Frost, rain and now snow in some areas are making the 2004 canola harvest a nightmare.
Normally, the optimum stage to swath for yield and quality is up to 60 percent seed colour change on the main stem, but frost has changed that recommendation.
Frost-affected areas fall into three main categories, with appropriate swathing strategies for each:
Little frost damage – The pods remain mostly green or tan-green, with few, if any, white spots on the outside of the pods. The insides of the seeds are mostly intact.
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If the outsides of the seeds are starting to turn, the insides should be yellow or a light lime green. If seeds are still green on the outside and the insides of the seeds are still watery, the outside seed coats should remain intact and turgid. In these cases, leave the crop to continue to mature until further seed or pod colour change occurs.
Moderate damage – Several signs can point to moderate damage:
- Pods that show only white specks on the outside.
- Only a few seeds in immature pods that are not intact.
- Only a few seeds in the upper plant parts that are prematurely browning.
Premature browning occurs when frost damages the outside of the seed and the inside of the seed remains dark green.
In these cases, the fields should be left and monitored daily to evaluate further crop changes. If no further damage is evident, the remaining crop may continue to fill and mature. If the seeds continue to deteriorate or pod integrity declines, begin swathing to conserve seed volume.
Severe damage – Considerable whitening of the outside of the pods is found in most plants. The pods will begin to shrink and desiccate rapidly, and swathing should begin immediately to reduce pod shelling and pod drop and to conserve seeds in those pods.
Mature but green – There are many reports of fields with seeds that are firm and intact for a week or longer, but with little to no seed colour change.
These fields may be good candidates to begin swathing at as early as 10 percent seed colour change, especially if the short-term weather forecast remains cool or cloudy.
In many cases, the crops have been in the ground for up to 120 days and the seeds may be physiologically mature, even though outside seed colour remains green.
Because the seed is mature, the green will slowly fade after swathing. With the cool, wet conditions, swath curing will take longer than usual. Expect to have the crop in the swath for at least three weeks to allow for curing and as much chlorophyll reduction as possible before combining.
Sprouting of swathed and standing canola has been reported in most regions.
The wet conditions, coupled with possible frost damage, have made the seed unstable and prone to sprouting damage.
Here are some ways to handle the problem:
Wide swaths – To reduce sprouting, lower the swath density as much as possible by decreasing swath roller pressure and making swaths as wide as possible.
This will also help reduce the spread of diseases such as sclerotinia and alternaria through the swath.
Reduce packing – Growers are encouraged to limit the degree of packing from swath rollers to allow as much air movement as possible through the swath, which will facilitate curing and limit disease spread.
Disease scouting – Sclerotinia continues to be reported in most areas. Many cases report late season infection, which will have limited impact on yield.
Scouting soon after swathing is an excellent time to assess the sclerotinia infection levels in fields and help gauge potential sclerotinia pressure for next year.
Straight cutting – A number of growers are considering straight cutting canola this year, including crops with frost damage. To be successful, consider the following factors:
- The crop canopy 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, which influences pod drop.
- The crop should be relatively free from diseases such as blackleg, fusarium wilt, sclerotinia and alternaria. These diseases can cause premature ripening, which can in turn cause pod shattering.
- Crops affected by hail are likely poor candidates for straight cutting because of the probability of greater disease infection through damaged tissue. Also, late-season hail often causes greater levels of damage to standing crops than swathed crops.
Dessicant – There continues to be questions about the use of Reglone or glyphosate to speed and even out crop development.
Both products kill the plant eventually, but applying either product too early will cause problems similar to swathing too early, with the additional possibility of increased herbicide residues in the crop.
Be diligent in following label directions when deciding when to apply the product.
As well, there are many reports of these products not working effectively this year.
The cool, cloudy conditions over the past few weeks are not conducive to quick herbicide activity.
Be patient in assessing herbicide activity under these conditions.
Grain drying – There are reports of harvested canola coming off at moisture levels of 13 percent.
Canola harvested tough or damp can start to heat quickly, especially if there are appreciable levels of dockage or green seed.
Dry this canola to safe moisture levels, especially if storing for longer periods. Proper conditioning is especially critical for frost-damaged canola.
