Trying to save a tree

[Dustin Lane]

I have a tree with a damaged section of bark. It seems it has been like this for some time. The wood where the bark was is decaying and insects are boring into the wood. I fear this will eventually kill the tree and would like to save/protect it. Is there something I can do to accomplish this? I was initially going to just paint the area to seal it off from the elements but I'm not sure that is a good idea. Here is a picture and for reference this damaged area is about 4 feet tall. All information I find elsewhere on the net is for freshly injured trees. Any advice you guys can provide is much appreciated.
http://dustinlane.com/gallery/d/49398-2/IMAG0090.jpg

[Chuck Wintle]

My suspicion is once rot and insects have gotten in then the tree is doomed.

[Myk Rian]

We have a couple maples with that. I spray painted the areas black. (It's what I grabbed off the shelf). Seems to be keeping the insects out.

[Larry Frank]

I will treat for insects and then a tar product to seal the area. You might also look at fertilizing the tree and making certain it gets enough water.

[David G Baker]

I have seen tree wounds filled with concrete. Not sure how well it worked. I sprayed a similar wound on one of my larger oak trees with the black spray stuff sold in nurseries for spraying on trimmed branches. It stopped the invasion of carpenter ants for around 5 years until I removed the tree because it leaned toward one of my buildings and I get straight line winds occasionally that have cost me around 20 trees in the past.