Fungicide Application At Wheat Flowering: Using Scab Prediction Tools To Aid Decision

Fig. 1. A screenshot of the webpage showing the risk of Fusarium head blight (scab) as of May 31, 2016 for a susceptible cultivar. The prediction model shows moderate risk for scab in a limited area in Gregory/Charles Mix Counties. The rest of the state has currently low risk for scab, if wheat is flowering. This is partly due to cooler average temperatures; FHB is favored by warmer temperatures.

 

The prediction webpage first shows a regional view and for the most recent date. The user can then select a state (South Dakota) and can then zoom in to their location. A user is also able to click on an individual weather station near their growing area and find the specific FHB prediction for that area. There is also a choice of whether the crop is winter or spring wheat as well as the level of susceptibility of the cultivar planted. If wheat flowering is anticipated in the next few days (24, 48 or 72 hours), the model uses forecast weather to predict the scab risk. A yellow color means the risk for scab development is moderate and a red color means the risk is high. When the scab risk is moderate or high, growers should plan a triazole fungicide treatment in the short window around flowering (within 3 days of flowering).

 

The second scab prediction tool is the Smallgrains disease model using SDSU Mesonet data page hosted by the SDSU Climate and Weather Center. This tool provides prediction for fungal leaf spot diseases as well. Unlike the National Scab Prediction tool, the results of the FHB prediction are displayed in a table form as opposed to a map for each location that is selected (Fig. 2). This online tool was deployed two years ago in collaboration with NDSU. The interpretation for this tool is similar to the national scab one. Yellow and red mean the risk is moderate to high, while green indicate low risk for scab.