Blossom-End Rot in Tomatoes: Causes and Prevention
Channel: Alabama Extension
Date: 2021-07-12

Tomato growers must take care to avoid blossom-end rot (BER), a disorder that can dramatically reduce fruit quality and quantity. By using a few simple irrigation and fertilization practices, damage from BER can be prevented or reduced.
Blossom-end rot is a physiological disorder or an abiotic disease (caused by drought, freezing, and other stressors). It is not a disease caused by fungi, bacteria, or other pathogens.

Blossom-end rot is easily identified as a brown, leathery rot developing on or near the blossom end of the tomato. It starts with a dry, brown lesion the size of a dime and generally increases in diameter as the condition worsens. In time, lesions often become covered with a secondary black mold. There is also a condition called internal blossom-end rot in which symptoms develop on the sides of the fruit or internally. You might not see the damage until you cut into the fruit.

For more information visit: https://www.aces.edu/blog/topics/lawn-garden/blossom-end-rot-in-tomatoes-causes-and-prevention/