Secondary organisms invade the affected tissue and cause the fruit to rot. Blossom-end rot is a physiological disorder caused by lack of calcium in the developing fruit. Wide fluctuations in soil moisture levels impair calcium uptake by the root system. Excessive nitrogen fertilization may also contribute to blossom-end rot. Avoid overfertilizing with nitrogen.
Initial symptoms are shiny white or yellow areas on the sides of the fruit exposed to the sun.
Later, the affected tissue dries out and collapses, forming slightly sunken, wrinkled areas. Secondary organisms invade the affected areas causing the fruit to rot. Sunscald occurs on fruit exposed to the sun during periods of extreme heat. Growing tomatoes in wire cages will provide more foliage cover to better protect the fruit from direct sunlight. Controlling diseases on the foliage will prevent defoliation of the plants and exposure of the fruit to direct sunlight.