See:
Squash (Cucurbita spp.) -Blossom-end Rot
Cause Lack of pollen or inactive pollen.
Symptoms Fruit fail to enlarge and can turn brown from the blossom end. Blossoms fall off. Often, part of the fruit develops normally but the rest does not, resulting in bottle- or dumbbell-shape fruit. Inside, seeds look normal in the enlarged area but are poor or missing in the underdeveloped area.
Cultural control
- Provide at least one beehive per acre. Sometimes, waiting for warm weather increases pollination.
- Place bee hives in groups around the field perimeter, not just in one location.
- Make sure bees are active before plants bloom.
- Some varieties need a pollinator variety; others produce an adequate number of male flowers.