Do Diverse Agricultural Landscapes Lower the Risk of Biopesticide Resistance Evolution?

Abstract

Pesticide resistance decreases food security and leads to increased pesticide use and associated environmental damage and higher costs to farmers from increased applications. Alternative pesticide resistance management systems are needed to sustain future food security while protecting environments. Using a spatial matrix of different biopesticides instead of synthetic pesticides could possibly impose enough fluctuating selection to prevent directional resistance evolution, as long as there are trade-offs between traits that improve survival in the presence of different biopesticides. However, the scale at which divergent selection is needed to prevent evolution is unknown, and field experiments to examine the importance of gene flow are too time-consuming and logistically difficult. My project uses computer agent-based simulations to examine the effect of using two, three or four biopesticides in different landscapes to look at how diversity in agricultural land use affects resistance evolution. These simulations allow evolution in populations of digital pests with complex genomes. I further extract information from real world maps having a range of field sizes to incorporate the characteristics of realistic landscapes. My simulations showed substantial resistance evolution when only two or three biopesticides were used, but that using a larger number of biopesticides arrested resistance evolution. Surprisingly, the size of fields had no effect on resistance evolution regardless of biopesticide number: even in landscapes with large monocultures, there was enough gene flow in the computer population to prevent local resistance evolution and create sustainable pest control. I discuss my findings in the context of fundamental evolutionary principles, the demographics and dispersal abilities of pests, and the applied implications of my work for sustainable agriculture.