Powdery Mildew Occurrence on Greenhouse Tomato Plants in New York. D. M. Karasevicz, Department of Plant Pathology, Cornell University. Ithaca, NY 14853. T. A. Zitter, Department of Plant Pathology, Cornell University. Ithaca, NY 14853. Plant Dis. 80:709. Accepted for publication 29 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0709C.

Powdery mildew has been identified on greenhouse-grown tomato (Lycopersicon esculentum Mill.) for the past 2 years in New York State. Dense, while patches develop on upper and lower leaf surfaces. Leaves in the middle and lower canopies arc most affected. Similar dense patches have been noted on stems; fruit, however, is unaffected. Infection is ecto-phytic. Only the Oidium imperfect state of the fungus has been found. Fibrosin bodies have not been found. Based on conidia morphology, the perfect state is assumed to be a species of Erysiphe. The disease is different from the powdery mildew caused by Leveillula taurica (Lev.) G. Ar-naud reported on tomato in warmer climates. Conidia average 35.8 µm long by 16.8 µm wide. These measurements are within the range given in other references on this pathogen. Cultivars affected include Caruso, Trust, FL93F1, Match, Pik Red, Rutgers, Celebrity, Glamour, and Mar-globe. A similar disease has been documented in greenhouses in Canada (1), England, and Greece, and in greenhouses and fields in Hungary (2). The disease has also been reported in greenhouses in Pennsylvania and Florida. This is the first known report of powdery mildew on tomato in New York.