Modeling the dynamics of adaptation to transgenic maize by European corn borer (Lepidoptera: Pyralidae)

A deterministic population dynamics model was modified to include single-locus, 2-allele genetics to simulate strategies for delaying resistance in the European corn borer, Ostrinia nubilalis (Hubner), population to transgenic maize. We evaluated seed mixtures of transgenic and nontransgenic maize, B-row strips of nontransgenic plants, adjacent but separate refuges of nontransgenic maize, and rotation of nontransgenic and transgenic maize. We studied how the choice of hybrid, planting time, and weather may influence the selection of a tactic for delaying resistance to transgenic maize. Our results indicate that separate refuges are superior to seed mixtures for delaying resistance. If a high toxin dose cannot be achieved and a small fraction of homozygous susceptible and heterozygous European corn borer neonates survive on transgenic maize, then resistance can develop in 10-33% of the time required under the assumption of a successful high dose that kills all heterozygous neonates. Planting e-row strips may be as good as separate refuges in delaying resistance, but their adoption carries greater risk because of the uncertainty surrounding movement and survival of neonates. The use of transgenic hybrids is the same whether or not they express the toxin gene in silks and kernels of maize ears. Toxin titer decline must be studied because our simulations indicate that development of resistance may be greatly hastened by this process.