The fruit on my zucchini squash begin to grow, but quickly turn brown and rot. Why

FAQ
Question: 

The fruit on my zucchini squash begin to grow, but quickly turn brown and rot. Why

Answer: 

The rotting of the small squash fruits could be due to poor pollination or blossom-end rot. 

For squash fruit to develop fully, bees and other pollinators must transport pollen from the male flowers to the female flowers.  If the female flowers aren’t pollinated properly, the fruit will begin to grow and then suddenly shrivel up and die.  Bees and other pollinators are less active in rainy weather.  Rainy weather could be responsible for poor pollination and rotting of the small fruits.  Drier weather conditions should increase pollinator activity. 

Blossom-end rot is a physiological disorder that occurs on tomatoes, peppers, eggplant,  and summer squash.  On zucchini and other summer squash, the blossom end of the fruit begins to rot and within a short time the entire fruit has rotted.  Blossom-end rot is caused by a lack of calcium in the developing fruit.  In most cases, there is no need to apply calcium to the soil.  Try to maintain an even moisture supply by watering once a week during dry weather.  Also, do not over-fertilize plants.  Uneven moisture supplies and excessive nitrogen inhibit calcium uptake. 
  

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