I have two dogs but that's not the problem , I have no grass under the tree in the back. I have over seeded two years in a row and the same think happens year after year. I see little holes in the ground and dead grass where the roots of the tree would be. Could I have some type of insect. Reason I say this is I see small holes in the bark that has fallen from the tree. Carpenter ants? Could they be killing the grass as well.