2010 Annual Report 1a.Objectives (from AD-416) Assess the effects of resistance alleles on the frequency, timing, and survival of interplant movement by European corn borer larvae on single- and multiple-toxin Bt hybrids. Evaluate how resistance allele frequencies influence entry into diapause, overwintering survival, and timing of European corn borer adult emergence. 1b.Approach (from AD-416) European corn borers resistant to Bt corn will be used to measure the impact of Bt resistance alleles on survival, development, and behavior. Experiments will examine how resistance alleles affect the frequency, timing, and survival of interplant movement by larvae on non-Bt, current Bt hybrids, and pending Bt hybrids ("pyramids"). The effects of Bt resistance alleles on corn borers entry into diapause, winter survival, and timing of adult emergence by overwintering generations also will be assessed. 3.Progress Report Laboratory studies evaluated one-day old European corn borer larvae that are resistant to Bacillus thuringiensis (Bt)-corn toxins, Cry1Ab, and another set resistant to Cry1F. The study, which tested their ability to move among Bt- and non-Bt corn plants, has been completed, and data have been shared with the University of Illinois cooperator for modeling purposes. The modeling is done to predict the effect of different farming strategies on the European corn borer’s ability to develop resistance to Bt-corn. Results indicate that a proportion of larvae will disperse from non-Bt corn plants, and an even greater proportion disperse from Bt-corn plants. It is likely that increased dispersal increases larval mortality due to the larvae’s exposure to environmental and biological (e.g., predation) factors. This new information will improve our capacity to evaluate strategies designed to delay the onset of European corn borers developing resistance to Bt-corn. Laboratory experiments are ongoing to evaluate the mortality of one-day old larvae and older larvae that sample or taste corn tissue before moving to another plant. Semi-field and field experiments are underway to assess movement of older larvae that are susceptible to Bt-corn. Studies testing the ability of Cry1Ab-resistant larvae to effectively go into diapause (a developmental pause) and then emerge as adults from pupae, have been completed. One trial with Cry1F-resistant larvae is complete; another trial is planned for the fall. Two manuscripts were published as a result of this research and are reported in the parent project # 3625-22000-016-00D. The progress of the project was monitored with phone calls, emails, and discussions with collaborators at professional meetings.