Question
while burying a cable line at a customers house we cut a root on this pear tree. the root was only about 3 inches under the ground. the customer claims that his tree is dying now because of this. this was done back in July and is now august. the root was about the diameter of a nickel. would this one little root being damaged kill this entire tree. the tree is already dead in the center top limbs and is now dying on the lower out side limbs.the tree is about 12 years old. please help? and thank you.

Answer
No I doubt the cutting of one roots would kill a tree. IF you cut more than 30 % of the roots of a tree you will get dieback on the side that the roots were cut. The trench through a root system should not cut more than the 30% or you can have dieback. So it will depend on where the trench was dug and how close it came to the tree. One root would not make a difference to the foliage or if it did it would effect the limbs on the side that was cut. It sounds like a coincidence that the tree is dying and not from the trench. With out seeing the tree and the cut that would be my thoughts.