The incidence of vims‐like symptoms and ryegrass mosaic virus in perennial ryegrass pastures in the West of Scotland

In 1972 and 1973 fields of perennial ryegrass in the West of Scotland were surveyed for ryegrass mosaic virus (RMV). Visual determinations of foliar symptoms were made in the field and leaf samples were collected for diagnosis of the virus by electron microscopy and by sap transmission to S22 Italian ryegrass. In 1972, ninety‐eight fields were surveyed and virus‐like symptoms were observed in 59%, but tests showed that only 21% were infected with RMV. In the more extensive 1973 survey, 201 fields selected on a stratified random basis were examined and whilst 45% had virus‐like symptoms only 5% proved to be infected with RMV. Symptoms were most readily seen in fields which had a high percentage of long, lush perennial ryegrass. Analysis of data collected in 1973 on management practices did not reveal any obvious association between the incidence of virus‐like symptoms and the cutting and grazing regimes, the grazing animal used or the level of nitrogen applied.