Verticillium Stripe in Canola
Overview
Verticillium stripe is a soil‑borne disease of canola caused by Verticillium longisporum. It was first detected in Manitoba in 2014 and has since been found across Canada. The fungus blocks water and nutrient flow in stems, leading to early ripening, weak stems and yield loss. There are no registered foliar or seed treatment fungicides for this disease and no fully resistant canola varieties at this time, so IPM approaches like prevention, rotation and minimizing extra stresses (blackleg and other diseases) are the main tools.
Verticillium stripe in canola is caused by Verticillium longisporum, while Verticillium dahliae mainly causes verticillium wilt in other crops. The disease in canola was previously called verticillium wilt until researchers confirmed that V. longisporum, not V. dahliae, was more prevalent.
What it looks like
As plants mature, symptoms often become obvious around swathing and remain visible after harvest.
- Early symptoms of verticillium stripe appear as a vertical yellow or brown band extending up one side of the stem, while the stem is still green (usually 3-4 weeks before harvest) (Fig. 1).
- Peeling stem skin with black specks: once fully ripe, the outer skin peels and reveals tiny, pepper‑like microsclerotia on the underside of the peel and in the pith. (Fig. 2)
- Greyish stem cross‑section: the fungus colonizes the plant’s vascular tissue, giving stems a grey interior. (Fig. 2)
Fig. 1 Early Symptoms Fig. 2 Microsclerotia
Tip: Diseased plants often stand out as patches of early ripening or dark grey stems at harvest.
How to tell it from blackleg and sclerotinia
Verticillium stripe can look similar to other stem diseases, but a few clues help:
- Striping is a giveaway. Verticillium often shows half‑stem striping; blackleg and sclerotinia do not. Sclerotinia can discolor stems, but not in a one‑sided stripe.
- Where the dark tissue appears. Verticillium’s grey discolouration can extend well up the stem. Blackleg is usually darker, wedge‑shaped and confined to the crown near ground level.
- Size and appearance of black specks. Verticillium produces tiny black specks (micro-sclerotia) underneath stem peels, which are smaller and more numerous than blackleg fruiting bodies (pycnidia) found on the surface of the stem, often within a distinct lesion. Pycnidia may ooze pinkish substance containing spores when conditions are favorable (i.e. moist).
When and how to scout
Early signs of striping should bring you back to the field to take samples at swathing or post-harvest. Walk fields when the stems begin to dry and peel. Pull suspect stems and check for peeling skin with black specks and cut at the base to see if there are grey cross‑sections. If identification is uncertain, submit samples to an accredited lab for V. longisporum testing.
Scouting checklist
- Focus on patches that ripen early or look weak.
- Pull stems and inspect the outer skin and inner pith.
Biology and spread
The fungus survives in soil as microsclerotia – small, hardy structures that can persist for 10 to 15 years. Numbers decline over time, but the pathogen remains long‑lived. Microsclerotia germinate near roots, enter through root tissue, and move upward in the xylem as the plant grows. Germination is influenced by root exudates and the soil microbiome, which helps explain patchy symptoms in a field.
Management and control
There are no registered fungicides for verticillium stripe in canola. Management relies on rotation and biosecurity.
Priorities
- Rotate canola: leave three years between canola crops to help reduce soil inoculum. Rotation alone will not eliminate the disease because microsclerotia are long‑lived.
- Strengthen biosecurity: minimize soil movement, clean and sanitize equipment, manage brassica volunteers and weeds, and plan field traffic. Treat verticillium stripe like other soil‑borne diseases such as clubroot.
- Variety selection: no cultivars currently claim major‑gene resistance in Western Canada. Some companies report enhanced tolerance, and researchers are developing disease severity scales to support screening. Ask seed suppliers about their most tolerant hybrids and how ratings were determined.
· After confirmation: map affected areas, adjust rotations, and apply stricter hygiene. The CFIA does not regulate V. longisporum as a quarantine pest.
Who it affects
Main host: canola (Brassica napus).
Other brassicas: broccoli, cabbage, mustard and cauliflower can also be hosts – keep these in mind for rotations and volunteer management.
Other brassicas: broccoli, cabbage, mustard and cauliflower can also be hosts – keep these in mind for rotations and volunteer management.
Potential impact on yield
Yield loss depends on the season, conditions and disease level. Severe outbreaks in Europe have shown large losses, while Canadian impacts are still being quantified. Ongoing prairie research is building tools to assess disease severity and support breeding for tolerance.
Contact
For diagnostics and management advice, contact Manitoba Agriculture or your local agronomist. Free lab testing is offered through the Manitoba Canola Grower’s Association for members and an overview of current research on verticillium stripe can be found on the Canola Research Hub.
