Questions of the Week

How to time swathing to achieve maximum yield and quality?

When swathers start rolling in neighbours’ fields, it can be hard not to follow suit. However, one of the easiest ways to maximize yield and quality is to avoid swathing too early. Canola achieves optimum seed quality and yield when swathed at 60% or more seed colour change (SCC). A study done in the early 2000s showed canola swathed at 30-40% SCC yielded 11% less than canola swathed at 60-70% SCC. Refer to this guide to help assess seed colour change. (Canola harvest guide) (Canola swathing guide) (Swath later for higher yield)

What risks does swathing in high temps bring?

Temps above 30oC are in the near-term forecast for several regions. Canola will mature quickly in the heat, so walk fields to assess maturity frequently. Pods are more likely to shatter when swathed in hot temperatures, especially if humidity is low. Heat will speed dry down after swathing, limiting the time green-clearing enzymes can work to reduce seeds’ chlorophyll levels. This is okay on a uniformly staged crop of plants that have few side branches, and/or where seeds on side branches have started seed colour change, as the risk of green seed is lower. However, a variably staged crop and/or plants with many branches will have higher rates of green seed. In these cases, aim to swath at night or during cooler parts of the day. Distinctly late patches or sections of the field may need to managed separately. (Early hot swathing can increase green counts)

Is it verticillium stripe? Or blackleg? Or both?

Pre-swathing, at swathing and post-swathing are key and critical opportunities to scout for diseases of all types. Verticillium stripe will now be visible, as will blackleg. Here are disease ID tips for pre-harvest scouting for the main diseases of note. Check especially carefully in patchy, unhealthy-looking parts of the field. A drive-by or ‘from the swather seat’ assessment does not replace  walking the field with clippers in hand. If blackleg is suspected, send samples to a lab to confirm the pathogen and specific races present, then keep careful records in order to choose resistant cultivars in future years. Manitoba growers can click here and Saskatchewan producers can click here for information about how to access free disease testing. The Prairie Disease Monitoring Network requests farmers contribute to regional disease tracking here.
While checking for disease, also scout for late-season insects too (diamondback moth continue to cause damage in some regions).

How to Keep it Clean?

With swathing and combining now on the horizon, carefully consider the pre-harvest interval (PHI) – the minimum number of days that must pass between product application and cutting a crop – before any and every chemical application. Swathing or straight-cutting before this interval passes can leave unacceptable residues on harvested seed. Keep it Clean’s pre-harvest interval calculator offers two options:

  • PHI calculation: enter the crop type and desired product to calculate how long to wait to cut after application.
  • Product finder: enter the crop type, pesticide type and desired cutting date to find a product (if any) that suits the intended timeline.

Before storing your canola, make sure the bin was not treated with malathion this growing season, since residues can linger for months after application. (Keep canola bins malathion free)

How to assess maturity in uneven fields?

Uneven emergence and challenging growing conditions mean plant staging is patchy and/or variable in many fields. Maximizing profitability depends on accurately assessing maturity and determining where the majority of yield will be. Refer to the Canola Council of Canada’s Canola Swathing Guide for tips on how to assess an uneven field. When assessing maturity, pull representative samples, not the best looking or most mature plants. (What to do with uneven fields) (Harvest management – timing, quality and yield)