Sustained susceptibility to Bt cotton was essential for eradicating the pink bollworm (Pectinophora gossypiella) from the United States and Mexico, which it had invaded more than a century ago.As part of a multi-tactic program, pink bollworm caterpillars were mass reared (as shown here) and 11 billion sterile moths were released by airplanes to overwhelm its populations in the field. By contrast, this pest evolved resistance to dual-toxin Bt cotton in India, where it was used extensively with scarce non-Bt host plant refuges and limited integration of other tactics. (Photo by Alexander Yelich, University of Arizona)