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Fusarium Head Blight Risk in North Dakota (06/21/18)

Winter wheat is in the flowering stages of development and some of the spring wheat has headed.

Fusarium Head Blight Risk in North Dakota

Winter wheat is in the flowering stages of development and some of the spring wheat has headed. Now is a good time to assess Fusarium head blight (scab) risk. Presently, a few pockets of moderate scab risk exist for susceptible varieties in northeast and southeast ND (Figure 1). For moderately susceptible (Figure 2) or moderately resistant spring wheat varieties, scab risk is low for the entire state. Conditions that favor scab development include prolonged periods (2-3 days) of high humidity, frequent rain events and warm temperatures. Therefore, continue to monitor the growth stage in small grain fields, take note of field conditions (i.e.: dew periods, rain, etc.) and pay attention to upcoming weather events that may elevate scab risk.

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The best time to apply a fungicide for scab in wheat is when a majority (>50%) of the main stems are at early flowering (Figure 3). For barley, the best time for a fungicide application is when a majority (>50%) of the main stems are at full head (Figure 4). Research conducted at NDSU and throughout the United States (funded by United States Wheat and Barley Scab Initiative) suggest that applying a fungicide to wheat 4-7 days after early flowering (late) provides more disease suppression than applications made prior to early flowering (early). The same trend is observed in barley where fungicides applied after full-head (late) provide more suppression than fungicides applied prior to full-head (early). Currently, triazoles/DMI/FRAC 3 are the only state labeled fungicides that provide suppression of scab and deoxynivalenol (vomitoxin). Also, there are efficacy differences among triazoles with prothioconazole+tebuconazole (Prosaro) or metconazole (Caramba) providing 45-60% suppression and tebuconazole (Folicur and generics) providing 20-30% suppression. For more information on scab fungicide efficacy and timing, please read CPN-3001 Optimizing Fungicide Use for Fusarium Head Blight (Scab) and Associated Mycotoxins and NDSU Extension Publication Deoxynivalenol (DON) in Small Grains.

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Andrew Friskop

Extension Plant Pathology, Cereal Crops

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