Hello Jack: Usually when any tree begins to suffer a lose of bark there is a larger problem behind it. Damage to that side of the trees root system, damage to the trunk itself or perhaps a lighting strike. You will often find a variety of insects behind the dead bark, mostly those using the area to hide behind, but also boring insects that have found the stressed tree after the initial damage, whatever that is/was. It can take several seasons for the bark to come off, so the damage may have been caused 2-3 years ago. Since a tree is alive around the outside, you can estimate how extensive the damage is. If it is a large tree with structures nearby, you have some safety concerns to deal with and you should consider finding a certified and properly insured arborist to evaluate your tree. If it is "out in the woods" you could let nature take it's course and do nothing. Insects and wildlife will live on it, in it, feed on it until in falls down naturally, then a different set of insects and decay organisms will take over.
Sincerely, Richard Hentschel
