Fungicidal effects on stem rust, green leaf area, and seed yield in ‘Grasslands Nui’ perennial ryegrass

Seed yield of Lolium perenne L. cv. ‘Grasslands Nui’ was increased from 65 to 91 g m 2 after a single application at ear emergence of a mixture of triadimefon + carbendazim + captafol, and to 100 g m ‐2 after two applications (at ear emergence and just before anthesis) of the same fungicide mixture. Triadimefon also increased seed yield to 82 g m ‐2 (single application) and 90 g m ‐2 (two applications). Carbendazim and captafol did not increase seed yield. Yield increases resulted from an increase in the number of seeds per spikelet, and an increase in 1000‐seed weight, and were related to reductions in stem rust ( Puccinia graminis Pers.) infection and delayed leaf tissue senescence. The way in which fungicide use may reduce seed abortion in perennial ryegrass is discussed and the number and timing of fungicide applications considered.