White fluffy spots, and black spots on my acer!

I had a pretty acer negunda and it developed the white fluffy spots, when I looked it up discovered they were scale insects which infest ornamental trees, very hard to get rid of because the damage is done once you see the blobs. I attacked mine with metholated spririts as it was quite a small tree, Look it up on the RHS site, they are very helpful or anywhere you can get advice on scale insects - Good luck
Queenie

Yes, scale insects, the black spots you mention are probably from a fungus that grows on the faeces of the scale insects. They are hard to get rid of I'm afaid, but you might have luck if your tree is small as Queenie said.