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Epidemiology and Control of Bean White Mold. J. J. Natti, Department of Plant Pathology, New York State Agricultural Experiment Station, Geneva 14456; Phytopathology 61:669-674. Accepted for publication 15 January 1971. DOI: 10.1094/Phyto-61-669.

Epidemics of white mold occurred 8 to 14 days after full bloom in snapbean plantings irrespective of planting dates and environmental conditions during the blossom period. First infections usually occurred in the axils of lower branches at the site of lodgment of cast bean blossoms, and were caused by mycelium that emerged from blossoms in which the causal fungus, Sclerotinia sclerotiorum, was established. Subsequent spread occurred by in situ contact of healthy with infected tissues, and by distribution of infected plant parts by various agents. Direct invasion of healthy growing bean tissues by the primary infectious agent was not observed. Senescent and dead blossoms invaded by the fungus thus are essential intermediaries in disease development. Foliage sprays with benomyl applied a few days before full bloom provided effective control, whereas sprays applied after full bloom did not. Effectiveness of benomyl was attributed to its systemic translocation into developing bean buds and blossoms, and to retention of its fungicidal activity in senescent and dead blossoms.

Additional keywords: Phaseolus vulgaris, Botran, Thiabendazole, Botrytis cinerea, gray mold.