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.
At this time there is only one winter canola variety that is registered in Ontario and readily 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 US for their own use with the appropriate permits, but should ensure end users will accept those varieties before seed is purchased. Please be aware that Mercedes does not carry a herbicide tolerance trait, and neither do most other available varieties. We do not have access to Liberty Link or Roundup Ready winter canola.
Herbicide application options prior to planting of winter canola are somewhat limited. The primary choices are glyphosate, glufosinate (Liberty), clopyralid (Lontrel) and trifluralin (e.g. Treflan) 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 2 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 (8 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 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 (i.e. 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. The guide can be found here: http://www.omafra.gov.on.ca/english/crops/pub75/pub75A/pub75A.pdf
We hope to continue to clarify herbicide carry over restrictions in future trials.