It's what I like to call
The Alien Fungus,
the plants don't seem to be happy about it, but they do give fruit - it grows in continental Croatia, Europe, typical yearly temperature range -20 to 40 and high humidity with heavy clay (surrounded by an old forrest).
Some of the affected trees are a bit weak and tend to fall under the snow more often, they do give fruit but not as much as one would expect.
I'm also looking for a remedy for this, if possible (as much as is possible):
- can be applied during fruiting/flowering
UPDATE this good answer seems to have ID-ed the brown thing and that it feeds on dead wood (ie wood already dead)- but it seems now that the blueish-whiteish growth is a separate growth and is possibly killing the wood, does someone recognize it?
UPDATE the same answer as above ID-ed the blue-white thing as lichen - not harmful