Sunscald occurs on tomatoes when they are exposed to the direct rays of the sun during hot weather. It is most common on green fruit, but ripening fruit is also susceptible. It is most prevalent on varieties with sparse foliage and on staked plants that have lost their foliage because of leaf diseases, such as early blight, late blight, or septoria leaf spot, fusarium wilt (see Fusarium Wilt), verticillium wilt, or leaf roll. Fruit on plants that have been pruned to hasten ripening are also subject to sunscald. Tomatoes are still edible if the sunscalded area is removed. Rot fungi frequently invade the damaged tissue, resulting in moldy and inedible fruit.
Cover exposed fruit with straw or other light material to protect it from the sun's rays. Do not prune leaves to hasten ripening. Control leaf diseases. Grow verticillium and fusarium wilt-resistant varieties (for a list, see Disease Resistance of Tomatoes).