Seasonal Responses of Corn Rootworm Beetles (Coleoptera: Chrysomelidae) to Non-pheromonal Attractants²

Western, Diabrotica virgifera virgifera LeConte, and northern, D. barberi Smith and Lawrence, corn rootworm beetles were captured in a cornfield at traps baited with volatile attractants during three portions of the season. In dent-stage maize (3–4 wk past flowering), traps baited with eugenol captured large numbers of D. barberi, whereas traps baited with p-methoxycinnamonitrile (p-MCN) or estragole captured large numbers of D. v. virgifera. The attactants were less effective in two earlier trials when maize was in the whorl or silking stage. Despite seasonal differences, baits containing p-MCN attracted significant numbers of D. v. virgifera during all three trials. Attractants were also tested simultaneously in plots of corn that were planted on one of three different dates. With D. v. virgifera, attractants were relatively less effective in plots of maize that were silking than in plots of whorl-stage or dough-stage maize; with D. barberi, attractants were effective only in plots of whorl-stage maize. Changes in phenology of maize appear to be at least partially responsible for seasonal variation in attractancy of non-pheromonal lures for rootworm beetles. This seasonal variation will affect the use of non-pheromonal attractants in management applications.