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First Report of Septoria Blight of Parsley in Ontario. R. F. Cerkauskas, Agriculture Canada, Vineland Station, Ontario L0R 2E0. J. Uyenaka, O.M.A.F., Milton, Ontario L9T 3J7. Plant Dis. 74:1037. Accepted for publication 17 August 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-1037B.

Severe Septoria blight, caused by Septoria petroselini (Lib.) Desmaz., occurred in 1988 in a 1O-ha commercial parsley (Petroselinum crispum (Mill.) Nym. ex A. W. Hill) field near Milgrove, Ontario. Foliar lesions were small, somewhat angular, and grayish brown, with a definite dark cinnamon-brown margin, and often contained dark pycnidia on the upper side of the foliage. Small, oval, cinnamon brown lesions on petioles were also occasionally observed. The fungus was isolated from both tissues onto potato-dextrose agar (PDA). Symptoms on spray-inoculated (1 X 105) spores per milliliter obtained from PDA plates, one plant per pot, four replicates) greenhouse-grown parsley cultivars Unicurl, Darki, and Bravour developed after 14 days and were identical to those observed in natural field infections. No symptoms developed on inoculated celery (Apium graveolens L.) cultivars Tall Utah 52-70 HK, Surepak, and Tendercrisp. The fungus was readily reisolated on PDA from artificially inoculated parsley plants. The hyaline, filiform spores observed from lesions were straight or flexuous with from zero to four cross-walls (generally one to three) and averaged 36.3 × 1.4 µm. This is the first report of Septoria blight of parsley in Ontario.