in the bud
ACanola Council of Canada agronomist is urging Manitoba farmers to act now to prevent a few isolated cases of clubroot from becoming an epidemic like it has in Alberta.
Alberta might have kept clubroot, a soil-borne, yield-robbing canola disease, in check had it quarantined the first infected fields in 2003, says Clinton Jurke, the Canola Council of Canada’s agronomy specialist for western Saskatchewan.
Now it’s too late. There are thousands of clubroot-infected fields in Alberta, Jurke said in an interview. “And that’s only in a period of 10 years. That’s a pretty dramatic increase.”
But Manitoba, where the disease has only recently been confirmed, can still keep it contained, he said. Identifying infected fields early, cleaning equipment before leaving infected fields, extending canola rotations, reducing tillage and planting resistant canolas are ways to slow clubroot’s spread.
“We really do have an opportunity in Manitoba to nip it in the bud,” Jurke said. “If we can encourage Manitoba growers to think constructively, and from a risk management point of view, I think they’ll have a better opportunity of controlling it than the Albertans have.”
Manitoba Agriculture, Food and Rural Initiatives’ (MAFRI) oilseed specialist Anastasia Kubinec agrees.
“We don’t want to get to the stage where all of a sudden it’s everywhere causing major yield loss,” she said.
Clubroot, a slime mould that cannot be economically controlled with pesticides, causes cankers on canola roots preventing the uptake of water and nutrients. It results in yield losses of up to 100 per cent.
MAFRI issued a notice Sept. 19 that infected canola plants were found in two unrelated Manitoba fields in August and September. The locations aren’t being released.
Most Manitoba farmers are within 50 kilometres of an infected field, although right now the infections are light, Kubinec said.
In 2012, clubroot DNA was found in soil samples from two Manitoba fields. In 2005 a low-level infection was found in a Manitoba canola nursery.
Low levels of clubroot were present in Alberta vegetable fields in the 1970s and ’80s, but in 2003 it showed up in a dozen or so canola fields, Jurke said. It has been spreading from ground zero in the Edmonton area ever since.
“Right in the heart of where clubroot is at its worst you’ve still got these guys who don’t know anything about it,” he said.
Long seed survival
Clubroot spores can survive in the soil 20 years. They build up the more often a host plant is present. Hosts include canola, volunteer canola, stinkweed, wild mustard and shepherd’s purse.
“Now that it’s in Manitoba, there is the potential it could go the same way as Alberta,” Jurke said. “But the advantage Manitoba has is that we have a lot better understanding of the disease now and much better controls available so there is the opportunity to try and restrict that movement.”
MAFRI is monitoring the two infected fields and encouraging the farmers who own them to clean their equipment, Kubinec said. They are also being encouraged to only plant canola in those fields one in four years.
Manitoba farmers shouldn’t be complacent, nor overly pessimistic about clubroot, Kubinec and Jurke said. Some Alberta farmers have stopped cleaning equipment because the disease has spread throughout their area.
Their options are limited to planting canola one in four years and sowing a resistant variety. But Jurke warned that is short sighted.
“Resistance (in the laboratory) has broken down on almost any brassica crop that they put resistance into within a couple of cycles,” he said.
“If we are using resistance, we need to follow a longer rotation, especially for those growers known to have clubroot on their land.”
Long breaks in growing canola will reduce the severity of clubroot in a field but won’t eliminate the disease nor prevent it from infecting a field, Jurke stressed.
It’s important for farmers to be searching for the disease, Kubinec said. Farmers need to determine what has killed canola plants in their fields, record the locations and monitor them. Several things can cause root cankers including herbicide injury and compaction.
Removing soil from equipment is tedious, but effective, Kubinec said.
“If a farmer can spend 15 minutes knocking all the big dirt clumps off their machinery they’ve probably removed quite a bit of the soil and their chances (of transferring the pest) quite a bit,” she said. “If you can get most of the dirt clumps you’ve probably removed 90 per cent of the soil and then your risk.”
Reducing tillage helps too.
“The more tillage that happens in the soil, the more chances the pathogen gets to spread,” Jurke said.
Mobile soil can carry clubroot, whether it’s via wind, water, earth-tagged seed, and animal hooves or in hay or straw bales. Clubroot survives animal digestion and can be transported in manure.
Manitoba farmers should look for the disease in hopes of finding it first in an isolated patch. It often shows up at a field entrance or water runway.
“But if you don’t find it early, by the time you do when it starts causing an economic yield loss, it has already spread to your entire farming operation,” Jurke said.
High-pH soils are not immune to clubroot. Boron will prevent a plant from being infected but only at rates toxic to the plant, Jurke said.
Manitoba farmers have been expecting clubroot, said Bill Ross, executive manager of the Manitoba Canola Growers Association.
“It’s a big thing and it’s not a big thing,” he said. “Alberta has had clubroot for at least 10 years and we’ve learned a lot of things from them.”
The association is helping to fund government testing for clubroot, he said.
View a Canola Council of Canada video on clubroots’ life cycle at http://archive.canola-council.org/clubroot/about_clubroot.aspx.
“We don’t want to get to the stage where all of a sudden it’s everywhere causing major yield loss.”