southern blight of tomato
Figure 1. Southern blight can be recognized by the small sclerotia at the base of the stem. These lesions will eventually result in the wilting of the plant. 
Figure 2. Close up of southern blight of tomato lesions. Sclerotia become darker as they age. Red arrow indicates sclerotia. 
Figure 3. Southern blight of tomato. 
Figure 4. Base of plant with southern blight of tomato. Note sclerotia.