Clubroot: How to scout

August 30, 2017 - Issue 23

To scout for clubroot, start with plants that have obvious symptoms. Look for patches of plants that are ripening prematurely. Often plants growing in the fringe around low wet areas will be large and green and healthy. If these plants are dead instead, this could be a clubroot patch. And because the plants are already dead, the galls may be decayed. In this case, stems may pull out of the ground with no roots attached – which can make clubroot seem like root rot. In this situation, dig down and look for brownish sawdust-like material around where the tap root would be. This is likely decayed galls. DNA tests can confirm this.

The prematurely-ripening plants are dying from clubroot. Credit: Dan Orchard


Early infection can lead to plum-sized galls. Credit: Brittany Hennig


Decaying galls will have a sawdust-like look and texture. Credit: Clint Jurke

While at this location, move beyond these dead areas by a foot or two and check the first living plants. Carefully shovel up the tap root and knock away soil to check for galls. When plants are still living, galls are white and fleshy, like a potato. Large galls can be the size of a plum, and grape-sized galls are common.

As fields dry down, diseased patches are harder to see because the whole field is starting to yellow. In this situation, another scouting option is to check for patches of green weeds. Weeds are often worse in patches where plants died off prematurely due to clubroot, and some of these weeds – brassica relatives such as shepherd’s purse, for example – are also clubroot hosts. If they have galls, then clubroot is present in the field.

If fields have no diseased patches (the obvious first places to scout), then dig up the root crowns for 10-20 random plants near field entrances or any other high-traffic areas, such as near bin-yards, beehives or oil wells. Plants that appear healthy can still have galls – and these galls will produce spores that can be spread around the field and then infect canola the next time around. High traffic areas are the first places to look because clubroot is soil-borne and it often spreads by equipment. Drill openers or tillage tools carrying clubroot-infested soil tend to drop this soil soon after starting work in a field.

Another option is to have the soil tested for clubroot DNA. Here are labs in Canada that currently provide clubroot DNA analysis of soil and/or plant material:

20/20 Seed Labs

507 11th Ave

Nisku, AB
T9E 7N5

(780) 955-3435

A&L Canada Laboratories Inc.

2136 Jetstream Road

London, ON
N5V 3P5

(519) 457-2575

Exova

7217 Roper Road NW

Edmonton, AB
T6B 3J4

(780) 438-5522
 

BioVision Seed Labs

#310 – 280 Portage Close

Sherwood Park, AB
T8H 2R6

1-800-952-5407
 

Discovery Seed Labs
450 Melville Street

Saskatoon, SK
S7J 4M2

(306) 249-4484
 

Pest Surveillance Initiative (PSI)

5A 1325 Markham Road

Winnipeg, MB
R3T 4J6

(204) 813-2171


Read more about clubroot identification, prevention and management at clubroot.ca.

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