The Development of Eyespot on Seedling Leaf Sheaths in Winter Wheat and Winter Barley Crops Inoculated with W-type or R-type Isolates of Pseudocercosporella herpotrichoides

In 1986–88 the development of eyespot lesions in winter wheat or winter barley differed plots inoculated with W-type isolates of Pseudocercosporella herpotrichoides and plots inoculated with R-type isolates. In the spring of 1986, after a cold winter, the incidence (%shoots infected) and severity (number of leaf sheaths penetrated) of eyespot lesions in wheat before GS 30/31 were greater in plots inoculated with R-type isolates than in those inoculated with W-type isolates. In 1987, after amild winter, eyespot incidence and severity in both wheat and barley were initially greater in W-type plots than in R-type plots. However, by GS 30/31 or 1987. In 1988, when the crop was October-sown, eyespot incidence and severity were greater in W-type than in R-type plots at GS 30/31. Differences in eyespot incidence and severity between W-type and R-type plots were smaller in barley than in wheat. Both the incidence and severity of eyespot were greater in early-sown than in late-sown plots. Seed rate, had little effect on the rate of lesion development in 1987, but in 1988 the rate of penetration was less at the low seed rate for both wheat and barley.