Root Rot
Agent: Fusarium oxysporum
Symptoms
Common in tomato gardens. Thrives in warm, acidic soils. Infects the plant through the roots, spreads through the circulatory system. The first symptom is yellowing of the lower leaves; dark brown spots are found when the stem is cut. Can affect potatoes, peppers, eggplants.
Control and prevention
Remove affected plants. Prevention: avoid acidic, too warm soils, resistant varieties, crop rotation (do not plant in the same spot for 3 years).
Related problems
Similar symptoms might indicate a different cause — compare them.
Early blight and black fruit rot
Alternaria solani
Usually appears when fruits begin to set. First affects the lower leaves, then the stem and fruits. Large brown or black spots with concentric rings appear on them. Around the spot, the leaf begins to yellow and dies. It also attacks potatoes and eggplants. The fungus is resistant and persists for several years.
Verticillium Wilt
Verticillium albo-atrum / Verticillium dahliae
Symptoms are very similar to root rot, the difference is that this fungus prefers cooler, neutral pH soils. Brown spots may also appear on the leaves in addition to yellowing.
Mold
Symptoms caused by various fungi. Mold only survives in high humidity.