The post-seeding, pre-emergence spray option

Applying a burnoff after seeding but before emergence is a risky option for those who want to get seeding. Consider the following risks with this practice:

If the weather doesn’t cooperate and the burnoff doesn’t get done before the crop emerges, the crop is in a significant yield loss situation. In-crop weed control needs to occur as soon as possible.

The longer the weeds persist from the point of emergence until they are controlled, the greater the yield loss. The larger the weed at the time of crop emergence, the greater the speed at which yield is lost following emergence.

The later into May we get, the greater the chance that air and soil temps will increase quickly. Warmer soils mean quicker crop emergence. The faster crops emerge, the more likely the pre-emerge weed control window will be missed altogether.

Preseeding is the only window in the glyphosate tolerant canola system to mitigate glyphosate resistant weeds. By failing to take advantage of the preseed window, there is a greater likelihood of selecting for glyphosate-resistant kochia (or wild oat or cleavers, etc.) because the glyphosate has to go on alone.
—Clark Brenzil, provincial specialist, weed control, with the Saskatchewan Ministry of Agriculture, provided these tips.