Blossom end rot occurs because the soil in your home vegetable garden is deficient in calcium. It also occurs when the weather in your area has been considerably wet followed by an immediate dry period.
Blossom end rot most notably affects peppers, squash, tomatoes and watermelon. As you can see in the picture, it looks like a dark circle and spreads to the end fruit as the vegetable will then look like it is rotting.
If not taken care of it could spread to the remaining of the unaffected portion of your garden and also lead to additional or secondary rotting.
Here are steps you can take to control blossom end rot in your home vegetable garden.