SUSCEPTIBILITY OF SPOTTED WING DROSOPHILA (Drosophila suzukii (Matsumura, 1931)) PUPAE TO ENTOMOPATHOGENIC FUNGI

Abstract

Spotted wing drosophila (Drosophila suzukii (Matsumura, 1931), Diptera, Drosophilidae) management is difficult mainly because of its short generation time, polyphagy and serrated ovipositor, but also because its larvae can pupate in the orchard soil and are thus protected from insecticide applications. We hypothesized that insect-pathogenic soil fungi could successfully infect Drosophila suzukii pupae in soil environment. We tested several entomopathogenic or soil fungi against pupae in a) conidia-spiked soil, b) via direct applications of conidia, and c) by dipping pupae into conidial suspensions. Metarhizium brunneum Petch strain H.J.S. 1154 significantly reduced fly emergence in conidia spiked soil and bioinsecticide Naturalis (based on entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill. in direct exposure tests. Our attempt to determine IC50 of pupal hatching rate by dipping D. suzukii pupae into conidial suspensions was unsuccessful. We conclude that the pupal stage is probably too brief to allow entomopathogens to cause a significant reduction of fly emergence. According to our results and published articles, the fungal biocontrol potential would probably best be evaluated in spray applications against adult flies.

Keywords

• biological control
• entomopathogenic fungi
• insect-pathogenic soil fungi
• insect
• organic
• pest