There are numerous causes of spots on the leaves of willows, some not very injurious and will need no treatment while others may. A good arborist should be able to tell which you have and what to do.

kimmq is kimmsr

i am never concerned about late fall leaf damage on a deciduous tree ...

is this such ??? .. if so.. the problem will fall off soon ...it is mid october ...

if not.. we need a tree ID.. and your location ...

ken

Willows as a genus are prone to a myriad of problems, however leaf spots - and they can get a variety of them - are generally not anything that can cause substantial harm to the tree and seldom need to be treated. At this time of the season - mid October - all you need to do or should do is clean up any fallen leaves and dispose of them. This will eliminate the potential for any fungal spores to overwinter and promptly reinfect the tree next spring.