Viburnum die back
About 3 weeks ago the leaves on a central bough of a large (around 10 feet) viburnum suddenly turned brown/black and died. I removed the entire bough and there was nothing adverse to see - the stem looked perfectly healthy, just dead leaves. Now half of the viburnum has dead leaves and it looks as though the leaves on the "healthy" half are just beginning to die. There is still new growth from the base. Any ideas?