By Allie Noble, AAg, Crops Extension Specialist, Regional Services Branch, Prince Albert
Verticillium stripe is a soil borne disease that can infect canola. It is caused by the pathogen Verticillium longisporum. It was first reported on the Canadian prairies in 2014 in Manitoba and the first positive case with visible pathogen signs and typical symptoms was found in Saskatchewan more recently in 2021.
Discolouration of cross section ofcanola stem with verticillium stripe.
The impact of this disease on canola yield across the Prairies is unclear. However, research in Europe, where they have been dealing with the pathogen for decades, indicates a 10 to 50 per cent yield loss is possible. Research is currently underway on the Prairies to answer more of these questions on a local level. In the meantime, there is great value in scouting fields to determine if it is present so we can better understand the disease distribution in the province.
Symptoms of verticillium stripe are more obvious later in the season as the disease begins to cause early senescence of the plant due to restriction of nutrient and water flow.
Symptoms include the following:
- Striping of the stem – a line up the stem where one side is yellow due to dying vascular tissue, while the other side looks like green healthy tissue;
- Cross section discoloration – cutting the canola stem at the soil level can reveal greying caused by microsclerotia;
- Stem peeling and shredding, and;
- Microsclerotia present – later in the season after peeling back the epidermis of the canola stems, microsclerotia may be evident.
with epidermis peeled back to show
microsclerotia.
The level of symptoms seen in the field can be impacted by the level of infection and the timing of scouting. Scouting of canola stubble is best done shortly after harvest by looking for symptoms at several different spots in the field. Stubble should be pulled from the ground, cut at the base of the stem to look for discoloration and check for the outer epidermis when peeled back, to see if there are microsclerotia present underneath. A small magnifying lens may be required to see the microsclerotia, as these microsclerotia are quite small.
Verticillium stripe is a newer disease to the Prairies and shares some very similar symptoms with other common diseases of canola like fusarium wilt, blackleg and sclerotinia stem rot. This can make it difficult to identify and the only way to confirm the presence of the disease, in most cases, is just to send samples to a lab for testing. There are many testing labs available across the Prairies that conduct verticillium stripe testing. Currently, there are no control products or resistant varieties available but getting indications of which fields test positive for this disease can help support management decisions to help prevent it from becoming a larger issue on the farm.