Winter canola requires herbicide vigilance

Limited varieties are sensitive to herbicide carryover

Producers interested in growing winter canola should consider the herbicide history of their field, and the herbicide options open to them following winter wheat harvest. There are a number of restrictions, and some herbicide labels do not mention safety on canola.

Only one winter canola variety is registered in Ontario and available to producers. It is named Mercedes and sold by C&M Seeds. Producers are allowed to bring seed of other varieties in from the United States for their own use with the appropriate permits, but should ensure end users will accept those varieties before seed is purchased.

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Mercedes doesn’t carry any herbicide tolerant traits, nor do most other available varieties. Producers do not have access to Liberty Link or Roundup Ready winter canola.

Herbicide application options before planting winter canola are somewhat limited. The primary choices are glyphosate, glufosinate (Liberty), clopyralid (Lontrel) and trifluralin (Treflan for example) as well as grass control products. Eragon and 2,4-D can cause crop injury and should be avoided in pre-plant burn downs.

There are also many herbicide carry over restrictions, and some products may not be safe for canola for up to two years after application. Products used in wheat that may not be safe on canola include Infinity (10-month re-crop interval to canola) and Buctril M (eight-month re-crop interval). Other products that have a 22-month re-cropping interval or more include imazethapyr (Pursuit, Optill), metribuzin (Sencor) and atrazine (Primextra, Marksman, etc.).

Treflan and Lontrel are safe to use post emergence in winter canola, as are a number of grass control products. However, Treflan requires incorporation.

Consult the Guide to Weed Control, Publication 75 (opens in PDF), for more information on herbicide carry over restrictions. The re-cropping interval information can be found in Table 2-2 starting on page 64. Conventional winter and spring canola (meaning those without herbicide tolerance traits) are the same species and have the same reactivity to herbicides. However they have different planting dates and crop rotations so herbicide carry over intervals should be considered carefully.

More research is needed to clarify herbicide carryover restrictions.

– Meghan Moran is an OMAFRA canola and edible bean specialist.

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