Generally Crop Control is very effective and rapid results (hours to days) should be expected when treating PM and other fungal infections. Taking humidity into account is very important. For best results, apply the product at a time when the humidity is low or anticipated to go low shortly after the application. For outdoor farming, this could mean applying just before the dawn, or watching the humidity forecast and planning accordingly. For indoor applications, humidity control is very important, and Trifecta will combat Powdery Mildew most effectively is humidity is kept low.