Why can insect pests develop resistance to Bt toxin?

Insect pests can develop resistance to Bt toxin primarily as a result of repeated exposure to the protein. When Bt crops are cultivated extensively, the consistent presence of the toxin creates strong selective pressure on pest populations. Individuals within a population that possess natural genetic variations allowing them to survive the toxin are more likely to reproduce, passing these resistant traits to subsequent generations.1

This phenomenon is a significant concern in agricultural science because it threatens to render one of the most environmentally benign insecticides ineffective. To mitigate this risk, experts employ management strategies such as the planting of refuges—areas of non-Bt crops grown near Bt fields—to maintain a local population of insects that remain susceptible to the toxin, thereby slowing the evolution of resistance.1