What’s the best fungicide to apply to protect wheat and barley from fusarium head blight? When should fungicides be applied for best results?

Andrew Friskop, North Dakota State University Extension plant pathologist, answered these and other key questions about applying fungicides to suppress FHB.

What fungicide is best?
Presently, the only labeled fungicides with FHB and deoxynivalenol (DON) suppression are triazoles. Do not use products containing a strobilurin for FHB management as these fungicides have been shown to increase DON levels. The key word to remember with fungicide use is “suppression” as no fungicide is considered a “silver bullet.” Based on studies completed by the U.S. Wheat and Barley Scab Initiative, the most effective fungicides for FHB management are Prosaro and Caramba. Generic formulations of tebuconzole are also used, but they do not provide as much suppression. The biggest response from a fungicide will occur when other management tools are incorporated, such as cultural practices and the use of less susceptible varieties. See the North Field Crop Plant Disease Management Guide for more information.

When should fungicide be applied?
The best time to make a fungicide application for wheat is when most of the main heads are at early flowering. Early flowering is defined as when the yellow anthers (flowers) start appearing on the center of the head. For spring barley, the best time to make an application is at full head. Recent studies conducted by the U.S. Wheat and Barley Scab Initiative have suggested being too late is better than being too early.

When is it too late to apply?
If a late fungicide application is being made, spray the fungicide within six days after early flowering. Studies have shown that a fungicide application is still effective at reducing FHB and DON within this window. Also, it is always important to check the label of the fungicide being used for preharvest restrictions.

What spray nozzle should be used?
Currently, it is recommended to use a forward backward flat fan nozzle angled between 30 to 45 degrees with preference given to 30 degrees. 

How much water should be applied as a fungicide carrier?
If making a ground application, at least 10 gallons of water per acre should be used. For aerial application, 5 gallons of water per acre is suggested. Fungicides are most effective when adequate coverage is achieved. Although triazoles are considered locally systemic, the fungicide is only able to move a short distance on a plant; thus coverage is very important.

Is ground or air application best?
Both ground and aerial application have their place in FHB management. The key thing to remember is to have adequate water and to apply the fungicides at the appropriate time.

What should you do if you don’t treat and want to save some acres for seed?
Although it is not recommended, if a scabby seed source is used for planting, there are several steps that should be taken before placing it in the ground. Make sure to clean the seed rigorously, treat the seed with an effective fungicide, conduct a germination test and adjust plant populations accordingly.