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.
Combine: 1 teaspoon baking soda 1 quart water A few drops of liquid soap Combine in a large container and transfer some to a spray bottle. Spray the leaves of plants where powdery mildew can be seen, then repeat a week later. For best results, treat plants as soon as you notice the powdery mildew.