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Disease Note.

Purple Spot (Pleospora herbarum) of Asparagus in Oklahoma. K. E. Conway, Department of Plant Pathology, Oklahoma State University, Stillwater 74078. Plant Dis. 71:376. Accepted for publication 14 January 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0376F.

Purple spot (Pleospora herbarum (Pers.) Rabenh., often referred to as P. allii (Rab.) Ces. & de Not., anamorph Stemphylium vesicarium (Wallr.) Simmons) (1) has been reported on preharvest asparagus spears (Asparagus officinalis L.) from Michigan, Washington, and California during periods of cool, wet weather, reducing spear quality. Purple spot occurred in Oklahoma during June 1985 and 1986 as basal lesions on main stems of postharvest ferns; no lesions were observed on spears. Occasional lesions occurred on cladophylls in the upper regions of the fern and resembled lesions of Cercospora asparagi Sacco Symptoms were more severe on cultivar UC 157 2 than on cultivars UC 157 F1 , Mary Washington, and Viking. Pseudothecia were abundant on overwintered fern residue left on the soil surface. Bitunicate asci measured 137-170 X 20-24 µm; ascospores, mostly biseriate, were honey-brown and measured 32-40 X 15-17 µm. Inoculation of cladophylls with the Oklahoma isolate resulted in typical purple spot symptoms. As asparagus production increases in southeastern regions of the United States, diseases such as purple spot will have to be considered in disease management systems.

Reference: (1) J. A. G. Irwin et al. Aust. J . Bot. 34:281, 1986.