Question
MY WILLOW OAK TREE BARK HAS TURNED BLACK. IT DOESN'T SEEM TO GROWING AS WELL AS LAST YEAR . IT IS AROUND TWO YEARS OLD. THE LEAVES ARE NOT AS GREEN (LIGTH GREEN TO YELLOW) AS THEY WERE LAST YEAR.

Answer
I would fertilize it with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. This should return the leaf color to normal. Not sure what the back bark could be it could be a sooty mold that is feeding on honeydew from aphids--if so the area should be sticky. If it is sticky you can control the aphids with a insecticide spray called Orthene sprayed on the foliage. The sooty mold will not harm the tree and will go away as the tree grows.