Bonide Rot-Stop Tomato Blossom End Rot helps to correct a disorder in plants caused by a lack of calcium. Blossom end rot is visible on the end of the fruit as a sunken brown spot opposite the stem. Use Bonide Rot-Stop Tomato Blossom End Rot to provide the nutritional calcium needed for developing fruit or after periods of heavy rain. Bonide Rot-Stop Tomato Blossom End Rot can be used on tomatoes, peppers, melons, cucumbers, and other listed vegetables.