Powdery Mildew

marvey(5)February 1, 2014

I know this is early for this question but the answer might affect the way I plan out this years vegetable garden. Does anyone have an effective way to deal with powdery mildew on Cucumbers and Zucchini? I am looking into some of the fungicides that are advertised. I am considering moving all squash and cukes to one end of the garden so that I can spray if needed and not get it all over everything else. Last year it took my pumpkins, zucchini and my cucumbers in early august. Any help is appreciated. Thanks.

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jean001a(Portland OR 7b)

- Plant resistant varieties, if you can find them.
- Plant in full sun -- all day every day.
- Allow plenty of space among the plants to permit good air circulation.
- Then realize that powdery mildew will likely strike anyway, especially if the plants are stressed or late in the season..

    Bookmark   February 1, 2014 at 12:57PM
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What jean said, but also I've read that you want to treat for PM in a preventative manner. That is, long before symptoms show.

Homemade potassium bicarbonate solutions and milk solutions supposedly work much better when you treat from day 1 of transplant to garden.


    Bookmark   February 1, 2014 at 3:05PM
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Dear Jean001a and woohooman,
Thanks for the follow-up. I will do both those things. I'm taking notes. The all day everyday sun will be a planning challenge.

    Bookmark   February 1, 2014 at 4:19PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Another ditto for what jean said above. No over-crowding allowed and that is the biggest contributing factor when it comes to cukes and squash. The more space and air circulation the better.

And maximize the sun exposure in any way possible even if it means having trees trimmed, wind blocks moved, or relocating the plants to a sunnier location. Using containers that can be moved allows for max sun exposure.

Then plan on planting successive crops of them so when and if it develops anyway you can rip out that plant and put in new ones.

Lastly, IF you are going to use fungicides then use real fungicides - chlorothalonil - rather than wasting time and effort on all the home-made concoctions.


    Bookmark   February 1, 2014 at 4:26PM
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little_minnie(zone 4a)

The zuc plants with narrow leaves get it less than the ones with big wide leaves. I like copper spray for that time of year but nothing really prevents it when you get a week of rain in August. The bigger and healthier the plant the better because it can lose leaves and still be ok. So you could cut off the bad ones and the middle good ones will be enough for a healthy plant. Oddly I had PM worse on my rutabagas last year. Never saw that before.

    Bookmark   February 1, 2014 at 8:24PM
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seysonn(8a WA/HZ 1)

I believe in doing a systematic programmed spraying(once in two weeks) from early on. After you get it (PM), you may keep it at check but can never get rid of it,
I don't think switching location (rotation) will be effective in this case. JMO. b'c the fungus is air born. I don't know where the hell it comes from.

milk formula, neem oil, daconile all work about the same. I like neem better.

    Bookmark   February 1, 2014 at 10:15PM
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I find that delaying planting of the fast-growing summer squash eliminates the problem. They don't show PM until they're geriatric. I grow OP processing pumpkins and start spraying them with milk/water after they set fruit provided the weather makes it worth the trouble. There are some cucumber varieties with excellent resistance, I think.

Here is a link that might be useful: using milk to control powdery mildew

    Bookmark   February 2, 2014 at 6:45AM
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seysonn(8a WA/HZ 1)

I have a question:

It has been said that PM spores are air born. Does it mean that the are not in the soil from previous season. If it is brought by the wind, where do they come from?

About milk/water spray:
I have used it in the past and will use it again. Some people add baking soda to it to: HOW MUCH BS do you add to be on the safe side and not to kill your plants? What the baking soda do ?

    Bookmark   February 2, 2014 at 7:22AM
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Seysonn: PM needs live tissue to survive, so I imagine it comes from plants that carry the spores but don't exactly exhibit symptoms. Trees, shrubs, bushes, I imagine.

Regarding Baking soda--- I've used it in the past but like most remedies, it isn't really effective if symptoms are already present. Never used it with milk though. I'm using Potassium bicarbonate now. it seems to do a much better job...available at wine shops and beer brew shops(got to shop around though). As with other home remedies( sodium and potassium bicarbonates, milk, etc), the idea is to change the ph of the foliage to a level that is unfavorable for the spores to thrive.


    Bookmark   February 2, 2014 at 1:55PM
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