Infection of Drosophila suzukii with the obligate insect-pathogenic fungus Entomophthora muscae

Paul G. Becher, Rasmus E. Jensen, Myrsini E. Natsopoulou, Vasiliki Verschut, Henrik H. De Fine Licht

Physiological constraints restrict specialist pathogens from infecting new hosts. From an applied perspective, a narrow host range makes specialist pathogens interesting for targeting specific pest insects since they have minimal direct effects on non-target species. Entomopathogenic fungi of the genusEntomophthoraare dipteran-specific but have not been investigated for their ability to infect the spotted wing drosophila (SWD;Drosophila suzukii) a fruit-damaging pest invasive to Europe and America. Our main goal was to study whether SWD is in the physiological host range of the entomophthoralean speciesE. muscae. We investigated pathogenicity and virulence ofE. muscaetowards its main natural host, the houseflyMusca domestica, and towards SWD. We found thatE. muscaereadily infected and significantly reduced survival of SWD by 27.3% with the majority of flies dying 4-8 days post-exposure. In comparison with SWD, infection of the natural hostM. domesticaresulted in an even higher mortality of 62.9% and larger conidial spores ofE. muscae, reflecting the physiological constraints of the pathogen in the atypical host. We demonstrated that pathogens of theE. muscaespecies complex that typically have a narrow natural host range of one or few dipteran species are able to infect SWD, and we described a new method for in vivo transmission and infection of an entomophthoralean fungus to SWD.