Photographer:

R.J. Reynolds Tobacco Company

Symptoms

Description:

Uneven growth of tobacco in the field is indicative of black root rot. Affected plants often become yellowed and are smaller than neighboring healthy plants. Stunting is more evident during the early part of the growing season and during cool, wet seasons. On hot days, leaves of the diseased plants wilt more rapidly than those of healthy plants, but recover during the night. Plants usually grow out of the problem as soil temperatures rise, unless the variety is highly susceptible to the fungus and cool, wet soil conditions prevail. the most distinctive symptoms of black root rot occur on the roots. The entire root system is greatly reduced with smaller roots exhibiting a typical brown to black discoloration of their tips, and larger roots having brown or black spots on their surface. The outer root tissue may slough easily.

Laboratory

Host:

burley tobacco (Nicotiana tabacum (burley type) L.)