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

Authors: BOLANOS-CARRIEL, CARLOS - University Of Nebraska; BAENZIGER, STEPHEN - University Of Nebraska; Funnell-Harris, Deanna; HALLEN-ADAMS, HEATHER - University Of Nebraska; ESKRIDGE, KENT - University Of Nebraska; WEGULO, STEPHEN - University Of Nebraska

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2020
Publication Date: 8/29/2020
Citation: Bolanos-Carriel, C., Baenziger, S.P., Funnell-Harris, D.L., Hallen-Adams, H., Eskridge, K.M., Wegulo, S.N. 2020. Effects of cultivar resistance, fungicide chemical class, and fungicide application timing on Fusarium head blight in winter wheat. European Journal of Plant Pathology. 158:667-679. https://doi.org/10.1007/s10658-020-02109-3.
DOI: https://doi.org/10.1007/s10658-020-02109-3

Interpretive Summary: Fusarium head blight (FHB), is a devastating disease of wheat that can result in huge economic losses. The fungus, Fusarium graminearum, causes shriveled, unusable grain (Fusarium damaged kernels or FDK) and produces a toxin called deoxynivalenol or DON. Combined disease management includes cultivar resistance, fungicide application at anthesis (flowering), and cultural practices. Two fungicide chemical classes are commonly used in wheat and applied before or during anthesis: triazoles for FHB and strobilurins for foliar diseases. Application is most effective at anthesis but sometimes this timing is hard for producers to arrange. This research concerned effects of fungicide chemical class (triazole versus strobilurin), fungicide application timing (at anthesis versus after anthesis), and environment (dryland versus irrigated) on FHB and DON. The elite hard winter wheat cultivars Overland (moderately resistant to FHB) and Overley (susceptible to FHB) were tested. Overland consistently had reduced FHB severity, FDK, and DON, and higher yield as compared with Overley. The most effective fungicide treatment in reducing FHB, FDK, and DON and increasing yield was Prosaro, a triazole combination (prothioconazole + tebuconazole) applied at anthesis. Application of triazoles 6 days after anthesis was slightly less effective but application later at 12 days was ineffective. A strobolorin fungicide (pyraclostrobin) also controlled FHB, FDK, and DON, but was less effective than Prosaro. In both cultivars, FHB severity, FDK, and DON were higher under irrigated compared to rainfed conditions and during wet compared to relatively dry growing seasons. This research pointed-out benefits of cultivar resistance for management of FHB and DON. Based on these results, triazole fungicides are recommended over strobilurins for control of FHB and DON, and the window of fungicide application can be extended by up to approximately one week after anthesis without significant loss of control.

Technical Abstract: Fusarium head blight (FHB), caused mainly by Fusarium 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® (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® (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.