Angular Leaf Scorch, a New Disease of Grapevines in North America Caused by Pseudopezicula tetraspora. Roger C. Pearson, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. Franzine D. Smith, and Bernadette Dubos. Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456, and Institut National de la Recherche Agronomique, Station de Pathologie Végétale, Centre de Recherches de Bordeaux, Pont-de-la-Maye, France. Plant Dis. 72:796-800. Accepted for publication 12 May 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0796.

Pseudopezicula tetraspora, a recently described genus and species of ascomycete, was shown to be the causal agent of a newly recognized disease, angular leaf scorch of grapevines, in eastern North America. The disease has been found in the Finger Lakes region of central New York and in the Lake Erie region of western New York and Pennsylvania. In September 1986, the percentage of leaves with symptoms of angular leaf scorch in Finger Lakes commercial vineyards of Vitis interspecific hybrid DeChaunac, Rougeon, and Ventura was 72, 78, and 78%, respectively. Symptoms of angular leaf scorch were similar to the symptoms of a disease caused by Pseudopezicula tracheiphila (= Pseudopeziza tracheiphila) in European vineyards and known as rotbrenner. Angular leaf scorch was observed on 18 species of Vitis, on interspecific hybrids of Vitis, and on Parthenocissus quinquefolia (Virginia creeper). Diseased tissue placed in a moist chamber at 20 C developed numerous, small, gelatinous apothecia containing paraphyses and asci with four binucleate, reniform ascospores typical of P. tetraspora. Ascospores produced in pure culture were used as inoculum to reproduce the disease in the greenhouse. Fungicide trials and grower experience indicated that mancozeb and benomyl were effective control measures, whereas captan was ineffective.