How to stop powdery mildew spreading?

Cucumber    USA

One of my cucumber plants has developed powder mildew and I wanted to get some advice on how people control this effectively without the use of chemicals. Is it enough to wash it off of the leaves with soapy water or is there a natural fungicide that I could try?

Posted by: Maggie Muffins (1 point) Maggie Muffins
Posted: July 8, 2013


I've had good luck spraying unaffected plants with a tablespoon of baking soda mixed with a gallon of water. I usually add a couple of tablespoons of light cooking oil to help the spray adhere to the plants. I'd pull out and destroy any already-infected plants or leaves.

Also, thin plants to improve air cirulation around the, avoid overhead watering and don't apply nitrogen fertilizers. The mildew prefers fleshy new foliage.

It's not too late for a second planting of cukes. I've had such good luck with Little Leaf. Very compact vines, but tremendous yields of nice-sized picklers. Resists cucumber beetles and all the fungi that afflict the other varieties I've tried.

Posted by: Peg Boyles (5 points) Peg Boyles
Posted: July 9, 2013

I use a foliar spray with diluted apple cider vinegar, 2 ounces per gallon of water, and add a pinch of archaea fungus powder (a product called Biozome)- sometimes it helps unless the plant has been affected for too long, then it really just holds it back for a week or two. I also remove leaves that are affected in hopes that it won't spread.

Posted by: Bradley Cahill (1 point) Bradley Cahill
Posted: July 9, 2013

Research has shown that diluted milk applied to cucurbits can help control powdery mildew. The dilution recommended is 40% milk, 60% water. Fat content of the milk doesn't matter. It won't cure existing powdery mildew but it helps prevent new infections. The baking soda recommendation described above may be helpful too.

Posted by: Joan Allen (6 points) Joan Allen
Posted: July 9, 2013

Don't use soapy water on the leaves of the plant! That will harm the plant severely. I know because I accidentally splashed a tiny amount of soapy water on leaves of a squash plant in my garden.

The only advice related to soapy water is that one use it for disposal of cucumber and squash bugs. (This is because the dish liquid breaks the surface tension of the water so that the bugs will drown.) Wash your hands and dry them well. Then pick the bugs off the plant with your hands and throw them in a bucket with soapy water. Don't dump the soapy water in your soil; dispose of it properly in a sink drain or equivalent.

When I cleared squash bugs from my plants last summer, I used a plastic spoon to flick the nymphs and adult beetles into a small disposable plastic dish (about 3" high) that was half filled with soapy water. Then I periodically dumped the tray into a larger pail of soapy water and replaced the soapy water in the smaller dish.

I removed squash bug eggs by rubbing them between my fingers while holding them over an empty disposable plastic dish.

Posted by: Alan Smith (2 points) Alan Smith
Posted: January 1, 2014

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