Simulation of western corn rootworm Bt resistance evolution in agricultural landscapes: The importance of insect and human behavior

It is becoming increasingly apparent that resistance to Bt toxins in western corn rootworm populations is not merely influenced by in-field management, but may also involve movement of resistance alleles in the landscape. Therefore, it is imperative to understand the probabilty of undetected resistant field populations as well as make predictions about possible future resistance evolution patterns. In order to address this need, we have developed a spatially-explicit simulation of resistance evolution in Iowa agricultural landscapes. We used crop cover data from USDA’s CropScape to generate corn and soybean fields throughout Iowa. We then generated initial problem fields with large numbers of resistant individuals, and then simulated the evolution of resistance in the landscape through in-field population and landscape dispersal dynamics. In general, we have found that human and insect behavior can both be influential in the level of resistance in the landscape, and that the location of the original problem field often determines whether resistance becomes common in the surrounding landscape or if it remains rare. The results from this simulation will be compared to initial results from a field evaluation of Bt resistance in random landscapes around Iowa.