PM is one crappy thing to get. First of all address issues in the grow. What are the temperatures? What is the RH? How much airflow is in the area? How dense are the plants?
If you're vegging/early flowering, I highly suggest using a sulfur burner. I've gone through N202 foliar sprays, neem oils, Mildew Cure sprays and none worked. I then tried a sulfur burner and it worked GREAT. Save your money from sprays and buy the burner & some garden sulfur, it is very worth it.