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Story Posted: August 25, 2010

Canola Watch 18: Think twice before swathing early

In This Issue: How to harvest damaged crop, Scout at harvest to help with 2011 planning, Questions and contacts.

Issues of the week
August 25, 2010 - With cooler temperatures and elevated frost risk for some regions in the coming week, growers may be tempted to swath early to guard against frost. Growers with sclerotinia or hail damage are also inclined to swath early. We encourage growers to think twice in all cases. Read on to find out why.

Crop and weather reports
Peace (B.C. and Alberta): Swathing is general across the Peace and the odd field has been combined in south, central and western regions. Rains of a few tenths at a time have hit the driest regions just as farmers are trying to harvest. Hail covered a large area from Woking to Wanham, burying swaths in some spots. Hawk Hills area had a frost of minus 2°C Saturday morning, although most growers were well into swathing by that time.

Alberta: The south was relatively dry the past week. Central Alberta received some rain - less than an inch in most places - and spotty hail. General swathing is still one to 3 weeks away in the south and 5 days to 2 weeks away in central Alberta. For most fields, seeds are firming up but colour change has not occurred. Read the Alberta crop report.

Saskatchewan: Swathing has begun for early crops and is general across the south. Late crops still need 2 to 3 weeks. Rain continues, with most regions getting at least half an inch. Grenfell got 4". "Getting stuck with swathers is going to be an issue," says Jim Bessel, CCC senior agronomy specialist for northeastern Saskatchewan. Yield potential varies widely, with some fields - even in rain-soaked parts - showing tremendous potential and many others at 15 bushels/acre or less. Read the Saskatchewan crop report.

Manitoba: Southwest is 80% swathed and 10% combined, with yields in the 20 to 50 bushel/acre range. Swathing in the northwest is just getting underway. Central and eastern regions are 25% to 40% combined, with no green seed to speak of and yields from 20 to 65 bushels per acre. Read the Manitoba crop report.

Quick Hitters
Seed colour change not typical. We have reports from southern Saskatchewan of plants showing a touch of colour on all seed, top to bottom. The whole plant is maturing at the same time. This can occur with abundant moisture, in dense stands with not a lot of branches, and in stands that had a short flowering period. If seed colour change occurs evenly and if pods are still green and pliable, growers could leave the crop longer so plants can continue to fill seeds, increasing yield. As long as pods are pliable, there is no immediate risk of shattering. If growers are tempted to swath right away, check that maturity is uniform throughout the field.

Drydown help for RR canola? The only desiccant registered for all canola varieties is Reglone. And even then, Reglone is only recommended on severely lodged canola. Otherwise the risk of shattering losses is too high, especially if harvest is delayed. There is also potential for locking in green seed if the product is applied too early, as the premature dry down of less mature plants and seeds may prevent proper curing. Any other product is unregistered and could leave detectable residues that put Canadian canola exports at risk. Glyphosate is also registered for fall application on canola but is considered pre-harvest weed management and not a desiccant. Both Reglone and glyphosate do not speed up seed maturity.

Lygus watch continues in central Alberta. Levels are still at up to 45 bugs per 10 sweeps, most of them adults. This is above the economic spray threshold, and spraying can still pay for crops a couple weeks from swathing. Check product labels for pre-harvest intervals. Click here for the latest chart of pre-harvest intervals.

Inspect the combine front to back for leaks. Canola seed can be lost through holes that even cereal grains can't get through. Make sure holes and cracks are sealed to limit costly losses. For more combine-prep tips, click here to hear CCC senior agronomy specialist John Mayko on ACPC radio.

Eager to get canola in the bin - even if it's tough? Then you need to dry it down and cool it off immediately for safe long-term storage. Growers in some areas have already been inquiring about delivering tough canola right away, but delivery points and processors can only accommodate so much this time of year. Growers can't count on this strategy. Canola should be not more than 8% moisture and cool for safe long-term storage.

How to harvest damaged crop
With heavy sclerotinia infection in many regions as well as hail damage and an elevated frost risk, we are getting a lot of calls on when to swath. Click here for last week's articles.

Here are a few more tips:

Sclerotinia stem rot

  • In fields with low sclerotinia stem rot infection, growers should swath when healthy plants are at the proper seed colour change in order to maximize yield and quality. Swathing earlier will not stop the disease and will not help save diseased plants.
  • If most of the crop is infected, then swath to limit shelling of pods that are diseased but contain healthy seed. These pods will provide most of the crop's yield.
  • When swath-rolling diseased canola, do it lightly to avoid excessive shattering of ripe pods. Sclerotinia can also spread throughout the swath, especially if windrows are packed tight. Since rolling knits the windrow together, protecting plants from blowing in the wind, a light rolling to tuck swath edges into the stubble is usually better than no rolling at all.

Hail

  • Hail tends to damage top pods worse than bottom pods. But top pods are at later stages and typically have lower yield potential, so there's no sense cutting early to save these pods, especially if seeds in these pods are still watery. Concentrate on doing what's best for the lower pods that are not damaged - which is swathing at 50% to 60% seed colour change.
  • An exception: Growers may want to swath early after a really late hail storm. If pods are bruised and seeds in these pods are still firm, then swathing right away may save these top seeds from shelling out. And if these top seeds are firm, seeds lower in the plant should be more advanced and suitable for swathing.

Frost

  • Some growers will cut canola in anticipation of frost. Note that this only works when the swath has 3 good drying days before frost hits. In that time, seed has time to dry to below 20% moisture. When seed is less than 20% moisture, enzyme activity that removes green from seed is complete. If light frost occurs before 3 good drying days, green levels can be reduced if there's enough time before the next frost and if there's adequate rain to rehydrate the seed. For an explanation how frost stops synthesis of chlorophyll in the seed, read the CCC factsheet "Understanding the maturing canola seed and the impact of frost."
  • When canola is fairly green and frost risk is only slight, there is more upside to leaving the crop standing. Swathing too early to avoid the risk of frost can often translate into yield and quality losses.
  • With frost, no situation is alike. On the last page of our CCC factsheet "Early Fall Frost. Now what?" we provide 4 frost scenarios with suitable harvest steps for each.

Scout at harvest to help with 2011 planning
At harvest, look for late-season diseases and insect damage that can help with decision making next year.

  • Break open the stems of any bleached white plants and look for hard black sclerotia bodies forming inside the stem. High levels of sclerotia returned to the soil this fall can increase the risk of sclerotinia next year in canola and other susceptible crops such as sunflowers, field beans and lentils. If sclerotinia is present and a fungicide was applied, evaluate that decision. Was a check strip used to determine if the disease was at least suppressed? Is it obvious infection occurred late in the flowering period, suggesting a later or split application may have been more effective? Was a fungicide not applied and perhaps should be under similar conditions in the future?
  • Look for blackleg. Check for black rimmed stem lesions and basal stem cankers. A variety with maximum tolerance ('R' rated) should be selected next time if high incidence of blackleg is observed. Also consider a longer rotation - one year in 4 - for canola.
  • Dig up some plants and check the roots for galls from clubroot or root rot symptoms. If clubroot is confirmed, proper equipment sanitation to prevent spread will be critical. Click here for more on clubroot.
  • Look for signs of insect damage that may indicate missed opportunities for control and a need for more thorough scouting in future years. Pod stripping and holes chewed in pods by bertha armyworm or diamondback moth larvae will be obvious. Less obvious are the tiny holes in pods and shriveled or devoured seeds beneath them, which suggest lygus bug and cabbage seedpod weevil feeding. Look for significant root maggot channels on the roots to determine if cultural control strategies should be considered in future years. Take note of fall flea beetle numbers. While high numbers in the fall do not always correlate with high numbers in the spring, these are the adults that will overwinter and emerge to feed on canola seedlings next spring.

 

Questions and contacts
If you have general questions about Canola Watch, direct them to Jay Whetter, whetterj@canolacouncil.org or 807-468-4006.

If you have questions on regional issues, contact one of the following Canola Council of Canada regional agronomists or provincial oilseed specialists:

This report is supported by each of the provincial canola grower associations. For more information on some of their activities, check out the following links:

  • The Alberta Canola Producers Commission (ACPC) has a free e-newsletter called Alberta Canola Connections. Visit canola.ab.ca and click the sign-up icon on the right site of the homepage.
  • In Manitoba, sign up for the Manitoba Canola Growers Association newsletter at Canola Growers E-update by visiting www.mcgacanola.org.

 

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