Economic analysis of transgenic maize and nontransgenic refuges for managing European corn borer (Lepidoptera : Pyralidae)

We simulated the population dynamics and population genetics of Europe;ln c orn borer, Ostrinia nubilalis (Hubner), and damage to maize in a hypothetic al region containing transgenic and nontransgenic maize and no other crops. The model assumes that the same level of refuge for resistance management is used every year over 15-20 yr and that no European corn borers immigrate into the region over the same period. When complete mixing across blocks b etween generations is assumed, the transgenic block significantly lowers da mage to maize in the refuges. For most scenarios without toxin-titer declin e during maize senescence, a 20% refuge is a robust, economical choice base d on current value. At extremes of initial pest density or crop value (pric e X expected yield), refuge levels as low as 8% or as high as 26% can be su perior. Nontransgenic maize can be planted as strips (at least 6 rows per s trip) within a field or as separate but adjacent blocks to be effective at delaying resistance and providing economic returns at a 20% refuge level. W ith toxin-titer decline during senescence, the model results are sensitive to several biological parameters and assumptions with a 10% refuge level of fering a robust, economic choice.