Leaf blight in Hawthorn

I have a problem with a leaf blight on a decorative hawthorn tree. Last spring, its leaves curled and died on a few branches. I thought this spring it was fine when the tree had grown bigger, the leaves all came out green and healthy...and now ALL the leaves have curled up brown and look dead. Some disease I think must have taken hold. How do I cure it? I don't want this to happen every year. (A nearby cherry tree is unaffected.)