Do you see a coating that looks like powdered sugar on your zucchini leaves? Well, don’t lick it.
You most likely have powdery mildew. Get rid of it before it kills your plant and infects other plants in your garden.
When powdery mildew shows up, I spray my zucchini every couple of days this concoction: a gallon of water, a tablespoon of baking soda and a squirt of dishwashing soap. The soap acts as a binding agent. I just mix the solution, pour it into my hose-end sprayer and spray my zucchini plants thoroughly.
To discourage the growth of powdery mildew, avoid overhead watering and, when you do water, do it early in the day so any drops that end up on the plant evaporate by nightfall.
Zucchini is destined to attract powdery mildew as it matures. One way to deal with the issue is to plant a second zucchini plant elsewhere in the garden a few weeks after planting the first zucchini plant. So when the first plant starts mildewing, the second plant likely won’t have reached that phase yet.