Challenges for the use of biopesticides in IPM

The burgeoning marketplace for microbial biopesticides and other biocontrol agents provides wider diversity of products for IPM than ever before. However, the current dramatic intensification in use of these biological products raises two urgent questions: will pests evolve resistance against these sustainable pest control products; and what can agriculture do to manage these risks? We investigate these questions by studying patterns of naturally occurring genetic variation within pest populations; genetic variation that influences the ability of pests to resist exposure to biocontrol agents such as microbial biopesticides. We show that insect populations have extensive pre-existing genetic variation for ability to survive attack by the pathogens and parasitoids used in biocontrol. This presents the threat that intensive application will lead to pest resistance evolution and crop protection failure. Yet, our studies also demonstrate that the distinctive properties of host-parasite interactions can be exploited to manage risks of pest resistance. The genetic basis of resistance to microbial biopesticides tends to be complex, involving multiple gene loci; furthermore, the efficacy of these loci in conferring resistance can be highly sensitive to environmental conditions. We show that resistance genotype fitness is strongly influenced by the identity of the crop on which an insect feeds. Thus, for polyphagous pests, farmers could manage resistance risks by diversifying the crops grown in agricultural landscapes, whilst also deploying more conventional rotations of biopesticides. Our research seeks to ensure that the escalating use of microbial biopesticides does not trigger the same resistance fate that has befallen many synthetic insecticides.