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Disease Note

Occurrence of Amphobotrys ricini on Prostrate Spurge in Oklahoma. V. M. Russo, USDA-ARS, South Central Agricultural Research Laboratory, POB 159, Lane, OK 74555. A. Y. Rossman, USDA-ARS, Systematic Botany and Mycology Laboratory, Beltsville, MD 20705. Plant Dis. 75:750. Accepted for publication 19 February 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0750C.

Prostrate spurge (Euphorbia supina Raf.) is a spreading, recumbent weed that is sometimes troublesome in vegetable production. The weed, growing in rows of bell pepper at Lane, Oklahoma, was infected with a gray mold. Symptoms, including girdling stem cankers, were observed in 1990. The growing season was categorized by a wet spring followed by a hot, dry July and August. All aboveground parts were necrotic within 4 days after expression of signs. Mycelia and conidia of Amphobotrys ricini (Buchwald) Hennebert, were produced from infected tissue on potato-dextrose agar. Koch's postulates were fulfilled using sclerotia from fungal cultures placed in contact with leaves and stems of prostrate spurge grown in the greenhouse. The range of the fungus, previously known from Florida, Louisiana (1), Maryland, Mississippi, and Texas (2), is extended to Oklahoma. A culture is deposited at the ATCC and a dried specimen, at the U.S. National Fungus Collections.

References: (1) G. E. Holcomb et aI. Plant Dis. 73:74, 1989. (2) N. G. Whitney and R. A. Taber. Plant Dis. 70:892, 1986.