Question
I live about 25 miles south of Southern Yosemite. I just noticed that one of my oak trees has turned black from the trunk to about 7' up. It has a shiny surface to it, almost as if it was painted black with a clear coat then put over it.  This makes absolutely no sense to me, although I do notice a TON of woodpecker holes in the tree, especially in this area.  Any help you can give me would be appreciated. Thanks!

Answer
Sounds like sap from the wounds made by the woodpeckers. These are more than likely sap sucker woodpeckers which make holes in the bark and the sap flows and insects come to the sap and the birds come back and eat the insects. The sap of oaks has a tannic acid in it and is dark colored. I would spray the wounds with an insecticide this will kill the insects and discourage the woodpeckers. You can check with your local nursery for an insecticide for bark beetles or you could use liquid Sevin.