Photo Credit: Angie Garrett

A study out of Iowa State University, published this year in the Proceedings of the National Academy of Sciences,  has documented the continued development of resistant pests in response to genetically modified (GM) crops. Specifically, the researchers examined resistant varieties of western corn rootworm to Bt corn. They show that western corn rootworms have developed cross-resistance to two different types of GM corn (Cry3Bb1 maize and mCry3A maize). They also report the severe toll these pests have taken on Bt corn in farmers’ fields. To account for pest resistance, many GM crop producers are now pyramiding multiple toxins into their crops. This study suggests that while pyramiding toxins can delay the development of resistance, once resistance arises to one of the toxins pests, it can rapidly develop cross resistance to both toxins. This study adds to the growing body of literature showing that the use of GM crops and their associated pesticides can lead to the rapid development of resistant pests.