First Report of Crown and Stem Rot of Orchid (Orchis palustris) Caused by Sclerotinia minor

Orchis palustris Jacq. is a wild orchid native to wetlands in eastern Anatolia. During June of 2003, near Erzurum, Turkey, a decline of this orchid was observed in several meadows that had been irrigated for forage production. Stems were chlorotic, wilted, and collapsed. There was a soft, watery rot at the crowns and lower stems. White mycelium and black sclerotia formed on necrotic stem and crown tissues. The fungus was isolated from sclerotia on potato dextrose agar (PDA) and identified as Sclerotinia minor Jagger on the basis of small sclerotia (0.5 to 2.5 mm long) scattered throughout the colonies (2). Pathogenicity was confirmed by inoculating stems of 8-week-old plants with mycelial plugs from 5-day-old PDA cultures and enclosing inoculated plants in transparent plastic bags for 3 days. After 2 weeks, symptoms similar to those in the field were observed, and S. minor was reisolated from inoculated plants. Noninoculated control plants remained asymptomatic. The disease was previously observed on O. laxiflora Lam. in Turkey (1), but to our knowledge, this is the first report of S. minor infecting O. palustris References: (1) C. Eken et al. Plant Pathol. 52:802, 2003. (2) L.M. Kohn. Phytopathology 69:881, 1979.