Question
We have a very large/old willow tree (trunk is ~4 feet in diameter).  While thinning out dead branches, I noticed bark peeling of one of the very thick arms of the main trunk.  Under the bark I found a worm (not a catepillar type).  A tree service came out and said that we do have worms - bad on that limb and likely through the trunk.  Can this be treated effectively to save the tree?  I am worried about safety since the arms coming out from the trunk are huge/heavy.  I am not sure if this is related, but I also notice that this spring the new growth/branches seem to have leaves only towards the ends and not all along the branch.  Is this related?

Answer
Sounds like borers--these can be controlled with an insecticide--check with your local garden /nursery type store and ask for an insecticide for borers. Mix this with water and spray the area of the trunk and branches affected. I would also fertilize the tree here is a web site that will give information on fertilizing a tree.
http://www.ext.nodak.edu/extpubs/plantsci/trees/h1035w.htm