Leaf Spot of Vitis vinifera L. Caused by Xanthomonas Sp.. T. J. Burr, Assistant Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. B. Hurwitz, Research Technician, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. Plant Dis. 64:698-700. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-698.

A bacterial leaf spot was identified on the grape cultivar Cabernet Sauvignon in 1978 on Long Island, NY. Numerous interveinal, water-soaked lesions, which often coalesced into large necrotic areas, were apparent on infected leaves. The pathogen was identified as a Xanthomonas sp. biochemically and physiologically different from X. ampelina, a known pathogen of grapevines that causes similar leaf-spotting symptoms. Greenhouse pathogenicity tests were positive on the cultivars Cabernet Sauvignon and Thompson Seedless.