C. Richard EDWARDS¹, Jeffrey HYDE², Marshall A. MARTIN², and Paul V. PRECKEL²
Departments of Entomology¹ and Agricultural Economics², Purdue University, W. Lafayette, IN 47907-1158 USA

Bt corn planted over large areas may lead to resistance in European corn borer (ECB), Ostrinia nubilalis Hübner, to these transgenic plants. Scientists recommend planting at least 20% non-Bt corn as an ECB refuge as part of a resistance management strategy. Different refuge configurations can be used, but they may impact farm profits differently. It is recommend that a refuge be planted near or within a Bt field. Several potential configurations for the refuge are under consideration. For example, the refuge may be planted in several strips throughout a field, in a block along a field's edge, or as the perimeter around a field. An alternative to the non-Bt corn refuge strategy is to plant a crop that is more attractive to ECB than field corn. Recent research has shown that densely planted popcorn is much more attractive to ECB than regular corn. Using a popcorn-based refuge allows for a smaller refuge, but harvesting of highly damaged popcorn may be uneconomical. This type of refuge is referred to as a sacrificial refuge. The net economic benefit of each potential refuge configuration is estimated in this study. The analysis uses detailed crop budgets to analyze potential differences in cost/benefits. Benefits are measured by differences in corn yield between alternative refuge configurations. Yield differences may occur because some configurations are likely to provide better control of ECB than others. Costs may differ because of different planting efficiencies. For example, total planting time may increase due to the time required to adjust or change seed in a planter. Increased time requirements may result in increased labor costs. Total planting time for the farm may also increase, which may reduce yields on later planted fields. On average in Indiana, corn yields are estimated to fall 94.2 kg/ha per day when planting is delayed past May 10. It is expected that farmers will choose to plant their Bt and refuge corn in the most economical way.