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Stop Powdery Mildew with Baking Soda

By July 30, 2009

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I've been lucky so far. I have seen no signs of powdery mildew yet in my garden, which is an absolute rarity for the month of July in Michigan. But, I just know it's coming, and I've gotten a few questions about it from other gardeners. The good news about powdery mildew is that if you catch it early, you can stop it from spreading and having an impact on your plant's overall health. The first step to stopping powdery mildew in its tracks is to remove any infected foliage and throw it away (DON'T compost it!)

Once that is done, mix up a batch of my powdery mildew spray. It couldn't be easier: water, baking soda, vegetable oil, and dish soap. And it is much cheaper than buying a fungicide at the garden center!

You'll have to spray once a week to keep powdery mildew at bay. Be sure not to spray in full sun to avoid burning the foliage. I use this in my own garden every year, and it really works well.


August 6, 2009 at 3:53 am
(1) Joanna says:


I’m just wondering about your powdery mildew spray. Could you give us an idea of the amount of each ingredient to use?


September 17, 2010 at 4:53 pm
(2) organicgardening says:

If you click the links in the post, they take you to a detailed recipe for the powdery mildew spray.

October 1, 2010 at 1:20 pm
(3) Dee Celestin says:

This stuff works great. I leave in San Diego CA and I like gardening and my squash plant always gets the powdery mildew disease and I keep it at bay with this spray. It cheaaper than those so call gardening spray you a lot of money that do nothing.

October 28, 2011 at 5:09 pm
(4) channa says:


Iím just wondering about your powdery mildew spray. Could you give us an idea of the amount of each ingredient to use?


April 30, 2012 at 12:04 pm
(5) Mikkel says:

Hello! Great stuff that spray is.. Got rid of the PM in two treatments. No signgs of it returning and it’s been 3 weeks!! :-) question, how long can the spray be stored for to reuse?

August 8, 2012 at 3:55 pm
(6) bearman says:

Thanks for your recipe, which I have used on my immature spinach, arugula, lettuce, broccoli, etc. OTOH, now I’m concerned about the organic (edible) nature of the dish soap. Can it get into the pores of the leaves and leave an unhealtful deposit?

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