Canola School: Post-Harvest Spraying and Mitigating the Risk of Carryover


Post-harvest spray applications are an effective way to deal with hard-to-control perennial and winter annual weeds like Canadian thistle, foxtail barley and dandelion. But, whether you’re dealing with frost, labour shortages or incredibly dry conditions, spraying in the fall can be  a challenge.

A dry fall can not only limit the active growth of weeds, it can also protect plants from herbicide applications by providing a protective layer of dust and chaff. These conditions can lead to a decrease in levels of herbicide control/suppression. The less obvious consequence of dry conditions, however, can occur the spring following spray application, with crop injury due to herbicide carryover.

So, when is the ideal time to spray?

In this Canola School, Neil Harker, research assistant with Agriculture and Agri-Food Canada, walks us through some of the weeds that should be targeted now and emphasizes the importance of timing in mitigating the risk of carryover.

If you cannot view the embedded video, click here.

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