Biological Control ofBotrytis cinereaPers. ex Fr. in Strawberry byPaenibacillus polymyxa(Isolate 18191)

Isolate 18191, obtained from mature strawberry fruit and determined asPaenibacillus polymyxahas shown an antagonistic potential againstBotrytis cinerea, the causal agent of grey mould in strawberries. Germ tube growth of conidia ofB. cinereawas strongly inhibited by the culture suspension of the antagonist in aqueous strawberry fruit pulp suspension (1%) but germination rate of conidia was not affected. The application of the culture suspension and the washed cells on detached strawberry leaf discs reduced conidiophore density ofB. cinereaby 67 and 84%, respectively. The treatment of detached leaf discs with culture suspensions of different cell densities (1 × 106, 1 × 107, 1 × 108) showed that the lowest density already reduced incidence ofB. cinereaby 68% after 8 days incubation period. Investigating the influence of the temperature on the effectiveness ofP. polymyxait was observed that the antagonist was highly effective already at 10°C and reduced incidence and conidiophore density ofB. cinereaby 53 and 58%, respectively. In 3‐year field trials the effectiveness ofP. polymyxawas in a range of 24–36% as compared to the water control.