Symbiotic bacteria and pest control: plant toxins, chemical pesticides, and fungal entomopathogens.

Bacterial symbionts in pests are being increasingly investigated to assess their potential uses for sustainable control approaches. We undertook a review and analysis of the impacts of endosymbionts and gut symbionts on responses to toxins from plants and pesticides, and to attack by fungal entomopathogens. Despite methodological issues affecting estimates of effect sizes, there is evidence for symbionts increasing resistance to all three agents. However, impacts can be small, and for pesticides, these may not reach levels required for resistance at field rates. Negative or neutral effects may be underreported. Further complications arise because host genotype and the environment impact symbiont effects. We anticipate rapid progress in this area over coming years that should clarify practical implications of these effects.