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.

WI 72 Hour Fusarium Head Blight Forecast

The prevalence of powdery mildew coupled with impending wheat flowering and risk of head scab many growers are considering holding off their fungicide application to target both pathogens. Based on our 24 to 72 hour prediction for Fusarium head scab using the Fusarium Head Blight Risk Assessment Tool the risk of Fusarium head scab for flowering wheat is low (May 10). However based on my observations and consultant and agronomist phone calls today we are still 5 to 7 days away from flowering in southern WI. I will rerun the model Sunday evening with and updated forecast.

Looking Ahead - Early Scab Forecast and Fungicide Labels

Winter wheat in southern Wisconsin is starting to head (Feekes 10.1) indicating we are ~ 7 days away from anthesis or flowering (weather dependent of course). Calendar wise this puts the WI wheat crop developmentally about 3 weeks ahead of normal. Anthesis is the last critical wheat management growth stage and accurate identification of this stage is important due to fungicide label restrictions as well as timing of fungicides for management of fusarium head scab. To better understand and identify the flowering growth stage, please check here for an UWEX YouTube Video.

Most commercial fungicide products are only labeled through Feekes 10.5 (full heading) and others have restrictions based on days to harvest. A partial summary of these products as well as those labels for head scab please access them here. Not all products may be listed and not all products (especially some generic forms of tebuconazole) may be approved in WI. It is important to always check the label for specific use requirements.

Our prediction for Fusarium head scab is based on the Fusarium Head Blight Risk Assessment Tool (please see below). In terms of Fusarium head scab risk as of today (May 8), pockets of medium to high risk are showing up in the western portion of the state, as well as a small pocket in the eastern portion of Winnebago and Outagamie Counties. The current increase in risk is most likely a function of the weather events of the past several days. Interestingly, when we checked the May 7 forecast map and did a 24 hour prediction, it did pick up the areas in the western portion of the state, although today's risk is somewhat higher than the forecast was. There is a chance for rain today around the state before some drying patterns move in. The risk for FHB may remain higher over the next several days. However, since we are approximately a week from flowering in the southern portion of WI, these conditions can, and will change, so we will continue to monitory and update the risk information, and management recommendations as we near flowering.