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.
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.