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Development of Apple Scab on Fruit in the Orchard and During Cold Storage. J. R. Tomerlin, Research Associate, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824. A. L. Jones, Professor, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824. Plant Dis. 67:147-150. Accepted for publication 16 June 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-147.

Apple fruits were increasingly difficult to infect with Venturia inaequalis (anamorph Spilocaea pomi) under orchard conditions as the fruits matured. Fruits of the cultivar McIntosh developed more lesions than those of Jonathan and Golden Delicious. Scab lesions expanded on McIntosh fruits held in cold storage at 0.5, 2.8 C or a cycle of 2.8 and 0.5 C. The rate of lesion expansion was inversely related to the number of lesions on the fruit. Few new lesions developed on fruits free of visible lesions when stored, but new lesions developed on 1847% of fruits that had visible lesions when stored. Scab-infected fruits stored at 2.8 C or a cycle of 2.8 and 0.5 C were more shriveled than fruits stored at 0.5 C. Shriveling was most severe on apples with numerous large lesions.