
Sycamore especially, also ash, maple, oak, dogwood. Brown blotches along leaf veins, early leaf drop, sometimes twig dieback. Worst after a cool wet spring.
Almost never fatal on an established tree. It looks alarming, the tree defoliates, and then it leafs back out. Most calls about it don't need a treatment at all.
Very common here in wet springs, particularly on sycamore. One of the most over-treated problems in the trade.