Anthracnose, caused by the fungus Colletotrichum coccodes, is probably the most common fruit-attacking disease of tomato in Iowa. Symptoms first become visible on ripe or ripening fruit as small, circular, indented spots in the skin. As these spots expand, they develop dark centers or concentric rings of dark specks, which are the spore-producing bodies of the fungus.
In moist weather these bodies exude large numbers of spores, giving diseased areas a cream to salmonpink color. By this stage, decay has penetrated deeply into the tomato flesh. Spotted fruits often may rot completely because of attack by secondary fungi through anthracnose spots. Anthracnose appears most commonly on overripe fruits.
The fungus survives the winter on diseased tomato vines, in the soil, and in seeds. Weeks before the fruit ripens, anthracnose can become established on leaf spots caused by other fungi or by insect feeding injuries. Spores are spread largely by rain splash. Warm, wet weather causes the disease to spread and symptoms to develop.
While insect or other wounds facilitate infection, tomatoes can also become infected in the absence of wounds. Control measures for anthracnose are the same as for Septoria leaf spot. In addition, harvest at frequent intervals and pick all ripe fruit at each harvest