Tomato Diseases: Identification & Treatment

Identifying tomato diseases early is critical to saving your crop. Here are the most common diseases and how to treat them.

Early Blight

Dark spots with yellow halos on lower leaves. Caused by Alternaria solani fungus. Treat with copper fungicide, remove affected leaves.

Late Blight

Water-soaked spots on leaves turning brown. The disease that caused the Irish Potato Famine. Use copper fungicide preventively in wet weather. Remove and destroy affected plants.

Septoria Leaf Spot

Small circular spots with dark borders. Very common in humid climates. Treat with copper or chlorothalonil fungicide.

Fusarium/Verticillium Wilt

Yellowing and wilting on one side. Soil-borne fungus. No cure — use resistant varieties (V, F ratings).

Prevention

• Rotate crops every 3 years
• Water at soil level
• Space plants for airflow
• Mulch to prevent soil splash