Wheat Scab/Fusarium Head Blight

Currently, Missouri is at "low risk" for wheat scab or fusarium head blight (Figure 1). However the rain this week across many portions of the state combined with persistent warmer temperatures may favor increased risks. (Check the Fusarium Risk Tool for the latest risks assessments: https://www.wheatscab.psu.edu/?_ga=2.183769126.1031526729.1713816727-210692034.1713816706) The fungal pathogen that causes FHB is Fusarium graminearum, and the pathogen can overwinter in crop debris including corn and wheat residue.

Figure 1 Fusarium Risk Tool on 4/23/2024. (Maintained by the Fusarium Head Blight Prediction Center at Penn State University.)

Figure 2 Wheat is at the beginning anthesis (10.5.1). Anthers are visible in the middle of the head (white arrow heads).

Fungal spores germinate on the wheat head and grow into developing kernels. We've previously shared fungicide application data on products applied at anthesis and on early applications of Miravis Ace, which has an extended application window compared to other products. (Visit figures 2 and 3 from article https://ipm.missouri.edu/croppest/2022/5/fusariumHeadBlight-MB/)

We have been part of a multi-state project for multiple years now to evaluate the effects of an anthesis fungicide application with a moderately resistant wheat hybrid. A fungicide application can suppress disease and deoxynivalenol (DON) levels in susceptible, moderately susceptible, and moderately resistant wheat. Figure 3 and 4 show results from 2022 for an ongoing study conducted across multiple states, including Missouri. Figure 3 shows wheat scab disease in susceptible, moderately susceptible, or moderately resistant wheat varieties in the presence or absence of a fungicide application at anthesis. Figure 4 is set up similarly except that the y-axis is accumulation of DON.

Figure 3 Fusarium head blight index in response to wheat genetics and an anthesis fungicide application. S = susceptible variety; MS = moderately susceptible; MR = moderately resistant. Study was conducted across multiple states and funded by the US Wheat and Barley Scab Initiative. Graphs courtesy of Kelsey Onofree at Kansas State University.

Figure 4 Deoxynivalenol (DON) accumulation in wheat kernels in response to wheat genetics and an anthesis fungicide application. S = susceptible variety; MS = moderately susceptible; MR = moderately resistant. Study was conducted across multiple states and funded by the US Wheat and Barley Scab Initiative. Graphs courtesy of Kelsey Onofree at Kansas State University.

The environment is always going to play a factor in the extent of FHB severity and subsequent control. Environmental conditions that favor infection include frequent rain, high humidity, and temperatures in the range of 70's to mid-80's. Extension tools available on this topic include:

• The Fusarium Risk Assessment Tool to help evaluate disease risk
• MU Extension Publication g4351 for guidance on scouting FHB
• Crop Protection Network publication on FHB