Ramularia epidemic dynamics in untreated trial plots: interactions with variety and other pathogens

摘要

Quantitative studies of the dynamics of Ramularia leaf spot on five untreated barley varieties showed that disease severity increased exponentially on the first leaf and linearly on the second leaf between late June and early August. Ramularia symptoms occurred concurrently with those of Rhynchosporium and also physiological spotting and chlorosis in a green leaf area reducing complex. A comparison of the incidence-severity relationships for Ramularia and Rhynchosporium highlighted a difference in the spatio-temporal increase in the two diseases that is probably related to their different dispersal mechanisms. A principal components analysis of the simultaneous development of all of the symptoms of the disease complex indicated that all five barley varieties followed a qualitatively similar trajectory of green leaf area loss over time, but that small differences in the development of each symptom could lead to large overall differences in the rate of green leaf tissue loss.