| Blossom-end rot, which begins with a small watery
bruise on the blossom end of the fruit, is the result
of a lack of calcium in developing fruits. This
calcium deficiency can be a result of slow growth,
damaged roots induced by extreme fluctuations in
the surrounding soil moisture content, an excess of
salts, or other fluctuating conditions during plant
growth. Calcium deficiencies cause actively growing
cells to die because they cannot retain water
and nutrients.
Symptoms and Diagnosis
Blossom-end rot begins as a water-soaked, sunken
spot on the blossom end (the end that isn't attached
to the stem) of the fruit. 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. It may
also be confused with rotting fruit that results from
the failure of female flowers to set fruit due to lack
of male flowers or pollinating insects.
Integrated Pest Management Strategies
1. Plant cucurbits in a location that has well-drained
soil.
2. Mulch the plants and water properly to maintain
a uniform moisture level in the soil. Avoid
damaging the root system when hoeing
or weeding.
3. Test the garden soil pH. Calcium may not be
available to plants if the soil pH is too low
or high.
4. Limit the use of high ammonia fertilizers and
fresh manure that may stimulate lush growth and
add more salts to the soil.
5. Add calcium nitrate to soil or spray with 1%
calcium chloride in order to boost the amount of
calcium available to developing fruit.
6. Cucurbits in containers. For cucurbits grown in containers, apply a fertilizer that contains micronutrients including calcium. Many fertilizers formulated for tomatoes meet these specifications. | 
