well the place im talking about actually dips em in a solution< some anti fungal, anti bug stuff if you request. i did have problems, once but that was due to my growing partner bringing in some ugly unrooted clones from another shop ( that really overcharged ) that had some mildewgrowing in the rockwool. at the time we were growing at his location so i didnt have too much say so to get rid of em, but after seeing how bad it got i pulled my girls out of there and cut ties with him....