Rhizoctonia Foliar Blight of Cabbage in New York State

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Abstract
Late in the 1983 season, small, irregular, brown to black lesions developed on cabbage heads grown in western New York. These symptoms were observed initially on cabbage cultivars Superdane aned Greenwinter, which are grown primarily for fresh market. Rhizoctonia solani anastomosis group 1 was isolated from these lesions. Cultures of these isolates were dark brown, produced numerous small sclerotia, and had an optimum temperature of about 28.degree. C for mycelial growth. Growth rates at 28.degree. C averaged 2.1 mm/h. Attempts to induce the sexual state of this fungus (Thanatephorus cucumeris) under laboratory conditions were unsuccessful. Inoculation of intact cabbage heads or detached leaf segments with a mycelial suspension, sclerotial masses, artificially infested soil, or 3-day-old potato-dextrose mycelial agar disks of R. solani produced lesions similar to those observed in the field. Similar isolates of R. solani were recovered from inoculated plants. Cabbage foliar blight isolates of R. solani were also pathogenic to snap bean hypocotyls and leaves under high moisture conditions.