Late-window applications of herbicide

July 8, 2020 – Issue 17

Always follow labels for rate, timing and pre-harvest intervals (PHI) when applying herbicides. Applications made after the label window can lead to reduced weed control due to advanced weed staging and reduced herbicide contact with the weeds through the increased canola canopy closure. Late applications can also cause canola buds to abort, increasing the potential for permanent yield loss. Finally, late applications and higher than recommended rates of registered herbicides can increase the risk of elevated residues in the marketable grain. Foreign buyers are testing for pesticide residues that exceed registered maximum residue limits (MRLs) or are not registered for use on that crop. Read more tips from Keep it Clean on following the label to avoid unacceptable residues.

This table shows the window of application for various canola herbicides and systems.

A second application of in-crop herbicide is not always economical if the crop is well established, competitive and ahead of the remaining weed population. A second in-crop spray only makes sense if…

Volunteers not controlled as expected. Volunteer canola populations with a combination of herbicide tolerance traits are found on the Prairies. You could have volunteers tested, but if you experience control issues, you might just assume that the volunteers are stacked and take the actions described here.

Canola Watch