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Thielaviopsis basicola: A Component of the Pea Root Rot Complex in New York State. M. C. Blume, New York State University College of Environmental Science and Forestry, Syracuse, 13210, Present address: Department of Plant Pathology, New York State Agricultural Experiment Station, Geneva, 14456; G. E. Harman, Department of Seed and Vegetable Sciences, New York State Agricultural Experiment Station, Geneva, 14456. Phytopathology 69:785-788. Accepted for publication 30 January 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-785.

Thielaviopsis basicola, previously unreported as a pathogen of peas in New York, was present in tissue of pea plants from 12 of 14 fields sampled near Mount Morris and Auburn in 1976 and 1977. Fusarium solani, Aphanomyces euteiches, Pythium spp., and Rhizoctonia solani also were found in diseased pea tissue in 14, 7, 14, and 2 fields, respectively. Average soil populations of T. basicola in the Mount Morris area ranged from 1,800 to 4,000 propagules per gram of oven-dry soil. The number of plants infected and root-rot severity increased consistently in five locations evaluated three times in a 4-wk period during the growing season. All isolates of T. basicola tested were pathogenic, but differed in virulence. In soils from Mount Morris that contained T. basicola, addition of benomyl or a benomyl-Dexon combination effectively controlled root rot, but Dexon alone was ineffective. In contrast, in soil from Auburn that lacked T. basicola, Dexon alone or a Dexon-benomyl combination controlled root rot, but benomyl alone was ineffective. The addition of T. basicola to Dexon-treated Mount Morris soil resulted in pea plants of less weight than the control. The addition of this pathogen to Dexon-treated or nontreated Auburn soil resulted in severe black root rot. Peas planted in a sandy loam infested with T. basicola and F. solani f. sp. pisi developed a black cortical rot similar to that found in plants grown in the Mount Morris soil. It was concluded that in some New York fields, T. basicola has become an important component of the fungal complex that causes pea root rot.

Additional keywords: Pisum sativum.