Pure Bt-crop and mixed seed sowing strategies for optimal economic profit in the face of pest resistance to pesticides and Bt-corn

- We developed a discrete pest growth model with evolution of Bt-corn resistance.
- The net present value with pure Bt-corn or mixed planting strategy is investigated.
- The effects of parameters on the net present values are studied.
- The optimal proportion of the field planted with non-Bt-corn has been discussed.

With the evolution of pest resistance to Bt-corn, farmers' economic losses are increasing. However, a planting strategy with Bt-corn mixed with non-Bt-corn to fight the development of pest resistance can be efficient. Nevertheless, this mixed strategy poses questions such as (1) what is the optimal ratio of Bt-corn to non-Bt-corn that should be planted in a field? And (2) what is the main factor affecting the farmers' net present value? To address these questions, we propose and investigate a discrete pest growth model with pest resistance to Bt-corn. According to the model's economic functions, the main factors affecting the farmers' net present value are presented and discussed. By comparing the net present values of a pure Bt-corn planting strategy with the mixed planting strategy, an optimal planting strategy was devised. Moreover, the optimal ratio of Bt-corn to non-Bt-corn to be planted when the mixed planting strategy is implemented in the field was also investigated.