Not trying to hijack the thread, but what dmccarty says about trees dying with no apparent cause reminds me of the sugar maple in my side yard, it was about 25 years old and 16" across at the base when cut down, about 8 years ago I noticed many of the limbs were dying for no apparent reason, the limb dieback got progressively worse until close to two thirds of the tree was dead. when I cut it down two years ago I found no hollowing of the trunk and no sign of disease. The only reason I could think it might have died is because back in 2002 and 2003, we hired an excavating contractor to come in and dig a new foundation hole, although the hole was at least 25' from the tree trunk, a LOT of heavy dump truck and front end loader traffic crossed dozens of times over at least a third of the roots and I suspect soil compression was the reason for the dieback.