August 21, 2013 – Issue 21

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  • Issues of the week

    Seed colour change

    Heat has moved the crop along, but resist the temptation to swath too early. The ideal time to swath is when 60% of seeds on the main stem have at least some level of brown colouration. Note that sunscald can make pods look more mature than they really are.

    We know that not all canola can logistically be swathed at 60% SCC. Some will have to be cut earlier. Keep in mind that cutting too early greatly increases green seed risk and yield loss. Canola Council of Canada research found that swathing at 60% SCC resulted in 8% more yield than swathing at 30-40% SCC, 12% more yield than at 10-20% SCC, and 19% more yield than swathing before 10% SCC.

    As bertha armyworms get bigger, they eat more. Berthas are continuing to grow this week, and will keep feeding right up until their pupate.

    Tweet of the week: @Michwoll posted this photo during today’s #ABbugchat, asking if it’s a bertha armyworm. Below the photo is Scott Meers’ tweeted reply.

    dead bertha

    Tweet of the Week August 22

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  • August 21 quiz

    Quiz August 22

    What is the seed-colour change of this pod?

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  • Top 10 tips to lower straight-combining risk

    straight combining in action small

    Here are a few of them. Click “Read more” for the rest…

    8. Harvest as soon as possible after the seed falls below two percent green content and is dry enough to store. Delayed harvest increases shattering losses.

    9. Consider your equipment options and take care to optimize header reel and knife position, speed settings, and anything else that may reduce shattering losses.

    10. Aerate straight-combined canola for at least a day or two after combining. Even if it comes off dry, green or wet plant material often makes its way into the sample.

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  • Swath timing for uneven crops

    Clint Jurke video on swath timing

    The ideal swath timing is when 60% of seeds on the main stem are showing some colour change from green to brown. Colour change is considered any amount of yellowing or browning on the seed. To determine ideal swath timing, fields need to be walked and pods need to be cracked. Pod colour change is not an accurate indicator or seed colour change. The swath decision becomes more difficult in crops with plants at multiple stages of growth….

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  • Swathing when hot increases yield loss

    With day time highs in the 30s or high 20s, growers should wait for cooler days before swathing the crop, if possible. Cutting canola in hot conditions will lead to rapid dry down and desiccation, which increases seed shrinkage — and leads to yield loss.

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  • Swath timing for hailed crops

    Hail damage can cause crops to mature unevenly. Judging when to swath multi-stage crops can be tricky. If the field has distinct late and early parts, the two parts could be swathed at different times. If not, then make the swath decision based on which plants are likely to contribute most to yield.

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  • Pre-harvest products for use in canola

    Glyphosate is registered for pre-harvest perennial weed control in canola. Glyphosate is to be applied when the majority of seeds are yellow to brown in colour and seed moisture is less than 30%. Heat fits between glyphosate and Reglone on the speed of dry down spectrum. Reglone is a contact herbicide (only kills what it contacts) and is registered in canola to dry immature green material to facilitate harvest. Reglone shuts the plant down quickly and basically STOPS it from maturing, which can lock in high green seed levels if applied prematurely.

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  • Insect update: Big berthas, weevil larvae, lygus

    Mature bertha armyworm. Source: Roy Ellis

    Bertha armyworms keep eating to within a few days of pupating. These 1.5” late-stage berthas eat much more than at smaller stages, doing a lot of damage in a week if numbers are at thresholds.

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  • Pre-harvest intervals (PHIs) for insecticides

    Many canola fields are within 5 to 10 days of swathing, which limits the choices for insecticides — based on pre-harvest intervals. Here are the pre-harvest intervals for insecticides registered for insect control in canola. Try the interactive PHI tool at www.spraytoswath.ca.

    PHI intervals table

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  • What to look for when disease scouting

    Sclerotia inside the stem. Source: Beth Hoar

    Check those patches of pre-mature ripened canola before or during swathing. Try to identify what cause this pre-mature ripening. Use the Canola Diagnostic Tool at www.canoladiagnostictool.ca to help with the assessment. It could be blackleg, clubroot, sclerotinia, root rot or something else entirely.

    Growers can use this scouting information to plan rotations, choose varieties, and update fungicide decision-making for next year. Here’s how to identify the major diseases of canola as fields get close to swathing stage:

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  • How to rate a crop for blackleg

    Blackleg field rating scale

    Plant pathologists from across the Prairies are surveying canola for disease levels. For each field surveyed, they select 20 random plants at 5 random locations for a total of 100 plants.

    For blackleg, they pull up each plant and clip the stem just below ground level. Each stem is then rated for what percentage of the stem cross section is discoloured by blackleg infection. A rating of “0” means no blackleg stem discolouration. A rating of “5” means the stem is completely discoloured and blackleg has killed the plant.

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