You will probably get some input from other folks, but you can also send a message directly to Walter through his profile (look at the bottom left):
Jacque, if your willow tree has been fully girdled, that is, the bark has been chewed all the way around, your tree is gradually going to starve to death, because the layer that transports carbohydrates from the leaves to the roots, called the phloem, is right below the bark and is probably gone, too. Your tree has one chance: a fairly tricky procedure known as a bridge graft. It's really done best by a certified arborist, and may not be worth the expense for a willow tree. Here is a link to what is involved:
Douglas is right....once the bark is girdled, the tree dies.
You need to wrap every other tree in your landscape with one-half inch mesh hardware cloth. You can purchase a thirty-six inch high roll from a hardware store. Loosely surround each tree trunk with a couple of layers of wire and secure the ends.
Yes my probem is solved except for getting rid of the beavers in our lake. I loved that willow tree. Thank you for the input.