Dispersal and mating system of European corn borer, Ostrinia nubilalis, (Hubner) [Lepidoptera: Crambidae], in relation to Bt resistance management

Bt corn is being used to control the damage caused by European corn borer, Ostrinia nubilalis (Hubner), [Lepidoptera: Crambidae]). Ostrinia nubilalis could evolve resistance to Bt corn rapidly without a proper management. Currently, the high dose plus refuge strategy is being applied to delay resistance evolution. In the field, refuge and Bt corn fields must be within 800 m distance of each other. My research is focused on testing this requirement in field conditions. First, I developed models to simulate the dispersal of Ostrinia nubilalis in relation to evolution rate. These models showed that male dispersal from refuge fields plays a critical role to delay evolution. Consequently, my field research was focused on male dispersal. First, I developed a technique that allows determination of the mating status of Ostrinia nubilalis males. Virgin and mated Ostrinia nubilalis males can be distinguished with near certainly when they are caught from field. Using this technique, I found that Ostrinia nubilalis virgin males from natural populations can commonly move over 800 m, which verified the 800 m distance requirement. A quantitative study about the dispersal of Ostrinia nubilalis males using release-recapture methods found that there are, at least 4000 Ostrinia nubilalis males that could move from refuge fields into Bt fields for every one male emerging from a Bt field, during the early stages of evolution. This suggests that sufficient numbers of males move across 800 m to reduce the rate of evolution.