Sorry to bump this old thread, but I use Actinovate on 5 different strains from clone to late flower, and it is really great. I've never had any negative result, and I use it 3-4 times the dosage rate. It's simply a concentrated beneficial bacteria in a powder form, so you want to add it to some chlorine-free water as not to kill the bacteria. You can tell it's bacteria because if you leave it in a spray bottle for more than a day, it really starts to smell funky. I had all sorts of fungus problems before PM, which is strange because they popped up after 3 years of growing fungus free. Plus I have great ventilation, air-movement and humidity. I think it's because my moms get over crowded in their tent right before I it's time to cut clones. Anyway, it suppressed all fungi, including PM. If I see any thing starting to return, I mix a quart and do the whole garden. I spray every 7-10 days as a preventative. I like it better than my sulfer burner...