Clubroot is a soil-borne disease of canola that causes significant yield reduction if the proper management tools are not used. It affects many plants in the brassica family including radish, cabbage and broccoli. Strathcona County's goals are to collaborate with farmers to identify clubroot infected fields, minimize yield loss and prevent the spread to other areas. The disease spreads most commonly on equipment, but also by transported topsoil, wind and water erosion.

Clubroot is best managed in canola by growing the crop at maximum once every three years and planting a genetically resistant variety. The pathogen that causes clubroot can rapidly adapt to canola's genetic resistance leading to new pathotypes. Clubroot pathotypes able to overcome first generation clubroot resistance are becoming more common in Strathcona County. In 2023, we began pathotyping a portion of fields covered in the annual clubroot survey in partnership with the University of Alberta. This pathotype information indicates it is beneficial for farmers to plant canola varieties with next generation resistance.

Clubroot pathotypes found in Strathcona County in 2023 include:

3B	3C
3H	5G

Two new clubroot pathotypes were identified in 2023 that remain unnamed. 

Which plants does clubroot affect?

Common brassica plant species that are affected by clubroot are listed below

Canola	Kale	Brussels sprout	Turnip
Stinkweed	Mustard	Bok Choy	Sheperd's Purse

The organism that causes clubroot persists in the soil as resting spores for up to 20 years. However, without a brassica plant to infect, up to 90% of the spores will no longer be viable after two years. Once a brassica plant is grown, the resting spores germinate and infect the roots of the plant, restricting the uptake of water and nutrients which reduces crop yield. 

Identifying clubroot

The most common symptom of clubroot is the clubbed roots that develop later in the growing season and can range in size and number. Early infection at the seedling stage can result in wilting, stunting and yellowing of plants in the late rosette to early podding stage. Infection at a later crop stage will show up as patches of white-brown plants that mature earlier than the rest of the field. 

Managing clubroot

Prevention

If clubroot is not already present in a field or garden, prevention is key. On a field scale, prevention can include cleaning soil clods off equipment, preventing unauthorized traffic on the field and sanitizing equipment with bleach solution. If ordering new soil for home gardens, be sure to ask the supplier if it is clubroot positive or request a clubroot test. 

Management once clubroot is detected

Once clubroot has been detected in an area, the disease can be managed using strategies that include:

• Reduced tillage in infected fields
• Proper crop rotation. We recommend planting canola, at maximum once every three years while using a clubroot-resistant canola variety to reduce the clubroot spore load in infected fields.
• Clubroot-resistant canola varieties. Scout your fields regularly to be aware of any clubroot resistance breakdown.
• Reduce soil movement from field-to-field through cleaning equipment and preventing unauthorized traffic.

Clubroot surveys and management in Strathcona County

Under the Alberta Agricultural Pests Act, Strathcona County's agricultural staff enforce clubroot control measures. From early July to late October, our staff survey canola fields across the County for clubroot. Staff may enter private land at a reasonable hour, without permission, to inspect for clubroot and other pests under the Act. Fields known to have clubroot from previous years will also be monitored to ensure that the disease is being managed. A notice may be issued under the Act to prevent the spread and establishment of the disease depending on the clubroot severity and control measures being taken. Owners and occupants of the land are responsible to take steps to prevent and control clubroot on their land. 

For more on identifying and managing clubroot, including labs that test soil for the disease, visit the Canola Encyclopedia from the Canola Council of Canada or the Alberta Clubroot Management Plan.

Canola diseases

Blackleg of canola

Blackleg of canola is a fungal disease that causes stem girdling and lodging. In fields of canola without genetic resistance, a heavy infestation of blackleg can cause up to 50% yield loss.

Common symptoms:

• Off-white leaf spots with small black dots (called pycnidia) on the inside
• Stem or branch cankers with a dark border and off-white interior. Cankers on the main stem are a serious concern for yield loss.
• Darkening of the inside of the stem in a wedge shape. This can be seen by cutting canola plants just above ground level at swathing time. 

Managing blackleg

• Scouting for the disease at the seedling stage and at swathing time
• Growing genetically resistant cultivars
• Rotating the genetically resistant cultivars used
• Crop rotation growing canola once in three years

For more on blackleg and its management.

Verticillium stripe of canola

Verticillium stripe is an emerging soil-borne fungal disease of canola, having first been discovered on the prairies in 2014. Its symptoms in canola include leaf yellowing, early maturity and stunting. Once the plant is mature, the stem can be easily peeled and small black microsclerotia that look like black pepper can be seen inside the stem. These then enter the soil as the stem decomposes and can survive for many years. The disease is spread by infected soil and plant material through water, wind, farm equipment, infested seed and people. 

For more on identifying and managing verticillium stripe. 

Fusarium head blight

Fusarium head blight (FHB) is a fungal disease of cereal crops that reduces yield and grain quality. FHB has a wide host range that includes wheat, barley, oat, rye, triticale, corn and many forage grasses. The most common cause of FHB is the fungus Fusarium graminearum. The disease is spread through crop residue and the pathogen infects cereal crops at flowering time. It is no longer considered a pest under the Alberta Agricultural Pest Act and the County encourages producers in the region to be aware of FHB and take necessary measures to manage the disease on their farm. 

To assess the risk of FHB at cereal heading timing.

For more about FHB and its management.

Grasshoppers

While Alberta has over 85 species of grasshopper, only five are considered regulated pests under the Alberta Agricultural Pests Act. Many grasshopper species are important to the function of their ecosystem, supplying food for grassland bird species like mountain bluebirds and meadowlarks. The five species of grasshoppers that are regulated pests are:

• Migratory grasshopper
• Packard's grasshopper
• Two-striped grasshopper
• Clear-winged grasshopper
• Slant faced grasshopper (although these are registered pests, they are rarely found in numbers requiring control)

For tools to identify different grasshopper species and for management strategies.

Further information: