A localized calcium (Ca) deficiency in the distal end of the fruit results in blossom-end rot. It begins with light tan, water-soaked lesions at the blossom end of the fruit. As the disease progresses, these lesions enlarge and turn black and leathery. Sunscald on tomato fruit. This physiological disorder occurs when fruit are exposed to direct sunlight during periods of increased temperatures. Image courtesy of Clemson University - USDA Cooperative Extension. Blossom-end rot on tomato fruit - closer view. Secondary pathogens can often be found on the fruit affected with blossom-end rot. However, this disorder is of a physiological nature and does not spread from plant to plant.

Tomatoes affected by blossom-end rot grow slowly and ripen prematurely. Symptoms may occur at any stage in the development of the fruit. Usually, the first symptoms are visible when the fruit is one-third to one-half full size. Advanced stage of sunscald on tomato. This is very common on green fruit. Image courtesy of Clemson University - USDA Cooperative Extension.