INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT Monitoring Western Corn Rootworm (Coleoptera: Chrysomelidae) Susceptibility to Carbaryl and Cucurbitacin Baits in the Areawide Management Pilot Program

Areawide pest management involves the uniform application of a pest control strategy overwidegeographic areas. Therefore, theseprograms are likely to impose intense selectivepressures, and the risk for resistancedevelopment amongpest species forwhich areawidemanagement programs are implemented is likely tobehigh.Pilot studies for areawidemanagementofwesterncorn rootworm, Diabrotica virgifera virgiferaLeConte, were conducted from 1996 to 2002 at four different sites across the Corn Belt. This program used cucurbitacin baits to deliver high doses of a traditional neurotoxic insecticide (carbaryl) to individual insects while reducing the overall rate of insecticide use. Because of the concern and potential for resistance evolution, annual assessments of susceptibility to the active ingredient carbaryl were conducted both within the managed area as well as from untreated control areas. SigniÞcantly reduced susceptibility to carbaryl based on survival at a diagnostic concentration was detected in three of the four management sites (Kansas, Iowa, and Illinois/Indiana), whereas susceptibility of beetles collected outside the managed areas remained unchanged. Additionally, signiÞcantly reduced responsiveness to cucurbitacin baits was observed in beetles collected from the managed area relative to the control area at the same three sites. These results suggest strongly that areawide management has the potential to select for resistance and that a strategy for managing resistance and reducing selective pressure should be proactively implemented.