grow, plants injured by grape colaspis remained stunted. I examined a field trial that the folks with Burrus Power Hybrids established near Arenzville in Cass County, and the differences between the untreated check and some of the plots treated with seed treatments and/or soil insecticides were quite noticeable. The data will be analyzed later this year, and we may be able to detect some significant differences among treatments.

· In last week's Bulletin (issue no. 13, June 21, 2002), I wrote a detailed article about potato leafhoppers. As it turns out, during the past week, we received numerous reports of large densities of leafhoppers in alfalfa, with some leafhoppers showing up in soybean fields. Omar Koester, Extension unit assistant (crop systems) in Randolph County, indicated that economic levels of potato leafhoppers were not "caught in time" on second cuttings in his area, and some yield loss occurred. Over the past couple of weeks, yellowing alfalfa fields have become more common. We urge you to scout for potato leafhoppers now, and be especially vigilant when the third crop begins to regrow after harvest.

· Kevin Black, with Growmark, observed twospotted spider mites in the margin of a soybean field near Carmi (White County) on June 25. The numbers were small, but their presence in soybeans is worth noting. If the weather is hot and dry, population densities of twospotted spider mites will escalate rapidly.

Keep monitoring fields, and send us your reports.--Kevin Steffey

Author: Kevin Steffey

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

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