Corn Rootworm Pressure Very Low in University Insecticide Trials This Season

August 27, 1999
Despite the very impressive rebound of western corn rootworm populations across the state this season, the level of root injury was very low in the control plots of our insecticide experiments. Root injury in our control plots (no soil insecticide used) averaged 2.39, 2.53, and 1.80 at Urbana, DeKalb, and Monmouth, respectively. Root injury ratings of less than 3.0 indicate that larval feeding injury was very slight (only scarring of root tissue, root pruning minimal). In order to adequately assess the performance of a soil insecticide, we believe that an average root injury rating (control plots) of 4.0 (one node of roots destroyed) is required. At this point, we're not sure why the level of root injury in our experiments was so low. In order to provide better information to producers as they make their soil-insecticide selection decisions for the 2000 growing season, we'll provide summaries of soil-insecticide experiments for corn rootworms from some other universities. We prefer to utilize the results from our Illinois trials; however, from time to time Mother Nature doesn't cooperate.--Mike Gray

Author: Mike Gray