Powdery mildew is a common fungal disease on roses and other ornamental plants and vegetables. It appears as a white powder on the leaf surface. Numerous studies have shown milk to be more effective at killing powdery mildew than chemical fungicides. It can also have a protective, preventative effect. Try spraying a 50-50 mixture of milk and water. Scientists are not sure why milk is so effective, but they believe that when milk interacts with the sun, it produces free radicals that are toxic to the fungus. Many say spraying on a sunny day works best.
Growing Home: Powdery Mildew
