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Etiology

Etiology of Necrotic Flecks on Dendrobium Blossoms. J. Y. Uchida, Research associate, Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu, 96822; M. Aragaki, plant pathologist, Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu, 96822. Phytopathology 69:1115-1117. Accepted for publication 24 April 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1115.

Dark necrotic flecks are common on field-cultivated Dendrobium flowers in Hawaii and are a significant factor in quality reduction. Microscopic examinations revealed one or more amerospores, dictyospores, or phragmospores near the center of 41.7% of the flecks. Among the many fungi isolated from the flecks, only Botrytis cinerea, Alternaria alternata, Bipolaris setariae, B. urochloae, B. sorokiniana, Exserohilum rostratum, and Stemphylium sp. incited flecks by artificial inoculation. A. alternata was the most frequently isolated organism. The recovery rate of A. alternata from flecks was 40.5% 3 days and 4.1% 6 days after laboratory inoculation. The low isolation rate of fungi from field-collected flecks and the rapid loss of viability of A. alternata after artificial inoculation are consistent with the proposition that flecks are predominantly aborted infections.