An analysis of yield reduction caused by stripe rust in Rongotea wheat.

Abstract

Natural field epidemics of stripe rust (Puccinia striiformis) were manipulated by seed treatment and foliar sprays to provide a range of disease severities and durations in several locations in three seasons. Yield in the absence of disease, disease severity and disease duration in the natural epidemics varied markedly between the three seasons. The effect of disease on yield and yield components was different in each season and there was no empirical model which consistently described the relationship between disease severity and yield reduction. Empirical models had little relation to the cause of yield reduction in specific crops and could not therefore be used for disease management purposes. The identification of action levels for management purposes based on mechanistic criteria is discussed.