Baking Soda/ Potassium Bicarbonate Fungus Control. Mix 4 teaspoons (about 1 rounded tablespoon) of baking soda and 1 tablespoon of horticultural oil into one gallon of water. Spray lightly on foliage of plants afflicted with black spot, powdery mildew, brown patch and other fungal diseases.
horticultural oil: What the hell is that?
There it is