Influence of Powdery Mildew on Yield and Growth of Rosette Grapevines. R. M. Pool, Associate Professor, Department of Pomology and Viticulture, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. R. C. Pearson, Associate Professor, Department of Plant Pathology, M. J. Welser, Technician, Department of Pomology and Viticulture, A. N. Lakso, Associate Professor, Department of Pomology and Viticulture, and R. C. Seem, Associate Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. Plant Dis. 68:590-593. Accepted for publication 20 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-590.

Different levels of infection by the powdery mildew fungus Uncinula necator were established on Rosette (Vitis interspecific hybrid) grapevines growing in a vineyard at Naples, NY, by deleting portions of the recommended protective spray program. Infected vines had lower pruning weights and hence lower yield. Fruit quality was reduced because of higher acidity. Wines made from infected fruit were reduced in quality. Infection also reduced the winterhardiness of canes.