I learned from this question that my birch tree is infested with Birch Polypore mushrooms. For two reasons, I'm wondering if I should remove them.
First, even though they grow because the tree is diseased, they also cause further decay. Would removal slow down the rate at which the tree dies?
Second, do the mushroom bodies release spores or any other substance capable of causing damage to nearby birches which currently seem healthy?
Removing the fruiting bodies will not slow the damage/decay to the host tree. They do not affect the rate of the mycelium growth within the tree, and, if anything, removing the fruiting bodies will divert energy to new mycelium growth. They are only present for one purpose: spreading the fungus around. Usually, in a case that bad, you will remove the tree. It won't live long.
If you can't remove it for a while, taking the fruiting bodies off will prevent the releasing of millions of spores, unless the spores have already been released. I suppose that could be a help, except that the air outside is already heavily laden with fungal spores of all kinds.
In other words, this is not a huge deal, you can remove them or leave them, but probably the best thing you can do is to remove the tree.
