Pre-Harvest Herbicide Options in Canola; Managing Re-Growth

Oct 07, 2019

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Spring canola harvest is not yet complete, with a majority of the crop still standing in northern regions. Many fields were ready to harvest up to two weeks ago, but the weather has not cooperated. Producers are now reporting that canola is re-growing and quite green in the lower canopy. Pre-harvest herbicide application may improve harvest conditions; some details to keep in mind are outlined below.
 
For starters, if the canola has already been swathed and is re-growing there is no longer an opportunity to apply herbicides. Canola Council of Canada addressed the issue in a short article in 2016, found HERE. Spraying over swaths will result in residue being deposited on the grain and potentially exceeding allowable limits.  
 
For standing canola, there are a few options for pre-harvest herbicides. The products, application rates, and other notes can be found on page 96 of the OMAFRA Guide to Weed Control – Pub 75. The details are also copied at the bottom of this article.
 
Before we discuss products, there are some important details to get right when spraying a pre-harvest herbicide. 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.
  • Aim at the target; regrowth is typically low in the canopy so to get good control 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.
  • Do not skimp on water volumes; use the water volume recommended on the product label for good results, especially in canola that has a thick canopy and a lot of plant material to cover.
  • Go to Sprayers101.com for “Pro Tips for Pre-Harvest and Desiccation Sprays” and various articles on boom height
Glyphosate should have good activity on actively growing plants but may take 1 to 3 weeks before the plants are effectively dried down for harvest. This may not be the best option at this time in the season, depending on the weather forecast. Glyphosate cannot be applied to seed production fields. It will not be effective at stopping growth of Roundup Ready varieties but can be applied to InVigor (Liberty Link) varieties.
 
Eragon is generally faster acting than glyphosate. It tends to work best when applied on warm, sunny days so at this time of year it is best to avoid applying it after 5:00pm. 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.
 
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 allowing the plant to take up the herbicide, prior to a warm, sunny day.
Source : Field Crop News