Southern Ag STOP Blossom-End Rot of Tomatoes corrects calcium deficiency and stops blossom end rot on tomatoes and other vegetables. You can always tell blossom end rot (BER) by the darkened sunken area at the end of the fruit. The affected area could be rather small or take up almost half of the fruit. Southern Ag STOP Blossom-End Rot of Tomatoes tackles the root cause of blossom end rot and quickly supplies the calcium needed to stop blossom end rot.