Canola growers on the Canadian Prairies are being asked to keep a pair of clippers in the cab this harvest and cut a handful of stems for disease testing, work that takes a few minutes but can shape which variety goes into the ground next year. The advice came from a canola and flax disease training workshop held at the Melfort Research Farm in Saskatchewan on 1 September.

Ian Epp, extension agronomist with Sask OilSeeds, said scouting fits into the harvest routine with little lost time. Growers running a swather or combine, or pre-harvesting canola with glyphosate, should stop in about three spots in a field, chop down a couple of plants and take a closer look. "That'll give you all the sample collection you need," he said, adding that the stops also let an operator stretch their legs.

Sandy Junek, molecular lab manager at Discovery Seed and Soil Labs in Saskatoon, which works with SaskOilSeeds on disease surveillance, recommended sending about 12 stems per field. The same stems serve for both blackleg and verticillium testing.

Both provinces offer some free testing. In Manitoba, members of the local canola association get one free test type per field, covering blackleg, verticillium stripe or clubroot, according to the Manitoba Canola Growers Association. In Saskatchewan, Sask OilSeeds pays for one sample per farm, tested for verticillium and blackleg, with the blackleg race reported when the disease is found.

The race result is the point of the exercise. Knowing a field's blackleg population lets a grower pick a variety whose resistance matches it rather than one that is merely labelled resistant; the Canola Council of Canada has a tool for making that comparison. Epp said the result is not a tissue test that triggers an immediate spray: "It's really next canola variety. It's the next year."

Blackleg results take at least two weeks because the sample has to be cultured before molecular analysis. Verticillium testing can be done in days, though Junek suggested allowing three to four weeks during the busy fall. His laboratory extracts DNA directly from vascular tissue, so verticillium stripe, still relatively new to Saskatchewan but well known to Manitoba growers, can be detected before stem shredding is visible.

A useful result starts with a useful sample. Junek advised pulling symptomatic plants, cutting the roots away while keeping the woody stem base needed for blackleg testing, clipping about 10 centimetres above ground, and using a paper bag rather than plastic, which traps moisture and lets secondary fungi grow. Samples left in a truck for days deteriorate badly.

Reported by William DeKay for the Manitoba Co-operator from the Melfort Research Farm workshop.

Source: Manitoba Co-operator