Spatially explicit economic effects of non-susceptible pests' invasion on Bt maize

Maize expressing the Bacillus thuringiensis Cry1Ab toxin (Bt maize) provides a more effective control of corn borers than the use of insecticides. Yet, the spatial expansion of Bt maize may offer ideal ecological conditions for the development and spread of secondary pests, i.e. pests not susceptible to the expressed toxin. This paper develops a bio-economic, spatially explicit population model to analyse the spread and economic consequences of a secondary pest outbreak. Results show that the present use and even an eventual expansion of Bt maize can be economically and environmentally advantageous as it would decrease insecticide usage intensity. However, we show that caution is required when considering its widespread use. If a pest outbreak is not identified and dealt with at an early stage, it could lead to severe economic impacts even if insecticides are used in combination with the Bt maize. We further discuss potential policy and subsequent management strategies to address this issue.