Baking Soda Recipe for Controlling Powdery Mildew on Plants

A Home Remedy for Fungus Diseases

Powdery mildew on rose foliage
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What is Powdery Mildew?

Powdery mildew is one of the most commonly occurring plants problems. It is a fungal disease that affects plant leaves and stems, coating them in what looks like a white or gray powder-like substance. Although any plant can get powdery mildew, some are very susceptible, crab apples, cucumbers and all types of squash, lilacs, phlox and roses. In severe cases, powdery mildew can even spread to the buds, flowers, and fruits of plants.

The white coating greatly diminishes the appearance of the plant, but it is not fatal unless left uncontrolled. However, as it spreads, it stresses and weakens the plant and makes it hard for photosynthesis to occur. It's wise to treat it as soon as you see symptoms, or maybe even before.

Controlling Powdery Mildew with Baking Soda

Baking soda has long been used as an inexpensive control for powdery mildew on plants. Unfortunately baking soda fungicide is mostly effective as a preventative, offering only minimal benefits after your plants have become infected. If you know which plants are susceptible, spraying them weekly with the baking soda recipes, during humid or damp weather, can greatly reduce the incidence of powdery mildew in your garden.

To control powdery mildew on plants, mix together:

  • 1 tablespoon of baking soda
  • ½ teaspoon of liquid soap
  • 1 gallon of water

Do not store unused mixture.

While this recipe has been known to be effective, it can burn the leaves of some plants. It is recommended that you water your infected plants well a couple of days before applying this mixture, and don’t apply it in full sun. Try on a small area first, to test the plant’s response before spraying the entire plant.

Some recipes also recommend applying 1 tablespoon of ultralight horticultural oil to the mixture. The oil coats and smothers the fungi. The soap is added to help the mix spread and cling to the leaf surface. Be sure to apply to lower leaf surfaces as well.

Control versus Cure

Unfortunately, this baking soda mixture works best as a preventative, applied before powdery mildew has a chance to spread on your plant. It is less effective as a cure, once the fungus has taken hold. If you know a plant is affected by powdery mildew year after year, as is the case with many monarda, pholx, and lilacs, they spraying early in the season may prevent any occurrence of powdery mildew that year. It is still worth trying after signs of powdery mildew appear, but it might not get rid of all the fungus.

Another Homemade Powdery Mildew Option

Spraying plants with a milk mixture, after they have been infected with powdery mildew, is showing a lot of promise for actually killing the fungus. Read more about how to use milk to control powdery mildew.

There May be More Uses for This Baking Soda Recipe

Researchers are still studying the effects of using a baking soda mixture on other fungal diseases such as: black spot, rust and anthracnose.