Mountain Hemlock

I have been having needle problems on a mountain hemlock for about 3 years, each year it becomes a little worse. The effected foliage is on the north side of the tree and the needles are very dark almost black colour, the new growth is very weak. I have been spraying with a copper fungicide but it has had no affect.
The tree is about 12 ft tall and gets full sun.

If anyone has any knowledge of this disease I would appreciate any help.
Thank you.

 

Looks more like sooty mould on aphid honeydew. Is there any overhead tree canopy?

 

Thank you Michael. There is no overhead canopy, tree is growing in an open area.