Tar spot

Disease

Tar spot

Rhytisma vitis

Photos

Black spots surrounded by a circular brown halo.

Tar spot is a minor disease that occurs mostly on wild grapevines. This fungal disease is characterized by black, slightly raised spots about 1/12 to 1/6 inch (2 to 4 mm) in diameter. A spot may be surrounded by a circular brown halo up to 2/5 inch (1 cm) in diameter. The fungus overwinters in these spots. In the spring, they release airborne spores, which infect the new leaves.

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