Disease Note

Distribution of Asparagus Virus 2 and Tobacco Streak Virus in Asparagus Plantings in Southern Ontario. D. J. Wolyn, Department of Horticultural Science, University of Guelph, Guelph, Ontario. L. W. Stobbs, Agriculture Canada, Vineland Station, Ontario. Plant Dis. 75:430. Accepted for publication 23 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0430D.

Fifty emerging spears were collected in mid-May from each of 20 asparagus (Asparagus officinalis L.) fields in Norfolk and Simcoe counties of Ontario, Canada. Nineteen fields were planted with cv. Viking and one field was planted with cv. Lucullus Mid-Season. Plantations were 5-20 yr old (median = 9 yr). A section of each field (50 X 100 m), containing several diagonal transects, was sampled where transects intersected rows. Fresh spears were triturated in 0.01 M phosphate buffer containing 0.1% mercaptoethanol, pH 6.8, and extracts were rub-inoculated on Chenopodium quinoa Willd. Spears were also assayed by enzyme-linked immunosorbent assay against asparagus virus 2 (A V2) and tobacco streak virus (TSV) antisera provided by R. Stace-Smith of Agriculture Canada, Vancouver. AV2 was detected at all locations (14-100% infection, median = 94%). Incidences of infection were higher in older plantations (r = 0.5). TSV was identified in four fields (4-10% infection, median = 7%) and occurred only as coinfections with A V2. The cultivar Lucullus, in Simcoe County, had the lowest and highest incidences of AV2 and TSV, respectively. The remaining TSV-infected plantings were all located in Norfolk County.