In 2003, the U.S. Environmental Protection Agency (EPA) approved the first transgenic rootworm-resistant corn developed by Monsanto under the trade name YieldGard. Larval western corn rootworm can cause severe injury to maize roots and reduce yield causing economic losses that exceed $1 billion annually from both management costs and yield loss.

The initial release of the first transgenic rootworm resistant corn followed several years of successful management of insect pests of maize and cotton. However, in 2009 the first cases of field-evolved Bt resistance were observed. Since then, field-evolved resistance to all available Bt traits has been documented, and resistance to some Bt traits is widespread within certain regions of the U.S. Corn Belt.