Prairie Giants Crop Report

The Prairie Giants Crop Report

Field observations at your fingertips

August 29, 2023

Taylor Kurtenbach

Verticillium Stripe

Verticillium stripe is quickly becoming more evident in canola fields throughout Manitoba, and the rest of the prairies. It is a soil-borne fungal disease, like Clubroot, caused by the pathogen Verticillium longisporum [1]. Once in soil, it can remain there for years (10 to 155!) even without a host [1]. Unlike other diseases, it is more prevalent in hot and dry conditions like we have been experiencing this growing season [2]. Plants infected with the disease can be found in almost every field this year.

The best time to scout for verticillium is after harvest as symptoms that are unique to the disease, like shredding of the stem tissue, does not occur until then [3][4]. Small, black microsclerotia can be found underneath the peeling stem tissue [4]. Plants are also likely to be more fragile or brittle, snapping as you attempt to pull them out of the ground. In season symptoms include leaf chlorosis (yellowing), stunting, yellow striping up one side of stem and pre-mature ripening [1][4].

In a 2022 Manitoba disease survey, the disease was found in 38% of fields surveyed. According to the 2022 Saskatchewan Disease Update at the Saskatchewan Agronomy Research Update in Saskatoon this past winter, there was a 64% prevalence of verticillium stripe in a targeted disease survey along the Manitoba/Saskatchewan border.

Although it is becoming more common, the impact on yield is still unknown. Oil content is unaffected. It appears to be less damaging than sclerotinia stem rot and blackleg since the onset of the disease is later in the growing season2. In Europe, yield losses range from 10 to 50% [1].

There are no seed treatments or fungicides registered to control the disease. Management strategies include:

1. Rotation – 3 years between canola crops is ideal.

2. Weed management of hosts – volunteer canola and other brassica weeds.

3. Biosecurity – limit soil movement.

4. Variety selection – some varieties show differences in susceptibility. Corteva has started to rate their varieties on a scale of 1-9. There is potentially better natural verticillium resistance in longer maturing varieties due to the timing of the disease and crop life cycle, but this is not confirmed.

5. Harvest management – swathing infected plants may help prevent pod drop/shatter, as well as not allowing the disease to spread as much. Swathing may not fully allow the disease to finish its life cycle and may spread less spores throughout the field.

Free testing of the disease is available through Pest Surveillance Initiative in Manitoba, and SaskCanola in Saskatchewan. If you are interested in having samples tested, or your fields scouted for Verticillium, reach out to an agronomist at Prairie Giants.

Sources

[1] Manitoba Canola Growers. Verticillium Stripe. [Online] Available: https://canolagrowers.com/resource/verticillium-wilt/#:~:text=Verticillium%20Stripe%2C%20caused%20by%20Verticillium,that%20contains%20infested%20crop%20debris.

[2] Canola Council of Canada. Verticillium Stripe. [Online] Available: https://www.canolacouncil.org/canola-encyclopedia/diseases/verticillium-stripe/.

[3] Alireza Akhaven. 2023. AgLink Agronomy Forum (2022 Prairie Canola and Pulse Disease Report session).

[4] Government of Saskatchewan. 2021. 2021 Crop Diagnostic Handbook.

[5] BASF Canada. 2021. Knowledge Harvest – Canola (2020 Canola Yield Robbers session).