Cultivation concept for preventing the proliferation of pesticide resistant insects
Sooner or later, the widespread cultivation of Bt crops is expected to promote the development of Bt resistant insects. This would eventually compromise the usefulness of the the Bt pest management strategy.
Steps for preventing the spread of resistant insects are mandatory in the United States. There, farmers must plant 20 to 50 percent of their fields with non-Bt crops. This gives Bt-susceptible insects a place to survive. When susceptible insects mate with resistant insects, their offspring is generally susceptible, which slows or stops the spread of resistance genes.
Based on experience, it is assumed that resistance genes will be recessive. In order to make certain that carriers of resistance genes are killed off, a higher amount of Bt toxin is produced in plants than is needed to kill completely susceptible individuals (high-dose strategy).