Farm Progress

Wheat worry: Where will Fusarium flare up next?

Always be prepared to protect wheat, because it's hard to tell what region will be the next to have an epidemic.

November 11, 2016

3 Min Read

Fusarium head blight (scab) continues to plague small-grain producers in North Dakota. The disease is responsible for significant reductions in wheat yield and test weight. Additionally, the scab fungus produces the mycotoxin deoxynivalenol (DON) — also known as vomitoxin (VOM) — resulting in quality reductions.


Historically, the disease has severely impacted areas along the Red River Valley in North Dakota. Recently, the state’s worst problems have occurred in “non-traditional” scab areas. In 2014 and 2016, growers in the northwest and northcentral region of North Dakota were significantly impacted by scab and DON. In 2015, southwestern North Dakota had high levels of scab. The sporadic nature of scab epidemics in specific regions can be attributed to weather conditions. The fungal pathogen (Fusarium graminearum) primarily infects wheat during the flowering stages and barley at heading, and is favored by periods of warm and wet (i.e., rain, dew, humidity) weather. During the 2016 growing season, wet conditions were common throughout June and July in the northern tier of North Dakota. This occurred at the time when most of the small-grain crop was heading. The weather, in addition to ample sources of Fusarium inoculum, contributed to yield reductions and high DON levels in durum and spring wheat.

Although it is difficult to predict scab epidemics, there are scab management tools available to help prepare for next year. Scab is best managed by using an integrated approach utilizing cultural practices, varietal resistance and a well-timed triazole fungicide application.

Fusarium is adapted to the North Dakota environment and can survive on cereal residue. Rotating away from a cereal-on-cereal rotation can reduce the amount of Fusarium spores within a field.

Having multiple planting dates can prevent an entire small-grain crop from heading during times of favorable scab conditions.

Several small-grain market classes have less susceptible varieties available, yet nothing is considered immune. Moderate resistance is available for hard red spring and winter wheat, while durum is generally more susceptible.

When considering a fungicide application, check to see if the small-grain crop is heading (or near heading) and determine if favorable scab conditions are occurring. To help assess risk, scab forecasting models are available for use. While models are very useful, they have limitations. Most importantly, scab risk is calculated from data received from North Dakota Agricultural Weather Network (NDAWN) stations. While there are 72 stations in North Dakota, weather is extremely variable, and dramatic differences can occur within a few miles or even within a field. Consequently, consider local conditions when making the decision to spray a fungicide; as your field may be more (or less) likely to have scab.

The best time to make a fungicide application is at early flowering for wheat and at full head for barley.

Triazole chemistries are the only effective fungicides against scab, and efficacy differences exist among products in this class. The most efficacious products offer approximately 50% in reduction of scab and DON.

Friskop is a North Dakota State University Extension plant pathologist.

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