#15 Western Canada – August 9, 2007
In this issue:
(click the bookmark links below to move to specific sections of this report)
Scattered showers bring some reprieve from heat
Concerns about damage from heat stress continue
Recent moisture may assist with ripening and curing
Aster yellows disease found in many fields
Late season insect control tips
Lygus spraying in Alberta
Diamondback moth larvae moving to pods
How to tell diamondback larvae from bertha armyworms
Adjust threshholds if there’s more than one pest
Bertha armyworm spraying underway in some areas
Timing of bertha control critical
Late season diseases showing up
Allow for adequate pre-harvest intervals
Assess seed colour change before swathing
Consider pre-harvest weed control
Thinking about straight cutting?
Keep malathion far away from canola bins
The Alberta Canola Producers Commission (ACPC) has developed an Alberta focused version of this report. Visit the ACPC website at: http://www.canola.ab.ca
With the exception of southern Alberta, scattered rain showers in most areas have brought a bit of a reprieve from the persistent heat. Crop development continues with the only reports of flowering coming from the Peace River region. Swathing is now underway on early seeded crops in most southern regions and is most advanced in southern Alberta and southwestern Saskatchewan where most non-irrigated fields are swathed already.
An overview of prairie vegetation conditions is available at (use the “start the prairies application” button on the left hand side): http://www26.statcan.ca/ccap/ccaphome_en.jsp
The latest crop report from Manitoba Agriculture, Food & Rural Initiatives is available at: http://web2.gov.mb.ca/agriculture/mwcr/index.php
The latest crop report from Saskatchewan Agriculture, Food & Rural Revitalization is available at:
http://www.agr.gov.sk.ca/docs/reports/crop_report/crprpt070730.asp
Concerns about damage from heat stress continue across western Canada. There are many reports of shortened bloom periods, as well as blanks (missing pods) on stems and pod-shrinking (pods looking as though they are shrink-wrapped around the seed) are occurring in many areas, particularly on later maturing fields. Reports from southern Alberta indicate that dryland crops are very short with few pods.
High humidity and good soil moisture have helped to minimize the damage in some areas, but in areas where surface moisture was depleted, damage is severe. During heat stress, flowers are less receptive to pollen and the duration of pollen release and viability is reduced. Air temperatures in excess of 30 degrees Celsius during flowering can result in flower abortion and reduced pod formation. Gaps (no pod formation) on the main stem are good indicators that flower blasting has occurred. However, hail, lack of available sulphur, late herbicide applications or feeding from insects such as lygus bugs, bertha armyworm and diamondback moth larvae may also result in gaps on the main stem.
Further information is available in the following Canol@Fact:
http://www.canola-council.org/PDF/Canola%20Fact%20Sheet%20-%20Missing%20Pods.pdf
Recent moisture from scattered showers in most regions was welcome but has likely come too late or in insufficient amounts to have a big impact on yield. However, it may aid seed development in later maturing fields and will certainly improve conditions for ripening in fields that are nearly ready to swath or curing in those fields already swathed. For current maps of moisture conditions from PFRA for western Canada, check the following links for precipitation since September 1 and April 1 respectively:
http://www.agr.gc.ca/pfra/drought/prpay07_e.htm
http://www.agr.gc.ca/pfra/drought/prpgs07_e.htm
Additional moisture information for Alberta is available from Alberta Environment at: http://www3.gov.ab.ca/env/water/WS/data/precipmaps/weekly.pdf
Unusually large numbers of aster yellows-affected plants continue to be reported in many areas of Manitoba, Saskatchewan and north eastern Alberta. This disease may have been mistaken for sulphur deficiencies or herbicide damage. Aster yellows is caused by a phytoplasma, a plant pathogenic micro-organism. The phytoplasma inhabits the phloem (nutrient-carrying vessels) of infected plants and is carried from plant to plant by sap-sucking leafhoppers. Infected plants are more conspicuous because they tend to stand taller and are discoloured compared to non-infected plants. Although highly visible, aster yellows is not usually present on a large enough percentage of plants to cause economic losses. There are no preventative or control measures that producers can do to manage or prevent aster yellows in canola. Following is the link to SAF’s factsheet on aster yellows: http://www.agr.gov.sk.ca/docs/production/asteryellows01.asp
Late season insect control tips:
Scout – While regional monitoring, local forecasts and reports of what the neighbours are doing can provide helpful clues as to what might be in your fields; there is no substitute for getting out there and looking.
Use thresholds – Economic thresholds are available for most pests. These thresholds are often based on large scale, regional models. Remember to adjust those thresholds for your conditions, the yield potential, and your expected price.
Crop stage – If you are close enough to harvest time, the crop will become less attractive for most insects after it is has been swathed and begins to dry down. If you are only a few days from swathing, this may be a more economical choice. Keep in mind that if you are close to swathing, there may not be any products with a short enough pre-harvest interval (see pre-harvest interval section). Always keep the preharvest interval in mind when choosing control products.
Water volumes – Increase sprayer water volumes to allow for better control by improving coverage and canopy penetration. This is especially important as many insects will “hide” within the canopy making it more difficult to get good control.
Method of application – In most circumstances, aerial spraying or application with a high clearance sprayer will work equally well.
Increasing levels of lygus bugs (from 40 to 80 per 10 sweeps) are being reported in southern Alberta in the highway 1 corridor from Calgary to Brooks, and in the northwest around Vegreville, Camrose, Olds and Trochu. There are concerns about crop damage from lygus, but growers need to carefully assess crop stage before considering insecticide application. In some cases, there may not be an adequate pre-harvest interval for insecticide application, and growers may be better off to advance their time of swathing to reduce lygus damage. Use a sweep net to determine lygus pressure. Economic thresholds at the podding stage will be around 20 in a 10-sweep sample, but consult the following link for more details: http://www.canola-council.org/lygusmonitoring.aspx.
However, be aware of the lygus stage. If a large number of nymphs are very small (aphid-sized), wait a week and sample again. The larger the lygus, the higher the potential damage. Lygus will do less damage to firm seed than watery, immature seed. Also sample in the good areas of the field as higher numbers will be found in poor or thin areas. "Sap spots" seen on pods are also a good indicator of lygus damage. For more information on lygus bugs, refer to the following link: http://www.canola-council.org/lygusbugs.aspx
Diamondback moth larvae continue to be reported in many areas. Growers should be on the alert for damage from the larvae that begin feeding on the leaves, and then move up onto the pods at the later crop stages. Chemical control is not effective on cocoons so it is important to spray only actively feeding larvae. For more information on diamondback larvae, refer to the following link: http://www.canola-council.org/Diamondbackmoth.aspx
Both bertha armyworms and diamondback moth larvae have been found in many fields. With both pests present in some fields, it is important to differentiate diamondback moth larvae from bertha armyworms especially when trying to determine if thresholds are being reached. A couple of tips for distinguishing between the two are:
- Diamondback moth larvae will hang from “threads” when disturbed in the canola where bertha armyworms will not.
- Diamondback larvae will wriggle backwards vigorously if tapped on the head while bertha armyworms will tend to curl up. Don’t forget to try both ends if you can’t tell the head from the tail!
Adjust your thresholds when many pests are present. Feeding damage by more than one insect pest at the same time can create more stress on plants. While neither pest may trigger an economic threshold on its own, the combined damage could be reducing yields faster. In this case, remember to adjust your economic thresholds to account for the increased damage. A good “rule of thumb” for adjusting thresholds when two pests are present in significant populations is to reduce the threshold for each pest by 25%.
Bertha armyworm larvae have reached the thresholds for spraying in some areas including parts of northwestern, southwestern and central MB and central SK and southern Alberta near Vulcan. Growers in all areas affected by bertha armyworms last year, as well as areas reporting bertha armyworm moth activity this year, should continue to scout for their emergence and development. Check out the following links for the risk maps of based on cumulative moth counts. Remember these maps are an indication of risk in a region. Field scouting is still required to ensure economic damage does not occur in individual fields.
For more information on bertha armyworm counts in Manitoba, please refer to the following MAFRI link:
http://www.gov.mb.ca/agriculture/crops/insects/bertha/index.html
For more information on bertha armyworm counts in Saskatchewan, please refer to the following SAFRR link:
http://www.agr.gov.sk.ca/docs/production/BerthaArmyworm_map.asp
For more information on bertha armyworm counts in Alberta, please refer to the following link:
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm11487/$FILE/baay7w7c.png
Control for bertha armyworm occurs at the larval stage, usually when the larvae begin feeding on the pods. Spraying should be delayed until the larvae have reached the third or fourth in-star stage, because they do the most damage duirng the final two in-stars. As well, delaying spraying to the later stages will allow for the majority of the bertha eggs to hatch, thereby reducing the need for a subsequent insecticide application. For further information regarding bertha armyworm, please refer to the following link: http://www.directfocus.com/canolamanual/chapter10b.html#ch10b_sec6a
Timing of insecticide application for bertha control is critical. It is important to ensure that the larvae are up on the middle to upper parts of the plant and feeding on the pods. If the larvae are still feeding on leaf material in the lower canopy or the leaf litter on the ground, there will be poorer control. Avoid spraying during high temperatures (above 25 degrees C), because the larvae are likely to be in the lower levels of the canopy. Use rates appropriate to the stage of the larvae. Most insecticides recommend a range of rates. Use higher rates when faced with high populations and/or larger stages. Also at the latest stage, ensure that the larvae are actively feeding. Larvae at the latest stage may be inactive on the ground as they prepare to pupate.
Reports of late season diseases are starting to come in, including high levels of sclerotinia in untreated fields in part of Manitoba, northern Saskatchewan and central Alberta; fusarium wilt in susceptible varieties in central MB and the Peace region; clubroot around Edmonton and St. Albert; and alternaria in northwestern SK and north central Alberta. During fall scouting for proper swath timing and late insect scouting producers should watch for abnormal areas that have wilted, or for prematurely ripening plants within canola stands that are otherwise healthy. These areas may be indicators of these diseases that restrict water and nutrient uptake by plants. It is important to accurately identify what is causing the damage and properly document the information for future reference and decision making. Identification of clubroot will allow growers to take steps to limit soil (and associated spore) movement to other fields through equipment sanitation. Fields with alternaria will be poor candidates for delayed swathing and should not be straight combined as pods will be prone to shattering.
Before considering any further applications of fungicides or insecticides, remember to allow for the required pre-harvest interval for any products being considered. Growers need to ensure that the appropriate pre-harvest interval is followed to eliminate chances of excess residues appearing in the harvested seed, and damaging markets. Refer to the following links for information on pre-harvest intervals for some common pesticides and description of the importance of following pre-harvest intervals: http://www.canola-council.org/pre_harvest.html
Early seeded crops in parts of southern Alberta and Saskatchewan are nearing maturity. Growers need to ensure that seed colour change is occurring when assessing the proper time to swath. The colour of mature plants and pods will vary among varieties as they mature. Some will appear ripe on the outside before the seeds are mature, so avoid using plant colour as a gauge to proper timing. Open up pods on the main stem and look at the colour of the seeds to accurately assess swathing timing. Refer to the following link for more information on swathing in hot, dry weather: http://www.canola-council.org/media_jul2606.html
Recent research indicates that the optimum stage to swath for both yield and quality is up to 60% seed colour change. This enables many growers to start swathing at 30% to 40% seed colour change without sacrificing significant yield or quality. It widens the "swathing days" window for all growers, including those with large canola acreages. When conditions are hot and dry, avoid swathing during the hottest part of the day. Swath during cool evening hours, at night or early in the morning to allow plants to dry down at a slower rate. This reduces the chance of green seed. This strategy will also help in situations where hail damage or diseases such as alternaria, black spot or sclerotinia have predisposed the plants to shattering. Growers may need to consider swathing earlier in these situations as well, but should try to wait for at least 20 to 25% seed colour change if possible. To learn more about proper harvest field assessment, refer to the revised Canola Council publication "Canola Time of Swathing Guide" or the following link: http://www.canola-council.org/pub_swathing.html
With swathing and harvest of other crops approaching, consider a valuable weed control tool to set up for next year's canola crop--pre-harvest glyphosate. It's the most consistent and effective treatment for many perennial weeds, providing an effective and economical alternative to in-crop applications. In early fall, perennial weeds are moving nutrients down into roots and rhizomes to prepare for winter. This is when they are most vulnerable to herbicide translocation to the roots and better control is possible. Keep in mind that generally the use of pre-harvest glyphosate on crops grown for seed should be avoided.
There are a number of growers considering straight cutting their canola this year. To be successful, consider the following factors:
Crop Canopy – the crop should be well knitted and slightly lodged to reduce the chance of pod shelling and pod drop. Remember that pod integrity (including petiole strength which influences pod drop) can be affected by frost and drought.
Disease – 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 - Crops affected by hail are poor candidates for straight cutting due to the probability of greater disease infection through damaged tissue and reduced pod integrity from physical damage. Also, any late season hail often causes greater levels of damage to standing crops than swathed crops.
Growers who have decided to straight combine some of their canola may also be considering pre-harvest weed control or desiccation. If a Roundup Ready canola variety has been grown, a pre-harvest glyphosate application will assist in some dry down of green weeds and offer perennial weed control, but it will not dry down the crop. For other types of canola, it will be even more critical not to apply the product too early. Apply when the crop has 30% 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 (72 hours) after application before cutting to allow thorough translocation of the herbicide to ensure extended long-term weed control. If applying any pre-harvest chemicals prior to harvest with ground rig sprayers, the use of crop dividers can reduce the amount of crop loss due to trampling and shattering. In addition, traveling back and forth in the direction of prevailing crop lean will further reduce losses. For a faster acting desiccant like Reglone, it is even more important to delay application to allow seeds to reach physiological maturity. The recommended stage is when 60 to 75% of seed has turned brown.
At this time of the year, as growers prepare their bins for storage of the upcoming harvest, it is important to note that oilseed crops like canola can absorb malathion from bin surfaces and the resulting residues have been found in crop delivered to elevators. Therefore, DO NOT use malathion to treat bins destined to store canola from the upcoming harvest. Refer to the following link for further information: http://www.canola-council.org/pesticide_link2.html
Direct questions regarding this report to John Mayko, Senior Agronomy Specialist, Parkland West (West Central AB), with the Canola Council of Canada at maykoj@canola-council.org ph/fax: 780-764-2593.
Direct specific questions regarding regional issues to one of the following Canola Council of Canada agronomy specialists or provincial oilseed specialists:
Derwyn Hammond, Agronomy Specialist, Manitoba, hammondd@canola-council.org, 204-729-9011
Arvel Lawson, Manitoba Agriculture, Food & Rural Initiatives, Arvel.Lawson@gov.mb.ca, 204-745-0340
David Vanthuyne, Agronomy Specialist, Eastern Saskatchewan, vanthuyd@canola-council.org, 306-946-3588
Jim Bessel, Senior Agronomy Specialist, North-central/eastern Saskatchewan, besselj@canola-council.org,
306-373-6771
Penny Pearse/Scott Hartley, Saskatchewan Agriculture, Food & Rural Revitalization, ppearse@agr.gov.sk.ca / shartley@agr.gov.sk.ca , 306-787-4671 / 306-787-4669
Doug Moisey, Agronomy Specialist, Parkland East (East Central AB & NW SK), moiseyd@canola-council.org, 780-645-3624
Matthew Stanford, Agronomy Specialist, Chinook (Southern AB & SW SK), stanfordm@canola-council.org,
403-758-6660
Anne Vos, Acting Agronomy Specialist, Peace Region, av@summit-ag.com, 780-835-4632
Murray Hartman, Alberta Agriculture, Food & Rural Development, murray.hartman@gov.ab.ca,
403-782-8024
Kerry Clark, BC Ministry of Agriculture and Lands, Kerry.Clark@gov.bc.ca, 250-784-2559
The Canola Watch Report provides just-in-time information on canola production to growers and industry. Contributors to the Canola Agronomy Network are:
Manitoba Agriculture & Food; Manitoba Canola Growers Association; Agricore United; Saskatchewan Wheat Pool; United Farmers of Alberta; Saskatchewan Agriculture, Food & Rural Revitalization; Saskatchewan Canola Growers Association; Saskatchewan Canola Development Commission; Alberta Agriculture, Food & Rural Development; Alberta Canola Producers Commission; BC Ministry of Agriculture; Food & Fisheries; and the Canola Council of Canada.