Many growers are considering desiccating canola crops this year to deal with variable maturity in individual fields. While this can be a useful strategy, care is required to ensure satisfactory results.
Desiccation has the same effect as swathing under conditions of rapid dry down. It must be delayed until there is significant seed colour change in the green areas to avoid premature dry down of the crop, which can minimize yield losses and increase green seed counts.
There are some questions regarding the use of Reglone (diquat) or glyphosate to speed up and even out crop development. Reglone is a contact herbicide and is much faster acting than glyphosate, but it does not translocate to the roots of perennial weeds. Remember that applying either product eventually kills the plant.
Applying either product too early causes problems similar to those encountered by swathing too early and increases the possibility of more herbicide residues in the crop.
If producers are applying pre-harvest chemicals before harvest with ground rig sprayers, they should use crop dividers to reduce the amount of crop loss caused by trampling and shattering. In addition, travelling back and forth in the direction of prevailing crop lean will further reduce losses.
A number of growers are considering straight cutting their canola this year. They should consider the following factors:
* Crop canopy Ð the crop should be well knitted and slightly lodged to reduce the chance of pod shelling and pod drop. Remember that frost can affect pod integrity, including petiole strength that influences pod drop.
* Disease Ð the crop should be relatively free from diseases including blackleg, fusarium wilt, sclerotinia and alternaria. These diseases can cause premature ripening, which can in turn cause pod shattering.
* Hail Ð Hailed canola is a poor candidate for straight cutting because of the probability of greater disease infection through damaged tissue and reduced pod integrity from physical damage.
As well, late season hail often causes greater levels of damage to standing crops than swathed crops.
Producers should also consider the benefits of using a valuable weed control tool for next year’s crop – a pre-harvest application of glyphosate.
Glyphosate offers the most consistent and effective treatment for many perennial weeds, providing an effective and economical alternative to in-crop control options.
In early fall, perennial weeds are moving nutrients down into roots and rhizomes. This period is when they are most vulnerable to herbicide translocation to the roots and better control is possible.
If a Roundup Ready canola variety has been grown, a pre-harvest application will help dry down green weeds and offer perennial weed control, but it will not dry down the crop.
Apply glyphosate when the crop has 30 percent or less seed moisture content. At this stage, the pods are green to yellow and most seeds have turned from green to yellow or brown. Wait three full days before swathing. This will allow thorough translocation of the herbicide to ensure extended long-term weed control. Do not use pre-harvest glyphosate on canola crops grown for seed.
Specific questions regarding canola harvest management can be directed to agronomists at the Canola Council of Canada.