Found a wonderful group of Polyporus squamosus, Dryad's saddle today on a sycamore.
Dryad's saddle
Thiose look quite good. Are they harmful to the tree? I see they're growing from cracks in the bark so must be in the heart wood. Does that weaken the tree overall?.
I think they cause white rot within the living tree, but can also be on dead wood. These were on an old sycamore.
I guess nothing lasts forever.