The Canola Council of Canada wants you to take a shotgun to your field — at least when it comes to clubroot.
[AUDIO: ‘Are we taking clubroot seriously enough?’ – Justine Cornelsen and Dan Orchard]
Council agronomists are urging farmers to avoid building a clubroot plan around a single silver bullet. Instead, agronomists Justine Cornelsen and Dan Orchard argue, farmers should dig into multiple tools for a wider safety net.
Three of those “bullets” should come as no surprise to farmers; experts have been highlighting them for years. Scouting will be critical to slowing the spread of the disease and detecting the problem while it is more easily managed, according to both Orchard and Cornelsen.
It’s a lesson that Orchard knows well. The Alberta agronomist was the first to identify clubroot in what is now considered the clubroot hot zone around Edmonton. By the time the pest had been identified, it had already been present in the soil for years, he said.
The disease is easy to identify from the roots, both said, but the soil must be badly infested before symptoms appear above ground. The pair urged producers to routinely dig up multiple plants through the field, even if they don’t think they have a problem.
Crop rotation is another often-cited tool, although it’s one that Manitoba farmers do not have the greatest track record with, Cornelsen said.
The wheat-canola rotation is still in full force in some parts of the province, she said. Rotational data around Riding Mountain National Park from 2009-14, for example, suggests that some fields spent four of the six years in canola, and some may have been planted to canola back to back every year.
That weakness is more prevalent in some areas of the province, Cornelsen noted. Northern areas are still in tight rotations (including the same regions in the northwest where the province has noted increased spore loads), while southern areas have seen crops like soybeans move in to replace canola.
A clubroot rotation is not as off putting as the canola council initially thought, Orchard also noted. When the pest first emerged, producers were warned that it could persist in the soil for decades, too long to realistically manage through an extended rotation. Producers were therefore unwilling to make a change for limited benefit, he said.
Recent research out of Alberta, however, suggests that a three-year rotation might get rid of 99 per cent of the spores, a prospect far more palatable for the producer.
That information could help Manitoba avoid the clubroot crisis he is fighting at home, Orchard said. Spore loads in his area often rise into the millions per gram, and the one remaining per cent of those spore loads after a three-year rotation is still enough to cause symptoms. Some farms in central Alberta have had to cut canola back to every seven or eight years, he noted. In contrast, most fields in Manitoba measure below 10,000 or even 1,000 spores per gram.
The shift to a three-year rotation is still not easy, he admitted. He estimates that it will take an average farm five years to adjust to the business and agronomic details of the longer rotation.
Resistant varieties form the last of the council’s “big three bullets.”
Again, Cornelsen says, it’s something Manitoba has fallen flat on.
“A lot of the practices just don’t happen,” she said, “like growing clubroot-resistant varieties. You look at the number of acres in Manitoba that are actually growing clubroot-resistant (varieties); it’s very low.”
Resistant varieties do not come with a yield penalty, she insists.
At the same time, both agronomists noted, producers should not rely on resistance alone. The genetics have begun to lose their potency in parts of Alberta, and Orchard noted that several farms in his area have had to give up on canola entirely.
[AUDIO: ’The difficulties in switching from a two to three-year rotation.’ – Dan Orchard]
Manitoba may be developing similar problems. Last fall, the province discovered Manitoba’s first cast of a 3A clubroot strain, a strain able to overcome first-generation resistance.
“It’s hard to put a value on each one of the management recipe ingredients, but certainly growing resistant varieties and crop rotation would be the top two, undoubtedly,” Orchard said. “And really, growing resistant varieties should be quite easy, in my opinion.”
Lack of seed availability is an issue, he admitted, but said that he expects that problem to resolve itself in the near future.
Clubroot has given producers another reason to reduce their tillage, according to the canola council.
The council’s “shotgun” approach argues that tillage puts soil in the air and spreads infected soil quickly through a region.
Clean equipment is another important point; one that Orchard says may have also turned producers off during the early days of clubroot management. Fully sanitizing equipment between fields may not be feasible, he admitted, and the prospect of doing so may have actually hurt the council’s efforts to push management strategies.
Instead, even brushing off dirt clods between fields will substantially reduce the risk, Orchard said. Again, he noted, Manitoba’s soils do not have Alberta’s spore load and moving small bits of soil comes with less risk.
“If someone’s coming to your farm from Alberta, you may want them to bleach and sanitize,” he said. “That’s a different story. But when you’re going from field to field on your own farm, I think you assess your own risk and decide your own level of sanitation that you’re going to do.”
Weed control is among the easiest management strategies to push, Orchard said, since it’s something producers want to do anyway. In terms of clubroot, eliminating brassica weeds also breaks up the clubroot life cycle and helps cut down spore loads during non-canola years.
The council also suggests patch management if producers already have clubroot in the field. The strategy may involve planting an infected patch down to a grassy species and leaving it untouched for several years.
‘When,’ not ‘if’
Clubroot is no longer something producers can ignore, even if their region has so far been in the green, the council says. While only sporadic fields in Manitoba have tested high enough for symptoms, Cornelsen said the pest’s ability to spread through soil, wind and water means that producers will eventually be dealing with clubroot, even if they are not right now.
As of last fall, nine municipalities had either reported spore loads of 80,000 spores per gram of soil or noted symptoms. The provincial monitoring program has noted a cluster of municipalities in south-central Manitoba with high spore counts, including one well-publicized case in the RM of Lorne last year, as well as a number directly south of Lake Manitoba, a more isolated case in the northern Interlake, and municipalities with growing spore loads in the northwest near Swan Valley.
“It’s like not exercising and eating healthy until the doctor tells you to do it,” Orchard said. “I find with clubroot, people don’t really address it until they have the problem and I think people in Manitoba, through education, are now realizing that this is a proactive approach and they have to not wait until they have clubroot before they deal with it.