Winter canola harvest will be happening soon in the southern counties of Ontario. Some producers and the researchers at AAFC Harrow have already applied a pre-harvest herbicide last week. Here are some resources on staging the crop for harvest. Resources from Canola Council of Canada and Kansas State U have been used to develop this article.
Staging the Crop for Pre-Harvest Herbicide
A pre-harvest herbicide is not required and the crop can dry down naturally, however winter canola is a high yielding crop with a lot of biomass. Weeds or green material moving through the combine may cause harvest losses, and ease of harvest is improved when the crop and stems are more dry, so using a pre-harvest herbicide may be beneficial. Pre-harvest herbicides do not speed maturity, so follow the label recommendations and do not apply them too soon or the plant may shut down prematurely. In the thick winter canola canopy, there may still be some green in the stems when a pre-harvest herbicide is used.
When checking the crop to determine if it is ready for a pre-harvest herbicide, look for seeds that have changed from green to brown/black. Any amount of coloured change is considered changed, i.e. a mottled green and brown seed is considered to be changed colour (Figure 1).
It is typically advised to only check seeds on the main stem. Colour change starts in pods at the bottom of the stem and moves up. Canola Council of Canada report that “spring canola seed colour change will advance an average of 10% every two to three days. Under hot, dry conditions, seed colour change can occur more rapidly and may take longer at cool temperatures.” Winter canola is the same species as spring, so these details are applicable to our winter crop. If the plant population is low or if plants have a lot of branches (e.g. 10+) check some seeds on branches to ensure they are not very far behind in maturity – they should be firm and not translucent.
Pre-Harvest Herbicide Options
The top options for pre-harvest herbicides are Reglone+ Agral 90, and Glyphosate + Eragon + Merge. Environmental conditions – sunny versus cloudy/dark – play a role in the herbicide activity.
Glyphosate should have good activity on actively growing plants but it may take 1 to 3 weeks before plants are effectively dried down for harvest. Labels typically state application should occur at less than 30% grain moisture. Note that when seed fill is complete, seeds are at about 40% moisture.
Eragon LQ is generally faster acting than glyphosate. It works best when applied on warm, sunny days. Control will be best with generous amounts of water; the label states 80 L/ac (21 gal/ac) and you may be disappointed if you use a lower volume. Merge is required with use of Eragon. Tank mixing glyphosate and Eragon can provide sharper weed control. Note that in Western Canada this product is named Heat, if you are reading resources developed by Canola Council of Canada. Apply when 60-75% of seeds have changed colour. It may take up to 14 days for plants to dry down.
Reglone is a contact product and therefore requires even higher water volumes for good control. The label indicates 90 L/ac (24 gal/ac) of water should be used. Agral 90 is required with use of Reglone. The product must make contact with green tissue for good control; it could be challenging to hit green tissue low in the canopy. Performance of Reglone will be best if you spray in the evening or on a cloudy day allowing the plant to take up the herbicide, prior to a warm, sunny day. Plant dry down with Reglone tends to be faster and more complete. Avoid shatter losses by harvesting promptly once seeds are at the appropriate moisture content. Apply when 90% or more of seeds have changed colour. It may take 7 to 10 days for plants to dry down, but in hot conditions it may change more quickly.
Additional info on using pre-harvest herbicides from Canola Council of Canada can be found here.
General Tips on Spraying Pre-harvest Herbicides
To get the best bang for your buck, and achieve the best results, producers should make an effort to:
- Drive slow; canola has a big canopy and the spray droplets will not land where you want them to if the sprayer is travelling too fast.
- Do not skimp on water volumes; use the water volume recommended on the product label for good results
- Aim at the target; if you have regrowth low in the canopy you may have to lower the boom height (e.g. compared to a fungicide application) to achieve the appropriate spray overlap and spray pattern uniformity.
- Note that even if a herbicide is applied, the plant stems may remain green, especially if they are very thick.
- Go to Sprayers101.com for “Pro Tips for Pre-Harvest and Desiccation Sprays” and various articles on boom height
Staging the Crop for Combining
Harvested canola should have fewer than 2% green seeds and be at 10% moisture or lower. On a hot, dry day the moisture can drop a few percent through the day so you may be able to start at 11 or 12% moisture. Canola Council of Canada resources say that when seed fill is complete, seeds are at about 40% moisture. Physiologically mature seed loses moisture at about 1 to 3% per day.
The harvest sample should not be too clean. At an ADM event this spring, an ADM representative shared that 2% dockage (chaff) in the sample is very common. Click HERE to view some resources developed by Kansas State U on combine settings and other info for direct harvesting canola.
