Published on Wed, 03/02/2016 by BASF Canada

Canola: Scouting and managing blackleg

Western Canada has seen an increase in the incidence and severity of blackleg over the last few years. Where blackleg is not managed carefully, it can cause increased lodging, slower harvesting and yield losses. Blackleg can reduce yields on large sections of canola fields and increase the risk for repeated blackleg infestations on future crops.

Levels of blackleg are increasing across Western Canada due to the fact that with tighter rotations, growers are putting more crop residue back into the ground without allowing the necessary three years between canola crops to break down and become unviable. “Blackleg lives on the residue left by canola and other brassica species,” said BASF Technical Marketing Specialist, Russell Trischuk. “Every time we increase the amount of that trash into the soil, we increase the amount of the disease present.”

According to the Canola Council of Canada’s (CCC) website, scouting is an important tool for blackleg management. The website states there are three distinct times to scout for blackleg during the season: prior to planting; the vegetative stage (3 to 6 leaf); and at swathing. Swathing is seen as the best and most accurate time to assess blackleg pressure.

While it is important to thoroughly scout canola fields for diseases each growing season, BASF supports the recommendation that growers also scout their canola fields in the fall. “We encourage growers to scout for blackleg symptoms at swathing as this is the time of year when we can most positively identify the disease,” said Trischuk. Trischuk noted that scouting for blackleg symptoms in the fall allows growers to collect information to help plan and assess their management strategies in the future.

Trischuk emphasizes the importance of gathering an accurate sample by avoiding areas such as headlands and slews, and scouting in a W pattern. “Growers should map out an area about 100 square feet and randomly collect 20 plants within that area; it is best practice to scout in a W pattern to collect and analyse 20 samples from each point of the W.”

Once samples are collected, growers can snip their canola stems at the point where it enters the ground and look for blackened tissue inside the crown of the stem. The amount of black tissue inside the stem can be rated on a scale of zero to five to determine the level of blackleg pressure in the plant, with visual references available from the CCC or BASF AgSolutions website. For those who are unsure or concerned about their samples, BDS Laboratories and Discovery Seed Labs in Saskatchewan, and 20.20 Seed Labs in Alberta and Winnipeg are able to confirm disease presence through diagnostic testing.

For growers with less than one in four-year canola rotations, those using similar seed genetics on a regular basis, or those who have identified blackleg in their fields, BASF recommends a preventative fungicide application as a tank-mix with your canola in-crop herbicide application as an additional mechanism to help manage blackleg.

“Fungicides should be used preventatively before blackleg symptoms appear, effectively stopping the disease before it starts,” added Trischuk. “A fungicide like Priaxor can be tank-mixed with all canola herbicide systems for ease of use. In addition to disease control, growers will also benefit from increased growth efficiency and better management of minor stress, which are the additional benefits associated with an AgCelence fungicide.”

Chris Grenier farms with his family near St. Leon, Manitoba, an area where blackleg is an ongoing threat. “The number one issue on our farm is blackleg because we run a very tight rotation of canola. This year we used Priaxor on all our canola because we feel it has very good control on blackleg. Another reason we like using Priaxor is for its AgCelence benefits. It keeps the plant healthier and greener longer. And by doing that, it reaches the crop’s full potential.”

BASF Canada provides more information about Priaxor and managing stresses and diseases on its website, www.AgSolutions.ca. There, growers can learn more about disease challenges in their area and hear from other growers who have tried various fungicides on their own fields.

 

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