Inoculum Densities of Thielaviopsis basicola in Tobacco Fields and the Role of Black Root Rot in Tobacco Stunting in Virginia

Abstract

Inoculum densities of Thielaviopsis basicola in 1984 were 74-166 propagules per gram of soil in five burley tobacco fields and 0-12 propagules per gram of soil in three other burley fields. Inoculum densities of T. basicola were 0-26 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.