Posted: 09/07/2014 at 23:05
Most fungi will only affect one species of plant so it's unlikely to affect anything else. On one of the affected branches, is there any black or brown staining of the wood when it is cut through, or beneath the bark if you peel it back? If so, that is indicative of a fungal infection. I think it's a good idea to feed it to help it fight whatever the disease is. The only other thing I can think of is that it's roots are in soil which is (or has been) too wet - any possibility of that? All of the rain we had over the winter has badly affected a lot of things which prefer free-draining soil like Cercis.