We have Willow (Golden and Red flanders) planted on an exposed site in a heavy clay on a slope which are about 3 years old and have thrived to date. Recently, the leaves have started to wither and die from the top down. I saw your response re. canker in a contorted willow, but in this case, the tree is affected from the top and the lower part of the tree is still healthy. The bark is also turning brown in the affected areas (top down). We have other will planted in another part of the garden that are not affected. Is there any treatment you would recommend?