Rhynchosporium leaf scald disease incidence: seed source and spatial pattern

A programme of field trials for the study of the winter barley – Rhynchosporium commune pathosystem is reported. The associated seed-borne disease Rhynchosporium leaf scald is regarded as having an important impact on barley yields. The analysis reported here relates to the impact of the seed source (commercial or farm-saved seed) on disease incidence, and to the spatial pattern of Rhynchosporium leaf scald disease incidence. Disease incidence data were calculated from field data recorded as disease severity. Mean disease incidence was higher in the crops grown from farm-saved seed than in the crops grown from commercial seed, although we cannot attach great agronomic significance to this result. The spatial pattern of Rhynchosporium leaf scald disease incidence was characterized in terms of the binary power law (BPL), and was indicative of an aggregated pattern. Programme-wide BPL results were described using a novel phytopathological application of a random coefficients model. These results have application in field sampling for Rhynchosporium leaf scald disease.