The Effect of Fungicides on Leaf Diseases and on Yield in Spring Barley in South-west England

Summary In nine experiments in 1966–68, fungicides applied on 8–12 occasions to plots of barley resulted in mean grain yield increases of about 40 per cent. Zineb increased yields by an average of 50 per cent in nine experiments and lime sulphur by 19 per cent in six experiments. In single experiments dichlofluanid increased yields but oxycarboxin did not. In 1968, fungicides applied on only two occasions failed to control disease and to increase grain yield. Large yield increases were associated with a good control of leaf diseases including leaf blotch (Rhynchosporium secalis), halo spot (Selenophoma donacis) and brown rust (Puccinia hordei). Mildew (Erysiphe graminis) was excluded by using resistant cultivars. The diseases were severe late in the season, usually at or after ear emergence. Yield increases were wholly due to an increase in grain weight (1000-grain weight).