I have a maple tree in my yard the I figure is at least 50 years old. The main trunk splits off into two. Where the trunk splits I recently noticed a rotted hole just above the split. The trunk seems to be rotting in that area. The hole is about 6-7 inches in diameter and about 4-5 inches deep. I didn't notice any fungus or insects, but the hole is damp. Besides the hole in the tree, it looks completely healthy. What should I do? I really don't want to lose the tree. Our yard is the only yard in the neghborhood that has more than four trees! Any suggestions would be very helpful. Thanks.