Random mating and factors influencing mate choice in western corn rootworm (Diabrotica virgifera virgifera LeConte)

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidea), is a chronic economic pest of field corn, Zea mays L. (Poaceae), in North America. Because corn rootworms are confined to corn as the sole host, selection pressure upon them to adapt to any current or future in-plant toxin is intense. This means that IRM plans must be durable. Resistance, if it evolves, is likely to be heritable and the pace of resistance evolution will depend largely on mating rates between resistance and susceptible insects. These are among the most important types of data we can gather from field populations. Our work focuses on using simple and field-tested methods to determine if non-random mating is occurring in the field.  Field trials using the stable isotope N¹⁵ were conducted in 2015 that compared the extent to which random mating occurs between adults that fed as larvae on Bt or refuge corn plants in two common refuge configurations: strip refuge and seed mix.  Concurrent observations were taken of physical characteristics of mating and non-mating adults to determine if these parameters predict mate choice.  Results from these trials and the implications for insect resistance management will be discussed.