Canola Watch #15

August 5, 2010

click here to subscribe to the Canola Watch email

Issues of the week

Swathing has started for April-seeded fields. The ideal time to swath is 50% to 60% seed colour change on the main stem, so don’t rush. This week, we’ve got swathing tips for thin stands and a reminder for all late-season insect control and desiccation: Be Export Ready, pay attention to pre-harvest intervals.

Crop and weather update

Peace (B.C. and Alberta): Swathing has begun in the earliest and thinnest crops in the dry western and central regions. Nice rains in the central region are welcome but too little too late for many crops. Canola in the east and north looks good.

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”. Click here for 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. Click here for 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. Click here for Manitoba crop report.

Quick hitters

Pay attention to pre-harvest intervals. These intervals — the time between spraying and cutting or straight combining — are important because we don’t want pesticide residues on export canola. For example, lygus bug numbers are high on some early-seeded crops in the Peace and some of these crops are a week from swathing. The shortest pre-harvest interval is 7 days. (See the table below.) Note that if pods are hard and leathery, they are beyond lygus damage at that point anyway. For more on pre-harvest intervals, listen to Denise Maurice, CCC vice president of Crop Production, speaking on ACPC radio. Or click your province to for a link to your guide to crop protection: Alberta Saskatchewan Manitoba



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

Growers who seeded clubroot-resistant hybrids should know that low-level infection — up to 8% of plants — is normal for these hybrids. These off-types will be scattered uniformly through the stand.

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

Visual symptoms of clubroot can be incorrectly attributed to heat stress or to diseases such as blackleg, fusarium wilt or sclerotinia. For that reason, proper diagnosis of clubroot should always include digging up plants to check for gall formation on roots.

    •    Start at field entrance. Pull up 10 random plants, remove the soil and examine roots for evidence of galls.
 
    •    Walk 10 paces into the crop and pull another 10 plants.
 
    •    Turn 90 degrees and walk another 10 paces. Sample this way in a zig-zag pattern until 100 plants have been sampled. Record the percentage of infected plants.
 
    •    When sampling, do not be selective in choosing plants. Do not look for sick plants. Make sure the plants sampled are random.

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 a thin crop?

Growers with thin crops are wondering whether straight combining is better than swathing. Straight combining tends to work best on thick stands with plants meshed together to prevent whipping in the wind. But thin stands are at risk of wind damage whether swathed or straight combined. When thin stands are swathed, often there isn’t enough stubble to hold the windrow in place and prevent it from rolling in the wind.

If growers decide to swath thin crop, keep the following recommendations in mind:

  • Swath parallel to the typical prevailing winds in the area.
     
  • Cut plants as high as possible, just below the lowest pod. That will provide the highest stubble possible to keep the windrow in place.
     
  • Use a properly-adjusted swath roller to push down the swath so the edges are nestled into the stubble. Because the swath will be on or close to the ground, curing and/or dry down time may take longer.

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

  1. Scout for disease prior to swathing. Assess levels to determine if premature ripening or pod damage from alternaria black spot may necessitate swathing earlier than normal — before seed shatter starts. Fields with lots of diseased plants may also be poorer candidates for straight cutting due to the increased shattering risk.
     
  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 multiple stage crops

Many fields in the rain-soaked regions have advanced crop on the high ground and much later crop in the low ground. These fields require some harvest planning. Does a grower swath the high ground first and the low ground a couple weeks later? That may be the best option as long as the low ground looks like it will mature in time and if the low ground has the potential to generate worthwhile volumes. Otherwise it may be simplest to cut the whole field when the majority of the crop is ready.

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

Canola Crop Walk, August 18 at Vulcan, Alta., with CCC agronomy specialist Troy Prosofsky and ACPC director Lee Markert. The walk starts at 8:30 and goes to noon. Click here for location and details.

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 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 agronomist or provincial oilseed specialists:

Doug Moisey, senior agronomy specialist, North East and East Central Alberta,
moiseyd@canolacouncil.org, 780-645-9205

Erin Brock, agronomy specialist, Peace Region,
brocke@canolacouncil.org, 780-568-3326

Troy Prosofsky, agronomy specialist, Southern Alberta,
prosofskyt@canolacouncil.org, 403-332-1412

Murray Hartman, Alberta Agriculture and Rural Development,
murray.hartman@gov.ab.ca, 403-782-8024


Derwyn Hammond, senior agronomy specialist, Manitoba,
hammondd@canolacouncil.org, 204-729-9011

Jim Bessel, senior agronomy specialist, Central Saskatchewan,
besselj@canolacouncil.org, 306-373-6771

Tiffany Martinka, agronomy specialist, Eastern Saskatchewan,
martinkat@canolacouncil.org, 306-231-3663

Clint Jurke, agronomy specialist, Western Saskatchewan,
jurkec@canolacouncil.org, 306-821-2935

Kerry Clark, B.C. Ministry of Agriculture and Lands,
Kerry.Clark@gov.bc.ca, 250-784-2559

Venkata Vakulabharanam, Saskatchewan Ministry of Agriculture,
Venkata.Vakulabharanam@gov.sk.ca, (306)787-4668

Ingrid Kristjanson, Manitoba Agriculture, Food and Rural Initiatives, ingrid.kristjanson@gov.mb.ca, 204-746-7504

This report is supported by each of the provincial canola grower associations.