Analysis On The Economic Benefit Model Of Bt Crop Resistance Management And Pest Development

In integrated pest management, chemical control, physical control and biolog-ical control are often used tactics for pest control. Chemical control can effectively kill pests, which making it to be one of the most frequently used control strategies in practice. However, high application rates and frequents of pesticides not only cause environmental pollution problem but also promote the resistance development of pests, leading to control failure of chemical control. Then, pests break out again or even rampantly. In order to delay the resistance development of European corn bor-er to Bt-corn, EPA and USDA addressed a resistance management strategy (EPA mixed strategy), which requires that an area planted with Bt-corn must be planted with not less than20%non-Bt-corn. To analyze this strategy, we proposed our economic model with pest population dynamic and resistance development.Assume that the pest follows the malthus growth and the resistance develop-ment at different generations follows a discrete equation, the economic model has been proposed and analyzed. Our results suggest that initial number and intrinsic growth rate of pests exist a threshold value separately which determines the optimal planting strategy. Moreover, our numerical analyses suggest that the larger value of initial population size or intrinsic growth rate of pests is, the longer planting time is needed to let the NPV of mixed strategy to be higher than the NPV of pure Bt strategy. So the larger value of initial population size or intrinsic growth rate of pests is, harder to put the EPA mixed strategy in practices.Moreover, if the pest population follows the logistic growth, then we develop the economic model with aims to justify the planting strategies. By using the similar methods as above, we can get the similar results. To understand whether initial number and intrinsic growth rate of pests exists a threshold value separately which decides when the EPA mixed strategy is better than the pure Bt strategy, three different cases concerning the relations between initial number and carrying capacity, and carrying capacity tends to infinite have been investigated. The conclusions obtained in this thesis can provide a basis for pest resistance management of Bt-crop and optimize planting strategies for pest control.