Pierce’s Disease on Muscadine Grapes in North Carolina. R. D. Milholland, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Pi-Yu Huang, Research Cooperator, C. N. Clayton, Professor Emeritus, and R. K. Jones, Associate Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 65:73-74. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-73.

Bacteria with rippled cell walls averaging 0.5 × 1.4 µm were consistently observed in the lumen of xylem vessels of muscadine grape leaf veins and petioles with marginal leaf burn symptoms. The rickettsialike bacteria in the xylem vessels and successful transmission of an infectious agent by grafting indicates that the marginal leaf burn problem on muscadine grapevines in North Carolina is Pierce’s disease. This is the first report of this disease on muscadine grapevines in North Carolina. The erratic symptom expression on the cultivar Carlos did not appear to be related to winter temperature.