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Hold Back the Economic Clap from Clubroot


This is a clubroot infested field, with a resistant variety grown on the left and a susceptible variety grown on the right. Source: Aaron Van Beers

Clubroot lowers the bottom line for more and more Western Canada canola growers each year. The disease has been advancing through Alberta at a fairly steady 20 to 25 km per year, and has been detected at low levels in Manitoba and Saskatchewan. All fields on the Prairies are at risk of economic loss from clubroot, with the highest risk fields those that are (1) in known clubroot areas and (2) whose owners are currently doing very little, if anything, to prevent or manage the disease.

These are the fields that “suddenly” experience an extensive infection of plants by clubroot — say, for example, on 25% of the field, or more. In fact, clubroot was building up in that field, likely over two or more canola rotation cycles, and could have been detected earlier with proper scouting and then managed without such a huge economic loss.

A long wet spring this year could add to this worst case scenario. Muddy field equipment greatly increases the spread of clubroot-infested soil. And a late spring increases the time pressure, which means growers may not want to take the time to sanitize equipment between fields.

Features of the “perfect storm” for a clubroot wipeout when clubroot is on your land are:

Not knowing clubroot is on your land (not scouting)
Wet warm soils
Canola in tight rotation
Not using restistant varieties
Not rotating between clubroot resistance sources
Not preventing soil movement
Not restricting access to your land
Risk reminders


Resistance risk, quantified. If growers wait for clubroot to show up before choosing R varieties, the selection pressure for resistance breakdown is literally millions of times higher than if growers begin using R varieties before the disease shows up. (See “The math of risk” below.) Short rotation also increases the risk. Growing canola every second year has twice the risk of selecting for resistance breakdown than growing canola every fourth year.

Using R varieties on non-infested land will not contribute to the breakdown of a resistance trait. In fact, R varieties are an ideal choice for those fields without clubroot that are situated in areas known to have clubroot.

High pH will not save you. There are clubroot infested fields in Alberta with high soil pH. Manitoba has high pH relative to most other parts of the Prairies, and clubroot has been detected on canola in Manitoba and is expected to continue to advance throughout the province. High pH only slightly lessens the severity of clubroot. Moisture will override any potential benefit from higher pH.

The risk is not equal in all areas. The risk of economic loss from clubroot is higher in central Alberta than in Saskatchewan or Manitoba — for now. Management steps taken now will help keep it that way for longer.

What increases the risk? Growing canola in areas with a lot of canola production, and a long history of canola production. Moisture at seedling stage. Presence of clubroot in area – within 50-100 km, the risk begins to increase. Oil patch activity in the area, especially new leases and seismic exploration. Land exposed to public access of any kind. Custom seeding, spraying, harvesting.

Buy clean equipment. When buying used or demo’ed equipment from a high risk area have it cleaned at the point of purchase, and then sanitize it again once it gets to the farm. Seeding, harvest, tillage, manure, hay, livestock, construction, and recreation vehicles, etc., that originate from high risk areas can import this pathogen to your land.

Test suspect fields. Growers can have soil or suspicious plant roots (canola, mustard related weeds) tested for clubroot if they suspect a problem area or if they’re leasing new land and want to make sure. A list of labs.

The math of risk

Suppose a newly infested piece of soil has Plasmodiophora brassicae spores at a concentration of 1,000 spores/g. And a highly infested soil near Edmonton at 1,000,000,000 spores/g.

Source: Alberta Canola Producers Commission


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