Top of arborvitaes dying
Your best resource for diagnosing and treating your trees is to consult a certified arborist. An arborist is a certified and generally insured expert in trees and their problems. He or she can examine your tree and make recommendations regarding the health of the tree, any needed judicial pruning, and whether or not (in his opinion) it should be removed. You can find a certified arborist in your area here:
Click on "Find an Arborist" at the top of the page; then click on United States from the pull-down menu. Then enter your State and City. This should bring up a list of certified arborists nearest to you. Or you may be able to locate one under "Tree Services" in your local Yellow Pages.