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Ascochyta tritici on Wheat. A. L. Scharen, Research Plant Pathologist, Crops Research Division, ARS, USDA, Plant Industry Station, Beltsville, Maryland 20705; J. M. Krupinsky, Agricultural Research Technician, Crops Research Division, ARS, USDA, Plant Industry Station, Beltsville, Maryland 20705. Phytopathology 61:675-680. Accepted for publication 20 January 1971. DOI: 10.1094/Phyto-61-675.

Ascochyta tritici was identified on wheat leaves collected in 11 localities of Pennsylvania and New York in 1969. Nine cultures of the fungus were compared with six isolates collected in Ohio and Pennsylvania in 1968. All were designated “atypical Septoria nodorum“ at that time. All isolates were stable in cultural characters, with a strong tendency to produce papillate, warty pycnidia. Ascochyta tritici isolates varied in pathogenicity when inoculated on 12 lines of wheat. Ascochyta tritici was a weaker pathogen than Septoria nodorum, producing less severe symptoms and fewer spores under similar conditions. Oats, barley, rye, corn, and triticale were inoculated with A. tritici and S. nodorum under greenhouse conditions. All hosts, except triticale, were less severely infected than was wheat, based on symptoms and numbers of spores produced. Redcoat wheat grown in soil collected from the same fields where leaf samples were taken failed to exhibit any symptoms of disease.