Maple Trees with Tar-like Spots?
Kalamazoo, Mich.- Have you noticed large yellow and black spots on maple trees in your neighborhood? MSU Extension offices across the state have been receiving numerous questions about these spots on their maple leaves that make the trees look unsightly and ill.
The yellow and black spots on maple leaves are caused by a disease called tar spot that has been visible in this area during the past several years. Not all varieties of maple trees are affected by this disease.
Tar spot is a harmless fungal disease that begins in the spring as a small pinpoint infection, and spreads in summer to a large yellow spot on the leaves.
At the current time, you can see raised black spots on the leaves that are actually the reproductive structures and the fungus that is causing the disease.
The spots will appear as black-colored shiny areas on the leaves and can be somewhat raised on individual leaves. Hence the name of the disease, tar spot, since it appears that someone has dropped globules of tar on the leaves.
This is a cosmetic, harmless and nuisance disease that rarely harms or kills trees. Because this disease shows up late in the season and near the time of leaf drop, it has limited impact on the health of your maple trees.
Maple tree owners may notice some leaves dropping prematurely. The only control available is to rake and remove all fallen leaves now and throughout the fall; this will reduce the amount of disease for next year (this fungus over winters in the soil). It is not a good idea to mulch diseased leaves back into the lawn.
Maintaining good plant health practices, like tree fertilization, may also help the trees fight off this infection next year. Tree fertilizer spikes for hardwood or deciduous trees may be purchased from any retail business selling gardening supplies. Follow package instructions for quantity and placement.
To obtain more information about tar spot or other home Horticulture issues, call Linda Whitlock, Consumer Horticulture Coordinator at the Kalamazoo County MSU Extension Office at (269) 383-8815 or email her at whitlo13@msu.edu
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