Suggestions for white powdery mildew on pumpkins and squash

6 years ago

Around this time every year, my pumpkins and squash develop that unfortunate white powdery spots covering the leaves. It's especially disappointing this year because everything has been looking so great.

Any suggestions for treatment and prevention?

I applied a mixture of milk/baking soda/detergent today, but I've had only mild success with this in the past. I know overcrowding is the issue, but I'm still wondering if there is a homemade cure or product that would help.

Featured Answer

gardengal48 (PNW Z8/9)

6 years ago

Once you actually see the white spotting - powdery mildew - it is really too late to treat. Spraying now with any sort of fungicide for this purpose - baking soda solution, diluted milk, neem oil, even registered fungicides - can help stop the PM from spreading to unaffected foliage but it won't cure it. Remove the most affected leaves. and water deeply but infrequently at the root zone.

Powdery mildew is pretty much a cosmetic issue on most ornamentals and woody plants but it can be severe enough to kill off the cucurbits.

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Comments (9)

sunnyvalley
6 years ago
Sorry to have this go by without comment, but the milk/baking soda was going to be my only suggestion since I've never tried a product. I hope you can find something that helps!
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Yes I think it is downy mildew. It was confusing at first because the leaves all looked covered in white. So it looked like powdery mildew. Then the white completely disappeared and there were yellow spots, so I thought maybe this was stage 2. But looking online it says that the dark spores under the leaves is a sign of downy, not powdery. Anyway, it just shrivels the leaves to brown crackly paper, which is worse than what I was reading about powdery mildew. And the cucumbers have had it for the past several days, with heavy foliage death and cucumbers stuck at half size. But I was out there with more dilute milk solution this afternoon spraying the cukes, pruning like crazy, taking off all the half-size cukes, and it seems to have worked, at least tonight the leaves look like their normal after-dark selves, perked up again. Will have to wait and see how the butternut and cukes do now.
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John (Sacramento Valley, CA 9B)
Original Author
6 years ago
Thanks gardengal48 (PNW Z8/9). Your description is consistent with most treatment plans I've been reading. About a week ago I removed the affected leaves and sprayed with a baking soda/milk mixture, and so far, it seems to have slowed the process and things are looking good. A few powdery spots appear each day, but it's manageable. In the past, I've had pumpkins/squash succumb to the mildew very quickly and die off within a couple weeks. As of now, it appears to be under control. Most of the affected leaves were right around the root base, the longer vines are perfectly fine.
farmerdill
6 years ago
I would suggest that you try PM resistant varieties if it continues to be problem for you.
gardengal48 (PNW Z8/9)
6 years ago
AFAIK, only a few cucumbers and melons have PM resistance........pretty much all pumpkins and squashes are extremely susceptible.
cathfleisch
6 years ago
I just heard about making a horsetail tea and spraying on plants as a preventative for this problem. I am in the process of looking for some horsetail plants to plant in containers (invasive) and doing this next summer.
Luciano Cortes
6 years ago
That's very easy to fix, just spray the affected leaves with milk, the earlier you start the better. I have been able to save 90% of my plants that way and they keep producing, otherwise, they are done. That is caused by sprinkling water over your plants, only water the soil to avoid this.
gardengal48 (PNW Z8/9)
6 years ago
"That is caused by sprinkling water over your plants, only water the soil to avoid this."

That is actually incorrect. Powdery mildew is not encouraged by wet foliage - in fact, its spores will not survive in contact with any moisture and one way to discourage the development is to spray down the plants frequently but early in the day so foliage has time to dry (other problems can be created by wet foliage at night).

The primary concerns are proper air movement, so avoid overcrowding; and maintaining proper humidity....neither too high nor too low, both with respect to ambient humidity and with soil humidity.
Luciano Cortes
6 years ago
There you go, now you have two choices, water the soil only, or sprinkle the plants and dry them afterwards.

Suggestions for white powdery mildew on pumpkins and squash

gardengal48 (PNW Z8/9)

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sunnyvalley

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John (Sacramento Valley, CA 9B)
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Suggestions for white powdery mildew on pumpkins and squash

Comments (9)

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John (Sacramento Valley, CA 9B)Original Author

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John (Sacramento Valley, CA 9B)
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