Nitrogen Management of Strobilurin-Treated Wheat Crops

Abstract

Five field experiments were performed in winter wheat crops over three years to study the effects of two strobilurin fungicides, trifioxystrobin and kresoxim-methyl, and different rates of nitrogen on foliar disease severity and the accumulation and partitioning of dry matter and nitrogen. The strobilurin fungicides were included within triazole, epoxiconazole, based fungicide programmes. A few positive interactions were observed between a mixture of triazole and strobilurin and higher nitrogen rates. It was observed that, the crops treated with a mixture of triazole and strobilurin tended to show, compared to those treated with triazole alone, better control of Septoria diseases and prolonged green leaf area duration. There was no evidence that aboveground dry matter accumulation was increased following the apphcation of fungicides irrespective of the programme used. However, it was observed in two of the field experiments conducted in the 3rd year, that yield was greater when the plots were treated with a mixture of triazole and strobilurin than when either no fimgicide or triazole alone was applied. There was no difference in aboveground nitrogen accumulation between fungicide programmes, however, greater nitrogen accumulation in grains was observed following the application of a mixture of triazole and strobilurin compared to when the plots were treated with either no fungicide or triazole alone. The greater nitrogen accumulation in grains observed with the crops treated with a mixture of triazole and strobilurin appeared to be attributable, more consistently, to an improved translocation of nitrogen to grains than to an increased nitrogen uptake from the soil. The two strobilurins, i.e. kresoxim-methyl and trifioxystrobin, tested in this study, performed differently, most of the time a better performance was observed with trifioxystrobin compared to kresoxim-methyl. Canopy size and accumulation of dry matter and nitrogen were significantly increased by the apphcation of nitrogen fertilizer