Manage Head Scab by Following This Rule

By Mark Lubbers, WestBred® Wheat Senior Technical Product Manager, Central Region

WB4792 is a hard red winter wheat variety with strong Western adaptation that has shown excellent yield potential in western Kansas since it was commercially released by WestBred Wheat in 2019.

This variety has very good wheat streak mosaic virus and yellow (stripe) rust resistance, making it popular with growers in the Western region. Like most Western-adaptable wheat varieties, WB4792 is susceptible to Fusarium head blight, and conditions in 2021 combined for a rare case of head scab infection in wheat crops across western Kansas.

8-80-8 Rule

Head scab infection occurs at flowering, and conditions have to be right at that time for the fungus to cause an infection. A certain set of environmental conditions is required for the pathogen to survive, and many years those conditions do not combine at the right time of flowering.

Typically, we do not see favorable conditions for many diseases in the drier climate of western Kansas, so 2021 was a very unusual year for weather patterns. Head scab is more likely to occur in wheat planted behind corn and under irrigation. That is where many of the 2021 cases in western Kansas were found.

A simple rule of thumb is the following:

• If you have consistent rainfall or humid conditions the eight days prior to fl owering, and you have daytime high temps of 80 degrees and a minimum eight hours of head wetness during the day, Fusarium head blight can occur.

WB4792 is still a solid variety choice for planting in western Kansas, and there are ways to help protect it from head scab.

Plant and Protect

In western Kansas, if you are planting WB4792 behind a corn crop and under irrigation, then conditions can become favorable for Fusarium head blight. It is highly recommended that the wheat crop be treated with Prosaro® fungicide.

In 2021, WestBred WB4792 that was treated with Prosaro fungicide at the right time experienced very few head scab infections. We generally saw 60% to 70% control with a fungicide, which is more than adequate to help control the fungus and preserve yield and quality potential. Even on dryland acres, WB4792 with a treatment of Prosaro fungicide will help provide an adequate level of control.

Growers in western Kansas plant WB4792 because of its excellent performance history in dryland conditions, and it does well under irrigation. Monitoring conditions for head scab and treating the crop if needed are key. Another option is WB4699, which is only positioned for irrigated acres but has good resistance to Fusarium head blight.

WB4792 is a very good variety choice for western Kansas and has been a solid performer. The 2021 season with its head scab issues was atypical, but it is still good to remember the favorable conditions for Fusarium head blight to occur and how you can protect your crop from this pathogen and preserve yield and quality potential.

For additional wheat management tips, contact Mark Lubbers at mark.lubbers@bayer.com.