D3252: Effects of aphid endosymbionts on sensitivity to entomopathogen Beauvaria bassiana

Integrated pest management (IPM) strategies balance chemical and alternative control methods such as biologicals. Biologicals are typically living organisms to suppress pest populations, while chemicals are synthetic. Some pests contain bacteria known as endosymbionts, which can affect  host phenotype, and maybe useful biological control agents for novel methods of pest control, but little is known about their contribution to entomopathogens and chemical tolerance. By experimental manipulation of the endosymbiont in different hosts, we can study its effect on IPM-based chemicals and biologicals. Aphids (superfamily Aphidoidea, order Hemiptera) are an excellent pest model system, as their populations can be controlled by entomopathogens and traditional chemicals. We used a novel transinfection of the bacteria, Rickettsiella, to examine both interspecific and intraspecific effects of endosymbiont manipulation on aphid chemical tolerance. Rickettsiella, found in Acyrthosiphon pisum, reduces fecundity in M.persicae, making its biocontrol effect useful. Whilst our interspecific experiments demonstrated that this endosymbiont does not increase chemical tolerance among three aphid species, our intraspecific experiment on four clonal strains of M. persicae  showed that while the transinfection had no effect on chemical tolerance, infected resistant strains have a higher susceptibility to the entomopathogen Beauvaria bassiana, showing a significant cost and trade-off for harboring the endosymbiont and providing resistance to chemicals. These costs can be exploited when used in conjunction with biologicals. Given the growing concerns of using synthetic insecticides, this study is important in ensuring that novel biological control methods such as transinfection, are compatible with traditional control methods and IPM-based strategies.