Ergot (Claviceps spp.) of Cereals in Western Canada

Claviceps purpurea is a fungal ascomycete that infects grass species including cereal crops. The pathogen colonizes the inflorescence and forms a black elongated ergot body (sclerotium) in place of the seed. Under Canadian conditions, ergot sclerotia survive in the soil and can contaminate harvested grain. Sclerotia germinate and form ascospores under cool, wet conditions and infect susceptible cereal crops and other grasses during flowering. Occurrence in rye (Secale) is particularly high , likely because it is open pollinated. The first sign of disease is an orange to yellow ‘honeydew’ oozing from infected florets, which contains conidia that are spread to neighboring plants. The disease rarely causes significant yield loss, but ergot contaminated grain is a concern because sclerotia contain mycotoxins (alkaloids), which cause health problems such as convulsion and gangrene if consumed. Ergot epidemics have been reported throughout history, particularly in the Middle ages, when the health of humans and livestock were severely affected. Management of the disease in Canada involves cultural practices such as proper crop rotation and nutrition, mowing of headlands and ditches to reduce honeydew inoculum produced on grasses, and deep ploughing to bury sclerotia after an infestation. Resistance has been identified in wheat lines, but resistance breeding is still in its infancy. Fungicides against ergot are not registered for use in Canada and have not been found to be greatly effective in other places. Seed cleaning may be used to reduce the content of ergot in grain post-harvest. The grain trade adheres to thresholds for ergot amounts in seed lots determined by the Canadian Grain Commission, and downgrading results in economic loss and reduced marketability. This plant health case provides an overview of the lifecycle and epidemiology of C. purpurea and disease management in Western Canada, followed by some points for discussion regarding future control options and promising research areas.