Ya, I meant the the IPM products\sprays that eventually build up in the plant tissues the more you use it. If you were treating only the mother plants though, the small cuttings you take would outgrow whatever systemic fungicides you used as they veg out.
Like you said, putting the cuttings in a moist environment to root out is also the right conditions for the PM and mold spores, so treating the infected mothers with the fungicides might be a worthwhile extra line of defense.
Thats another reason I'm a fan of air layering propagation, because you can keep the host plant dry the whole time the clones are rooting out. No domes or anything needed, just keep them in veg mode with fans (or better yet, BFFUs!) blasting it as usual. The AL'd clones won't wilt no where nearly as easily as cuttings would, because they can still wick moisture up through the branch.. You CAN clone in dry conditions inhospitable for pm or mold spores this way.
Also, you can take huge clone\s off your mother plants via AL, so your not wasting as much when you toss her out to replace with a new one. Basically take the biggest branch, or upwards of 50% of the plant at once if you want. Like cutting her in half, so you can toss the old medium that might be harboring even more spores or gnats and whatnot.
As far as white PM not being systemic.. I heard there are at least 4-5 or so out of the 1000's of strains that for sure can infect cannabis. No one ever really talks about that part. I wouldn't be surprised if there is a fungicide resistant borg like strain (kinda like 2 spotted spidermites), that does go dormant and somehow hides out in the plant meristem tissues, and waits for generations before reactivating. All I know is that its in the air everywhere, and can spread via infected cuttings/tools/etc. Thats systemic enough for me.. Man, have you seen the microscopic zoomed in pics of affected cannabis leaves from that one study?!
I also wouldn't be surprised if you could blast your way out of the current situation just by adding some BFFUs to whatever you still have growing in your tents, without messing with the carpets or changing or spraying anything else. Not the flowering plants though..
I know I won't grow weed without them again. Heck with regular or oscilatting fans.