Sclerotinia sclerotiorum – what’s the resistance risk?

The Fungicide Resistance Action Committee (FRAC) considers Sclerotinia sclerotiorum a low-risk pathogen for developing fungicide resistance thanks to the pathogen’s single disease cycle per season, short window for spore dispersal, and rarity of sexual recombination.

The Canola Council of Canada agrees. In April 2021, the council’s Sclerotinia sclerotiorum steering committee considered whether fungicide resistance was a cause for concern here in Canada. The group concluded that, based on the pathogen’s biology, there is low risk of the pathogen developing resistance to fungicides in field settings.

However, the Canola Council also reported there is little to no publicly available information regarding the baseline sensitivity of field isolates in Canada.

So, what does this mean for Canadian canola growers?

In the short-term, using Miravis^® Bold – a single mode of action Sclerotinia fungicide – offers no significant resistance issues based on average cropping rotations and fungicide use intensity in a typical year.

For more information about Miravis^® Bold or managing fungicide resistance, contact your Syngenta Representative.

GO DEEPER: Watch our on-demand Sclerotinia webinar

Factors that increase the risk of fungicide resistance

According to FRAC, the risk of a pathogen developing fungicide resistance increases when:

• The pathogen undergoes many short disease cycles per season
• Dispersal via spores across time and distance is high
• Sexual recombination is mandatory in the disease cycle
• Competitive ability of the resistant individual is at least as high as that of the wild type
• Resistance evolves after a few years of product usage

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