Story Posted: August 24, 2011

Canola Watch: Don't be tempted to swath early, desiccation, straight combining

Issues of the week: High temperatures (as high as mid 30's in some areas) are occurring across the Prairies as swathing timing nears. Swathing under such hot conditions can result in rapid dry down (moisture loss) but longer curing (time for green seeds to clear chlorophyll). Swath as close to 60% seed colour change (SCC) as is practical under these hot conditions and do not swath during the heat of the day.

Click here to hear Canola Council agronomist Dan Orchard's general tips on how to scout and assess for proper swath timing. For those that listened to this information last week, click here to hear Canola Council agronomist Doug Moisey's swath timing tips for more specific situations (e.g. how to choose swathing timing when dealing with large acreages, uneven plant maturity, or frost or hail damage).

Insect pressure is easing but still hearing reports of lygus and bertha armyworm spraying. Keep scouting for late-season insects in late maturing crops.

It is crucial that all of Canada's canola is Export Ready. If spraying for late-season insects or spraying herbicides for crop dry down or desiccation always read and follow product labels. All crop protection products have been granted a specific registration by PMRA for product rate and pattern of use (e.g. stage of crop during application). Only products that have a registration for the desired use (e.g. pre-harvest) can be used. Pay particular attention to product pre-harvest intervals (which is the time between spraying and cutting).

Strong winds in Manitoba on Tuesday continued through the night and into Wednesday. There are reports of significant swath movement (and subsequent shattering) especially in fields with short canola – not enough stalk and weight to hold the swaths down. The best defense is to start combining as soon as moisture and green seed levels are acceptable. Green seed levels can be monitored quickly by inserting a scoop shovel underneath the swath and use your hands to thresh pods near ground level into the shovel. These plants will have cured more slowly and if any plants have higher green counts, it will be these ones. If this sample rolls out with acceptable green, then the field may be ready and time can be taken to get a field sample (for moisture and green seed) with the combine.

Crop and weather update
Peace: Warm temperatures last week and over the weekend were welcomed for crop development. The crop is progressing well but still about 10 days behind. Some fields are at late pod with some early swathing started. Swathing will become more general in about 10 days to two weeks. There is a fair amount of the canola acreage that will not be cut until September 15 or later.

Alberta: Warm weather over the past week was needed for crop development. Crops in the south that started off three weeks behind are now about 10 days behind. There are still late crops (latest just coming out of flower) in central and northern areas. Some rain fell in southern parts (up to ½ an inch) and in the north around St. Paul. Crops look good in the south and swathing is occurring this week. Crops get later further north and crop stages within fields become variable. Some swathing has begun around Provost. Latest fields need frost to stay away until mid or late-September.

Saskatchewan: Hot conditions last week spawned isolated thundershowers with some hail in eastern areas. Swathing is about a week away in southeastern parts with reports of some combining in the Moose Jaw area with good yields. On the western side, swathing is wrapping up in the south and becomes less as you move north. Fields in northwest in Meadowlake area are still 1 to 2 weeks away from swathing and excess moisture is still an issue.

Manitoba: Rainfall amounts ranged from nothing to 3 inches at The Pas where crops are now in standing water. Up to an inch of rain with two hail storms fell north of Winnipeg (towards Beausejour). Lots of crop was already swathed so the hail did considerable damage. Most of the province is extremely dry. On average about 30% of the crop is swathed with swathing well underway this week. Earliest fields are combined (about 5% across the province) with yields varying widely (10 to 50 bu/acre) but generally somewhat below the five year average. Some volunteer canola fields have been combined with disappointing results (5 to 8 bu/acre). Generally eastern areas are ahead of the western side and latest fields still need a month before they are swathed.

Most recent crop reports issued in Alberta, Saskatchewan and Manitoba.

Don't be tempted to swath early
Swathing early before the recommended 50 to 60% seed colour change in the high temperatures occurring lately will not necessarily mean earlier combining. Under hot, dry conditions crop dry down can occur quickly (drop below 10% moisture) but not crop curing (seed maturation and removal of chlorophyll). Fields that are swathed early (e.g. 20 or 30% seed colour change) and/or swathed during the heat of the day will not cure as quickly as dry down occurs. Curing may take as long as two to three weeks in these fields cut on the early side. In fact, some fields may require additional moisture (rain) in order to re-hydrate the swath and facilitate curing. In southern Alberta, irrigation has been used post-swathing in some instances to help cure the crop. Click here for more information on rate of crop dry down under different weather conditions. If fields must be cut early (large acreage base) then cut at night to help reduce the rate of swath dry down and hence the potential for locking in the chlorophyll. Click here for more specific swath timing information from Canola Council agronomist Doug Moisey.

Insect update
Lygus populations continue to be high and exceed thresholds in parts of Alberta and Manitoba (around Morris and Altona). Once pods become leathery (rule of thumb is about two weeks before swathing), then even adult lygus cannot cause damage and control is not economical. Economic control thresholds for lygus bugs are based on adult and late instar counts. When canola prices are $12 per bushel and application costs are $12 per acre, the threshold is 11 adults or late instar bugs per 10 sweeps. Click here for more infomation on lygus bug. Spraying for Bertha armyworm is wrapping up in most areas but is still occurring in southeastern Saskatchewan. Populations below threshold are being monitored in north central Alberta (around Hairy Hill and St. Paul). The threshold for bertha is 17 per square meter when canola is $12 and application costs are $12 per acre. Click here for more information on bertha armyworm. Reports of heavy populations of Imported Cabbageworm larva continue in western Saskatchewan. Remember that this insect tends to feed on leaves and it is not usually economical to spray them. Click here for information on how to identify late-season insect larva such as bertha armyworm, diamondback moth, and imported cabbageworm.

Keep scouting latest crops for late-season insect pressure. Pay attention to pre-harvest intervals (defined as the time between spraying and cutting) this late in the growing season. Once a crop is within 7 days of being swathed, no insecticides can be applied. It is vital that all of Canada's canola is Export Ready. Click here for a quick reference of pre-harvest intervals for insecticides and fungicides in canola.

Disease update
So far relatively low levels of sclerotinia infection are being reported in most areas. Blackleg is appearing in eastern Manitoba and southern Alberta.

Scouting and identifying disease(s) present can be a valuable tool for assessing this year's production practices and preparing for next years. Here's what to look for with blackleg: symptoms showing up at this stage of the season are greyish lesions on the stem with the black picnidia spots, and also basal lesions (cankers) — which are the most serious. Basal lesions can't really be properly identified until you cut through the base of the stem and look for blackened infection. This infection will eventually grow through the stem, cutting off nutrient flow. If you see plants drying up, cut a few open at the base of the stem with clippers to check. With sclerotinia look for white lesions or fuzzy rot on the main stem or on branches. Sometimes the plant may look healthy at the base, but there will be dead branches. Infected stems and branches will have white-grey tissue (not green) and will often start to shred apart easily. Click here for more information and photos to help with identification.

If sclerotinia is present, assess the % of infected plants since half of this number will give a yield loss estimate. If 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?

If a high incidence (anything greater than 15% of plants) of blackleg is found, then this field should not be used in a tight rotation – consider rotations of one in three or one in four years. Also, the next time canola is planted on this field, ensure it is not the same variety, especially in tight rotations.

Swathing tips
Scout fields individually and often. Determine swath timing by breaking open pods and assessing the level of seed colour change. Scouting based on field colour change is not a good indication of seed maturity. Maturity can change quickly and it may help to open up the field with a swath cut around the perimeter to grasp where the field is at. Scout fields individually since varieties may respond differently and different plant populations will influence the amount of branching. Click here to watch a video about assessing crops for swathing time with Canola Council agronomist Jim Bessel.

When to swath. The best timing for yield and quality is to cut when 50% to 60% of seeds on the main stem are turning from green to brown. Click here to view a copy of the Canola Council of Canada's Canola Swathing Guide.

If need to swath earlier. Fields that have extremely late stages may benefit from being cut earlier (e.g. 20 to 30% seed colour change on average) to prevent green seed issues from later maturing platns. Remember that these fields will take longer for the swath to dry down and seed to cure. However, if possible leave the crop ripen longer and swath at night to reduce shattering losses from the more mature plants. This would be preferred as long as the risk of frost damage or excessive shattering losses remains low.

Avoid swathing in mid-day heat. Swathing during the heat of the day may result in green seed issues because the enzyme that breaks down chlorophyll can be interrupted under high temperature conditions. Be prepared to swath in the evening, overnight, and early morning if high daytime temperatures occur. For more information, click here for a general pod cast on time of swathing with Canola Council agronomist Dan Orchard. Click here for a pod cast on dealing with specific situations (such as strategies to: cover all canola acres on the farm and deal with multi-staged or hail damaged crops) at time of swathing with Canola Council agronomist Doug Moisey.

Lay swaths parallel to the direction of prevailing winds. This reduces the odds of crosswinds flipping swaths and shattering pods.

Open swathed piles (beaverhuts). After swathing, when the crop is pliable (early morning or late evening) piles should be opened and spread out to allow for adequate dry down and limit lumps being fed into the combine and causing plugging or poor threshing because of the large volume of material passing through at once.

Large dense swaths take longer to condition. Large swaths (wide swath width with heavy crop canopy) with a large volume of material take longer to cure than smaller, narrower swaths. Thin swaths lying close to the ground may also take longer.

A number of canola crop walks on swath timing and other harvest management topics are being presented in Alberta by Canola Council agronomists Gregory Sekulic and Doug Moisey. Click here to attend a crop walk near you.

Using a swath roller takes skill
Swathing widths have increased in recent years to 30 feet and beyond. A heavy crop cut at thirty feet or more needs only gentle downward pressure on the middle of the swath to be anchored properly. Air movement within the swath is important during curing and dry down.

The swath roller should lightly tuck edges. Being too aggressive with the swath roller may cause shattering of the more mature plants. The roller should gently roll over the windrow without much pressure while tucking the swath edges into the stubble. Using too much pressure, might press the swaths right into the ground making them more difficult to pick up with the combine (especially thin swaths). Also, a swath roller used too aggressively may cause the plants to flip up and back onto themselves which can make smooth feeding into the combine difficult, contributing to harvest losses. The swath roller should be adjusted with the goal of smoothing the swath to reduce the opportunity for wind to catch it and anchoring the swath into the available stubble, as opposed to packing it into the ground.

Evaluate field conditions and adjust the roller accordingly. The pressure (or height) and angle of the swath roller may need adjusting from field-to-field depending on differences in crop maturity and other crop characteristics such as height, canopy density, stubble density, disease levels, etc.

When to swath hailed crops
A number of hail storms in Alberta earlier in the season have resulted in regrowth at the top of the plant. This regrowth is now considerably late and it is questionable whether that portion of the plant can contribute to yield before frost. Growers with such crops are encouraged to concentrate on the growth and yield in lower branches. Decisions (e.g. swath timing) should be determined based on staging of this lower growth in the canopy, since in most cases it represents the bulk of the remaining yield potential.

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.

Deciding to straight combine?
Practice leads to perfect. Growers who successfully straight combine say that experience leads to success. If straight combining for the first time in 2011, be sure to start on a small number of acres. This will allow for some experimentation to determine how to make it work with an individual's equipment.

Choose suitable fields. Fields that make good candidates for straight cutting are those with heavy crop canopies that are well knitted to prevent whipping and shattering in the wind.

Point of no return. Once the decision to straight cut is made and crops are allowed to ripen standing, shattering losses will be high if the decision to swath is then made late (beyond 70 to 80% seed colour change). If a field that mature must be swathed, it must be done in very moist conditions (rain or heavy dew) to limit shattering as much as possible. The final decision on whether to swath or straight cut really needs to be made prior to the optimal swathing stage (up to 60% SCC). Click here for more information on swathing and combining canola.

Determining green seed levels
With uneven maturity and later canola crops, this will be another year to watch green counts. Here are some tips to follow when testing for green seed:

• Rather than start up the combine to take a sample, insert a scoop shovel underneath the swath and use your hands to thresh pods near ground level into the shovel. These plants will have cured more slowly and if any plants have higher green counts, it will be these ones.
• Collect the seeds, put them into 100- or 500-count test strips and roll them out.
• Do a few strips and come up with an average. Five green seeds out of 500 represents 1% green.
• Repeat this a few times through the field, making sure to check hillsides and flats rather than hill tops and field edges, which tend to be thinner and more advanced.
• If this sampling suggests that the green seed levels are low enough to harvest, then collect a sample with the combine. Be sure it is a representative sample for the field. This year with uneven maturity throughout fields this may require harvesting several swaths across the field to get a good composite sample. Be sure to confirm your assessment of the grade with your planned delivery point before harvesting significant quantities of the crop.

Combining in high temperatures
Combining has begun in some areas and high temperatures are predicted across the west in the coming days. It is important to remember that canola storage can be a concern even at seed moisture levels considered dry when the canola is binned at high temperatures. The high temperatures can make canola volatile for the first few weeks. Canola should be put into bins with aeration and it should be turned on to cool down the temperature of binned canola. It should be conditioned to below 15 °C and 8% moisture for long term storage. Click here to view a video of Les Hill's combine tips.

Keep malathion out of canola bins
Malathion CANNOT be used to treat bins where canola will be stored or to treat canola as it goes into storage. These applications can result in residues in the canola that are unacceptable in some of Canada's key export countries with low minimum residue limits (MRLs) or zero tolerance for malathion. If a bin was treated previously, do not store canola in the bins within six months of treatment. Detection of malathion residue in canola seed above the allowable limit will result in rejected shipments and increased monitoring.

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