I have a maple tree with black spots on the leaves. What is it and will it kill my tree?
The black spots are a fungus disease called Tar Spot. It infects Norway maple (including all of the horticultural forms such as "Crimson King"), Silver maple and Freeman's maple. The disease infects leaves late in the season and has little impact on the overall health of the tree. The disease is already widespread and sanitation (leaf removal) is not effective in reducing the infestation level for the following year, so let the leaves decay under the trees to at least improve the soil health. Norway maples are generally short lived along city streets, but the seeds move through storm sewers into natural areas where, once they germinate and grow, they are able to shade out native plants. Consider planting a replacement for your Norway maple.
Norway maple often gets powdery mildew (a white surface on the leaves) at the same time of year and it is also considered harmless to the tree.