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Growth of Sclerotinia minor on Media Containing Chlorothalonil and Benomyl. D. M. Porter, Plant Pathologist, U.S. Department of Agriculture, Science and Education Administration, Agricultural Research, Suffolk, VA 23437. R. K. Lankow, Senior Research Biologist, Diamond Shamrock Corporation, T. R. Evans Research Center, Painesville, OH 44077. Plant Dis. 65:591-594. . This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/PD-65-591.

Radial growth of Sclerotinia minor was strongly inhibited on potato-dextrose agar containing benomyl at 12 µg/ml. This sensitivity of S. minor to benomyl was not affected by the physiologic age of mycelium when transferred to amended media. Radial growth was inhibited on media containing chlorothalonil at 0.5128 µg/ml, but sectors of rapidly growing mycelium developed at irregular points on the periphery of colonies. Inhibition of radial growth on media amended with chlorothalonil was directly related to physiologic age of mycelium at time of transfer. Growth was inhibited when mycelium was transferred from colonies of S. minor that had begun to differentiate sclerotia, but growth was not inhibited when mycelium was transferred from colonies that had not begun to differentiate sclerotia. The insensitivity of vegetative mycelium of S. minor to chlorothalonil may help to explain the increased severity of Sclerotinia blight in peanuts treated with this fungicide.