My trident maple has come down with a case of leaf spot (Phyllostictum).

My suggestions:
Give it more air and sun.
Use Pro-TeKt. This toughens the leaves & makes them more resistant.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)