Disease Note.

First Report of Gray Mold Blight Caused by Amphobotrys ricini on Crown of Thorns in Thailand. N. Sanoamuang, Department of Plant Pathology, Faculty of Agriculture, Khon Kaen University, 40002, Thailand. Plant Dis. 80:223. Accepted for publication 2 January 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0223D.

In August 1994, a grower of crown of thorns (Euphorbia milii Des Moul. var. splendens (Bojer ex Hook.) Ursch & Leandri) in Khon Kaen Province, in northeastern Thailand, reported severe problems with disease symptoms typical of gray mold blight on blossoms and leaves. The problem became widespread in the following year (August and September 1995) among many commercial growers in the same province, as well as in Bangkok, Nakhonpratom, and Samulsakhon in central Thailand, and Chiengmai, Lampang, and Prae in northern Thailand. The symptoms included rot on flowers, blight on leaves, and dieback of stems, which the fungus invaded through the petiole. Pieces of infected flowers, leaves, and stems were surface sterilized for 5 min in NaOCI and plated onto water agar. The emerging mycelia were transferred onto potato dextrose agar. Amphobotrys ricini (Buchwald) Hennebert (syn. Botrytis ricini Buchwald, perf. Botryotinia ricini (Godfrey) Whetzel) (1,2) was the only fungus isolated from diseased pieces. Inoculation by placing a drop of conidial suspension (1 x 105 conidia/ml) of Amphobotrys ricini onto wounded flowers, leaves, and steins under very moist condition reproduced the symptoms observed in the commercial operations, thus completing Koch's postulates. This is the first report of Amphobotrys ricini on crown of thorns.