Some effects of stem rust ( Puccinia graminis Pers.) on the growth of cocksfoot ( Dactylis glomerata L. ‘Grasslands Apanui’)

Some effects of stem rust ( Puccinia graminis Pers.) on the growth of cocksfoot (Dactylis glomerata L. ‘Grasslands Apanui’) were studied at two levels of nitrogen fertiliser in a plot trial. Half the plots were kept relatively free of rust by spraying with a mixture of maneb and nickel sulphate; the remainder became rusted from natural infection. The disease caused mean reductions of up to 36% in green cocksfoot and 37% in tiller number. There was widespread death of cocksfoot leaves as shown by increases of up to 109% in yellow and brown cocksfoot in the rusted plots. There was no effect of nitrogen fertiliser on the incidence or effects of stem rust. The possible role of stem rust as one factor responsible for the low occurrence of cocksfoot in pasture is discussed. Methods of reducing the incidence of the disease through grazing management and plant breeding are suggested.