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%. Applications made even slightly before the 30% moisture stage (physiological maturity) greatly increase the risk of excessive glyphosate residue in the seed. Canola is very efficient at moving glyphosate or other systemic compounds into the grain prior to physiological maturity. Excessive pesticide residues in the grain can result in export problems.
Some growers who straight combine canola that is not a glyphosate tolerant variety will apply glyphosate to even out the crop for easier harvest. When using glyphosate in this fashion, make sure a very minor portion of the field is immature for the reasons indicated above.
The rate of drydown with preharvest glyphosate is heavily dependent on environmental conditions, so weed control should still be the main goal. Glyphosate will not hasten crop maturity.
Heat LQ (Group 14 saflufenacil) fits with any canola herbicide system, including glyphosate-tolerant varieties. Crop is usually ready 7 to 21 days after application, but it could be longer in cool, cloudy and rainy conditions.
Application timing is 60-75% seed colour change. The pre-harvest interval is three days.
When applied pre-harvest in canola, BASF only supports Heat LQ when tank mixed with glyphosate. The benefit over straight glyphosate is more rapid dry down of crop and weeds. Merge is recommended with the tank mix. The tank mix provides crop dry down in any HT system as well as broadleaf weed control, including perennials. Use a minimum water volume of 40 L/ac (10 gal/ac).
BASF has a webinar for anyone using Heat preharvest for the first time.
If desiccation alone is the goal, Reglone is a contact herbicide 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.
Pod sealants are polymer sprays meant to reduce shattering when straight combining. Western Canadian research at a limited number of trial locations has not indicated significant benefits overall, but some individual trials and producer experiences have occasionally been positive. If farmers do use them, leave a test strip to assess whether the sealant made a difference on yield. Ensure application timing is optimal and water volumes are adequate to maximize the odds for success. Crops that are hail damaged or have a high disease incidence, such as alternaria, may not be good candidates for a pod-sealant. Lesions or hail scars on pods have damaged the outer waxy layer and the physical integrity of the pods and have increased the risk of pod shattering and have the potential to disrupt the pod-sealant’s effectiveness.