Yield losses in wheat from yellow spot: a disease-loss relationship derived from single tillers

Abstract

The effect of yellow spot (Pyrenophora tritici-repentis) on wheat yield has been examined with a single-tiller technique. The disease was assessed on c. 1000 tagged main stems in each of five wheat crops. Grain yield, its components, and harvest index were measured on each tiller. In most cases these response variables were significantly correlated with yellow spot levels. The disease-loss relationship, L = 0.26X, was developed where L is the percentage loss in grain yield per main head and X is the average level of yellow spot on the top two leaves at around the milk stage of grain development. From four of the crops examined, an average loss of 12.7 % in grain yield per main head was estimated. Under environmental conditions which particularly favour disease development, the losses derived from this relationship are probably underestimated.