First Report in Michigan of the Teleomorph of Stemphylium vesicarium, Causal Agent of Purple Spot of Asparagus. T. A. Evans, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. C. T. Stephens, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 68:1099. Accepted for publication 17 September 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-1099e.
In the spring of 1984, small black pseudothecia (0.25-0.55 mm diam) were found on the surface of asparagus debris. Bitunicate asci and muriform pigmented ascospores were observed in hand sections from pseudothecia. The structures were identified as pseudothecia of Pleospora allii (Rab.) Ces. & de Not. Single ascospores produced hyphae and conidia identified as Stemphylium vesicarium (Wallr.) Simmons. Ascospores collected from pseudothecia produced small elliptical purple lesions on wounded asparagus spears in vitro; lesions were identical to those produced by the conidia of S. vesicarium. No symptoms were produced by conidia or ascospores on unwounded spears. This is the first report of the teleomorph (which we believe to be the main overwintering mechanism for the fungus) of S. vesicarium in Michigan.