I'm wondering if these two fungus growths on opposite sides of the base of an old Quercus robur are Ganoderma applanatum. The scratch lines are mine, and they seem to be light greenish-brown. I thought I had learned that polypore fungi were opportunists, but I see the Wikipedia says about Ganoderma applanatum - Wikipedia: It is a wood-decay fungus, causing a rot of heartwood in a variety of trees. It can also grow as a pathogen of live sapwood, particularly on older trees. It is a common cause of decay and death of beech and poplar, and less often of several other tree genera, including ... oak ... . So these are killing the tree? Does it help the tree to remove them, or would there just be too many spores left behind to matter?