The Use of Hoverflies as Multi -Tool for Pollination and Biological Control of Aphids and Grey Mould

Abstract: The ascomycete Botrytis cinerea is a major pathogen in strawberry (Fragaria x ananassa) and causes enormous fruit losses if not controlled. In biological control, microbes such as the yeast Metschnikowia fructicola are sprayed on the flowering crops to alleviate the infestation. Besides spraying, biological control agents can be applied by entomovectoring which is established for bumble or honey bees. In this study, the aphidophagous hoverfly species Eupeodes corollae was tested as a vector for M. fructicola. First, the antagonistic effect of M. fructicola to B. cinerea was evaluated in a dual culture test. Then, the capacity of adult E. corollae to vector M. fructicola cells was examined In vitro and In vivo towards strawberry flowers. The efficiency of yeast dispersal was compared to spray application of M. fructicola on the flower. The final aim was to survey whether the application of M. fructicola by fly-vectoring on flowers decreased B. cinerea severity on developing fruits in comparison to spray application of M. fructicola. The results showed an inhibitory effect of M. fructicola (UDA 10) on B. cinerea (B05.10) in a dual culture. In vitro, the yeast was vectored by E. corollae. In vivo, E. corollae vectored M. fructicola cells to the flowers. In a small-scaled preliminary experiment, yeast cells vectored by hoverflies to the flower could not reduce the grey mould severity on later strawberry fruits kept in cold storage. This was the first attempt to explore the potential of the hoverfly species for the entomovector technology. Further research is needed to survey if E. corollae can complement existing entomovectoring systems, and if the hoverfly-vectoring can be an alternative to spray application of fungicides. Confirmation that E. corollae is an efficient vector of yeast to suppress grey mould, the hoverfly species could be used as a multitool in strawberry production combining biological control of aphids, grey mould, as well as pollination services.