Biological Control of Postharvest Diseases of Apple and Pear under Semi-commercial and Commercial Conditions Using Three Saprophytic Yeasts

The yeasts Cryptococcus laurentii (strain HRA5), Cryptococcus infirmominiatus (strain YY6), and Rhodotorula glutinis (strain HRB6) were tested as biocontrol agents of postharvest diseases of apple and pear in semi-commercial and commercial trials. The yeasts effectively controlled decay when applied in a drench or line spray. The yeasts were not adversely affected when treated fruits were stored in a controlled atmosphere consisting of 1% oxygen and 99% nitrogen. In a commercial trial, the most effective treatments for control of blue mold of pear were a combination of C. laurentii and C. infirmo-miniatus (91% control) and the commercially recommended high rate (528 μg/ml) of thiabendazole (88% control). In the commercial apple trial, the most effective treatments for blue mold were C. infirmo-miniatus combined with 264 μg/ml thiabendazole (91% control), C. infirmo-miniatus combined with C. laurentii (84% control), and thiabendazole alone at 528 μg/ml (79% control). The combination of C. laurentii with 264 μg/ml of thiabendazole was significantly more effective for control of blue mold on pear than thiabendazole at 528 μg/ml whenever any thiabendazole-resistant spores were present in the inoculum.