Posted: 11/10/2012 at 21:40
There are two possibilities that I can think of. If the blossom is fading very fast and the leaves are falling early you may have blossom wilt, described, with treatment, here.
Alternatively, and perhaps more likely, you may have canker - see here.
Although there is treatment for both these problems, if you tree is badly affected I would be tempted to replace it with a fresh one.