Water it! It looks like it needs watering. Certainly don't dry it out, out of worry for the white stuff.
If it's fuzzy, I'd say a type of fungus. It's a good fungus.
I watched a David Attenborough, kingdom of plants. Was very good, but I do love his docs. He talked about fungus and how beneficial they are for 90% of all plant life and trees in the world. The forest floor has miles and miles of white fungus roots and network running under the soil, all beneficial.
It's the closest I can relate, white fungus, stringy. Yours is white and fuzzy, seems similar enough lol.
Perhaps tell us about the plants care, conditions, soil/substrate? More info could help. But I would say look out for health issues on the tree trunk, branchs and leaves. Actually in the tree. Discolourations. If it is all good, no issues, spots, black etc, then I wouldn't worry.