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The challenging conditions this year resulted in less than ideal weed control in some fields. Plus, harvest appears to be late this year so there will likely be greater risk with post-harvest herbicide timing due to frost. Preharvest applications of glyphosate can be a valuable tool in preparing for next year’s canola crop. Generally, fall applications provide the most effective and consistent control of perennial weeds as herbicide translocation into the root system is enhanced. Wait three full days after application before cutting to allow for thorough translocation of the herbicide. If considering this tool to control weeds in canola crops prior to swathing, keep in mind that the recommended timing of application is when grain moisture is less than 30%, in order to avoid issues with residues in the seed. At this stage in canola the pods are green to yellow and most seeds are yellow to brown. Waiting another three days after this will typically increase seed colour change an additional 10 to 15%, so this may push the maturity past the stage where swathing is appropriate. As a result, this strategy may be more suitable for fields destined for straight cutting. Finally, growers should keep in mind that in general, the use of preharvest glyphosate on crops grown for seed should be avoided.
