As the leaves begin to descend down to earth, you may be noticing some of your maple trees having little black spots on the leaves. These spots are probably not a cause of concern because there is a good chance they are what we call Maple Tar Spot.
Maple Tar Spot is often found on Silver maples and Norway maples. The disease is caused by two fungi and often start as greenish yellow spots early in the summer. During the fall the spots begin to turn black as the fungus develops.
Although the spots are aesthetically unappealing, they often cause very little damage. They can accelerate leaf drop in the fall, but during this period the leaves are beginning to fall naturally. At this point, the leaves have been able to photosynthesize enough and little damage is done to the development of the tree.
Fungicide applications are rarely practical or recommended. If the tar spots are bothersome, work to remove those leaves from around the tree. This can help to remove spores that may cause future problems.
Guest Author: Andrew Muntz received his Master’s of Science in Turfgrass science and his Bachelors of Science in Landscape Horticulture at The Ohio State University, Columbus OH.