I live in the Welsh valleys, UK.
We have a Weeping Kilmarnock Willow,1.5 mts high, and about 5 years old, and has a mass of of leaves, it does bear lots of catkins.
For the last 3 years, in June, the underside of the leaves develop a bright yellow/orange powdery spotted groath, the leaves curl, and drop of,the deterioration being quite rapid.
After winter the tree regenerates,and is quite wonderful again until early june. Any help would be apreciated.