Hi, My brother has a forty-foot Douglas fir tree. The top one-fourth of the tree has exfoliated. I have examined the tree at the bottom to the extent I am able and could find nothing that appears amiss. I have searched online for diseases but could find nothing on exfoliation for this tree. There is another Douglas fir whose trunk is about five feet away, which appears healthy. Two different arborists from tree services have come to see the tree and had no comments about it's health but just offered to cut it down. He would like to save the tree. Any leads you can provide about what might be going on with this tree or what kind of expert he should approach would be greatly appreciated. Thanks so much.