Question
I live in South Texas and have an oak tree in my front yard.  The tree has a rather large gaping hole in it and I noticed there were many carpenter ants and some termites on the wood.  When I pulled on some of the bark and wood of the tree it broke away fairly easily making the hole even larger.  One area of the tree is quite hollow.  When I look up into the tree it appears to be healthy with green leaves all the way to the top.  I sprayed the carpenter ants and termites with insecticide and put some tree paint on the exposed wood.  What do you think about this situation?  Any suggestions?  

Answer
The insides of a tree is composed of wood that is not a live. And if anything damages the bark protecting the wood an insect of a decay fungi can enter and rot out the tree. It will continue to live and be healthy. The hollow tree will lose some of its strength and sometimes limbs will break off due to the hollowness and during high winds. You can actually fill the hole similar to what a dentist would do for a cavity in a tooth--but all the old dead decaying material would need to be gotten out an the surface cleaned. Not something I would recommend. I would cut any bark that is loose off and spray the area with an insecticide but not use the "tree paint" this paint will actually slow the cells around the wound down and slow the healing process. The tree will try to grow over the wound and if the wound is not very large will close the outside hole--the inside will still be decaying and hollow. As long as the foliage is green and healthy looking the tree is OK and should live a long time.