POSTHARVEST DECAY OF WINTER PEAR AND APPLE FRUIT CAUSED BY SPECIES OFPENICILLIUM

In surveys conducted during two fruit packing seasons, P. expansum and P. solitum were recovered most frequently (65 and 96% of collections, respectively, in 1990-91, and 77 and 54% of collections, respectively , in 1991-92) and in highest densities (1,893 cfu/ml and 749 cfu/ml, r espectively, in 1990-91, and 308 cfu/ml and 667 cfu/ml, respectively, in 1991-92) from pear and apple dump tank water. Penicillium solitum w as collected most frequently (89% of collections) and in greatest conc entrations (1,634 cfu/ml) from drench solutions followed by P. expansu m and P. commune (47 and 42% of collections, respectively, and 495 cfu /ml and 249 cfu/ml, respectively). Penicillium expansum was recovered from about 27% of field bins sampled while P. solitum and P. commune w ere recovered from about 10 and 8%, respectively. Penicillium expansum and P. solitum were the Penicillium spp, most frequently recovered fr om fruit sampled from packinghouses and markets. Pear fruit were treat ed with 2 X 10(2) conidia per milliter of P, expansum in challenge ino culations 0, 1, 7, or 28 days following initial treatment with 2 X 10( 3) conidia per milliter of either P. solitum or P. commune to determin e the competitive ability of P. expansum relative to these species. Wh en incubated at 20 C for 7 days immediately following the challenge in oculation, P, expansum became established in wounds 0, 1, or 7 days fo llowing initial treatment with P. solitum and in water controls. Penic illium expansum did not become established in wounds challenged 28 day s after initial treatments or in wounds challenged 7 days after initia l treatment with P. commune. Incidence of infection by P. expansum fol lowing challenge inoculations 28 days after initial treatment with P. solitum was greater than in water controls when fruit were incubated a t -1 C for 28 days followed by a ripening period of 7 days at 20 C. In cidence of infection by P. expansum generally decreased with increasin g periods of time at which fruit were inoculated following initial wou nding. Of 12 Penicillium spp, tested, only P, aurantiogriseum, P, comm une, P. crustosum, P. expansum, P. griseofulvum, and P. solitum produc ed lesions in wounds of newly harvested, mature pear fruit (cv. d'Anjo u).