From my research, that white fuzz is fungal. Apparently amanos are one of the few inhabitants that eat it.
I might be wrong, but I don't think the fuzz comes from the bark. It only appears on areas where the wood is exposed, like at the ends where the tip has been broken off or on areas where there are cracks in the bark. The rest of the bark has no fuzzy growth at all.
This stuff also originally grew on that piece of Malaysian driftwood in the tank, but it went away in a few weeks. Right now, there's nothing there.
I'm not too concerned about it, though. From what I've read, the fuzzy fungus usually go away in 2 weeks to a month.