Potassium bicarbonate for mildews

woohoomanJuly 5, 2013

I posted this in the Organic gardening forum, but I thought I'd post here also---

Well, in years past, I've tried baking soda, neem oil, milk, and vinegar for powdery mildew. Then I found out that plants need to be treated PRIOR to exhibiting symptoms. I had read that potassium bicarbonate was better than baking soda, but had never tried it.

This year, I was going to get a jump on it, but the humidity and heat came about 2 months early... Voila! Powdery mildew.

Recently, I read that potassium bicarbonate could not only control PM, but could actually cure it some -- even after symptoms.

So I went and found some at a wine making shop. I clipped the most affected leaves off my cucurbits and gave all of them a good spraying.

I plan on going with a 1 week schedule for a few weeks and then a 2 week if there's no further damage.

I'll let you all know how it goes later this summer.


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Where do you buy it and at what concentration, such as grams/gal or oz/gal.


    Bookmark   July 6, 2013 at 11:30PM
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Rossello44: I got mine at a local wine and cheese making shop-- 1 lb for $6. But, beer making shops also carry it.. Problem there was the one I called wanted $2 for an oz. Amazon has it for $15 or so per lb.

The recipes I see online call for 4tsp/gal water. So, even at a inflated price such as Amazon, it comes out to about 192 gal of fungicide. If it works, that's a helluva lot cheaper than the milk recipes and store bought products.

I should have an update to effectiveness in a couple weeks or so.

By the way, apple cider vinegar is off the table for me. I noticed some discoloration on leaves of some of my pepper plants.


    Bookmark   July 6, 2013 at 11:48PM
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Thanks Kevin. As you say even at the high price, still is (if it works) a cheap solution.
I picked 7 zucchini (5 green and two yellow) and 5 cucumbers yesterday.

    Bookmark   July 7, 2013 at 8:16AM
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newyorkrita(z6b/7a LI NY)

How well is it working?

    Bookmark   July 16, 2013 at 1:09PM
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Pretty darn well on the zukes, cukes and squash. I've only had to pull just a couple leaves from the squash and zukes and they're the oldest leaves that are tuckered anyhow The cantaloupes are surviving but because I sprayed that vinegar solution, I've had to trim a lot of leaves. And the PM seems a bit more stubborn on the melons. I imagine if the monsoonal crap hadn't moved in so early this year and I had begun the preventative sprays earlier, that they would be fine now.


Note to self: Plant cantaloupes further apart... the side shooting vines take up way too much trellis space.

This post was edited by woohooman on Tue, Jul 16, 13 at 14:44

    Bookmark   July 16, 2013 at 1:35PM
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newyorkrita(z6b/7a LI NY)

Yes, it is always easier to prevent instead of cure. But still it sounds pretty effective!

This is my first year growing zucchini and squash so I never realised they were prone to getting powdery mildew until they came down with it. I have been using Neem to control it but am very interested in the effectiveness of the Potassium bicarbonate.

    Bookmark   July 16, 2013 at 2:28PM
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Thanks, Kevin, for telling us about this! I just used it tonight on all my cucurbit leaves. I also used it on the night shade family plants. I read it can be great for preventing and helping slow down some of the fungus diseases too like blights and septoria. I will post my tomato results here. Thanks again!

    Bookmark   July 23, 2013 at 2:25AM
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seysonn(8a WA/HZ 1)

OK. Hope all goes well.
Please report on results soon, if you will.

    Bookmark   July 23, 2013 at 8:48AM
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I will :)! Maybe posts some pics too.

    Bookmark   July 24, 2013 at 12:49AM
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