Using Baking Soda to Combat Powdery Mildew

I heard you could use baking soda to control powdery mildew. Is this true? If so, do you have the recommended rate?

Cornell University discovered baking soda was an effective control against powdery mildew. It has been used by gardeners on vine crops, roses, perennials and other edible and ornamental plants. Start by mixing 1 tablespoon of baking soda in a gallon of water. Add a teaspoon of insecticidal soap OR lightweight horticulture oil to act as a spread sticker for the solution. Spray the plants at first sign of the disease. Repeat every 7 to 10 days throughout the season.