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Disease Note.

Outbreak of Verticillium Wilt of Alfalfa in Quebec. C. Richard, Agriculture Canada Research Station, Sainte-Foy, Quebec G1V 2J3. Plant Dis. 71:761. Accepted for publication 5 May 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0761E.

The first discovery of Verticillium wilt of alfalfa (Medicago sativa L.) in North America was made in Normandin. Quebec, in 1962. Plants in the plot area were destroyed. and the disease was not observed in the province for 24 yr. Verticillium wilt wa reported in Washington and Oregon in 1976 (1) and in British Columbia in 1977 (2), then made its way east, but the province of Quebec was apparently not affected. No suspected plant was detected during the rainy summer of 1986, but suddenly in September 1986 the di case appeared at many locations in six different agricultural regions of Quebec. Verticillium albo-atrum Reinke & Berth. was isolated. positively identified, and tested for pathogenicity on the susceptible alfalfa cultivar Saranac by the bare-root-soak method. In severely infested experimental plots, alfalfa cuhivar Dekalb-135, Oneida YR, Trumpetor, WL 316, 5444 (Pioneer), and 88 (Cal West) were less affected than A1ouette, Apica. Armor. Drummor, Iroquois, Minto, Peak, Preserve, Riel, Saranac, Thor, Thunder, and 526 (Pioneer). The disease is known to be spread by secd and possibly by hay. This epidemic threatens the future of alfalfa and emphasizes the need for resistant adapted cultivars.

References: {1) J. H. Graham et a1. Planl Dis. Rep. 61 :337-340, 1977. (2) J. W. Sheppard. Can. Planl Dis. Surv. 59:60. 1979.