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Treating Plants with Powdery Mildew

I am very inexperienced in gardening. There is a white powdery look and white flecks on the underside of a sweet potato vine. Is this powdery mildew? The white flecks are not insects. But I do not know what they are.


Hardiness Zone: 10b

By Lynn from South FL

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November 11, 20090 found this helpful

Powdery mildew. The scourge of the garden. Sometimes fatal but mostly just annoying, it covers foliage with a white powder that makes plants look bad.

Two things you can do to help keep powdery mildew from forming on your plants: space them far enough apart so the air can circulate freely around them and do not water after noon. Wet foliage after sundown is a favorite host of mildew spores.

It's not necessary to mount a full frontal assault with a host of toxic chemicals. Powdery mildew can be treated and sometimes even eradicated by using common household ingredients. Below are 7 home made preparations you can use to treat powdery mildew in your garden.


But first, some general instructions for treating white powdery mildew with anti-fungal preparations: Hose off the plants with a strong spray from the hose prior to treating with these preparations to remove as much mildew from the surface as you can. Be sure to cover all parts of the plant with the treatment spray, including the undersides of the leaves and the stems. Spray some on the soil around the plant as well. Finally, spray for mildew early in the morning before the sun rises too high in the sky. Spray plants once or twice a week in dry weather and more often if rainy.

Apple Cider Vinegar. Mix 3 tablespoons of cider vinegar with one gallon of water. Also works on black spot on roses and aspen trees.

Baking Soda. Mix 1 tablespoon baking soda, 2 1/2 tablespoons vegetable oil and one gallon water. Shake well then add 1/2 teaspoon of Castile soap. Shake the container as you spray your plants to keep the oil and water from separating.


Chives. Use a bunch of freshly cut chives, about as many as you can hold in your closed hand without dropping them. Chop the chives and place in a heat-proof glass container. Cover with boiling water and let sit until cool. Strain.

Corn and Garlic. Take a handful of corn leaves, along with a handful of clematis leaves and as many of the papery outer skins of garlic as you can. Pulverize in blender or food processor. Mix in enough water to make a thin liquid. Let the mixture sit for an hour, then strain. This also works as a preventative against powdery mildew.

Horseradish. Place one cup of chopped roots into a food processor and process until finely chopped. Combine with 2 cups of water in a glass container. Let sit for 24 hours then strain and discard solids. Mix strained liquid with 2 quarts of water. This mixture is also an effective preventative against molds and mildews.


Hydrogen Peroxide. Spray regular hydrogen peroxide (the kind from the drugstore, not the food grade kind) full strength on the affected plants. Do not spray on newly transplanted plants or young seedlings until they become well established. Test on a small area of the plant and wait 24 hours to see if it has any negative reactions to the hydrogen peroxide. This works as both a treatment and a preventative.

Milk. Mix one part of milk with 2 parts of water. Spray every 3 to 4 days at the first sign of mildew. Milk changes the pH of the surface of the plant leaves and prevents mildew from adhering to them. Can also be used as a preventative measure. Good luck.

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November 12, 20090 found this helpful

One thing that I found helps with powdery mildew is to make a solution of dry powder milk, and spray your plants. Learned this at a mg. class

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November 12, 20090 found this helpful

I've seen this on my plants. If it's not powdery mildew it's the residue of the bad bugs that the good bugs ate.

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November 12, 20090 found this helpful

If this white powder is on the bottom side of your leaves, it may be mealy bugs and they are easily washed off. You can use clear water or mix a drop of dishwashing liquid with it. Keep a close watch on this plant as they may show up again and mealy bugs will kill the plant. They will move to other plants they like so watch the neighbor plants.

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November 13, 20090 found this helpful

I use the milk method but I use skim milk full strength.

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November 15, 20090 found this helpful

Go to your Nursery, Home Depot or Lowe's for some plant treatment that will kill the white powder.

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