Tar Spot in Illinois
LOWFungus
Tar Spot is currently active in Illinois. Watch your susceptible trees closely and act early.
About Tar Spot
A very common and distinctive fungal disease of maple leaves. The raised black spots are dramatic in appearance but the disease is almost entirely cosmetic and does not harm tree health. It is most severe in cool, wet years. The fungus overwinters in fallen leaves.
Symptoms to watch for
Raised black tar-like spots on upper surface of maple leaves, spots are roughly circular and up to half an inch in diameter, spots start as light green-yellow areas in early summer then darken to black by late summer, mostly cosmetic with no significant impact on tree health, heavy infections may cause minor early leaf drop
Trees at risk in Illinois
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Treatment options
Fall Leaf Cleanup
Rake and remove fallen maple leaves in autumn to reduce the fungal inoculum for the following spring. Composting or municipal leaf collection are both effective since the fungus does not survive composting.
No Treatment Necessary
Tar spot is cosmetic and does not harm tree health. No fungicide treatment is recommended for landscape trees. Raking leaves is the primary management strategy.
Recommended Products & Tools
Helpful supplies for managing Tar Spot. Always read and follow label directions, and confirm a diagnosis before treating.
Broad-spectrum protectant for many fungal leaf and bark diseases.
Preventive spray for needle cast, leaf spots, and blights.
Sharp, clean cuts to remove affected wood — a tree-care essential.
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Browse all Illinois arborists →Frequently asked questions
Is Tar Spot in Illinois?
Tar Spot is currently active in Illinois. Watch your susceptible trees closely and act early.
What does Tar Spot look like?
Raised black tar-like spots on upper surface of maple leaves, spots are roughly circular and up to half an inch in diameter, spots start as light green-yellow areas in early summer then darken to black by late summer, mostly cosmetic with no significant impact on tree health, heavy infections may cause minor early leaf drop
What trees does Tar Spot affect in Illinois?
It affects Sugar Maple, Red Maple, Japanese Maple. Susceptibility varies by species.
How do I treat Tar Spot?
Options include: Fall Leaf Cleanup, No Treatment Necessary. Confirm the diagnosis before treating, and consider a certified arborist for high-value trees.