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Etiology

Etiology of Stemphylium Leaf Blight of Onion. Nina Shishkoff, Anna E. Jenkins postdoctoral fellow, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853; James W. Lorbeer, Professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853. Phytopathology 79:301-304. Accepted for publication 13 September 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-301.

A species of Stemphylium was isolated from lesions on leaves of onion plants grown commercially on organic soil in New York in 1985 and identified as Stemphylium vesicarium. In controlled inoculations the fungus caused lesions on leaves of all ages of onion plants, especially on older leaves. Rubbing leaves of greenhouse-grown onion plants with bleached, nonabsorbent cotton to damage the cuticle increased the number of lesions per leaf. The number of lesions per centimeter of leaf length increased the longer plants were incubated in a mist chamber after inoculation with the pathogen. Lesions similar to those produced by the New York isolates were formed on onion leaves inoculated with isolates of S. vesicarium from asparagus in Washington and from onion in Texas.