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.
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.