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Pumpkins, Squash & Gourds Tomato Pests & Diseases Container Gardening

How to Prevent Powdery Mildew

5 years ago

Hello! Looking for an effective, cheap, (possibly DIY) way to prevent powdery mildew, It severely weakened my zucchini, cucumber, and tomato plants last year, so I'd really like to stop this before it happens. Thanks in advance! :)

Featured Answer

gardengal48 (PNW Z8/9)

5 years ago

Ladybird larvae?? How would they possibly help to prevent powdery mildew?

A baking soda solution (or even better, potassium bicarbonate) or a milk solution sprayed on the foliage in 7-10 day increments can help, So can neem oil.

And good cultural practices can go a long way. Make sure there is plenty of air circulation (you can remove some of the foliage if things get crowded), as much sunlight as possible and keep fingers crossed for heat (PM spores do not tolerate above 90F). And hosing down the plants will help, as many types of PM spores are killed by direct contact with water. Do this very early in the day so foliage has plenty of time to dry.

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Comments (7)

SW (Sydney, USDA 10b)
5 years ago
Plant in full sun if it’s not too hot. Ladybird larvae also help.

I have found alternating between copper sprays and milk-water (1:10) sprays to be somewhat effective.
HU-397624596 thanked SW (Sydney, USDA 10b)
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To Ken_adrian: Thanks for the advice, but I am not one to give up on a plant because I had a problem with it for a little while during 1 season. I have dealt with issues with dahlias as well from time to time, like slugs, spider mites and tree hoppers, but I stiIl grow them. I think some things are worth a little extra effort, and its really not that much more effort anyway to be honest. I grew the same variety of zinnias about 2 years prior to last year's powdery mildew, and at that time I had more zinnias in a more shaded area that tended to hold moisture/humidity moreso than this new area does, yet I didnt have any problem with powdery mildew at that time. I dont mind having to take 10-15 minutes 2-3 times a season mixing up some spray solution and coating the plants with a safe, relatively non-toxic spray that helps prevent fungus if it means having 5-6 foot tall flowering plants that continuously flower from June til early November. I will also try to keep them more ventilated. Maybe they were too close last year. But we also had a generally wet first half of summer.
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I understand your question but I'm not sure of the answer. I wonder about coverage using the fine mist of a pump sprayer. I see the spray material bead up and wonder how much good it is doing the new growth. I've been doing this as a hobby (20+ years) and a business (16+ years) and generally I just trust that the funcide is going to work and it does. Although you get finished with you spray job faster and easier with the hose end sprayer you are using more spray material. Just keep that in mind especially if you live in Florida where everything leaches right through our sand.
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There are about a bazillion different strains of powdery mildew but they tend to be rather plant specific. So the powdery mildew on your roses (Sphaerotheca pannosa var. rosae) is not the same sort of powdery mildew that affects cucurbits (squashes, melons, cucumbers, etc. (Podosphaera xanthii and Erysiphe cichoracearum). I would not be concerned about one plant affecting the other, although the melons and cukes can certainly pass on their type of PM to any of their cousins :-) Spraying preventatively is the ONLY way to control PM. If you wait until you see signs of it before spraying, it is already well established. Milk, baking soda solution, neem or other horticultural oil or most other prepared spray fungicides (e.g. Actinovate) should help to keep things under control. I will say that cucurbits developing PM, especially later in the season, is almost a given - they are extremely prone to this pathogen.
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K, gardengal is exactly right that there's nothing you can do now. It's possible to prevent a severe infection but you can't cure a plant when it's so heavily involved. It's essential that you make a big effort this winter, however. Rake up all of the fallen leaves and dispose of them.....do not use as mulch. I strongly suggest that you plan on spraying the dormant tree a couple of times in the late winter-early spring with a horticultural oil, even neem. The oil can smother spores that are lurking on the twigs and buds waiting to infect the new leaves. When the new leaves emerge, don't forget gardengal's advice regarding a quick rinse of water. There are fungicides on the market that can prevent and cure PM, but with aggressive preventative measures I've never found it necessary to resort to chemicals.
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edweather USDA 9a, HZ 9, Sunset 28
5 years ago
If you Google diluted bleach solution for tomatoes, you'll hit on an effective way to treat tomato plants. The guy who uses this writes a lot about it over on TV. He uses it for a mold, but last year I noticed powdery mildew on my cucumbers, and used a VERY diluted spray, like 1 tbsp per gallon of water, and it worked very well.
HU-397624596 thanked edweather USDA 9a, HZ 9, Sunset 28
SW (Sydney, USDA 10b)
5 years ago
last modified: 5 years ago
Gardengal - oops I didn’t realise but it’s only a thing here in Australia - https://en.wikipedia.org/wiki/Illeis_galbula

https://www.sgaonline.org.au/powdery-mildew/

They’re good at getting it off and they flock to cubiter plants.
HU-397624596 thanked SW (Sydney, USDA 10b)
gardengal48 (PNW Z8/9)
5 years ago
Would seriously advise AGAINST using a product as caustic as bleach on any living plant, even highly diluted!! And then there is the issue of phytotoxicity and chlorine contamination........

Why not try one of the almost totally harmless home remedies like baking soda or milk first before you resort to something that could just as easily kill the plant rather than save it.
HU-397624596 thanked gardengal48 (PNW Z8/9)
edweather USDA 9a, HZ 9, Sunset 28
5 years ago
last modified: 5 years ago
I'm just relaying the information. You probably know way more than me about this anyway. It is a nuclear option, as stated in the linked thread. Try other methods first. I used way less than is even recommended, and it worked like a charm for me almost immediately. The information is there, and the process and methods are well documented by a highly respected grower in the community, and used successfully by many.

http://www.tomatoville.com/showthread.php?t=28509&highlight=bleach+spray
HU-397624596 thanked edweather USDA 9a, HZ 9, Sunset 28
Meyermike(Zone 6a Ma.)
5 years ago
I'll never forget when my father used bleach to kill weeds one day, very diluted and in the process killed all the surrounding plants, frogs and living creatures..Never again..

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