Figure 1.

Figure 2.

Symptoms begin as small, depressed lesions that are circular in shape. Lesions enlarge and become more sunken (figure 1.). If you were observant and caught these symptoms early, you could slice the lesion off and observe that the flesh underneath was pale and the texture granular. As the lesion develops, target-like rings appear. As the lesion matures, the center turns tan and small black fruiting bodies appear (figure 2.). If the weather is wet, salmon-colored spores can be observed on the lesion surface. Lesions can coalesce if infection becomes severe. It is not uncommon for secondary pathogens, particularly bacteria, to invade and quickly render the fruit more inedible than it already appears to be. For this reason, infected fruit does not have an appreciable storage life and should be discarded.

If infections are particularly severe, fruit infections may serve as an inoculum source for stem, leaf and root infections. Foliar infections appear as small, round, brown lesions with yellow halos. Stem lesions may have small, black fruiting bodies in a concentric pattern. Root infections, although unusual, can occur. Symptoms appear as an overall root rot that occurs as the fruit ripens. Black fruiting bodies, like those on the fruit, can be found on any excavated roots. Secondary (feeder) roots are stunted or rotted. Diseased plants can be easily yanked from the soil due to the poor state of the root system.

Despite all this apparent destruction, Colletotrichum is considered a weak pathogen and can often be controlled through good cultural practices. The pathogen overwinters on infected plant debris, so it is very important to dispose of rotten fruit and infected plants. Do not compost! Because of the ability of this fungus to persist in the soil, tomatoes and other solanaceous crops, like peppers and eggplants, should be rotated on an every-other-year basis. Weed control is extremely important because of the broad host range of this fungus. Staking plants and mulching around them will help reduce losses due to this disease. Water plants at their base, as overhead watering splashes and spreads the fungus that causes this disease. Pick fruit promptly to prevent over-ripening.

Minimizing overhead watering, staking and mulching plants, and removing infected fruit will lessen or even prevent this problem next year. However, if this is a repeated problem in your garden, you may wish to consider the use of copper-based fungicides when fruit first develops.

P250T
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