Corn growers would use crop rotation and “stacked” seeds to prevent corn rootworm from developing widespread resistance to Bt corn under a framework proposed by EPA and open for public comment until March 16. Problems with resistance to two Bt corn traits have been reported in part of Illinois and Iowa, the two top corn-growing states. EPA said it “believes that the proposed enhancements would prolong the effectiveness of Bt PIPs (plant-incorporated protectants) for corn rootworm control significantly – which is important because of the long safety record of these PIPs.”
Seed companies would be required to see that at least 70 percent of growers in high-risk areas use tactics such as crop rotation, seeds with multiple Bt traits or non-Bt varieties along with a soil insecticide. An advisory panel of scientists told EPA that “refuge alone has not been sufficient to manage (corn rootworm) resistance to Bt corn,” which is genetically engineered to use a natural toxin against insects. In announcing the framework, EPA said, “The proposed framework would change the way farmers use Bt corn, in order to slow the development of resistance. Our goal is to prolong the durability and effectiveness of these plants to control the corn rootworm pest.”