Tar Spots

Leaf Diseases of Hardwoods

Tar Spots

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Tar spot caused by Rhytisma punctatum on maple.

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Tar spot caused by Rhytisma acerinum on maple.

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Rhytisma americanum on silver maple.

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Section through the black stroma of Rhytisma showing asci and ascospores. A few long, thin ascospores that have broken out of the asci can be seen.