Random mating within field populations of western corn rootworm (Diabrotica virgifera virgifera LeConte) subjected to Bt corn hybrids and refuge strategies: Fact orfiction?

Western corn rootworm (WCR) is the most significant pest of field corn in the United States, and has recently increased its range into Europe. Since 2004, hybrid corn containing Bt toxins targeting the corn rootworm complex have been heavily adopted and are now the primary control measure against this pest in North American corn production. The evolution of resistance is an ongoing concern, and to ensure that Bt products will retain their usefulness, insect resistance management (IRM) tactics using various refuge structures have been adopted. One of the key tenets of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly. A violation of this largely untested assumption would lead to acceleration of resistance development. To generate empirical field data on mating rates between beetles emerging from Bt and refuge plants, we used field cage studies of N15-marked beetles from natural field populations of WCR emerging from different refuge configurations. The data collected include emergence rates, timing, sex ratios and mating preferences of WCR beetles emerging from each refuge type. These data will then be evaluated in the context of existing IRM strategies and used to highlight opportunities to improve current refuge strategies in order to facilitate random mating.