I have an oak tree that is producing sucker trees all over the lawn surrounding the tree. They are not coming up at the base of the tree but from the roots. I believe that the reason is because the lower large branches and their smaller branches that are coming off of them are covered with spanish moss, which has killed them. The only part of the tree that is healthy is the top branches. How do I remove and stop the sucker trees from growing without killing the entire tree. If I have to cut it down, how do I kill the root system, which seems to cover my whole lawn and even under my fence to the backyard.