Humptulips
ArboristSite Guru
I was thinking the laminated root rot. A couple of varieties that affect different species. Depending on which kind you have tells you what to plant. Mostly is bad in fir and hemlock and the ground is infected as long as there is any fir or hemlock roots in the ground. Takes generations to eliminate. The cure is to plant alder, cedar, spruce. I think I remember there is a variety that infects cedar but never seen that as a problem.