Questions of the Week

Seed first or spray weeds?

Juggling seeding and effective weed control is challenging. Where possible, opt for a pre-seed rather than pre-emergence burndown because: 

  • poor spraying conditions and the busyness of seeding may squeeze (or close) the very small pre-emergence application window;   
  • weeds in dry regions are likely to be dusty after seeding, decreasing herbicide efficacy; 
  • later control allows weeds more time to steal moisture in dry conditions; and 
  • a number of tank mix partners allowable at pre-seed timing cannot be applied at pre-emergence.  

In ideal conditions, canola can emerge in as little as four days. If considering post-seeding, pre-emergence herbicide, assess germination carefully across all growing zones of the field to avoid the risk of killing seedlings.  

Regardless of application timing, always scout to determine target weed species, and always tank mix for effective control. (Can I spray at night?) (Best tips for weed management) (See weeds spray them)

What to expect for insects this week?

Hot weather in some regions has sped along insect development. Reports are now coming in of large numbers of both flea beetles in NE Saskatchewan and grasshopper nymphs in the Rosetown, SK area. Click here for proper sweep net sampling technique for grasshoppers. Be prepared to correctly assess flea beetle damage once the crop emerges. (Insect thresholds drive profitable pest decisions)

Prairie Pest Monitoring’s first weekly update of the year is available here. Sign up for their weekly newsletter updates here.

How to support emergence in dry soils?

Seeding depth strategy can change with the warm soils of late May. If seeding at the deep end of the recommended range, spend extra time checking placement both across the drill and in several adjacent rows to make sure that all openers are seeding at the intended depth. Consider how seed-placed fertilizer risk increases in dry soil. (Big weeds and seeding into dry) (Important tips for best management)

Are flea beetles in pre-emergent fields a concern?

Manitoba growers who have tackled back-to-back years of heavy flea beetle pressure may feel tempted to spray insecticide prior to crop emergence if they see flea beetles on volunteer canola and other weeds. Resist the temptation: it is likely a waste of money and decreases the number of allowable applications in-crop. A high population in early season weeds does not necessarily correlate to pressure at crop emergence as the pests may move on in the interim. Scout on an ongoing basis and use early populations as a reminder that in-season pressure is a risk. When planning seeding order, consider later seeding for fields with high pre-seed flea beetle populations on volunteers in hopes establishment is more rapid and uniform in those fields.  

Flea beetles are attracted both to a glucosinolate that canola plants release when they are being upon and to the aggregation pheromone that male flea beetles release. Weak, slow to emerge canola is most at risk of feeding damage; canola that establishes quickly and has five to eight plants per square foot is usually less impacted by flea beetle feeding. Optimize seeding to give an emerging crop its best chance for strong, quick growth. (Canola seed treatments) (Flea beetle management tips) (Tips for a more integrated approach to flea beetle control)