Current approaches to slowing the evolution of resistance to insecticides rely on refuges of untreated or conventional plants acting as reservoirs of susceptible alleles. We show how the success of these refuges depends on accurate understanding of movement behavior to design refuges of the right sizes. Refuge design must balance different effects of movement onto the treated area. Too little movement and highly resistant individuals will mate with each other and not with susceptible immigrants. Too much movement and too many susceptible individuals leave the refuges and are selected out of the population. To study movement in Colorado potato beetles we used resistance to insecticides as a natural marker. Clines are areas where one genotype shifts to another, shaped by the opposing forces of selection and dispersal. We created a cline in resistance to insecticides in Colorado potato beetles by treating half of a field with an insecticide that is starting to fail. We then analyzed the shape of the cline, modifying methods used to analyze natural clines or hybrid zones, to extract the beetles' dispersal distribution. The movement estimates are then integrated into the simulation model of resistance evolution to determine the optimal refuge size.
Species 1: Coleoptera Chrysomelidae Leptinotarsa decemlineata (Colorado potato beetle)
Keywords: refuge, imidacloprid
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA