Photo and text used courtesy Clemson University
Cooperative Extension Service.

Distinguishing sign is white mold, often with "seed-like" sclerotia, present on infected stem near soil line. This fungus also causes rot of tomato and other plant parts in contact with soil. The fungus lives in the soil for many years. It causes wilting and dying of many different kinds of plants.

Southern blight is more common in the South in hot summer months. Tomato varieties have poor resistance to this disease.