Mycoflora of Stone Fruit Mummies in California Orchards

Abstract

Stone fruit mummies infected by Monilinia fructicola were periodically collected in winter from trees and from the ground in eight orchards in 1995-96 and from five orchards in 1996-97. Mycoflora were determined by spreading mummy washings and plating inner tissues onto petri dishes containing acidified potato dextrose agar, then counting colonies of individual fungi after incubation at 23°C for 4 days. Twenty genera, representing 29 fungal species, were isolated from both mummy washings and inner tissues. Aspergillus japonicus, A. terreus, and species of Harknesia, Paecilomyces, and Trichoderma are the first recorded from species of Prunus in the United States, and Aureobasidium pullulans and Epicoccum purpurascens are the first reported for California. The principal mycoflora recovered from mummy washings were species of non-filamentous yeasts (32.1%), Penicillium (28.8%), Cladosporium (11.4%), and Mucor (10.8%). Major mycoflora of mummy inner tissues were species of Penicillium (23.7%), Mucor (19.6%), Cladosporium (17.3%), and Rhizopus (11.1%). The relative recoveries of individual fungi from mummy inner tissues differed with location, Prunus species, and sampling position (tree or ground), and changed as the season progressed. The relative recovery of M. fructicola from mummy inner tissues was negatively correlated with Botrytis (R = -0.53, P = 0.0052), Penicillium (R = -0.58, P = 0.0681), and Rhizopus (R = -0.50, P = 0.0696). These results could help obtain naturally occurring antagonists and maximize their use in biocontrol systems aimed at reducing primary inoculum for blossom blight of stone fruits in California orchards.