My false acacia tree has no leaves yet

I was reading recently that the RHS Advisory Service has been receiving many enquiries about ailing Robinia trees. Their research continues evidently as they cannot put down the deaths to one particular pathogen etc. One contributory factor may be wet - they like free draining conditions - and the proliferation of a leaf spot fungus which prefers wet conditions. Honey fungus and root rot is another possibility. Symptoms of the decline are leaves falling early and sadly, most, if not all, do not recover.