Fusarium Head Blight Risk Remains Low for WI

Wheat will begin flowering in the southern portion of Wisconsin over the next several days. This is a critical time to determine if the crop is at risk for Fusarium head blight (FHB). Following from our previous updates, a check of the risk map for today indicates a low risk of infection across the state. Weather over the next week is forecasted to range from overnight temperatures around 50F to daytime highs around 75-80F (Air Resources Laboratory, ready.arl.noaa.gov). A similar check for rainfall suggests an extended dry period, with isolated showers or thundershowers in the forecast. An examination of several weather stations in the main wheat production areas indicates low amounts of accumulated rainfall. Based on this, the risk for FHB this week appears to be low. Fungicide decisions should be based on a combination of this risk as well as active scouting of fields to determine if any foliar diseases pose a risk to the upper canopy. 

A reminder, as the wheat crop moves into flowering, it is critical to understand the difference in harvest restrictions related to the different fungicide products. Primary compounds recommended for control of FHB have harvest restrictions of 30 days (Proline, Prosaro, and Caramba). These products also carry good to excellent ratings for control of several major foliar diseases (powdery mildew to the different rust diseases). However, as we earlier pointed out, it is important that you take the time to scout fields to determine if the level of disease warrants a fungicide application.

The most effective timing for FHB management is Feekes 10.5.1 Recent work has shown (Christine Cowger, USDA and NCSU) that post-flowering infection can occur. However, I would say that going in early doesn’t get you the best efficacy. There are still questions related to the early, pre-anthesis risk of infection however, because the greatest risk of infection is at that early flowering period, this is the optimal timing.

Joint contribution from Shawn Conley; State Soybean  and Small Grain Specialist; University of Wisconsin, Madison and Dr Paul David Esker, University of Costa Rica.