Bt is a bacterium that is toxic to a large class of common insect pests called lepidopterans. Because of the damage they inflict, lepidopterans provoke some of the greatest use of pesticides world-wide. Bt is a naturally-occurring killer of lepidopterans. As such, it is a priceless gift from nature to row-crop farmers who need to control outbreaks of lepidopterans. By inserting a gene from the Bt bacterium into plants, Monsanto and others have created crops that are themselves pesticidal to lepidopterans.
Resistance is a well-understood phenomenon.
When a group of insects is sprayed with a poison, those that are least affected survive and reproduce. EPA assumed their silence meant all was well. Traditionally, farmers get reliable information from the land grant colleges that Congress created in 1862. However, beginning with the Freedom to Farm Act of 1996, Congress has systematically reduced the role of the public sector in U.S. agriculture. Now development of genetically engineered crops is largely in private hands and the new technology is cloaked in secrecy.