Evaluation of microbial antagonists for biological control of Botrytis cinerea stem infection in cucumber and tomato

Of fifteen isolates of yeasts, filamentous fungi and bacteria and a commercial product, tested in a bioassay with stem segments, eleven isolates consistently reduced incidence of disease and sporulation of Botrytis cinerea Pers; Fr in tomato and seven isolates in cucumber. Several isolates reduced disease by more than 75% in all experiments. Six antagonists that performed well in the bioassays and that were fairly easy to produce in vitro, were selected for further testing in two glasshouse experiments with cucumbers. After application of spores of B. cinerea and the antagonists or the fungicide tolylfluanid to pruning wounds, disease incidence was reduced by 50-100% by all antagonists in both experiments and only in one experiment by tolylfluanid. For Trichoderma harzianum T39, Aureobasidium pullulans and Cryptococcus albidus, biological control efficacy in bioassays with cucumber stem segments was not strongly influenced by temperatures in the range between 18 and 30 degrees C, but at 24 degrees C the efficacy of the three antagonists strongly decreased at relative humidities of 90% and 80% (vapour pressure deficits 0.299 and 0.598 kPa, respectively) compared to 100%.