Use of honeybees (Apis mellifera) to protect strawberry from grey mould (Botrytis cinerea)

Summary

BICOPOLL is a CORE Organic II European project on protecting strawberries from its most important disease, the grey mould (Botrytis cinerea). Protective spores of fungi Gliocladium catenulatum in Prestop® Mix (PM) are delivered to the flowers of strawberry by honeybees. We assessed effectiveness of honeybees as vectors under field conditions. Flower visits of bees, and fruit yield were monitored and departing and returning bees and strawberry flowers were sampled. Bees visited strawberry flowers the whole flowering period, but more abundant were in warm weather and in the afternoon. The quantity of spores on honeybees was determined by plating on media and a new method, qPCR that we have developed specifically for the protective fungi. The highest number of spores on bees was determined directly after administration of PM followed by a steady decline during the day until stabilization at a low number. The spores could also be detected in returning bees at a relatively constant low number. PM increased proportion of healthy berries for approximately 50 %. Results of first field experiment in Slovenia confirmed effectiveness of bees as vector of PM. We suggest some changes in application of PM.