Do’s And Don’ts of Desiccation
Variable stages and late crops are leading to questions about drying down green material to facilitate harvest. Fields with variable stages need to be scouted carefully to determine which stage will contribute most to overall yield. If later stages represent a significant portion of the plant population, then killing the crop before they are mature (through either swathing or a chemical application) will mean sacrificing a significant portion of the yield potential of the field, in addition to possible downgrading from increased levels of green or damaged seed. Keep in mind that if the plan is to swath the field the benefits of a chemical application for dry down will be limited mainly to weed control, as one of the main benefits of swathing is to manage uneven maturity by allowing the less mature plants to dry down and cure in the swath.
If growers decide they need to spray for late season weed control the best choice would be a glyphosate application. Glyphosate is registered for pre-harvest perennial weed control in canola. Glyphosate may have harvest benefits if green weed and crop material is killed so that dead material can dry out prior to harvest. This may happen quite quickly when weather is relatively warm and dry but applications late in fall (when days are shorter and tend to be cooler) may take longer to dry and harvest management benefit may be less. Any benefit to crop dry down should be seen as a bonus to perennial weed control. If the canola is glyphosate tolerant, then no crop dry down will occur so any benefits will be limited to control of green weed growth. Glyphosate is to be applied when the majority of seeds within the pod are yellow to brown in colour which is at least 30% seed colour change (which corresponds to when seed moisture is less than 30%).
For growers that decide speeding dry down of the crop is their primary goal, Reglon is likely a better option but is likely only a fit for straight cutting situations. 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 60 to 75% 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 and/or reduced yields. 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 higher water volumes (91 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.
Only Reglone and glyphosate are registered for use as a pre-harvest application. Reglone is the only product registered as a desiccant on glyphosate-tolerant canola. ALWAYS BE EXPORT READY! DO NOT USE UNREGISTERED PRODUCTS ON CANOLA PRIOR TO HARVEST.
Source: Canola Council of Canada