Client of mine has a mountain hemlock, it had 3 main leaders and one just broke off. It appeared to have root rot. It's been growing for the last 8 years appearing to be doing well. It has great twig elongation in upper 50% of canopy but in lower canopy it has some compressed growth and on the needles there is a black color type of stuff on the needles. She was told soap and water would clear the issue up so she did and it worked. Yet it has come back again, I cannot figure out what it is that is the black film on the needles. Can anyone help me identify what it is ? And what I could do to treat it for her ?