Fungicidal control of Pyrenophora tritici-repentis in wheat

The use of fungicides to control yellow spot in wheat, caused by Pyrenophora tritici-repentis, in the northern wheat region of Australia, was examined in three field experiments. Field conditions were conducive to disease development. This was aided by spreading stubble infested with P. tritici-repentis and by regular spray irrigations, and moderate yellow spot epidemics resulted in all 3 years. Within the three experiments, 12 fungicides were evaluated for their ability to reduce the impact of yellow spot on grain yield. Single spray applications of the fungicides, some at varying rates, were made at 90% flag leaf emergence. Treated controls had 3-4 applications of propiconazole at 62 mL a.i./ha or tebuconazole at 72.5 mL a.i./ha throughout the season. Grain yield losses of up to 59% were recorded in the untreated plots. A reduction in grain size rather than a decrease in the number of grains was responsible for the yield losses. Yield losses were significantly lower following application of flusilazol, prochloraz, propiconazole and tebuconazole in cw. Hartog and Banks, in the first experiment. Application of azoxystrobin at 125 and 250 g a.i./ha, difenoconazole at 125 mL a.i./ha, epoxyconizole at 72 mL a.i./ha, propiconazole at 125 mL a.i./ha, tebuconazole at 125 mL a.i./ha or trifloxystrolin at 150g a.i./ha significantly reduced losses in the third experiment, sown with cv. Sunstate. This work has demonstrated that fungicidal control of yellow spot in wheat in the northern region can be a viable control option in years of high yield potential and high disease pressure.[PUBLICATION ABSTRACT]