Wilt of basil (Ocimum basilicum L.) branches was observed in home gardens with a past history of Sclerotinia rot in Ste. Anne de Bellevue, Quebec, in the summers of 1994 and 1996. The wilt was accompanied by brown, longitudinal discoloration of the stem, with dark brown to purple-colored advancing margins. No rot or external mycelium was seen on mature woody portions of the wilted branches. Sclerotinia sclerotiorum (Lib). de Bary was isolated from wilted stems on 2% water agar and potato dextrose agar (PDA). Symptoms were reproduced in the greenhouse in 1995 and 1996 by inoculating stems of 10 1-month-old plants with mycelial plugs from 7-day-old PDA cultures. Wilt and necrosis of the outer layer of the inoculated stems were observed in all plants and the pathogen was reisolated from stems. During rainy periods in July 1996, sclerotia (3 to 6 mm diameter) formed on the stems and leaves of some infected plants in gardens. S. sclerotiorum has been reported in the U.S. on greenhouse-grown basil (1), but this is the first report from Canada and from field-grown plants. This disease may be confused with Fusarium wilt on mature plants, because of the dark discoloration of the stem, severe wilting, and lack of white, cottony mycelium.
Reference: (1) G. E. Holcomb and M. J. Reed. Plant Dis. 78:924, 1994.
