Verticillium Stripe in Canola

Are your canola plants ripening before reaching maturity? Are stems shredding and wrapping around the header? Verticillium stripe could be the yield robber behind these symptoms. 

Verticillium stripe was first identified in Manitoba near Winnipeg in 2014 and has since been found across six Canadian provinces. Symptoms are now widespread in Manitoba, with suspected cases appearing in Saskatchewan and Alberta. 

Justine Cornelsen, Agronomic and Regulatory Services Manager with BrettYoung, has extensive experience working with this disease. She explains that although it is relatively new to Canada, “other canola-producing regions have dealt with this disease for many years and lots has been learned from them that we can incorporate here into scouting and eventual management.” 

Recognizing Early Symptoms 

Verticillium damage appears late in the season as plants begin to ripen prematurely. Early on, you may see half the stem still green while the other half dries down. As the disease progresses, stems dry, turn beige, and begin to shred. 

These symptoms are often confused with sclerotinia. The distinction is in the structures left behind: 

• Sclerotinia leaves sclerotia bodies inside stems 
• Verticillium stripe leaves microsclerotia — tiny black dots giving the inner stem wall a greyish hue 

Verticillium also causes roots to turn grey, which differs from the typical black spots caused by blackleg. 

Cornelsen notes that because disease symptoms can mimic environmental stress or other pathogens, “it’s best to understand the disease lifecycles and look for signs of the disease-causing pathogens.” 

How to Identify Verticillium Stripe 

Key Field Checks 

• Peel back the outer stem wall 
• Look for microsclerotia (tiny black dots creating a greyish hue) 
• Compare shredded stems to sclerotinia-infected stems 
• Check if roots have turned grey 
• Use a hand lens to observe fine details 
• Send samples to a commercial lab if uncertain 

The easiest time to confirm verticillium stripe is post-harvest, when microsclerotia have spread through the stubble. Infected stems tend to shred and break easily when pulled. 

Managing a Soil-Borne Disease 

Management strategies for this disease closely resemble those used for clubroot, as verticillium stripe is also soil-borne and is easily spread during harvest when stems are cut and microsclerotia are released. 

Management Tips 

• Reduce soil movement; clean equipment between fields 
• Avoid excess field traffic during wet conditions 
• Use longer crop rotations to disrupt the disease cycle 
• Scout fields annually to track progression 

How Environment Influences Verticillium Stripe 

Verticillium stripe thrives under hot, dry conditions. Cornelsen notes that it has been easier to find in the past two seasons due to extended dry periods. She also highlighted an inverse trend: as sclerotinia pressure decreases in dry summers, verticillium stripe becomes more common. 

Environmental factors to monitor: 

• Hot, dry weather 
• Reduced sclerotinia pressure 
• Seasonal precipitation shifts 
• Extreme weather years 

Research and What Comes Next 

Because verticillium stripe is still relatively new to Canada, research continues to focus on developing: 

• Yield loss models 
• Severity scales 
• Genetic resistance tools 

Projects funded through the Canadian Agricultural Partnership are expected to advance understanding of the disease. For now, Cornelsen emphasizes that accurate identification is the essential first step: “You have to know what you are dealing with before a management plan can be put in place.” 

Growers are encouraged to: 

• Prioritize early identification 
• Stay connected to new research 
• Work with extension services and labs 
• Integrate new tools as they are available 
• Share field observations 

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