Question
Each year my zucchini develop end rot (end turns yellow and fruit does not grow beyond a hew inches.

Answer
Mary:

This is most likely caused by a fungus that is in the soil. You can go to your local nursery and ask for a general fungucide and apply. At the end of the season turn the soil good and spray with a fungucide. Try to rotate your crop so that you don't have the fungus there.

Best wishes.

Don