Tar spot

Tar spot - Rhytisma vitis
Annemiek Schilder, MSU Plant Pathology

Tar spot is a minor disease that occurs mostly on wild grapevines. This fungal disease is characterized by black, slightly raised spots about 1/10 to 1/5 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.

Additional information

Search MSU Fruit CAT Alert newsletter for articles.
MSU Diagnostic Services
Special grape disease problems and controls (from Michigan Fruit Management Guide)

Site map About us Copyright/Linking

Funding for this web site provided by Project GREEEN, American Farmland Trust, EPA Region 5's Strategic Agricultural Initiative program, The National Foundation for IPM Education, the Center for Agricultural Partnerships and the MSU Integrated Pest Management Program
in collaboration with MSU Extension and the Michigan Agricultural Experiment Station.
Updated 12/03/07 Contact: J.N. Landis.