Pre-harvest glyphosate needs time to work

Glyphosate is registered for pre-harvest perennial weed control in canola. Glyphosate is to be applied when the majority of seeds are yellow to brown in colour and seed moisture is less than 30%.

Glyphosate and straight combining canola. Some growers who straight combine canola that is not a Roundup Ready variety will apply glyphosate to even out the crop for easier harvest. Once plant are killed by the glyphosate, rate of drydown will be dictated by environmental conditions, so weed control should still be the main goal with these products. If desiccation for direct harvesting is the primary goal then a true desiccant may be a better option (see below).

If desiccation is the goal… Reglone is a contact herbicide (only kills what it contacts) and is registered in canola to dry immature green material to facilitate harvest. Reglone does not hasten crop maturity. It shuts the plant down quickly and basically STOPS it from maturing, which can lock in high green seed levels if applied prematurely. The recommended timing for application on canola is when 80-90% of the seed has turned brown, which is past the stage when swathing would typically be recommended. Applying Reglone earlier may result in higher green seed. The label indicates that it should be only applied to B. napus canola to facilitate dry down of lodged canola crops. Efficacy will be maximized with the highest water volumes feasible (minimum 91 up to 222 L per acre ground or 18 L per acre aerial). Growers using Reglone on canola to be straight combined take note: Reglone can significantly increase both pod shatter and pod drop if harvesting is delayed, so be prepared to combine as soon green seed and seed moisture have reached suitable levels. A tip for Reglone use: Reglone is activated immediately in day light, so application in the evening will allow the herbicide to spread slightly from the droplet contact point before activation the next morning and result in more complete coverage on plant tissues.