Thanks to recent rainfall, head scab risk remains moderate-to-high in central and southern Ohio, for wheat flowering today and later this week, while the remainder of the state is at medium-risk for infection (Figure 1). These risk estimates were generated by The Fusarium Risk Tool available at https://www.wheatscab.psu.edu/. This tool uses temperature, rainfall, and relative humidity to estimate the risk of infection by Fusarium graminearum that causes Fusarium head blight or head scab in wheat. The fungus also produces the mycotoxin deoxynivalenol (DON) or vomitoxin. Keep in mind, the estimate shown in the map is applicable to fields flowering today if a susceptible variety is planted. You should check the tool periodically as more fields begin to flower to see if the risk changes.
Figure 1. Fusarium Risk Assessment Tool Ohio map generated on May 19, 2025. Red = high risk, Orange = medium risk, and Yellow = low risk for Fusarium head blight.
Fungicide applications to reduce head scab development and DON contamination should be made at early flowering (Feekes 10.5.1) when yellow anthers are seen at the center of the wheat spike (Figure 2). (Wheat flowering stage video: https://www.youtube.com/watch?v=pEJrX6UqF_E&list=PLYlh_BdeqniJ8oD8TnyGhQHRd96ptV0Yt&index=5) However, applications delayed 4 days after initial flowering can still suppress head scab and DON. Be sure to select a triazole-based fungicide and follow all product label instructions.
Figure 2. Wheat head flowering.
Fungicides with a ‘good’ efficacy rating based on multi-state fungicide trials, include Proline 480 SC, Prosaro 421 SC, Sphaerex, Miravis Ace SE, and Prosaro Pro SC. Access the complete wheat fungicide efficacy chart provided by the Crop Protection Network at https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-wheat-diseases.