Regional agronomists offer tips on scouting for clubroot as well as on disease prevention
By Kate Ayers
Staff Writer
Farm.com
Although harvest season is well underway, the scouting season is not over.
Now is the time to check for clubroot in your canola fields. So, here are some tips to help you look for this damaging disease.
Clubroot is a soil-borne disease that can cause significant yield damage in canola. Once producers find the disease in a field, it can be difficult to manage as spores can live in the soil for 20 years, the Government of Manitoba website said.
“It is so crucial to keep spore concentrations low,” Angela Brackenreed, an agronomy specialist in Minnedosa, Man., said to Farms.com today.
“It only takes two cycles of susceptible canola to move concentrations from essentially undetectable to millions of spores per gram of soil that will produce symptoms and take yield.”
The map shows positive clubroot findings by Rural Municipality (RM), discovered through visual field symptoms and/or presence of clubroot spores in soil through laboratory testing for DNA. Source: Province of Manitoba
The primary way clubroot moves into fields is through soil, Greg Sekulic, an agronomy specialist in the Peace Region, said to Farms.com on Wednesday.
Its spread is mainly caused “by soil movement from field to field. In most cases, we find that it’s moving on a producer’s equipment.”
A secondary way the disease travels is by wind-blown soil. Producers are encouraged to keep the soil covered to reduce soil movement.
At this time of year, producers should be out in their fields looking for clubroot, Sekulic said. A field drive-by is not sufficient to accurately assess the crop.
“Right now is actually a fantastic time to scout because (growers) can pull a few plants out … and look for small galls on the roots. When the (nodes) are small, you won’t see any above ground symptoms at all – the plants above ground will probably look very healthy,” he said.
“But when you pull the roots out, you will actually find the swellings and the galls on the (root’s) side-branches as well. (Now) is a much more effective time to find the disease (rather) than later, when 20 acres are dead.”
Indeed, it is better to be proactive rather than reactive.
"If the disease has established itself, the symptoms are quite severe and there’s no mistaking it,” Brackenreed said.
“Where it becomes a little trickier to identify is in areas where spore concentrations are lower. The galls on the roots can be very inconspicuous. Prior to swathing is a good time to check roots, as any galls are still likely to be white, firm and intact. By the end of the season, they will decay and fall apart, with a brown, peaty look to them.”
Since the disease can be spread by a producer’s equipment, a good place to start looking for clubroot is at the field entrance.
In addition, “low lying areas of the field that tend to be wetter or areas near water runs are places (producers can) concentrate scouting efforts,” Brackenreed said.
Producers are encouraged to scout throughout harvest as well.
“While (producers) are out swathing and combining, when there’s a dead patch or some unhealthy-looking canola, don’t just assume that it was drought or drowned out. Pull that plant up and have a look at the roots,” Sekulic said.
In the event a producer finds clubroot in the crop, he or she may need a new field management strategy.
“If you find clubroot, you need to change your management tactics. First and foremost, that is going to be rotating to resistant varieties, of which there are plenty now in every herbicide and canola-breeding system in Canada,” Sekulic said.
“Second, you want to give that field as much of a break as possible – like two or three years before you plant canola again.”
The best ways to prevent disease movement are to clean equipment when moving from field to field and keeping the soil in the field.
Clubroot is “very much a soil disease,” Sekulic stressed.
“Anything that we can do to keep the soil in place and covered, to prevent it from blowing around, will help prevent transmission from field to field and within the field.”
Reducing tillage can also limit soil movement.
“Consider limiting field activity in really muddy conditions, particularly in fields with clubroot,” said Brackenreed.
“Consider equipment sanitation in fields with clubroot. For producers that are hiring custom applicators or renting equipment, they should make sure it is cleaned off in the area it came from before bringing it onto their farm and clean it again before sending it away.”
UPDATED: Aug. 17, 2018
Province of Manitoba photo