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Ecology and Epidemiology

Production and Dispersal of Ascospores and Conidia by Physalospora obtusa and Botryosphaeria dothidea in Apple Orchards. T. B. Sutton, Assistant professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650; Phytopathology 71:584-589. Accepted for publication 4 November 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-584.

Ascospores and conidia of Physalospora obtusa and Botryosphaeria dothidea were produced from naturally colonized apple prunings throughout the apple growing season. Conidia of both fungi were primarily dispersed in rainwater; ascospores were airborne and waterborne. Ascospores of P. obtusa were detected in greatest numbers during April and May. Conidia of P. obtusa and ascospores and conidia of B. dothidea were most abundant in May and June. Amount and duration of rainfall were the most important factors in waterborne dispersal of ascospores and conidia. Current-season prunings were rapidly colonized by B. dothidea and P. obtusa. Ascospores and conidia produced in fruiting bodies in these prunings could have caused fruit infections during the same growing season. Management programs for B. dothidea and P. obtusa may be developed based on sanitation to reduce inoculum levels, a knowledge of factors favoring infection, and fruit susceptibility during the season.

Additional keywords: black rot, Malus sylvestris, white rot.