Factors affecting FHB impact on hard red spring wheat quality
Rainfall was the most contributing factor to Fusarium Damaged Kernels. Glyphosate application did not affect grain quality or Fusarium Damaged Kernels.
Fusarium head blight is one of the most damaging diseases on hard red spring wheat on the Prairies. A research study led by the University of Manitoba looked into how weather, variety, fungicide application at anthesis to control FHB, and pre-harvest glyphosate application affected wheat grain quality.
Research plots were established at four locations at Lethbridge, AB, Indian Head, SK, and Carberry and St. Adolphe, MB in 2015, 2016, and 2017. Carberry 2015 and St Adolphe 2016 were not harvested due to production issues, leaving 10 site-years of data. Target seeding rate was 30 seeds/ft2 (300 seeds/m2).
Glenn (I), Carberry (MR), Cardale (MR), CDC Stanley (MS), Stettler (S), and Harvest (S) were the Canadian Western Red Spring wheat varieties grown at each site. Note that the classification for Harvest was revised by the Canadian Grain Commission to Canada Northern Hard Red after the study had been conducted. Fusarium resistance ratings for these varieties are shown in brackets: moderately resistant (MR), intermediate (I), moderately susceptible (MS) and susceptible (S).
Four pesticide treatments we applied to each wheat variety: a control with no pesticide application; Prosaro (prothioconazole/tebuconazole) fungicide applied at anthesis; Roundup WeatherMax with Transorb (glyphosate) herbicide applied at pre-harvest; and a treatment with both fungicide and herbicide.
The fungicide was applied according to label directions when at least 75% of the wheat heads on the main stem were fully emerged up to when 50% of the heads on the main stem were in flower. Glyphosate was applied when wheat grain moisture content was ≤30% at about 7–14 days before harvest.
The grading factors analysed included test weight (TW), damage caused by ergot, sawfly midge, sprouting, and Fusarium Damaged Kernels (FDK). Grain protein and thousand kernel weight (TKW) were also calculated. For the CWRS Fusarium grading factor, No. 1 CWRS is allowed 0.3% FDK, No. 2 is 0.8%, No. 3 at 1.5% and CW Feed at 4.0%.
Over the three years, diverse weather variations provided a wide range of weather conditions across the sites, and the most variable factors were precipitation and water deficit/surplus. The 2016 growing season generally had higher rainfall.
For the warmer and drier years in 2015 and 2017, wheat had higher grades, test weight, thousand-kernel weight, and grain protein content but lower FDK. In 2016, the wetter conditions resulted in higher FDK with lower wheat grades compared to 2015 and 2017. For example, Indian Head 2016 had 1.73% FDK compared to Indian Head 2017 at 0.001% FDK.
Weather is the driving factor
Weather was the major factor affecting grain quality, contributing 39% to 77% of total variance in grading and quality factors. Rainfall variation was the main weather factor affecting quality, and was greater than the effect of air temperature. Generally, FHB is influenced by higher levels of rainfall, warm and humid weather during flowering, and optimal temperatures of 25-28C.
Relationship, by site-year averaged across genotypes and treatments, between (a) Fusarium damaged kernels and cumulative rainfall (planting to maturity) and (b) Fusarium damaged kernels and average temperature.
Source: Dorrian et al. 2024
Variety had a significant impact on grain quality, as would be expected, and contributed 1–20% of total variance in FDK levels. The FDK levels generally lined up with the FHB resistant ratings. Stettler and Harvest, both susceptible varieties, were the most affected by FHB. Stettler had significantly similar FDK levels as Harvest and Carberry, but higher than Cardale, Glenn and CDC Stanley, when averaged across site-years and pesticide treatments.
Fungicide application significantly reduced FDK level in the four of five site-years that were conducive to FHB. At the other five site-years where FHB pressure was low, there was no impact from fungicide application on FDK. Pre-harvest glyphosate application did not affect FDK content.
Overall, the study found that rainfall variation was the main factor that contributed to variation in FHB, as indicated by FDK levels. Glyphosate had no adverse effect on grain quality. Fungicide application in accordance with label directions can significantly reduce FDK percentage when weather conditions are conducive to disease development.
This research was supported by the Western Grains Research Foundation, Agriculture and Agri-Food Canada (AAFC), Manitoba Crop Alliance, Saskatchewan Wheat Development Commission and Alberta Grains.
Kathleen Dorrian, Manasah Mkhabela, Harry Sapirstein, and Paul Bullock. 2024. Effects of genotype, weather, FHB fungicide, and pre-harvest glyphosate on grain quality of hard red spring wheat in western Canada. Canadian Journal of Plant Science. 104(5): 472-484. https://doi.org/10.1139/cjps-2023-0151
Photo by Taurai Matengu, University of Manitoba
