Story Posted: September 21, 2011

Canola Watch: Green seed, Fall weeds, Prep for 2012

Issues of the week: Turn on the aeration fans and leave them on. A lot of canola went into bins hot, and one crusher has already received some 2011 canola with 18% heated seed. With hot weather forecast again this week for some areas, conditioning canola is a top priority.

Wait a few hours after a frost before making the swath decision. If pods are translucent 4-6 hours after the frost ends, they may start to pop open within 24 hours. In that case, the field should probably be swathed to limit yield losses. If pods have white spots but are otherwise OK, the frost was light and the crop could be left standing to continue maturing. Read more.

High green is an issue for some canola fields. If the crop is still curing, leave it and see if green seed counts drop. If the crop is dry and green is still high enough to cause downgrading, the crop will need a few days of moisture to restart the green clearing enzymes. If you don't expect a lot of moisture or you don't like the idea of waiting for several days of rainy weather, you may just want to get it in the bin.

This is our last weekly Canola Watch for 2011. We are going back to once a month for the fall and winter, with timely alerts as required.

Crop and weather update
Peace (B.C. and Alberta): The entire region had rain the past few days, with 1” to 1.5” general across the north and less elsewhere. Some fields in the east have standing water - again. Most canola in the Peace is swathed. General combining is still a few days away, except in the north where combining is about half complete.

Alberta: Harvest is progressing well in the south, with combining at 60-70% complete. Swathing is close to complete in central regions, but general combining has not started. The area could use a rain to help cure what's in the swath. Alberta crop report.

Saskatchewan: Harvest is wrapping up in the southwest and is about 60% complete in the southeast. The north has some acres left to swath and combining is just getting started. Saskatchewan crop report.

Manitoba: Combining is 70-80% complete. The northwest corner has the most crop left to combine and was hit hardest by frost in the past week. Manitoba crop report.

Planning for next year
Harvest is a good time to assess your canola results and prep fields for canola in 2012. If yields were disappointing given the large biomass of the crop, take time now to check for clues as to why.

What was your plant count? Determine the average number of canola stalks per square foot or metre to get a better sense of the plant population that survived to swathing. Low populations may have led to bigger, branchier plants. In this case, many of these side branches may not have matured completely leading to smaller seed size or shriveled seeds that were blown out the back of the combine.

Did the crop run out of nutrients? The crop may have used up available nutrients to build biomass, especially with good rains early, and didn't have enough left to meet seed yield potential. A fall soil test will help answer this question. If the soil is drained, consider higher nutrient rates for canola fields next year, based on soil test residual levels plus fertilizer applications.

Are all pods present and filled? Take a look at the plants before or during combining. A large swath doesn't necessarily mean a high number of pods were produced or that they were filled properly. Missing pods could indicate environmental stress (heat blast, frost), stress from delayed herbicide applications or insect damage to pods or flowers. Short or poorly filled pods could be more likely to result from nutrient deficiency later in the season, although environmental stress could be a factor as well. Smaller seed with reddish seed coats are often a sign of late season heat and drought.

Look for disease. Clubroot, sclerotinia and blackleg can be responsible for yield losses. Clubroot severity seems fairly high this fall in traditional clubroot areas and higher than expected in some newer areas. This suggests that the disease has been present in some of these “newly infected” fields for at least one previous canola rotation, maybe two. Symptoms are not always evident above ground. Random surveying in high risk areas uncovered clubroot galls on plants that looked healthy. Growers with previously unaffected fields in regions bordering areas known to have clubroot should take a close look at their canola fields, including a thorough inspection of the roots for signs of clubroot galls. Growers in all regions should include a regular inspection of their canola's roots as part of their regular scouting program. Discovering clubroot early will help prevent or delay its spread throughout the farm. A combination of machinery sanitation, crop rotation and variety selection can limit its spread and impact on future canola crops in affected fields. In wheat fields planned for canola in 2012, look for clubroot galls on volunteer canola or related weeds.

	Clubroot galls can be found on plants that don't show above-ground signs of disease.

• For general information on clubroot and some good examples of galls at various stages of development check out this video.
• For tips on identifying possible clubroot affected areas in fields and sampling techniques click here.
• For tips on scouting for clubroot during or following swathing click here.
• For tips on using resistant varieties as part of your clubroot management strategy click here.

Look for cabbage seedpod weevil holes in pods. With the expansion of the range of the cabbage seedpod weevil eastward in Saskatchewan, some growers may be encountering the weevil for the first time. A survey conducted annually in Saskatchewan provides approximate areas of weevil presence and level of infestations, but it is not possible to sample all fields. At harvest time, look for exit holes caused by larvae emerging from canola pods. Presence of these holes should be a warning for growers to scout for the weevil next year. See the photos below. Click here for the 2010 map.

	Look for cabbage seedpod weevil holes and larvae in canola pods. If you find them, remember to scout for adults next year. Photo credit: Saskatchewan Ministry of Agriculture

Harvest tips for high green canola
A lot of canola hit by frost or swathed in the heat is now stuck with high green counts. Every field is different, so there is no one best answer. Here are a few questions to ask and sample scenarios to consider before making the decision to combine now or give the crop more time.

• How long has the crop been down? If canola has been down for three weeks and is at 6% moisture and 6% green, this crop has likely cured as much as it will without a lot of moisture to reactivate the chlorophyll-clearing enzymes. Two to 3 days of continuous showers may be required. One big rain is less effective because it does not keep the pods moistened for the time required to absorb high levels of moisture. Warm weather in conjunction with the moisture also helps. Once daytime highs are cooler than 15 C, the chance of any significant de-greening is reduced even with the required moisture. Warmer weather is currently forecast and it's still September, so you could leave the crop for a few more days to see what happens. If the crop has only been down a week, it may still have time to cure - but if it's already at 6% moisture (which is possible) curing may be over without some wet weather.
• If the crop has been down for a week or two and moisture is still at 10%, green counts could continue to fall. Added rains would be a bonus, so patience is encouraged.
• Green locked in by heat vs. frost.
  Heat: Green locked in by quick dry down due to excess heat at swathing can be cleared again if seed moisture returns to 20%.
  Frost: A killing frost to standing or just-swathed crop will stop the enzyme process in affected seeds, locking in green regardless of subsequent of weather conditions. But if crop lower in the canopy was not hit hard by frost, it may continue to cure naturally and clear the green. Waiting will benefit the seed in these pods. Waiting may also cause seeds in severely damaged pods at the top of plants to shell out. This may reduce overall yield but could increase grade if seeds in top pods have a high green count. Scout closely to identify the extent of frost damage throughout the canopy.
• Killing frost may not be as killing as you think. We've had reports this fall of canola fields being at -4 C for a few hours but not showing signs of serious frost damage. Monitor these fields regularly to make sure shattering losses are not excessive. If no shattering, the extra time will benefit chlorophyll reduction.
• How much canola do you have to harvest? If you have one or two fields left, you may be in a better position to wait than someone who still has a week or more of steady combining to do.
• How is your other canola grading? If the rest of your canola is No.1, you may be in a position to negotiate a better deal for a few loads with higher green.
• What is the forecast? Moisture and above average temperatures are going to offer the best chance of further curing for crop that has already been down for quite a while. If a week of warm and dry harvest weather is in the forecast, and the crop needs moisture to restart the enzyme process, then binning the crop now may be the best option. October is around the corner and snow is not the moisture you're looking for.

Click here for companies the buy high green canola.

Don't spray weeds right after frost
Post harvest weed control can be a valuable step in preparing fields for canola next year, especially if winter annuals and perennials are present in high numbers. Dandelions and thistles, for example, move a lot of energy into their roots this time of year, so fall is an effective time to control these weeds.

Here are some tips to improve the success of fall weed control in fields planned for canola in 2012:

1. Make sure the plants are actively growing with new supple leaf area to target. Weeds cut off at harvest need time to accumulate new leaf tissue. This is essential for herbicide uptake and efficacy.

2. Frost damaged leaves may look green but they're not healthy and will not take up herbicide. If frost has occurred, avoid application until leaf condition of the target weeds can be evaluated.

3. Spray in the afternoons when temperatures are warmer and dew is off the plant. Ideally, you want to apply when temperatures are above 10 C and rising. Check product labels for specific recommendations as this may vary.

4. Use registered products. Glyphosate is effective and can be economically applied at the higher rates needed for some larger weeds. Bromoxynil, Heat and tribenuron (Express SG) are potential tank mix options with glyphosate if needed to effectively control the spectrum and size (or stage) of weeds present. Check the guide to crop protection for the list of weeds these tank mixes control. Click your province for a link to your guide: Alberta Saskatchewan Manitoba. With tribenuron in particular, the label says to wait 2 months before seeding canola, and these should be non-frozen months. DuPont's recommendation is to spray before Oct. 15 on fields planned for canola.

5. Are they perennials, winter annuals or annuals? It helps to know whether the weeds present in the fall will last the winter. Canola volunteers, for example, that emerge in the fall are unlikely to last the winter and do not need to be sprayed.

Leave the fans ON!
A lot of Prairie canola is in a serious storage situation. A crusher has already received one load of 2011 canola with 18% heated kernels. The canola was combined only three weeks ago and was binned dry - but at 30 C or more. Excess heat is dangerous. The Prairies have had two heat waves during this harvest and some regions are forecast to hit 28 C again this week.

As soon as you harvest canola, put it on aeration and leave the fans on until the whole bin is at 15 C or cooler. Bin cables make it easy to monitor the temperature front as it moves up through the bin. The worst case scenario is to shut off the fans before the warm front moves through the grain mass. This warm front is a band of warm air with high humidity. If that band sits for a day in one location, seeds within that band absorb the moisture, creating a pocket of hot and moist grain. Bad combo.

The key with aeration under current conditions is to COOL canola, not dry it. Keep the fans going - even through the heat of the day and humidity of the morning. Don't stop for a cloudy rainy day. Aeration with natural air is unlikely to increase moisture very much. Incoming air at 70% relative humidity, for example, would equilibrate to moisture levels of between 8 and 9% for canola seed, assuming the humidity stayed that high until the bin reached equilibrium. Click here for more on this concept. If you're worried the bin isn't cooling fast enough, take out a few loads, leave them in the truck overnight, and put them back in.

Canola, even dry canola, continues to respire and give off moisture for 4-6 weeks after harvest, so keep monitoring closely throughout this time.

Straight combining canola hit by frost
Experienced straight combiners often want a frost to desiccate the crop and whatever weed patches might be present before they start harvest. If the crop is mature, the frost should not hurt quality at all.

• If the stand is ready for harvest when the frost hits, prepare to straight combine shortly afterward to limit shattering losses.
• If frost hits before the crop is fully matured, swathing may give the crop time to cure and rescue more yield in the process. Check for major frost damage to pods before making this decision.

Assess each field individually. Some may benefit from the frost and remain good candidates for straight combining. Others may be better suited to swathing.

Reglone. Growers who want to speed drydown for straight combining and don't want to wait for a killing frost can use Reglone. This desiccant stops maturity, so make sure the crop is sufficiently mature before application to avoid yield loss or green seed issues. Recommended timing is when 60 to 75% of the seed has turned brown. Use high water volumes and spray on a cloudy day or in the evening for improved performance. Canola crops treated with Reglone should be harvested within 7-14 after application to avoid potentially significant shattering losses. Glyphosate can also be used to manage green weeds and late maturing plants in non-tolerant crops, but its activity will be much slower, especially in cool temperatures.

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