The Problems Driving Resistance to Bt Crops—and Some Proposed Solutions

By Dominic Reisig, Ph.D.

Bt crops—those genetically engineered to produce an insecticidal toxin from the bacterium Bacillus thuringiensis—are special due to their benefits: reducing foliar insecticide applications, which increase populations of beneficial insects and minimize environmental harm; reducing pest populations throughout the landscape; and preserving yield, to name a few.

Therefore, preventing resistance to Bt crops is important and is usually formalized in a set of Insecticide Resistance Management (IRM) practices. Because bollworm (Helicoverpa zea,also commonly known as corn earworm and tomato fruitworm) is now resistant to two Bt toxin families (Cry1A and Cry2A) in cotton, IRM practices may have to change to slow resistance to other Bt toxins.

Although bollworm field resistance to single-toxin Bt has been known for many years, cotton farmers are now experiencing problems in the field due to resistance, spraying more insecticides forbollworm in two-Bt-toxin cotton.

However, the implications of this resistance for IRM are bigger than just an increase in foliar insecticide sprays. In a forum article published in Environmental Entomology this month, cotton industry researcher Ryan Kurtz and I sought to detail many of these implications for the U.S. production system from our field-based perspective, listing current challenges and providing suggestions to meet those challenges...........To Read More.....