Question
We bought our first house about five years ago, and we had a couple of maple trees that were approximately 7-8 years old on one side of the house.  A year or two after we moved in, I noticed that both of the trees had scars in their trunks around which they lost all of their bark. I believe these scars have gotten bigger with time  One of the trees died a couple of years ago (it budded leaves in the spring, but the leaves turned black within a couple of weeks).  I recently had gentlemen from a nursery come out to take a look at the other tree, and he mentioned that it had dry rot and would only last a few more years.  Since I am thinking that this is probably what caused the first tree to die, I was wondering if there might be an explanation for why they both succomed to dry rot and if there is anything I can do to prevent this in the future. Thanks for your help.

Answer
decay fungi get into the woody part of trees through wounds. maples have a thin bark and if the bark is wounded then these decay fungi can enter. Decay fungi cause little growth problems with maple BUT can cause the trunk to weaken subjecting the tree to wind throw.
I would suspect the cause of the wound being an insect called a borer. There is not anything that can be put on the decay fungi to stop it--the best thin is to fertilize the tree helping the overall health. use 10-10-10 fertilize at the rate of 1 lb per inch of tree diameter --spread this around the tree and water in good. fertilize now and again in the spring and summer. I would also spray the wound area with an insecticide for borers --Merit is one of the newer insecticides for borers. Check with your local  nursery. garden type store for Merit.