Stop tomato blossom-end rot with ferti-lome Yield Booster in a ready-to-use spray. Yield Booster helps stop and prevent blossom-end rot caused by calcium deficiency. Blossom-end rot is characterized by a dark, sunken area at the blossom end (bottom) of tomatoes. Yield Booster can also be used on tomatoes and other plants to correct other calcium deficiencies and produce larger, firmer fruits. Apply to foliage and growing fruit every 7 to 10 days as needed. Active ingredient: calcium. Concentrated 16 fluid oz. bottle.