The incidence of bacterial wilt caused by Xanthomonas campestris pv graminis in pasture grasses in the West of Scotland

Temporary hay and silage fields with a high proportion of perennial or Italian ryegrass (Loliumperenne and L. multiflorum) in Ayrshire, Dumfriesshire, Lanarkshire, West Perthshire and Stirlingshire were surveyed in mid‐summer in 1979 and 1980 for the presence of bacterial wilt. The preliminary survey in 1979 showed that the disease was present in approximately half of the fields in the area. A quantitative survey of 24 fields in 1980 revealed the disease in 71% of these fields at densities between 100 and 380,000 symptom‐bearing tillers per hectare. Most disease was found in ryegrass, but occasionally diseased plants of cocksfoot (Dactylis glomerata) and timothy (Phleum pratense) were found. Tall and meadow fescue (Festuca arundinacea and F. pratensis) were also susceptible to infection in the laboratory (cut leaf and root dip inoculations). Ryegrass cultivars varied in their susceptibility to laboratory inoculation. Cultures of Xanthomanas campestris pv graminis showed no loss of virulence following freeze‐drying and revival.