Powdery mildew seems an endless problem for me. I am about to start a sulfur burning routine as a way to prevent the crap. Also, I spray the leaves with "alkaline water" (pH =8.4: 1/2 tsp. baking soda /1 liter of water) which kills the mildew on the plants. BTW, PM Wash is the same but effing expensive. Hope this helps.