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Inoculum Densities of Thielaviopsis basicola in Tobacco Fields and the Role of Black Root Rot in Tobacco Stunting in Virginia. L. P. Specht, Former Graduate Research Assistant, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. G. J. Griffin, J. J. Reilly, and D. A. Komm. Professor of Plant Pathology, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061; and Former Assistant Professors of Plant Pathology, Southern Piedmont Agricultural Experiment Station, Virginia Polytechnic Institute and State University, Blackstone 23824. Plant Dis. 71:876-879. Accepted for publication 5 February 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0876.

Inoculum densities of Thielaviopsis basicola in 1984 were 74166 propagules per gram of soil in five burley tobacco fields and 012 propagules per gram of soil in three other burley fields. Inoculum densities of T. basicola were 026 propagules per gram of soil in 12 flue-cured and two sun-cured tobacco fields and 101 and 402 propagules per gram of soil in two other flue-cured fields. Environmental factors and cultivar resistance apparently influenced disease development, because inoculum density was not necessarily related to the severity of black root rot among the fields examined. Black root rot was the primary disease associated with tobacco stunting in the burley region of Virginia. Black root rot also occurred in the flue- and sun-cured region but was not generally a significant problem there.

Keyword(s): Acaulospora spp., Glomus clarum.