Effects of fungicide chemical class, fungicide application timing, and environment on Fusarium head blight in winter wheat

Fusarium head blight (FHB), caused mainly byFusarium graminearum, can result in devastating economic losses in small grain cereal crops. Management of FHB is by a combination of strategies and tactics including cultivar resistance, fungicide application at anthesis, and cultural practices such as crop rotation, tillage, and irrigation management. This study evaluated, under field conditions, the effects of fungicide chemical class (triazole versus strobilurin), fungicide application timing, and environment on FHB and its associated mycotoxin deoxynivalenol (DON). A moderately resistant hard red winter wheat cultivar, Overland, consistently had lower levels of FHB index (= index),Fusarium-damaged kernels (FDK), and DON, and higher yield compared to the susceptible hard red winter wheat cultivar Overley. The most effective fungicide treatment in reducing FHB, FDK, DON, and yield loss was Prosaro (R) (prothioconazole + tebuconazole) applied at early anthesis (BBCH 61; hereafter referred to as anthesis). Application of Prosaro 6 days post anthesis (DPA) achieved a slightly lower but comparable efficacy to that achieved by the anthesis application. Application of Prosaro at 12 DPA was least effective. The strobilurin fungicide Headline (R) (pyraclostrobin) was less effective than Prosaro in controlling FHB, FDK, and DON. In both cultivars, index, FDK, and DON were higher and yield was lower under irrigated compared to rain-fed conditions. These differences were more pronounced in a wet compared to a relatively dry growing season. The results from this study indicate that effective management of FHB can be achieved by combining cultivar resistance with a triazole fungicide applied at anthesis, and the window of fungicide application can be extended by up to 6 days post anthesis.