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Story Posted: August 05, 2010 Canola Watch 15: Scout for clubroot, harvest tips for thin canola In This Issue: Clubroot shows up in resistant hybrids, How to scout for clubroot, Should growers straight combine thin crop?, 7 swathing tips for 2010, When to swath multi-stage crops, Coming events, Questions and contacts. Issues of the week Crop and weather reports Alberta: Crops in the south look good and continue to get regular rains, but they are 2-3 weeks behind in general. Through the central region, crops are good to excellent and are more advanced the farther north you go. Rain varied from nothing in some spots to 4". Read the Alberta crop report. Saskatchewan: Crops in the west have good yield potential but could benefit from one more rain. Hail wiped out many good-looking crops in the southeast. Acres of flooded crop in the north central and northeast region continue to be ripped up. Around Wadena, the fields worth harvesting are so wet, growers wonder how they're going to swath without getting stuck. Overall, the earliest crops are a week to 10 days late. Crops seeded in June are about 3 weeks late. Read the Saskatchewan crop report. Manitoba: April-seeded fields have been swathed across the south. Remaining fields range from within a week of swathing to full bloom for the latest fields. The northwest and north Interlake are generally less advanced. Many growers have multi-stage canola crops, which present a challenge for harvest timing. More on that below. Read the Manitoba crop report. Quick Hitters
Keep scouting. Lygus bugs, diamondback moth larvae and bertha armyworms can do a lot of damage fairly quickly. Some good-looking fields in north central Alberta, for example, are at or near thresholds for lygus. Click here to see threshold tables for key insects. Don't rush to swath. With many regions one to 3 weeks later than normal, growers may be tempted to swath earlier than optimal. Swathing at 60% seed colour change on the main stem is generally the best time for both yield and quality. If growers can't wait that long, at a minimum make sure green seeds are firm when rolled between the thumb and forefinger. Swathing prior to 15% to 20% seed colour change will likely reduce yield potential and could contribute to green seed issues under hot and/or dry conditions. For more on swathing timing, click here to see a CCC video. Growers needed for combine loss study. As part of a CCC-funded project, researchers are looking for growers in select regions to take part in a combine-loss survey. Growers remain anonymous and researchers do most of the work. Growers around Lacombe and Edmonton, click here for more information. Growers around Saskatoon, click here. And growers around Winnipeg, click here. Clubroot shows up in resistant hybrids If resistant hybrids have levels higher than this, a patch of susceptible volunteers is the most likely reason. Volunteer canola densities can easily exceed 10 plants per square foot in canola-on-canola rotations, and will be part of the current crop unless a different herbicide-tolerant system was used. With canola-wheat-canola rotations, volunteer canola in the next canola crop may persist at levels of about one plant per square foot in certain situations. If volunteers cannot explain high infection rates in resistant varieties, then growers should contact their seed rep for further diagnosis. How to scout for clubroot
When unsure if a field has clubroot infection, then it is appropriate to sample affected plants to first identify the disease. Then use the above technique to quantify the level of infection. The top photo shows canola roots with young clubroot galls. The photo at the bottom of this article shows developed galls. (Photos courtesy Stephen Strelkov.) Yield losses due to clubroot are about half of the percentage of infected stems. For example, if 10% to 20% of plants are infected, yield loss will likely be around 5% to 10%. No control products are registered for clubroot in canola. The recommendation is to rotate out of canola for four years in slightly infested fields and seven years in severely infested fields. Control volunteer canola and susceptible weeds (mustard family, dock and hoary cress) in the rotational crops. And consider a clubroot-resistant hybrid the next time canola goes on that field. For more on identification, prevention and management of clubroot, visit the website www.clubroot.ca.
Should growers straight combine thin crop? If growers decide to swath thin crop, keep the following recommendations in mind:
We continue to get questions about pod sealants - products for the purpose of reducing pod shatter when straight combining canola. Limited research to date has produced variable results, often similar to straight cutting without the use of pod sealants. If growers do choose to try them, they are encouraged to leave a test strip and see if they make a difference to yield. Ensure timing of application is optimal and water volumes are adequate to maximize the odds of success. Don't expect these products to completely "rescue" crops that are at high risk for shattering due to factors such as disease or hail damage. 7 swathing tips for 2010 2. Hail damage can cause crops to mature unevenly. When swathing a hailed crop, assess the seed-colour change at the earliest and highest-producing parts of the field, especially if the delayed maturity creates a high risk for fall frost damage. 3. Check weed pressure. Green biomass in the swath will extend the curing time, and weed seeds and green plant material can be starting points for heating in storage. Fields with high weed counts may benefit from a pre-harvest spray to dry them down. 4. When to swath. The best timing for yield and quality is when 50% to 60% of seeds on the main stem are turning from green to brown. For more on this, click here to read the CCC's "Canola Time of Swathing Guide." 5. Lay swaths parallel to the direction of prevailing winds. This reduces the risk of swaths blowing and pods shattering. 6. Set the roller low enough to anchor swath into standing stubble with slight pressure. Use a roller that tucks swath edges down into stubble. 7. Large dense swaths tend to take longer to condition and cure canola before combining. Thin swaths lying flat on the ground may also take longer. When to swath multi-stage crops Key to the decision is this: Don't put the best and biggest part of the crop at risk of shelling in order to save a few acres of later, higher-risk and possibly low yielding canola. Click here to download a 4-page PDF called "Swathing and Harvesting Multiple Stage Canola Crops." Coming events Preharvest/Late Summer Diagnostic Clinic at the Ian N. Morrison Research Farm in Carman, Man., Wednesday, August 18 from 1:00 - 4:00 p.m. Canola topics include time of swathing tips. Registration is free for Crop Diagnostic School participants and $25 (cash or cheque at door) for others. Call 204- 745-5663 to register.
Questions and contacts 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:
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