Looking Ahead: Canola Disease

Saturday, March 11, 2023

Keeping your crop clean in 2023

By Colleen Halpenny

For almost 50 years now, canola has been the pride of Canadian growers. And canola diseases have challenged Prairie farmers for almost as long.

To get a jump on what's ahead in a few months' time, Better Farming interviewed industry experts and canola growers to discuss the diseases which could impede yields, and the measures you might consider to prevent them through 2023.

The Big 3

Clinton Jurke, agronomy director of the Canola Council of Canada (CCC), certainly knows that diseases can be significant and cause yield loss and trade issues.

He notes that a multitude of pests and diseases can impact canola in the Western provinces, but Jurke and his team focus in on what they call the Big 3.

"These are the diseases which the industry is most concerned with and can cause the largest losses."

For Jurke, the No. 1 yield-robbing disease affecting growers is sclerotinia stem rot. Caused by a fungus, infection occurs during the flowering stage of the crop.

CCC reported that during the 2016 growing season, sclerotinia was so widespread across Western Canada that over 90 per cent of the fields surveyed had some symptoms of infec-tion.

With the fungus able to overwinter in the soil, the lifespan can be five years or more. Increased levels are seen when canola rotations are short, or when other susceptible pulse or forage crops are grown.

Colette Thurston, market development agronomist for central Alberta with Bayer CropScience Canada, knows the importance of early detection and the value of investing in pro-tection.

"Bayer has worked hard to deliver a variety of really effective fungicide options for producers. We know they're looking for fast-acting and long-lasting results against sclerotinia, given that it is heavily impacted by environmental conditions, making outbreaks difficult to predict," she says.

Farming in Fillmore, Sask., Jake Leguee says that heat and lack of moisture during the typical southern summers mean "we don't typically get enough sclerotinia presence to make the cost of spraying pay out, but in 2022 all the factors came together, and we made the call to spray the crops and stay ahead of what we were finding."

Even with many years of genetic development for resistant hybrids, blackleg prevalence is still increasing across the Prairies, says Trevor Herzog, Western Canada agronomy lead-er for Corteva Agriscience.

"All hybrids today have some resistance built into their makeup. Our offerings lean on adult blackleg protection, aiming to prevent stem cankering from becoming prevalent in the fall," he says.

Research from the University of Alberta, along with Alberta's Ministry of Agriculture, Forestry and Rural Economic Development, found that for every unit of increase in disease severity, a 17.2 per cent loss in plant seed yield can be expected. Pod number and seed yield both declined linearly as blackleg severity increased.

Jurke reflects that blackleg has been around just about as long as canola.

"When the first resistance cultivars came to market in 1995, growers were so relieved. Resistance worked so well, but by 2010 there was a widespread and widescale reduction in the effectiveness. The pathogen had evolved and was able to get around the resistance," he says.

As producers try to increase rotation length, and seed companies bring more hybrids to market, Jurke says producers still need to understand which specific resistance gene will work best in their affected fields.

He explains that researchers have developed a way in which growers can sample their canola residue, finding the rate of the pathogen, and then link them to the seed which will be most beneficial.

Thurston stresses that prevention starts before you seed, especially when it comes to clubroot.

As a soil-borne disease, clubroot causes swelling or galls to form on the roots of the canola plant, causing premature death. Having a management strategy in place is key to keeping clubroot in check. Remember to scout for patches of infected plants in season, minimize soil movement, control host weeds, utilize a minimum three year rotation, and grow a hybrid with appropriate clubroot genetics for your area.

Jurke feels that clubroot is the disease causing the most turmoil for canola growers currently.

"The loss potential, and the adaptability of this disease is such a tinderbox moment. The rate at which this disease's genetics adapt and its reproduction rate – this is a tough one for any farmer to manage in the long term. The industry as a whole is really working on finding strategies with which to manage it," he says.

Herzog emphasizes the importance of clean equipment, isolation of exposure areas, and always moving into those areas last during your cropping are keys to stop the spread.

New emergences

With its first presence reported in 2014, verticillium stripe is relatively new, and thus there is still much to learn about the disease, severity, impact and management strategies.

The CCC shares that after the initial discovery, follow-up soil surveys were conducted by the Canadian Food Inspection Agency in 2015. Those studies found presence of stripe from B.C. to Ontario.

"While established across the country, there seems to be the heaviest presence in Manitoba, although we don't have the 'Why?' answer to that," says Jurke.

"Stripe is a fungus and is soil-borne like clubroot, and as of yet no fungicide has been found to work against it.

"Stripe is able to build up heavily and quickly in the soil, and initially focusing on those management practices to keep soil in its place was thought to be the solution. However, stripe can also travel up into the plant and as you harvest canola, as the plant shatters, the pathogen is spread everywhere.

"As we work to find solutions, we stress to producers to increase rotation times to allow the presence to break down in the soil, but only time will tell which strategies are going to give the best results."

Knowledge is power

Canola plant diseases can have a large impact on canola yield and longevity, so effective scouting strategies, proper identification and accurate assessment of diseases is crucial to successful crops.

Jurke points out that canola, like every crop, experiences diseases, and producers need to be aware of what is likely to put their crop most at risk, and stay up to date with changing pathogens and evolving diseases.

Leguee knows that the increased cost per pound of seed means he needs to have strategies in place to get his crop off to the best start, and keep it growing well throughout the season.

"Starting clean, and getting that first herbicide on during the one- to three-leaf stage – usually we don't need to go back in. Being adaptable with each year, and each variable growing condition, is great, but for us, the key is scouting.

"You need to look at the crop every few days to keep yourself ahead of any potential presence of pests and disease," he says.

Herzog: "Seek out your agronomists to work alongside you to find the best solutions and protections that will improve your yields at the end of the year.

"It doesn't have to be complicated, but with minimal changes to the varieties chosen or rotation patterns, you leave yourself exposed to have these disease pressures overcome the resistance and suddenly you're on the back foot."

Thurston knows internal crop competition can be as detrimental as weeds and disease, so "while pest and disease losses are more at the forefront of the conversation, ensuring your plant stand has optimal population will help manage weed control, even maturity, lodging, and disease presence when the canopy is optimized."

"Our goal is to not give the disease the conditions it needs to develop. All management strategies are best delivered when scouting is optimal, and growers make the right decisions on how to manage their crop.

"Not relying solely on resistance, growers need integrated strategies through longer rotations, fungicides, and seed treatments," says Jurke.

Jurke points out that seed companies and agronomists across the industry are working to find new and better results, and that the CCC has set aggressive targets on what they aim to see in terms of yields.

He believes that Prairie farmers have the tools and knowledge necessary to hit those yields, but these diseases are standing in the way.

"Collectively, canola farmers in Western Canada have a lot of support to help identify, monitor, and stay ahead of these diseases, and we encourage each and every one to reach out and put their farm into a proactive situation, which in turn will reap the benefits of successful harvests," he says. BF