Questions of the Week

Herbicide: one pass or two?

It’s a little early to determine whether a first pass of herbicide will offer adequate weed control. Scout carefully for resistant weeds (especially kochia) and second flushes. Even if the preferred plan is just a single pass system, be prepared to apply a second pass if – and as soon as – necessary. Warm weather, especially in regions with adequate soil moisture, will help weeds grow very quickly, but a fast-growing crop may be able to outcompete some weeds all on its own.  

A variably staged field is more likely to require a second herbicide application. To protect a variable crop from damage, always follow the label and assess appropriate second pass timing by the most mature canola plants in the field. (Economics of early weed control) (Second pass herbicide why and when) (Weed control strategies for each HT system) (Surveillance and strategies to manage HR weeds)

Top reasons to walk the field this week?

Careful scouting is especially critical in early season canola stands. Many weed, pest and crop health issues are now appearing that can shape management throughout the season. Walk the fields: an 80km/hr scout will not provide the insight required. 

Now also is the best time to count plants. Variable plant staging is currently easy to assess and plants are small enough to be easily counted within a hoop. If the plant count is very high, remember that unusually good growing conditions may have played a role, so seeding rate should not necessarily be cut next year. If the plant count is low, ask why, but keep in mind that even two plants/ft2 still bring a 90% possibility of achieving one’s yield target. Variable staging is more problematic than low plant count. (Plant populations: How to count? Why Low?)

Contact the CCC here if you still need a Canola Counts ring to make your plant population checks easier. After counting, enter plant count data at If the CCC receives enough spring data, we can generate aggregated (not farm specific) emergence and plant density maps that are helpful to all.  

How to help canola recover after hail?

Little can be done to support a crop after hail. Though many so-called rescue treatments exist, there is no robust evidence that foliar nutrition or fungicides will help the crop heal. If you choose to apply a rescue, ask: was it effective? Run a check strip to determine whether the investment paid.

The good news is that early-season hail rarely has an impact on a canola crop’s yield potential, but it can delay maturity. Though individual plants may die, remaining plants compensate by growing larger, producing more branches, and developing both more pods and more seeds per pod. Blackleg infection on stems can be higher after hail and may warrant fungicide, but only if the field was already at high risk of blackleg and the crop is in its earliest stages. (Will canola recover after hail?) (Fungicide strategies for blackleg)

What to watch for this week on the insect front?

Cutworms are causing significant damage in central Alberta and the Peace. Cutworm concerns are elevated and widespread with even some Lumiderm-treated fields reporting cutworm pressure, says CCC agronomy specialist Keith Gabert. Use this cutworm guide to identify larvae and to check species-specific thresholds (ex. 4-5 larvae/m2 for pale western and redbacked; 5-6 larvae/ m2 for darksided cutworms in canola) before making a spray decision, noting that control is most effective when cutworms are small/young (early instars). For maximum cutworm control, spray in the evening. If available, use insecticides with a high specificity to reduce impact on insects that feed on cutworms. To report cutworm findings, view this week’s Community Connections here (link). (Identifying and controlling cutworms)

Canola has largely outgrown flea beetles in Alberta and most of Saskatchewan, but they remain a concern in pockets in Manitoba and eastern Saskatchewan. “The bad areas are bad – some fields at the 4-5 leaf stage have very high levels of defoliation – but warm soils and good seed treatments have been helping,” says CCC agronomy specialist Chris Manchur. (Flea beetle findings that shape management choices)

Wireworms are appearing in patches. Little can be done to manage them beyond keeping good records for next year’s cereal seed treatment. There is some grasshopper activity reported in drier areas in southern Alberta and Saskatchewan, and first sightings of cabbage seedpod weevil have been reported in southern Alberta. (Integrated pest management) (Canola insect scouting guide)