Rhytisma Affects Maples This Year

This maple is typical color intensity here in southwest Oakland County. The brilliant yellows, oranges and reds are dimmed this year by Rhytisma, a genus of fungi called tar spot because that's just what it looks like. It affects silver, sugar, red and Norway maples and box elder. The fungus doesn't damage the tree's overall health, but it's nasty looking and it's everywhere. I noticed the spots early in the year, and thought it was just immature maples that were impacted, but big trees have it, too. Leaves not raked up will overwinter the fungus to appear next year as well. The sidewalks are strewn with green maple leaves covered in big black spots. Hopefully, these will be raked and destroyed. If your maple is ailing with the fungus, get the leaves away from the trees as soon as they drop.