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Fusarium Head Blight Risk in North Dakota (06/27/19)

Winter wheat is in the flowering stages of development or beyond, some barley will start to head soon, and spring wheat is still a week or two from entering heading and flowering stages.

Winter wheat is in the flowering stages of development or beyond, some barley will start to head soon, and spring wheat is still a week or two from entering heading and flowering stages. Presently, a few pockets of moderate to high scab risk exist for flowering susceptible wheat varieties in northwest and southeast ND (Figure 1). For moderately susceptible (Figure 2) or moderately resistant (Figure 3) varieties, scab risk is moderate to high for a pocket in southeast ND. Scab risk will likely remain elevated or may even increase in the coming days. Conditions that favor scab include prolonged periods (2-3 days) of high humidity, frequent rain events and warm temperatures. Several areas of the state will see favorable conditions for scab, so it is extremely important to monitor the growth stages of small grains and apply a fungicide when needed.

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 has started (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). Fungicides that provide the most suppression of scab and deoxynivalenol (vomitoxin) are prothioconazole+tebuconazole (Prosaro), metconazole (Caramba), prothioconazole (Proline) and pydiflumetofen+propiconazole (Miravis Ace) when applied at early-anthesis (or a few days after). For more information on scab fungicide efficacy and timing, please read CPN-3001 Optimizing Fungicide Use for Fusarium Head Blight (Scab) and Associated Mycotoxins (https://cropprotectionnetwork.org/library/) and NDSU Extension Publication Deoxynivalenol (DON) in Small Grains (https://www.ag.ndsu.edu/publications/crops/plant-disease-management-deoxynivalenol-don-in-small-grains-1/pp1302.pdf).

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Andrew Friskop

Extension Plant Pathology, Cereal Crops

 

Joel Ransom

Extension Agronomist, Small Grains and Corn

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