苜蓿的毁灭性病害——黄萎病(Verti-cillium albo-atrum)已经传入北美,病区正迅速扩大。黄萎病最早在1918年发现于瑞典,二次大战前后已随带菌种子侵入西欧大陆和英国并进而向东欧和南欧扩展。1962年该病曾一度传入加拿大魁北克和不列颠哥伦比亚两省,但未能定殖。此后虽然美、加两国对进口苜蓿种子都采取了防范措施,但未能阻止黄萎病的传入。1976年突然在华 The devastating disease of alfalfa, verti-cillium albo-atrum, has spread to North America and wards are rapidly expanding. Verticillium wilt was first discovered in Sweden in 1918, and it had encroached upon Western Europe and the United Kingdom before and after World War II and further expanded to Eastern and Southern Europe. The disease was once introduced to Quebec and British Columbia in 1962 but failed to colonize. Since then, although the United States and Canada both adopted precautionary measures for the import of alfalfa seeds, they failed to prevent the introduction of Verticillium wilt. Suddenly in 1976 in China