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Ecology and Epidemiology

Epidemiology of the Perfect Stage of Glomerella cingulata on Apples. T. B. Sutton, Department of Plant Pathology, North Carolina State University, Raleigh 27650; W. W. Shane, Department of Plant Pathology, University of Minnesota, St. Paul 55121. Phytopathology 73:1179-1183. Accepted for publication 24 March 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1179.

Perithecial isolates of Glomerella cingulata grew more rapidly than chromogenic isolates at 28 and 32 C, induced more rot in wound-inoculated fruit, and were equally pathogenic when fruit were inoculated with a spore suspension. Perithecial and chromogenic isolates of G. cingulata produced conidia on potato-dextrose agar (PDA) from 8 to 32 C; from 24 to 28 C was the optimum range. Chromogenic isolates generally produced more conidia on PDA; however, one perithecial isolate produced conidia copiously. Ascospores, produced in perithecia in dead wood, were released during rainfall and were dispersed in the air. Ascospores were usually trapped within 2- 3 hr after rainfall began. After the rainfall ended, ascospores often continued to be trapped until the relative humidity dropped and branches began to dry. Ascospore dispersal in rainwater was not an important dispersal mechanism. Airborne ascospores were trapped throughout the apple-growing season, indicating the potential for early season epidemic development. An extensive epidemic, initiated by airborne ascospores, was monitored in one orchard in 1979.

Additional keywords: bitter rot, Colletotrichum gloeosporioides.