摘要：Genetically engineered crops expressing
Bacillus thuringiensis (
Bt) Cry toxins have transformed insect management in maize and cotton, reducing insecticide use and associated off-target effects. To mitigate the risk that pests evolve resistance to
Bt crops, the US Environmental Protection Agency requires resistance management measures. The approved resistance management plan for
Bt maize in cotton production regions requires a structured refuge of non-
Bt maize equal to 20% of the maize planted; that for
Bt cotton relies on the presence of an unstructured natural refuge comprising both non-
Bt crop and non-crop hosts. We examined how abundance of
Bt crops (cotton and maize) and an important non-
Bt crop (soybean) component of the natural refuge affect resistance to
Bt Cry1Ac toxin in local populations of
Helicoverpa zea, an important lepidopteran pest impacted by
Bt cotton and maize. We show refuge effectiveness is responsive to local abundances of maize and cotton and non-
Bt soybean, and maize, in its role as a source of
H. zea infesting cotton and non-
Bt hosts, influences refuge effectiveness. These findings have important implications for commercial and regulatory decisions regarding deployment of
Bt toxins targeting
H. zea in maize, cotton, and other crops and for assumptions regarding efficacy of natural refuges.
