Widespread farmer adoption of Bt corn hybrids and new Bt traits for caterpillar pests in addition to corn rootworm have increased the number of acres where target insect pests are exposed to Bt active ingredients each growing season. The purpose of Insect Resistance Management (IRM) is to maintain the effectiveness of Bt crops as an insect pest management tool by preventing or delaying development of insect resistance to Bt traits. The IRM plan is implemented by planting refuge corn acres on each farm where a Bt corn hybrid is planted. Refuge corn acres do not contain the Bt insect trait used in the Bt planting. A refuge provides a corn crop habitat that allows target pest insects to feed, mate and reproduce without being exposed to the Bt trait. Mating between Bt-susceptible insects from the refuge and potential resistant insect ensures that susceptibility to the Bt toxin is passed on to the next generation. Without a refuge, target insect populations that are exposed to Bt corn each growing season over multiple generations will eventually become resistant to Bt.
Soil Science Extension
University of Wisconsin Madison