What’s that White Stuff on My Zucchini?



When powdery mildew attacks your zucchini, it can decrease the plant’s production and even kill its host.

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.



Filed under Produce Dept.

4 responses to “What’s that White Stuff on My Zucchini?

  1. Thanks for the post! My yellow squash has had this for about a week and has now infected my armenian cucumbers. Ack! I will mix up this solution tomorrow morning and give it a spray. Thanks again!

    • You’re welcome, Marisa. Just remove the most infected leaves and then spray the remaining leaves diligently. Although the powdery mildew may not go away completely, you’ll keep it under control enough so that your plants don’t stop producing vegetables.

  2. Angie

    Thank you for your helpful post. My cucumbers started this powdery mildew and now my zucchini has it. I keep cutting off the worst leaves and it keeps coming back. Somewhere I read to use 10 tablespoons of hydrogen peroxide mixed with a liter of water and that didn’t work very well it still kept getting worse. I will try your recipe but your post did not say if we need to refrigerate the mix in between application since it does contain milk.

    • My recipe contains water, baking soda and dishwashing soap, so there’s no need to refrigerate it. I have read about using solutions containing milk. If you decide to use one, I would suggest refrigerating it between applications in case warm temperatures affect the chemical composition of the solution.

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