I live in subd. full of very large Oak trees. Recent storms contributed to substantial limb breakage on my backyard neighbor's Oak tree. When he had an arborist take a look to see if it could be saved or should be cut down, he was told that it had been infested with black ants and that they had hollowed it out. They salvaged the tree by cutting off most of it's limbs and sure enough the remaining limbs appear to have a hollow section in the middle. His tree had appeared completely healthy before and produced plenty of leaves and billions of acorns. My neighbor was also told that once his tree was cut back, the ants would migrate and look for another tree to attack. So, now I'm concerned for our oak trees nearby. Sure enough, we now have black ants walking up the trunk of our tree. I've researched pest problems with trees and find lots of posts that claim that ants do not hurt trees. The arborist said they can be treated with some chemical that is illegal in US but is available online. I sure don't want ants but I don't want to poison my kids either. Any advice or input you could offer would be great. I'm not sure if my neighbor is being scammed or what could have caused his tree damage. Are ants to blame? How can we protect our trees from being hollowed out next? I love my trees but don't know much about them. Please help! Thanks!!