Maybe pseudomonas, maybe verticillium...this one seems to be particularly prone to dieback but Japanese maples generally are having quite a bit of trouble, it seems. Inadequate sanitation in production nurseries has been blamed for frequent problems with verticillium specifically, which is spread by infested soil.

What does this all mean? It's a six or seven year old tree, would the onset take that long? And what do I do?

And thanks

Search pseudomonas (on maples) and verticillium wilt on www.