Question
Do carpenter ants move under ground? I have a large oak tree that you would never know is in any trouble except for the sawdust falling from an old wound. Looks healthly enough Can see no ant movement on ground or tree. HELP

Answer
If you are not seeing ants it more than likely not carpenter ants but borers that are leaving the sawdust. Spray the area of the trunk with an insecticide called Onyx or Merit. This will kill the borers and the sawdust will stop. The insects are just taking advantage of the softer wood that the decay fungi has created. The decay fungi is in the dead woody cells and will not cause the tree any real health problems. The living area of the tree is just under the bark. Borer insects infest when the tree is under stress. I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Apply the fertilizer just before a good rain storm and you will not have to water. This will increase the overall health of the tree and help the tree fight off insect and decay fungi. Fertilize now and again in the spring.