Have you noticed anything strange while raking leaves this fall? If you look closely at some of your maple leaves you might notice a different color than the usual yellows and reds.
Some maple leaves have black spots on them, as if they’ve been speckled with tar. Fear not, tar isn’t raining from the sky.
The black spots on maple leaves, often referred to as tar spot, are actually a fungi. The fungal disease is of the genus Rhytisma, and only affects the leaves of maple trees. Sugar maples, red maples, and Norway maples are susceptible among others in the genus Acer. Fortunately this disease is purely aesthetic and does not affect the overall health of the tree. However, some leaves that are heavily infected might drop off the tree early.
If you notice the fungi on a maple tree in your yard it is actually quite easy to manage. The fungi overwinter on fallen leaves, waiting for the warm spring weather to ripen the spores. When the spores are released they float up and blow in the wind hoping to land on a new maple leaf host. To reduce the number of spores floating around it is best to rake up infected leaves in the fall and destroy them. Maybe an extra bit of motivation to rake up those leaves!