Ergot trends in Canada
The highest ergot incidence and severity occurred in rye, followed by bread and durum wheat, barley and oats. Ergot incidence has increased in the last decade, but severity has not increased and remains low.
Ergot is a fungal disease that is caused by the pathogen, Claviceps purpurea. The disease occurs on cereals including wheat, barley, oat and rye, and also affects grasses. The pathogen infects the floret, and individual kernels can be replaced by darkly coloured fungal bodies called sclerotia. These sclerotia contain ergot alkaloids, and can cause serious health issues in humans and livestock.
Ergot can affect grain quality, and is a grain-grading factor for cereals, with tolerances established by the Canadian Grain Commission. The presence of ergot sclerotia in durum wheat results in black specks in semolina and pasta.
The Canadian Grain Commission conducts annual Harvest Sample and Cargo Monitoring Programs. This surveillance helps track ergot incidence and severity, and the presence of ergot alkaloids in different cereals, geographic areas and years.
Researchers at the CGC analyzed harvest samples from bread and durum wheat, barley, oat and rye from 1995 to 2020 to explore trends in ergot incidence, severity, and ergot alkaloid presence in western Canada. More than 230,000 samples were analyzed from across the Prairies.
The highest ergot incidence and severity occurred in rye
Ergot incidence in rye was the highest of all crops in all years. The incidence of ergot in rye was the highest in 2013 when it reached 90% of all samples, and has remained above 50% incidence in the years since.
There was also a trend of higher incidence of ergot in rye in later years. From 1995 to 2009, ergot incidence was 27.6% and rose to an average of 65.6% from 2010 to 2020. However, median ergot severity remained the same at 0.08%. CGC tolerances for No. 1 rye are 0.05%, 0.20% for No. 2, and 0.33% for No. 3.
Trends in annual ergot incidence (% of samples inspected in a year that contained ergot sclerotia) from 1995 to 2020 for Canadian cereal samples submitted to the Canadian Grain Commission Harvest Sample Progra
Source: Walkowiak et al. 2022.
Prior to 2008, the incidence of ergot in bread and durum wheat was low, with a minor increase of 9.8% in bread wheat and 3.9% in durum wheat in 1999. After 2008, there has been a trend to higher incidence in both durum and bread wheats.
For bread wheat from 1995 to 2009, ergot incidence was 4.2% and median severity at 0.02%. From 2010 to 2020, incidence rose to 19.5% but severity remained at 0.02%. The current tolerances for ergot is 0.04% for No. 1 CWRS wheat.
Similarly, ergot incidence in durum wheat was 2.9% and severity was 0.02% from 1995 to 2009, and rose to 13.1% incidence from 2010 to 2020, but again, severity remained at 0.02%. For durum, the grading tolerance is 0.02% for No. 1 CWAD.
Sample data for barley goes back to 2010. For the period from 2010 to 2020, ergot incidence was 65.6% and median severity was 0.02%. CGC tolerances are 0.02% for No. 1 Select Malting Canada Western/Canada Eastern two-row and six-row barley, including hulless barley grades.
For oat, only two recent years of data were available and found ergot incidence at 0.7% and severity at 0.01%. For oat, CGC tolerances are 0% for No. 1 and 0.03% for No. 2 and 3.
Ergot alkaloids in bulk shipments
Bulk wheat, durum, barley, and oat shipments exported between August 1, 2013 and July 31, 2020 were analyzed for 12 ergot alkaloids. Ergot alkaloids were found in 97% of durum shipments, 88% of wheat, 60% of barley and 22% of oat shipments. Conversely, 13% of durum, 20% of wheat, 2.4% of barley and 0.7% of oat harvest samples had ergot sclerotia.
The researchers theorized that the more frequent occurrence of ergot alkaloids compared to sclerotia could be due to the bulk nature of Canadian grain exports where grain from different areas, and in some cases years, are mixed together to dilute the presence of sclerotia. In addition, ergot sclerotia can be broken up during handling, which can distribute ergot alkaloids through a wider volume of grain.
As of 2021, only the EU has set maximum limits for ergot alkaloids at 0.050 to 0.500 mg/kg in cereal milling products depending on the cereal grain, and 0.020 mg/kg in processed cereal-based foods for infants and young children. However, these limits do not apply to the raw grains imported by the EU. Additionally, based on other research, grain cleaning at milling facilities will further reduce the amount of ergot alkaloids in milled and processed grain.
Overall, the incidence of ergot has increased over the last decade, but severity has remained low and with limited impacts on the grain marketplace. The Canadian grain-grading system helps to ensure that ergot contamination remains within allowable limits, and that any samples that exceed limits can be mitigated throughout the grain handling system. Continued monitoring will ensure that risks associated with ergot can be managed through the Canadian regulatory system.
The researchers acknowledge the Industry Services Division of the Canadian Grain Commission for the inspection services and rating of ergot in samples from the Harvest Sample Program, and former researchers and program managers from the Grain Research Laboratory of the Canadian Grain Commission for data collection and curation.
Walkowiak, S., Taylor, D., Fu, B. X., Drul, D., Pleskach, K., & Tittlemier, S. A. (2022). Ergot in Canadian cereals – relevance, occurrence, and current status. Canadian Journal of Plant Pathology, 44(6), 793–805.
OPEN ACCESS: https://doi.org/10.1080/07060661.2022.2077451
Photo by Sheryl Tittlemier
