Calcium deficiencies cause actively growing cells to die because they cannot retain water and nutrients. The spot may enlarge and become depressed as the fruit grows. The spot may turn from brown to black and become moldy. Blossom end rot can be distinguished from other rots by its confinement to the blossom end. Integrated Pest Management Strategies 1.
Plant cucurbits in a location that has well-drained soil.
Mulch the plants and water properly to maintain a uniform moisture level in the soil. Avoid damaging the root system when hoeing or weeding. Test the garden soil pH. Calcium may not be available to plants if the soil pH is too low or high. Limit the use of high ammonia fertilizers and fresh manure that may stimulate lush growth and add more salts to the soil.