Effects of powdery mildew at different growth stages on grain yield of barley

SUMMARY Pot‐grown barley plants (cv. Proctor) were exposed to infection by powdery mildew during four stages of development, G.S. 2–6, G.S. 7–9, G.S. 10‐10‐5 and G.S. 11 (Feekes scale, Large, 1954). All combinations were examined (i.e. 24 factorial). The numbers of fertile tillers at harvest were significantly reduced by mildew during periods G.S. 2–6 and G.S. 7–9. Numbers of grains per head and grain size (1000 grain weight) were significantly reduced by mildew only during G.S. 2–6. Effects, on components of yield, of the four mildew treatments were found to be almost entirely additive. The only significant interactions found were for grain size: in this instance there was some interaction between treatments at G.S. 2–6 and G.S. 10‐10‐5 and between treatments at G.S. 2–6, G.S. 7–9 and G.S. 10‐10‐5.