Hey there fellow growers, I have been dealing with PM for the last 6 months and it always seems to come back fresh with each grow, even after hard core cleaning sessions lol. I have ALWAYS overcame PM just have not been able to kill it off in my environment and don't have the resources to change the current environment. What I use, and it works fucking great, is H202/water spray and it works fan fucking tastic. Of course, I do this every time I see some white build up on my medium and never let it get to my plants.
There are a couple measures you can take to prevent spreading if you dont have the perfect room:
1.) make sure you trim the bottom of your plant, those leaves will spread that shit faster than an std in a dorm.
2.) Try to give your girls a nice H202/water spray down every week at lights off; might sound a little excessive but this shit works.
3.) Of course make sure you have a good ventilation system and low humidity (first rule and should just be common sense).
4.) USE NEEM. At first I was skeptical of the uses for this oil but the shit is amazing and you should be applying every other week until you flush.
If PM isnt gang raping your garden these steps should be enough to help you guys out. I forgot to mention that I run RDWC so this shit spreads like wild fire, but Ive been able to keep it at bay following these steps. I use hydroton, so its not too much to just replace that shit if I ever see a hint of PM.
Alot of first timers freak out about PM like its the white plague, but this shit is easy to fix as long as you keep up with it. Living with it is doable if you dont have the funds to make your room perfect. Just my 2 cents.
Peace RIU hope I helped out a bit.