I usually wouldn't spray anything on them either.. but that stuff that I mentioned will completely dissipate. So it's 100% safe to do so.
And yes PM is 100% systematic.. it lives all throughout the plant. The key to not getting it is environment of course.. getting rid of it can be a nightmare.
When I had it, I tried everything.. including Greencure.. I was at my wits end with it. Nothing worked.. the shit would come back like the plague no matter what I did. Powdery mildew fungi can develop resistance to any of the fungicides, except sulfur they say. A sulfur burner was the only thing I hadn't tried at that point.. besides the easier alternative.. Eagle20EW because that stuff actually kills the PM from inside the plant, not just outside on the leaves. Most PM treatments and cures only treat exterior symptoms. Eagle20EW's active ingrediant Myclobutanil will dissipate as well and it commonly used in the agricultural industry on fruit plants.. but takes much longer to do so.. it is only something that a grower should use during the Veg cycle. It is considered to be "for professional use only" and is hard to get in some states. But I tell you what.. it works better than anything I have ever seen in my life on PM.
When I had PM.. my friends had PM.. my local buddies... cuz we of course swap clones and I like to give them things. So naturally.. next thing I know the whole neighborhood has PM. It was a lot of spraying that week.. but alas.. it was gone.. Never had PM since.
Re: the Ozone Generator.. I actually have a really good one of those.. it's not going to help you cure PM.. but is good to run regardless if it helps keep your environment in check as a preventative option. I love mine and is nice for musty smelling basements or anywhere that smells lol. But I wouldn't rely on it for PM treatment.
Just trying to help..cuz I fought that battle and won that war. It was hell.
What was equally as hellish was the troves of organic gardeners from the forums ganging up on me yelling at me for advocating the use of Eagle20EW.. lol.. some of those old timers ROLS people and whatever u wanna call them... the nature people... they go crazy when you advocate a chemical or something that comes out of a bottle with a caution label that over exposure to "said chemical".... over a period of many years ,studies shows that workers in a grape field from blah, blah California... had prolonged exposure to said chemical from spraying it regularly and for many many years.. leading to believe that could Myclobutanil could cause cancer." So this of course leads to the inevitable people just writing it off and saying iggnorant things like ... DONT USE EAGLE20EW.. IT CAUSES CANCER!!! and shit like that... you know how people can get...
Truth be told.. if you burn your breakfast toast or cook it too brown.. the black dark spots on the top of the toast is also carcinogenic.
It's the truth. Acrylamide, which is produced when sugars and certain amino acids, the building blocks of proteins are heated together during the cooking process.. and that is a carcinogen.
So.. I tell the Organic people.. I'll give up on Eagle20EW when they give up on toast. And we usually have a stalemate.
Re: you asking if it kills Fungi on soil.. it is only meant to be used on turf.. so plants only.. I would recommend taking clones of your plant.. even if in flower.. and treating those.. and ditching the rest of it.