Experts and BHG readers answer.
moss balls on oak trees
Moss on trees is perfectly normal. You don't have to do anything to get rid of it and you sure don't have to cut down the trees. I'm not sure what you mean by moss balls--the moss is so thick that it's lumped up, maybe? That's not a problem, either. The moss doesn't harm the trees and usually it's attractive and has a damp woodsy or earthy smell.