Isolation of microbial antagonists for biocontrol of grey mould disease of strawberries

A screening programme is described for the assessment of the potential of biocontrol agents to control grey mould of strawberries caused by Botrytis cinerea. Bacteria were isolated from strawberry fruits, leaves and flowers from a commercial field site and screened for antagonism towards B. cinerea using two vitro and one in vivo screening techniques. From 559 microorganisms isolated, 108 inhibited pathogen growth on agar plates and 27 of these prevented spore germination on Cellophane membranes. The ability of these 27 isolates to inhibit infection of young strawberry leaves by B. cinerea on whole plants under glass was then tested. Seven isolates reduced grey mould development and were subsequently assessed in a field trial. Two isolates, one of Bacillus pumilus and one of Pseudomonas fluorescens, were as effective or more effective than standard dichlofluanid sprays and may therefore be of potential value as antagonists of B. cinerea.