Petersson, Malin2024-08-222024-08-222024-08-22https://hdl.handle.net/2077/83084Pesticide resistance has evolved in insects for as long as the use of insecticides, and has caused us to continually develop new ones. An alternative to synthetic pesticides is biopesticides, which can consist of either living organisms or substances from organisms. Biopesticides containing living organisms can include bacteria, virus, fungi, as well as predators and parasites. They can be preferable to synthetics since they usually are less dangerous to humans, disintegrate faster and tend to be more targeted to specific pest species. Pest species ability to develop resistance to a synthetic insecticide seems to vary depending on the number of plant families the species feed on. The reason for this can be that polyphagous insects are better adapted to handling secondary metabolites from more or different plant species than do specialist insects. In this meta-analysis, I investigate whether a similar relationship exists among living biopesticides. The underlying hypothesis is that since plants have microorganisms in and on them, an insect feeding on several plants can have a history of being exposed to more diverse microbial communities compared to insects feeding on just one plant species throughout its life. I used a Bayesian multilevel regression model to answer the question: Are polyphagous pests less susceptible to novel pathogens and living biopesticides than specialist pests? The result showed no evidence for polyphagous pests to be more resilient against novel biopesticides. However, the posterior distribution is not mean centred, which can indicate a small effect of polyphagia on mortality. Further and more detailed studies of this question are strongly needed.engText