Blog: The Wheat Sheaf

Managing FHB in wheat crops

As an agronomist I am fascinated by Fusarium head blight (FHB) and the challenge of managing this disease in wheat crops. Although FHB is affected by environmental conditions beyond anyone’s control, there are still several management practices producers can employ to reduce or minimize the impact of FHB on their operations. 

Variety selection:  Varieties of Cereal and Oilseed Crops For Alberta This website or similar industry publications, include a rating for resistance/susceptibility to FHB. Current AF research funded by the Alberta Wheat Commission (AWC) and Alberta Crop Industry Development Fund (ACIDF) has used Canada Western Red Spring (CWRS) varieties with MR (moderately resistant), S (susceptible), and MS (moderately susceptible) ratings for FHB.  In this research we have not had Fusarium Damaged Kernel (FDK) differences or mycotoxin (deoxynivalenol – DON) level differences between our CWRS varieties, when FDK and DON are present at levels affecting grade or grain quality.  This current Agriuclture and Forestry (AF) research has also included Canada Western Amber Durum (CWAD) varieties rated either S or MS for FHB. We have found that MS rated CWAD is far more susceptible to FHB than a CWRS variety with a MS rating.  In our experience, durum wheat is more susceptible to FHB than CWRS varieties and there are minimal FHB differences between CWRS wheat varieties regardless of FHB susceptibility ratings. 

Stand uniformity: Fungicides for FHB suppression are one of the management tools available to producers. However, for the fungicides to be effective they must be applied as anthers are just becoming visible in the middle portion of the wheat head. A uniform wheat stand will have a greater proportion of the heads at the same staging and this will affect both the decision of when to apply fungicide and the effectiveness of that crop protection product. Appropriate seeding rates and a quality seeding operation that encompasses residue management, accurate seeding depth, and adequate seed-fertilizer separation, are all manageable and will affect stand uniformity.

Weather awareness: FHB predictive models for helping producers make fungicide application decisions include weather factors for the period during flowering and/or the week or so leading up to heading and anticipated weather for the week(s) after flowering. In our current research we know we can raise FDK and DON levels with daily light irrigations during flowering.  We have also seen elevated FDK and DON from multiple irrigation events in June, leading up to heading, when we didn’t see comparable Fusarium Damaged Kernels (FDK) and DON levels when we applied similar total irrigation in a single application. We don’t currently have enough data to make a definitive recommendation, but I tend to think that multiple (five or so) precipitation events of about five mm or more during the 7-10 day period prior to heading puts a crop at risk for FHB. 

Fungicides: Fungicides for FHB management in Canada are currently registered for “Suppression”, not “Control”.  Realistically, registered fungicides are not going to eliminate the effects of FHB, but hopefully a properly timed application will maintain economically valuable grade and quality.  Fungicides for FHB suppression such as Caramba or Prosaro are to be applied within a fairly narrow application window between heads fully emerged on 75% of mainstems until anthers are visible on up to 50% of the head.  In the heat of early July this application window may only be about 5 days.  Also to be effective, fungicides need to cover the majority of the wheat head. In our current research project our spray nozzles have a front and rear spray pattern and we use 80 L/ac spray volumes. If producers are going to invest in a fungicide, I think it is also important to invest in the application of that product. If a fungicide application can maintain a CWRS number 2 grade compared to a CWRS number 3 grade without fungicide, then the economic return to the producer should be well in excess of chemical and application costs. 

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