I have a enclosed GH going, previous two pulls this season was blacking it out for 12/12. We use a sulfur burner for the GH, and burn sulfur once the plants are transplanted in it. Im not sure if botrytis is the same as powder mildew? But the sulfur burner was used as a preventive for that and haven't had any powder mildew. knock on wood
not at the same thing....both suck though!