This plant disease is caused by a fungus (Colletotrichum coccodes) that rots ripe tomatoes. Green tomato fruit is also attacked, but the spots don't appear until the fruit ripens. Infected fruit is inedible. Anthracnose is most common on overripe fruit and fruit close to the ground. Fruit on plants partially defoliated by leaf spot diseases is also prone to infection. The leaves may be infected, but are usually not severely damaged. The fungus is most active in wet weather with a temperature range of 60° to 90°F, and when infection is severe fruit is damaged in a short period of time. Infections frequently become epidemic in hot, rainy weather. Water from heavy dew, overhead watering, and frequent abundant rain provides the moisture necessary for infection.
Spray tomato plants at the first sign of the disease with a fungicide containing chlorothalonil. Repeat at intervals of 7 to 10 days until harvest. Destroy all infected fruit. Pick tomatoes as they mature and use promptly. To reduce the spread of the disease, do not work around wet plants. Clean up and destroy plant debris after harvest.
Plant Care for Tomatoes