Insect-weed interactions were discussed earlier this spring in the Bulletin in "Insect-Weed Interactions in 2002" by Christy Sprague, Matt Montgomery, and Aaron Hager. Last year, herbicide performance was questioned in several areas around the state. In some instances, after applications of glyphosate, the tops of weeds appeared to be killed, but lower portions were not. New growth appeared from the lower part of the stem, allowing the weed to survive. However, these control failures had little to do with herbicide resistance. The failure of the herbicide to work effectively was due, at least to some extent, to the presence of stem-boring insects that appeared to reduce the translocation of the herbicide throughout the plant.
In an effort to better understand this phenomenon, a survey is being conducted to determine the distribution and occurrence of these insect-weed interactions in Illinois. This project focuses on the identification and frequency of insects in fields where a herbicide application (glyphosate) failed to control weeds such as ragweed, common lambsquarter, cocklebur, marestail, and common water-hemp. Please report any instances of herbicide performance failure that may be associated with insect feeding to Kelly Cook (333-6652, kcook8@ uiuc.edu) or Dawn Nordby (244-4424, email@example.com) for follow-up sampling.--Kelly Cook and Dawn Nordby