by Dr. Charla Hollingsworth, U of MN Extension Plant Pathologist
Crop growth stages of spring wheat are rapidly approaching early flower in some locations. This is the time of year that managers must make a decision to apply a fungicide application targeted for Fusarium head blight (FHB) management.
What's happened in other states?
This year FHB has been a production issue across many winter wheat producing states. The disease has been reported from areas of Arkansas, Georgia, Illinois, Indiana, Kansas, Kentucky, Maryland, Missouri, Nebraska, North Carolina and Virginia at various levels for incidence and severity.
The Fusarium fungus is adept at colonizing corn, wheat, and barley residues. During the growing season it produces spores from these plant materials which are either rain splashed or wind-blown to local or regional plant hosts. If our weather conditions disease development when wheat is at a susceptible growth stage (flowering), an FHB epidemic could result.
What's different this year?
This year we have a large amount of corn residue and stubble remaining in our agroecosystem which is partially or wholly exposed on soil surfaces. Many growers burned corn fields to mitigate issues with residue, but this is much like bailing water from a sinking boat using a shot glass. It might feel productive to be doing something, but the overall benefit is questionable. If the weather supports spore production, then microscopic, airborne Fusarium spores will be mass produced on residue lying on the soil surface.
One can go to http://mawg.cropdisease.com/ to determine the local estimated risk for having the disease in wheat. This website also offers a two-day FHB risk forecast estimate based on expected weather. Data inputs which support the forecast are exclusively weather-based, such as air temperature and relative humidity.
A word of caution.
The model predicts risk based on weather conditions from the last seven days. It doesn't factor in additional risk if soils were saturated prior and remain wet immediately before this time period. This "snapshot" approach to risk forecasting can contribute to underestimating the risk of disease in high clay, water-logged soils. This has been an issue with the model in the past. Please factor in additional risk if this describes the situation in your field. Always keep in mind that each FHB risk prediction is only an estimate.
Be mindful of the additional production risks this year as well as the disease's track record south of us on winter wheat. With the lush wheat crop that's developing, this could very likely be a good year to manage production risks with a fungicide application. Keep checking the scab epidemic risk forecasting website to stay informed about the risk for FHB in your crop.