Our neighbor is obsessed with digging up roots that come into his property. We witnessed him doing this activity and spraying the roots. One tree has already died and been removed. Now a second tree has dead spots on only one side. This tree is one of four lombardy poplar trees on our property that he seems intent on killing. What actions should we take? We have talked with him and he assures us what he is spraying won't kill the tree but the root severing is another story. Not sure what we should do?

One suggestion would be to find a copy of arboriculture and the law by victor d. merullo and michael j. valentine, look through to find cases that apply to your situation, find an environmental lawyer and go after the culprit for funds incured sofar.