Mushroom photo gallery
The Tar Spot Fungus, Rhytisma punctatum, grows on the leaves of Big Leaf Maple and other deciduous tree species. When the leaves drop in the fall, you can often see the black spots (groups of spores) surrounded by green areas on some of the leaves. The fungus stimulates the leaf to retain chlorophyll and continue photosynthesizing after it drops, providing food for the fungus. Tar Spot Fungus is not believed to harm the trees much, if at all.