INTEGRATION OF CULTURAL METHODS WITH YEAST TREATMENT FOR CONTROL OF POSTHARVEST FRUIT DECAY IN PEAR

Pear fruit from trees managed for high or low fruit nitrogen and calcium content were harvested either early or late in the normal maturity range, wounded, and then treated with either water or yeast suspensions (Cryptococcus laurentii, C flavus, or C laurentii + one-tenth the label rate of thiabendazole [Mertect 340F]). Prior to storage, wounds were inoculated with spore suspensions of Penicillium expansum, causal agent of blue mold, or Phialophora malorum, causal agent of side rot. Fruit were stored 2-3 mo in air or controlled atmosphere (2% O2, 0.6% CO2) at 0 C. Early harvest, low fruit N, high fruit Ca,yeast or yeast + fungicide treatment, and controlled atmosphere storage all reduced severity of blue mold and side rot. When optimum levels of each treatment were combined, blue mold severity was reduced by about 95% in 1991, 61% in 1992, and 98% in 1993. In 1991, side rot was completely controlled in all treatments that included C laurentii + early harvest or C. laurentii + high fruit Ca. In 1992, no side rot developed when treatments included C laurentii + early harvest + high fruit Ca. Without yeast treatment, the combination of early harvest, low fruit N, and high fruit Ca-in air storage reduced severity of blue mold by 64% and reduced side rot by 97% in 1991. More disease developed in pears treated with C flavus than in those treated with C laurentii.