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

doi:10.1007/s10340-017-0915-3

Abstract

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 genus Entomophthora are 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 species E. muscae. We investigated pathogenicity and virulence of E. muscae towards its main natural host, the housefly Musca domestica, and towards SWD. We found that E. muscae readily 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 host M. domestica resulted in an even higher mortality of 62.9% and larger conidial spores of E. muscae, reflecting the physiological constraints of the pathogen in the atypical host. We demonstrated that pathogens of the E. muscae species 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.

Highlights

The Asian spotted wing drosophila (SWD; Drosophila suzukii) is an invasive and serious economic pest in fruit and berry
We demonstrated that pathogens of the E. muscae species 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
Entomophthora muscae causes natural epizootics in housefly populations (Kalsbeek et al 2001), and here we explored the infectivity of E. muscae towards SWD

Summary

Introduction

The Asian spotted wing drosophila (SWD; Drosophila suzukii) is an invasive and serious economic pest in fruit and berry. Active suppression of pest populations can be approached through different strategies of biological control ranging from measures that protect or enhance specific antagonists in the environment, to the intentional release of control agents (Eilenberg et al 2001). Antagonists such as entomopathogenic fungi are generally accepted as a safer alternative to chemical insecticides, direct and indirect ecological effects on non-target organisms are common and need to be considered in risk assessment of any control measure (Flexner et al 1986; Cory and Myers 2000; Goettel and Hajek 2000; Shah and Pell 2003). Negative effects on beneficial and other non-target arthropods were for example shown for entomopathogenic fungi from the genera Metarhizium and Beauveria (Vestergaard et al 2003)

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Conclusion