Too much of a good thing: Lessons from compromised rootworm Bt maize in the US Corn Belt.

Widespread use of genetically engineered maize targeting the corn rootworm complex (Diabrotica species) has raised concerns about insect resistance. Twelve years of university field trial and farm survey data from 10 US Corn Belt states indicate that maize hybrids expressing toxins derived from the bacterium Bacillus thuringiensis (Bt maize) exhibited declining protection from rootworm feeding with increased planting while pest pressures simultaneously decreased. The analysis revealed a tendency to overplant Bt maize, leading to substantial economic losses; this was particularly striking in eastern Corn Belt states. Our findings highlight the need to go beyond the "tragedy of the commons" perspective to protect sustainable use of Bt and other crop biotechnology resources. We propose moving toward a more diversified and transparent seed supply.