Clubroot research takes to the air in Alberta

Alberta municipalities have been using Burkard volumetric spore traps to pull potentially contaminated wind and dust into the sampling chamber. The collected soil is then tested for clubroot.  |  Hannah Musterer photo

Municipalities study the role wind may play in spreading the disease as clubroot resistance breaks down in the province

Six Alberta municipalities have taken to the air as they continue to monitor clubroot movement and pathotype presence in the soil.

Using a research grant from the Canadian Agricultural Partnership, members of the Plant Health Surveillance program are focusing on wind, which many people are concerned is another conduit for the pathogen.

The six municipalities taking part in the three-year study are the County of Vermilion River, County of Two Hills, County of Lac La Biche, County of St. Paul, Lamont County and the Municipal District of Provost.

Previous clubroot studies took place in the Edmonton area because the disease was first discovered in Alberta within Leduc County and there was little information about conditions elsewhere.

“We’re trying to see if there’s any style of wind erosion that would transfer clubroot spores through the air. We know that it transfers through soil, but there’s not very many studies done on if it transfers to the air,” said Brett Weeks, Lamont County’s agricultural environmental co-ordinator.

Further east in the County of Vermilion River, researchers are also testing what pathogens are present by monitoring clubroot spore movement by wind and dust particles.

They are trying to understand what prevalent pathotypes could be causing resistance in canola crops to break down in their area.

Year one of the study recently finished, and samples are being analyzed at the University of Alberta to determine what pathotype of clubroot is infecting the plants.

The results will give the municipality, producers and researchers a better understanding of the strains of the disease that are present in the area and help determine what canola resistant varieties will be the most effective at preventing and managing clubroot.

Initial evidence suggests clubroot resistance has broken down in some previously resistant varieties.

“We received some concerning results from our 2019 results showing the breakdown in some clubroot-resistant varieties in the area,” emailed Hannah Musterer, agriculture services technician in the County of Vermilion River.

“This is extremely alarming as it can take years to develop new resistant varieties.”

Musterer said clubroot continues to be most prevalent in north-central and central Alberta, “up to 1,000 fields per county.”

In comparison, the northeastern area has a relatively low presence of the pathogen with about two to three percent of fields infected.

However, the Canola Council of Canada says that number could grow as the disease steadily progresses eastward from the Edmonton area.

“We’ve been tracking it right from 2003. It seems to move out 30 or 40 kilometres a year and seems to be this wave, but we do get instances of where the pathogen has jumped ahead, where it’s usually been machinery that has moved out of the Edmonton area and carried soil all the way to Manitoba,” said Clint Jurke, the canola council’s agronomy director.

A single infection can produce billions of new and diverse individual spores that are not all the same as the original ones infected.

“A Smartie-sized piece of soil either transferred on your boot, truck or equipment can infect your fields for many years,” said Musterer.

Functional resistance decreases as the pathotypes build up, which is what happened in many fields in the Edmonton area when the pathogen defeated the first wave of resistance.

Jurke said it’s feasible that some soil from fields where resistance failed has made its way to fields in the County of Vermilion River.

Added Musterer: “There’s 90 pathotypes and we’re finding more each year. It’s almost like the flu, (where) you have to get a new flu shot each year. It’s kind of growing and then spreading.”

Besides monitoring clubroot dispersal through dust and spore movement, researchers are focused on determining what kind of pathogens are in their areas.

“If the Vermilion River region has pathotype 8 but the County of Two Hills has pathotype 3, then we can inform our producers and they actually plant clubroot resistant varieties that will be resistant in their area,” she said.

Weeks said the CAP grant has enabled the purchase of four Burkard volumetric spore trap instruments, which are transferred between municipalities during spring seeding and fall harvest when soil movement is highest.

The spore-collecting trap has a solar powered pump that pulls potentially contaminated wind and dust into the sampling chamber. Collected soil is then tested for clubroot.

While the first year of the study has produced no conclusive evidence of air transfer, resistance to breakdown was expected.

“There are many clubroot-resistant varieties that corporations sell, but in terms of resistance breakdown, it’s kind of across the board on which pathotype it is. Pathotype is like the DNA of the clubroot, so there’s different strains. We have different varieties of canola and we have different varieties of clubroot. They kind of act slightly different from each other, but we do see more and more breakdown across the board,” he said.

“From our study, so far we tested 19 samples for pathotypes and we had six that showed resistance breakdown.”

In order to mitigate clubroot, the researchers recommend that producers switch varieties as well as their herbicide options.

Killing volunteers is also important, as is lengthening crop rotations.

Jurke said managing clubroot is not easy.

“I wish that we could have just one solution that would fix the clubroot problem, but it’s not, it doesn’t work that way. Like any solutions that we throw at it, it seems to work its way around it. So our best strategy is an integrated pest management approach where we are using multiple strategies in order to control it.

“Our best thing to emphasize is that no region of the Prairies is immune to clubroot. Clubroot is being found in many areas around Saskatchewan, Manitoba, and almost all areas of Alberta. So we need to treat this disease as being present (everywhere) and not something that can be assumed is not going to be a problem for another 10 years type of thing.”

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