Conk was at 4’, undercut was above it and hinged fine. Crown looked very healthy too which was surprising until I saw that the sapwood was decent all the way around. Different rot column than many other poplar pathogens I’ve noticed.
Thanks SL, yes, you've got it. Most workers now would refer to it as the segregate species: Phellinus laevigatus or Phellinus tremulae, both formerly considered varities of P. igniarius. I still call it "igniarius" in my head.
A white rotter, it can't really handle the high moisture content of living sapwood. These poplar don't produce much in the way of heartwood extractives so the wood in the core, absent the living symplast and associated high moisture content, the wood readily decays for fungi that can handle the low oxygen environment of the core. Looks to be some zone line spalting in the decaying wood.
What would you guess as to the “final straw” with a tree like this @KTSmith ? If the sapwood stays complete will the fungus target roots and lead to a failure there, stem breaks at a pre-existing defect, or fungus runs out of heartwood and attacks the phloem etc?