Baking soda makes an inexpensive control for powdery mildew on plants. The baking soda fungicide is mostly effective as a preventative, offering only minimal benefits after your plants have become infected. Weekly spraying of susceptible plants 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
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.
Researchers are still studying the effects of using a baking soda mixture on other fungal diseases such as: black spot, rust and anthracnose.