Host: flue-cured tobacco (Nicotiana tabacum (flue-cured type)
Description: This fungal disease appears first on the older leaves as circular, brown spots (1/4 to 1 1/4 inches in diameter) with sharply defined margins. Concentric circles (rings) are often noticeable within the spots. As the leaves approach maturity, a yellowish "halo" of varying width often forms around the lesion. Lesions may merge, forming large areas of dead tissue. During humid weather, sporulation of the fungus may be abundant, giving the lesions a black, dusty appearance. Brown spot is most severe as the plant approaches maturity, and the disease progresses from the lower to the upper leaves. Disease severity depends much on the weather, the overall health of the plant, varietal tolerance, and harvest rate.
Image type: Laboratory
Image location: United States
Name: R.J. Reynolds Tobacco Company Slide Set
Organization: R.J. Reynolds Tobacco Company
Country: United States