When canola is at multiple stages within one field and when weeds are at multiple stages, it can be a challenge to choose the right spray timing. The key is to assess the stage that represents the majority of canola plants.
If most plants are within the spray window, then go ahead and spray. Choose a spray rate that will control the largest weeds — as long as there are enough of these large weeds to reduce yields. If large weeds are few and far between, then you could consider a lower rate. Assess the threat. The first emerged and largest weeds are the biggest threat to yield.