From a distance, the stubble in the top photo looks ready for seeding. But as you can see in the close up photo below, scouting gave a more realistic perspective: a significant weed population had already emerged. Growers should take a close look at the weed spectrum and stage in each field prior to planning their early season weed control. It may be worth controlling those weeds before seeding, since early emerging weeds out-compete young canola for nutrients and moisture and can significantly reduce yield potential.
The chart below, titled “Timing is Everything,” provided by Neil Harker with Agriculture and Agri-Food Canada, gives a visual explanation of the best spray timing.
With a pre-seed burnoff, growers reduce the risk of missing the ideal weed control window, especially if conditions turn wet after seeding. For growers seeding without a pre-seed burnoff, it will be important to manage weeds with either a pre-emergent burnoff or an early in-crop herbicide application.
Pre-emergent sprays should be applied shortly after seeding — given the potential for rapid crop emergence. But growers with high disturbance seeding systems should note that weeds need time to get reestablished and to have the dust blown off them before you spray.
Refer to product labels, company representatives or the provincial guides to crop protection for application rates based on the size and type of weeds present. Click your province for a link to your guide: Alberta Saskatchewan Manitoba. Also, this time of year, frost damage will impede herbicide uptake. After a hard frost, wait until weeds start growing again and daytime temperatures warm up before spraying. Again, check labels for specific instructions. For more on weed control timing, click here for a Canola Council of Canada factsheet on the benefits of early weed removal.
Published on May 6, 2010