PHYLLOSTICTA LEAF SPOT, sometimes called frogeye leaf spot, is caused by the fungus Phyllosticta minima, and is common on red, silver, Norway, and sugar maple species. Round spots or lesions will appear on the leaves, usually in the lower third of the tree where there is more moisture. Leaf spot disease is more severe in rainy seasons. Most trees are able to tolerate the disease but measures can be taken to prevent further spread of infection. Avoid excessive water on the tree and rake up leaves that fall. In rare severe cases, fungicides can be used in the spring.
Info from University of Delaware Cooperative Extension