Over the last few years, various public disease surveys show an increase in the incidence and severity of the canola disease blackleg across Western Canada. According to the Canola Council of Canada, blackleg was the most damaging canola disease throughout the 1980s and early 1990s and if it is not managed carefully, blackleg can cause significant yield losses.
It’s too late to manage blackleg this year, but now is the opportunity for growers to identify how much disease is present in each field, gain valuable information about how their current disease management strategy is working and begin to make decisions on how to better manage these strategies in the future.
“The reason it is recommended to scout for blackleg in recently swathed canola is because this is the time we can most accurately identify the disease in canola,” said Russell Trischuk, Technical Marketing Specialist with BASF. “Surveys are showing that blackleg is starting to increase in Western Canada again, so growers need to know how to scout effectively for the disease.”
Scouting for blackleg symptoms in the fall (ideally during swathing) enables growers to collect valuable information that will be used to make decisions for future years to plan and assess management strategies. Fields with high blackleg levels can be an indication that the resistance mechanisms that have been bred into the canola variety may be breaking down, most likely due to a shortened rotation. Trischuk recommends the following tips to effectively scout and manage blackleg:
Gather an accurate sample: Samples should be gathered from parts of the field that are accurate representations of the crop. Avoid areas such as approaches, headlands and areas around telephone polls or slews.
Sample five areas in a W pattern: Random sampling throughout the field is important to obtain accurate data. Map out an area of about 100 square feet and randomly select 20 plants from that area. Scout in a W pattern and collect 20 samples at each point for analysis.
Score samples for blackleg: Snip crop samples with clippers at the base of the stem right where the plant interfaces with the soil (e.g. no higher than 5 cm above the soil) and look for blackened tissue inside the crown of the stem. The amount of infection present will help identify the level of risk and the best management practices for that field in following years.
Plan a fungicide application: A preventative fungicide application at the 2-6 leaf timing, such as Headline or new Priaxor (registered by BASF for the 2015 season), provides another mechanism in addition to genetic resistance to help growers manage blackleg. 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. These benefits result in crops that often exhibit taller plants with greener leaves, stronger stems, and fewer aborted flowers and pods. Spraying a fungicide in the spring will decrease blackleg pressure in the future, protecting a grower’s investment and will help maximize yield potential.
“With increasing acres of canola and the tighter rotations required to achieve these acres, diseases including blackleg will continue to be an issue for western growers,” added Trischuk.
Late season (e.g. during or shortly after swathing) disease scouting lets growers better identify the level of disease present in their canola fields and plan an integrated management strategy. Proper rotation intervals, rotation of seed genetics, and a strategically timed fungicide application at herbicide timing will enable growers to manage blackleg and produce a profitable crop.