Project Number: 3625-22000-016-25
Project Type: Reimbursable

Start Date: Sep 01, 2007
End Date: Aug 31, 2010

Objective:
The first objective is to assess the effects of resistance alleles on the frequency, timing, and survival of interplant movement by O. nubilalis larvae on commercialized and pending (pyramided) Bt corn. The results will allow the relative value of narrow strips or seed mixtures as refuge strategies to be assessed, particularly as multiple toxins are combined for lepidopteran pest control. The second objective is to evaluate how resistance allele frequencies influence induction of diapause, overwintering survival, and timing of European corn borer adult emergence. Experimental outcomes will help assess how genotype-specific estimates of mortality between seasons or emergence time are likely to influence resistance evolution by O. nubilalis. The third objective is to incorporate genotype-specific parameters and other improvements into a model of European corn borer resistance evolution to estimate risks for a variety of IRM strategies. The model will integrate improved information on pest biology and behavior to determine refuge strategies that present low risks of resistance for both O. nubilalis and Diabrotica.

Approach:
Colonies of Cry1-resistant European corn borers (Ostrinia nubilalis) will be used to measure the impact of alleles conferring resistance to Bt on survival, development, and behavior. Laboratory and semi-field experiments will examine how resistance alleles impact the frequency, timing, and survival of interplant movement by O. nubilalis larvae on current and pending (pyramided) Bt hybrids. The effects of resistance alleles on induction of diapause, winter survival, and timing of adult emergence by overwintering generations also will be assessed. Because these genotype-specific estimates are key to estimating the risks of resistance evolution, new parameters and other improvements will be incorporated into a predictive model. The model will evaluate (a) IRM plans with single- or multiple-toxin Bt corn, (b) refuges planted in blocks, strips, or seed mixtures, and (c) economic effects on Bt corn growers. Using comparisons to other O. nubilalis and corn rootworm (Diabrotica) models of resistance evolution, results will help design future IRM plans that appropriately balance risks for both major Corn Belt pests.