THE PREVALENCE OF TOMATO SPOTTED WILT VIRUS IN WEEDS AND CROPS IN SOUTHWESTERN BRITISH-COLUMBIA

A survey was conducted to determine the prevalence of tomato spotted w ilt virus (TSWV) in southwestern British Columbia. Over 2600 samples f rom 38 commercial operations were collected and tested by enzyme-linke d immunosorbent assay (ELISA). Twenty-five of the 38 sites had plants infected with TSWV. The incidence of the lettuce and impatiens strains of TSWV was equal outside the greenhouses, but the impatiens strain w as more prevalent inside the greenhouses. TSWV was detected in four pe rennial weeds (Trifolium spp., Cirsium arvense, Rumex acetosella, and Oxalis sp.), one biennial weed (C. vulgare), three winter annuals (Ste llaria media, Senecio vulgaris, Capsella bursa-pastoris) and five annu al weeds (Cardamine oligosperma, Medicago lupulina, Galium sp., Gerani um molle and Sonchus oleraceus). Nine of the infected weed species gre w outside the greenhouses. The only viruliferous thrips species collec ted during the survey was the western flower thrips (Frankliniella occ identalis) and it was the only thrips species collected inside greenho uses. TSWV is widespread in southwestern British Columbia and appears to be established in weeds outside the greenhouse operations.