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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. |