Insecticide resistance management policy

Bt-cotton refuge policies are derived that maximize the net present value of profit flows attainable by producers using a dynamic-programming model that accounts for important short- and long-run features of producer behavior and resistance development. The economic model accounts for the relationship between resistance and policy-constrained producer behavior in the short run, the development of resistance in two cotton insects to Bt and a popular conventional insecticide, toxin-mixture effects on resistance development, and producer adoption of alternative pest-management technologies in the long run. The analysis affords a number of implications for resistance-management policy and a more thorough understanding of primary policy determinants.;Producers may be expected to experience significant losses and use significantly more conventional insecticides under the current treated-refuge policy relative to the policy that maximizes long-run production value. The need for and the ultimate form of the policy is highly sensitive to the number of years Bt must be maintained as a profitable insecticide, thus information regarding the arrival of replacement technologies is shown to be vital. Likewise, factors that affect the profitability of Bt and the potential for resistance in cotton insects are important policy determinants. Variation in the profitability of Bt cotton across U.S. production regions leads to the implication that social welfare may be increased at no additional cost by deriving national Bt-refuge policy with respect to the needs of regions wherein it is expected to be significantly adopted. As expected, allowing the producer to adopt alternative insecticides is shown to reduce refuge requirements significantly. Surprisingly, cross-resistance and cost increases associated with alternative pest-control technologies have negligible policy impacts.;The use of untreated refuge is shown to dominate significantly the use of treated refuge. Attainable long-run production value is significantly increased and conventional-insecticide usage is significantly reduced under the untreated-refuge policy relative to the treated-refuge policy. Remarkably, insect susceptibility to a conventional insecticide is shown to regenerate using a relatively small untreated refuge, leading to a toxin-mixture effect that reduces the rate of Bt resistance development.