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Man carrying child over his shoulders overlooking a canola field

  

The dirt on clubroot.

Clubroot is a serious soil-borne disease in canola. Infected roots develop galls that impede water and nutrient uptake. This slows or halts crop growth and development, leading to lower yields. Industry research has shown that yield loss can be estimated by dividing the percentage of infected stems by half.

 

The best way to confirm the presence of clubroot is to dig up plants that appear to be dying or prematurely ripening. Infection leads to galls on the roots, ranging from tiny nodules to large club-shaped outgrowths. Galls are firm and white but become soft and greyish-brown as they mature and decay. Infected plants show signs of wilting, stunting and yellowing, but considerable damage can be done below ground before symptoms aboveground begin to appear. The crop may also ripen pre-maturely and lead to shriveled seeds.

 

Implementing an integrated pest management plan (IPM) is a critical step to managing any disease including clubroot, and every farm should have a plan in place regardless of the current disease status on your farm.

Clubroot-resistant genetics from InVigor.

Using a hybrid with built-in resistance is one tool available to help manage the disease. Growers can maximize and protect the potential of their crop with InVigor® hybrid canola that contains a “C” within their name, as they’ve all been designed to help defend against clubroot and maximize yield.

 

All InVigor clubroot-resistant hybrids have been developed to be resistant to the most predominant clubroot pathotypes found in Canada at the time of their registration. 

 

InVigor L356PC, InVigor L340PC, InVigor L345PC, InVigor Choice LR344PC, InVigor L255PC, InVigor L241C and InVigor Health L258HPC share the same first-generation clubroot resistance profile. InVigor L343PC and InVigor L234PC have the same first-generation resistance profile, plus they contain second-generation multigenic clubroot resistance to additional clubroot pathotypes to help combat evolving clubroot pathogens. We recommend growing InVigor L343PC or InVigor L234PC with second-generation clubroot resistance in clubroot-affected areas after two cycles of growing first-generation clubroot-resistant hybrids in clubroot affected areas or when clubroot symptoms appear in first-generation clubroot-resistant hybrids, which ever occurs first.

Best management practices for clubroot.

Clubroot is a particularly difficult pest to control that can cause significant yield losses in canola. There are currently no registered chemical products to control clubroot, so the strategy to control clubroot is to integrate multiple best practices to preserve canola for years to come.

Woman in a field examining crop roots in her hand

Clubroot management in the field.

Practice good sanitation.

This helps reduce the transfer of diseases through contaminated soil and crop debris. Be sure to clean equipment, farm vehicles and even your footwear prior to moving to another canola field. Limit or eliminate external traffic on fields.

Pull infected plants.

If you catch the disease early and there is a relatively small patch of incidence, consider pulling the infected plants and either burn them or bury them in a landfill and follow up by planting grass in the affected area.

Use resistant hybrids.

Grow first-generation InVigor clubroot-resistant hybrids at the first sign of clubroot in the field or if clubroot is present in the farming community that includes the area where you or others conduct your farming activities. This community can include equipment or contractors that have travelled from other fields. If growers are still (or start) seeing issues in their first-generation clubroot-resistant hybrid while still following a one-in-three-year canola rotation, or have grown first-generation clubroot resistance in fields known to contain clubroot for two cycles, we recommend growers consider switching to a second-generation hybrid. Planting clubroot genetics preventatively in areas where the disease is emerging can also help decrease the rate of spore buildup.

Control weeds and volunteers.

Brassica and other weeds, such as wild mustard and shepherd's-purse, can serve as hosts for clubroot in non-canola years.

Limit tillage.

Use soil conservation practices to reduce spread of resting spores.

Monitor moisture levels.

Frequently monitor your fields for moisture levels. Well-drained soils can help prevent the movement and may help minimize the development of the disease.

Rotate Crops.

A one-in-three-year or greater rotation is recommended. Note that cruciferous crops can also act as hosts to clubroot.

Scout crops regularly and carefully.

Assess the field as a whole and look for patches of crop showing wilting, premature ripening or stress symptoms. Pay particular attention to field entrances and areas of high traffic. Dig up plants at or after swathing to check for galls on the roots.

Patch Management.

Once you have identified a clubroot-infested patch, your next step is patch management, a protocol pioneered by Agriculture and Agri-Food Canada research scientist Dr. Bruce Gossen in Saskatoon. The first step in this process is to pull all the affected plants. This could take hours or a few days depending on the size of the infestation but it’s key to stopping the spread of clubroot. Dispose of the diseased plants carefully – either store them in plastic bags and bring them to the landfill or burn them.

For more information on clubroot and the strategies mentioned above, visit clubroot.ca

 

Resistance doesn't last forever.

The genetic components within an InVigor hybrid that provide resistance do not break down, however the populations of clubroot pathotypes within a field will shift due to selection pressure. Even the most robust genetics will no longer provide protection if grown too many times consecutively.

If characteristic galls are found on canola in areas of thin and early-ripening patches, it is likely the clubroot population in the field has shifted. 

Fields that are infected with clubroot are likely to have more than one pathotype present in the soil. With the use of resistance genetics, you can grow canola in fields that contain the pathotypes that your hybrid has resistance to, but over time, because there are spores from other pathotypes present that your canola does not possess resistance mechanisms for, you could see the predominant pathotype shift in your field. Also, selection pressure on the pathotypes being controlled can cause genetic changes in the virulence of the pathogen to overcome resistance. 

The shifted or newly-introduced population should be pathotyped and we recommend growing InVigor L343PC or InVigor L234PC with second-generation clubroot resistance.

Water droplets on canola pods