Prevent powdery mildew with this spray: 1 gallon of water 1 tablespoon of baking soda 1 tablespoon of vegetable oil 1 tablespoon of dishwashing liquid Mix the ingredients together and add them to a spray bottle. Spray your plants weekly, preferably on overcast days to prevent it from burning the foliage.
Aspirin is the remedy for fungal plant problems, Black spot, powdery mildew, and rust are a terrible trio of fungi, which can attack and destroy your plants. Scientists have found that two uncoated aspirin tablets (325 milligrams each) dissolved in 1 quart of water and used as a foliar spray can thwart these diseases. I have not tried this, but I will.