When a grower plants transgenic Bt corn, he/she ensures that his/her crop will not suffer significant yield loss due to injury by European corn borer (ECB). However, this does not ensure that the grower will enjoy an increase in profits, because Bt corn is substantially more expensive to purchase than nonBt corn. The goal is to develop a method for on-farm within-field mapping of ECB damage that combines Bt/nonBt strip planting with yield mapping. The premise is that insect damage leading to yield reductions within nonBt strips can be identified through paired comparisons with yield data from undamaged corn in flanking Bt strips. Initial experiments involve artificially infesting plots within strips of nonBt corn with different levels of ECB to determine the sensitivity of the yield-mapping method. On-farm trials also are being conducted with cooperating growers. If it proves workable, this methodology will allow growers to identify spatial patterns of damage that are stable over years, so that he/she can determine where it is cost-effective to plant Bt corn and where it is more cost-effective to plant nonBt corn. Prescription planting made possible via comprehensive damage-mapping will in turn reduce the acreage planted to Bt corn, while increasing grower profits and slowing development of insect resistance to the Bt toxin. In addition, this methodology will provide scientists with an effective tool for mapping oviposition preferences of ECB, with possibilities for large scale acreage and replication heretofore unimaginable, and yet necessary for tackling the complex questions of landscape effects on behavior.