THE SWEETCLOVER WEEVIL, SITONA CYLINDRICOLLIS FAHR.

Abstract

Farmers in Manitoba and Saskatchewan have reported considerable losses of sweet clover from the attacks of a small, dark grey weevil, Sitona cylindricollis Fahr. This insect is widely distributed in central and southern Europe and occurs in Ireland, England, Germany and France. It is not known when it was first introduced to the North American continent. Brown (2) found it abundant in 1927 from Montreal, Que., to a point on the International Boundary near Hemmingford, Que., and the Canadian National Collection contains specimens taken at Hemmingford in 1924 and 1925. Brown also reports that this species, was very abundant in the Ottawa, Ont., district in 1928 and that he took it at Shediac, N. B., in 1939. Hyslop (6) wrote thal S. cylindricollis was first found in the United States in 1933 at Middlebury, Vt., and that it was collected at Storrs, Conn., Amherst, Mass., and on the New York side of Lake Champlain Valley. In 1935 Caesar (3) found it near Lindsay and Newmarket, Ont., where it war causing severe damage to sweet clover. It was first recorded in Manitoba in 1939 when a widespread infestation occurred. In 1940 it completely defoliated a field of sweet clover near Waldeck, Sask., and by 1943 it was abundant at Medicine Hat, Alta. Following this rapid spread through the continent it has shown periodic fluctuations. Severe damage occurred in Manitoba in 1939 and 1940. In 1941 and 1942 it was somewhat reduced, becomming severe again in 1943, 1944 and 1945.