Postharvest biological control of blue mold of apple and brown rot of sweet cherry by natural saprophytic yeasts alone or in combination with low doses of fungicides

Six yeast strains isolated from the surface of pear fruits were evaluated for their ability to control postharvest blue mold (caused by Penicillium expansum) on Golden Delicious apple fruits. All strains significantly reduced blue mold incidence and severity when applied simultaneously with the pathogen. Cryptococcus infirmo-miniatus strain YY6 and Cryptococcus laurentii strain HRA5 were the most effective, and populations in apple wounds increased approximately 1.2 log units within 10 days at 0 degrees C and approximately 1.4 log units in 2 days at 5, 10, or 20 degrees C. Control of blue mold by these two yeasts alone or in combination with a low dose of thiabendazole (15 mu g/ml) was tested at 5, 10, and 20 degrees C. Yeasts combined with thiabendazole controlled the disease significantly better at all temperatures (except at 10 degrees C during 1994) than the low dose of thiabendazole alone, and the control was comparable to that achieved using a commercially recommended high dose of thiabendazole (525 mu g/ml). C. infirmominiatus controlled disease incidence better than C. laurentii at 5, 10, and 20 degrees C during 1993 and 1994. On sweet cherry, C. infirmo-miniatus or C. Laurentii combined with a low dose (20 mu g/ml) of iprodione controlled brown rot caused by Monilinia fructicola as did a high dose (1175 mu g/ml) of iprodione. (C) 1996 Academic Press, Inc.