Incidence and Geographic Distribution of Sweet Clover Necrotic Mosaic Virus in Alberta. C. Hiruki, Professor, Department of Plant Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada. Plant Dis. 70:1129-1131. Accepted for publication 2 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1129.

During a survey period from 1979 to 1983, sweet clover necrotic mosaic virus (SCNMV), a member of the dianthovirus group, was found widespread in the central and northern areas of Alberta where major soil types are black soil and dark gray soil, respectively. In these areas, SCNMV occurred predominantly on sweet clover; the only exception was a SCNMV variant found on alfalfa (Medicago sativa). The virus was not detected in alsike clover (Trifolium hybridum), red clover (T. pratense), white clover (T. repens), and crown vetch (Coronilla varia) growing in the areas where the virus was prevalent. Root and leaf infection occurred when sweet clover seedlings were dip-inoculated in a virus suspension or inoculated by pouring virus inoculum around the seedlings. The presence of Olpidium brassicae zoospores in the inocula caused no significant differences in SCNMV infection rates. Sweet clover weevil (Sitona cylindricollis) was found infesting both SCNMV-infected and uninfected sweet clovers (Melilotus officinalis and M. alba). When virus-free S. cylindricollis was fed on SCNMV-infected sweet clover for 5–10 min, the virus was detected in the head, body, and feces. However, weevil transmission experiments to young sweet clover seedlings were unsuccessful.