Eric Yu, Iowa State University, Department of Entomology
M.S. defense seminar.
Abstract. The refuge strategy for insect resistance management (IRM) depends on the principle that gene flow constrains local adaptation. Dispersal and gene flow in western corn rootworm, Diabrotica virgifera virgifera, which are composed of both short-range and long-range components, are difficult to study because of the inherent challenges of tracking individuals over space and time. Long-distance dispersal is clearly demonstrated by the range expansion of rootworm during the 20th century. However, uncertainties remain concerning the proportion of a population that engages in long-distance dispersal and the distance traveled by those individuals. Additionally, larval density often serves as a facultative cue for adult insects to engage in long-distance flight. Characterizing rootworm dispersal is particularly urgent given the development of resistance to Bt corn, and the need to develop effective IRM strategies for future RNAi-based transgenic products. To better understand dispersal by western corn rootworm, adults were collected from the field to obtain eggs for use in laboratory experiments. The resulting larvae were reared at three densities on mats of corn seedling, and females then tested for flight distance and duration. Females were then allowed to oviposit until death, at which time the eggs were counted to determine lifetime fecundity. The results of this study will be useful in better parameterizing computer models for IRM and in refining approaches to mitigate resistance.