Control of sooty blotch and black rot of apple through removal of fruit mummies

Several popular apple cultivars retain their aborted fruits as mummies on the tree. In laboratory conditions, overwintered fruit mummies collected from a Northern German apple orchard under organic management released inoculum, which caused black rot due to Diplodia seriata and sooty blotch due to Peltaster cerophilus on ripe apples. In a field trial conducted over four years in another organic orchard, the manual removal of fruit mummies in winter and again in late June of each year significantly reduced the incidence of both these diseases. However, fruit mummy removal did not significantly affect the development of storage rots due to Neofabraea alba and N. perennans. The potential, limitations and costs of this phytosanitary measure are discussed in the context of organic apple production.

Mycoflora of Stone Fruit Mummies in California Orchards

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.

Springtime dispersal patterns of Monilinia laxa conidia in apricot, peach, prune, and almond trees

Numbers of airborne Monilinia laxa conidia were related to the maturity of the sporodochia, the nature of the host structure bearing them, and the presence or absence of rain or fog. Hirst spore traps collected more airborne conidia during rains and on rainy days than on dry days among prunaceous hosts during the spring of 1966 and 1967. Numbers of conidia were greatest (6440 m−3 h−1) in the first 3–4 h of rain, while in dry periods, numbers were greatest (1200 m−3 h−1) when ambient humidity was lowest and temperature and wind speeds were highest. Fruit mummies, twig cankers, limb cankers, pedicels, and peduncles all bore sporodochia. Rains washed off successive crops of conidia, and with 52 800 conidia cm−2 were collected directly below a sporulating peach fruit mummy. The significance of these dispersal periods in disease development and control is discussed.