Maple leaves have black spots

Maple Leaf Tar Spot

Q. I noticed that the maples in my neighborhood have black spots on them. Are the trees sick?

A. Based on your description, it sounds like the trees are infected with maple leaf tar spot, known scientifically as species of Rhytisma fungi. Leaves that are infected with this fungal disease have round, light green to yellowish-green areas approximately ½ to 1 inch in diameter that eventually blacken. Heavily infested trees may lose their leaves prematurely. Trees infected with maple leaf tar spot are unsightly, but the fungal disease does not affect the overall health of the plants. Fungal spores can overwinter; therefore, it is important to remove all leaves as soon as they fall to lessen the impact of the disease next year. Because maple leaf tar spot is primarily a cosmetic disease, fungicide treatments are usually not necessary.

Please contact Plant Information Service at (847) 835-0972 or email plantinfo@chicagobotanic.org for a positive diagnosis and if you feel chemical treatment options are warranted.