When Should I Swath My Canola?

Staging canola for swathing or pre-harvest desiccation is critical to maintain high quality seed and maintain yield. Ideal swath timing is when 60% of seeds on the main stem have turned colour, meaning 60% of all the main stem seeds are showing some form of colour (yellow, brown, black) other than green.

For 60% seed colour change, the bottom third of the main stem of the plant will have totally brown/black to purplish seeds, the middle third will have turned, or be showing some spots of colour, and the top third are green. The green seeds must be firm and should roll between your fingers without squishing. At this stage, the average moisture content is about 30%.

Producers are reminded that more than one area in a field will need to be assessed for seed colour change. Relying on a visual assessment of canola pod colour alone will not provide an accurate estimate of crop stage. In many cases, the outside of the pod colour can turn brownish yellow but seeds inside may still be green.

Swathing

Delaying swathing of canola until the 60% seed colour change stage usually allows for:

  • Improved yield and quality through increased seed size
  • Reducing green seed
  • Higher oil content
  • Minimizing economic shattering losses

Earlier swathing tends to lock in green chlorophyll in underdeveloped seeds, reducing oil content and potentially causing marketing issues. Canola can be swathed in the 30-40% seed colour change stage to manage a large number of acres ripening at the same time, but producers should be aware that swathing at this stage can cause yield losses up to 8%.

Dry growing conditions and damaging weather have impacted canola development across Manitoba in 2018. Evaluating canola fields for evenness and uniformity is important to selecting the right time to swath or desiccate the crop. If growth conditions allowed large patches of delayed emergence, or hail set back crop development, estimating the patch size and managing the crop according to the largest percentage area is a good recommended practice.

Pre-Harvest Aid/Desiccation

Glyphosate, Heat and Diquat herbicides are all registered for use as either a pre-harvest aid or a desiccant on canola. Check the labels or the Guide to Crop Protection (https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp) to know their specific use.

In general, a pre-harvest aid (glyphosate and Heat LQ) should be used to increase plant tissue drydown and kill green weeds. The correct stage is 60-75% seed colour change. Expect to harvest the crop 1-3 weeks after spraying, similar to the time expected between swathing and harvesting.

A desiccant with the active ingredient diquat works more quickly, forcing removal of crop moisture. A fast-acting product, expect to harvest 4-7 days after application. Target a minimum of 90% seed colour change, as diquat will lock in any remaining green chlorophyll in the seed.

Points to Consider

Caution is advised when swathing or desiccating a canola crop, since that is considered growth and development termination, according to pre-harvest interval (PHI) standards. Know the length in days PHI of the fungicide and/or insecticide used on the crop; swathing or desiccating should not take place before that PHI window closes.

More tips on canola harvest management can be found here: https://www.canolacouncil.org/media/530966/canola_swathing_guide.pdf

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It’s Probably Not Giant Hogweed – 2018

Because of our experience with crops and weeds, it’s no surprise that the general public often turns to agronomists for plant identification and management advice. And it’s usually about this time of year – when Ontario puts out giant hogweed advisories and big white umbels are in bloom across Manitoba – that these calls start to pour in.

Cow Parsnip

Fortunately, it’s probably not giant hogweed (Heracleum mantegazzianum) since that invasive species has yet to be found in our province.  It’s more likely another member of the carrot family – cow parsnip (Heracleum maximum).  Unlike its giant cousin, cow parsnip is native to Manitoba and non-invasive.  It’s also very attractive to pollinators.

But even though it’s probably not giant hogweed, it’s still best not to touch it. Because, much like its giant cousin, the sap of cow parsnip may cause dermatitis when in contact with exposed skin.  Symptoms include photosensitivity, a rash and/or blisters.  Reactions to cow parsnip sap are generally much less severe than those to giant hogweed sap.

For more information, see poster on Poisonous Plants in the Carrot Family on Manitoba Agriculture Weeds landing page

 

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Scouting & Management of Sunflower Rust

Rust in sunflower is caused by the fungus Puccinia helianthi, which overwinters on plant stubble and produces five spore‐stages throughout the year. Early in the season, orange rust pustules appear on the upper surfaces of cotyledons of seedlings and volunteer plants, with later infections moving to the underside of the leaf (Figure 1).  The most yield-damaging stage occurs in late July to early August, when symptoms of infection show up as dusty, dark brown pustules on leaf surfaces, petioles and flower bracts (Figure 2). As the disease develops, black teliospores form, overwintering on the crop residue.

 

Figure 1: rust on leaf underside (photo: MB Ag)

 

Figure 2: Rust on leaves, stem. Wilting plants (photo: MB Ag)

Sunflower rust becomes a more severe issue in later-planted crops, or crops with weaker genetic resistance. Warm, moist weather favours rapid multiplication of rust spores, and windblown spores can travel quickly from field to field.  Early stages of sunflower rust in 2018 have been observed in the Cypress River area the week of July 3rd.

High plant populations and dense, leafy canopies allow humid conditions to remain in the crop throughout the day, compounding injury from rust spores.

Scout sunflower fields regularly to monitor the development and stage of rust infection. Watch for dense clusters of brown, powdery pustules scattered over all plant surfaces.  Orange-brown ‘dust’ on clothing after being in a sunflower field is a key indicator that rust is present, and more careful scouting is needed. Withered lower leaves are an indication that the surface is heavily infected.

Controlling rust after infection is primarily done using triazole-based and strobilurin-based fungicides. Recommended action in rust-infected crops is to use a fungicide from the triazole group after the first onset of symptoms, at the 2-3% pustule coverage on the upper four leaves at flowering (R5).  Strobilurin-based fungicides act more as a ‘protectant’, applied earlier before widespread infection occurs.

See more information on sunflower rust at https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp

See Guide to Field Crop Protection for more information on fungicides registered at https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp

National Sunflower Association of Canada information on Sunflower Diseases: http://www.canadasunflower.com/wp-content/uploads/2012/11/Disease.pdf

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Are the conditions right for sclerotinia in canola?

There are a few points to remember when considering a fungicide application for sclerotinia in canola this year:

  • In order for sclerotia to germinate and produce apothecia, they require at least 10 days of moist soil conditions (surface soil – as we aren’t concerned with sclerotia that are buried more than an inch or two below the surface).
  • Spores cannot infect leaves and stems directly – they grow on senescing tissue (i.e. canola petals) and then spread to the leaves and stems.
  • Dew/rainfall after petal drop is required for the pathogen to spread from the infected petals to the stem. Petals that dry up in leaf and branch axils without any moisture will not spread the infection.
  • The recommended timing for a fungicide application for sclerotinia management in canola is 20-50% bloom. This is because typically the canopy has filled in after 50% bloom. Petals can still be infected after 50% bloom, but when they fall, they tend to land on upper branch axils. Infection that only affects minor upper branches will not have a large impact on yield. If a crop is stagey or the canopy thin, infected petals may land on lower leaf and branch axils even after 50% bloom and infect the main stem. As long is there are petals present on the plants there is potential for infection to occur, the question is where will those petals land when they fall?
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What Does Seedplaced Fertilizer Injury Look Like?

Submitted by John Heard, Soil Fertility Specialist, Manitoba Agriculture

Already we are hearing of spotty emergence with cereal crops in Manitoba.  Possible culprits may be dry seedbeds, poor quality seed, seed depth, herbicide residues, or seed placed fertilizer injury.Past Prairie studies suggested a 15% stand reduction was tolerable for cereals since surviving plants tillered and filled in the stand.  But maturity is less uniform and is delayed up to 4 days.
How might one confirm seedplaced fertilizer injury?  Close inspection can show a range of symptoms:
1.        Seeds that imbibed water but did not develop any root or shoot
2.       Seeds that developed shoots but no roots
3.       Seeds that developed root and shoot but leafed out below ground
4.       Those that did germinate and emerge (about 44%) were ½ to 1 full leaf stage behind normal seedlings in the low fertilizer strip.
In other crops injury can show as:
Canola – seeds just do not germinate and remain intact.   Fields simply appear to have very poor crop establishment.
Soybeans – stands may be injured, especially with wider row spacing and on sandy soils under dry conditions.
For more information, see the full .pdf document on Manitoba Agriculture Current Crop Topics – What Does Seedplaced Fertilizer Injury look like in Cereals
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2018 Crop Diagnostic School

Registration is now open for the 2018 Crop Diagnostic School in Carman, MB.

School dates are July 10-13 and 17-19.

Topics this year will include insect scouting, dicamba drift, pea disease & soil erosion damage mitigation and others.

For more information see Crop Diagnostic School webpage

Registration can be called into 204-745-5663.

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Volatilization of surface applied urea/UAN

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist
Surface broadcasting of nitrogen (N) fertilizers has become popular to increase operational efficiency – increasing the speed of seeding and reducing risk of seed injury.  But, in a dry spring with limited rain prospects, growers may choose not to till and avoid further drying out seedbeds.  Then growers must consider the risks of nitrogen volatilization loss and take precautions when risk is high.
Volatilization of ammonia (NH3) from urea or the urea portion of UAN (28-0-0) affected by several factors and can be increased under specific situations.
For more details on the risk factors and ways to minimize losses, see full .pdf 
More topics on soil fertility can be found on Manitoba Agriculture’s Soil Fertility webpages.
 
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Can Sidebanded Nitrogen Cause Injury in a Dry Year?

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist

With a lack of seedbed moisture, there are justified concerns about seedplaced fertilizer injury to canola and other crops.  How safe is sidebanded nitrogen? Research studies by  Dr. Cindy Grant documented considerable canola stand thinning when high rates of sidebanded urea or UAN solution were applied.  Agrotain (AT) served to reduce stand injury, but is no longer supported for this use by the manufacturer. 

Points:
  • Stands were thinned at even modest N rates, on a clay loam soil.  At high rates stands were reduced to 50%
  • Crop growth compensated for reduced stands and generally produced as good a yield as the Agrotain protected stands, except at the highest rate.
For more detailed analysis and discussion on the issue see the full .pdf
More topics on soil fertility can be found on Manitoba Agriculture’s Soil Fertility webpages.
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Seed Placed Fertilizer Cautions for Canola

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist

Spring 2018 has brought many questions about seedplaced fertilizer rates for canola.  Several factors are causing concern:

  • Drier soils – which increase the risk of seed toxicity
  • Desire to apply sufficient P to meet crop removal – since many fields have seen decreasing P levels due to high yield.  P removal is about 1 lb P2O5/bu, so high yield potential fields are looking at high P replacement rates.
  • Increased use in low disturbance, low seedbed utilization (SBU) drills.  Many new openers are arriving on the scene, which are “close-to-seed” sidebanding for which one may need to consider as seedplaced.
  • Desire by growers to reduce seeding rates for cost savings.  Most research studies investigating seedplaced fertilizer injury were seeded at some 150 seed/m2, about double what some farmers are now targeting.
For more detailed analysis on the issue, see the full text in .pdf format 
 
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What Would an Early September Frost Do to My Sunflowers?

September 5, 2017 – Risk of Frost in Pinawa, Winnipeg, Whiteshell and Steinbach tonight……….

Frost anytime before the sunflower crop reaches physiological maturity (R9) can cause damage. Once sunflowers reaches the R7 stage (ray petals have dropped, back of head starting to turn yellow), sunflower can withstand temperatures as low as -4° C, but temperature, duration and crop stage will influence the type and amount of damage.

A killing frost in sunflowers is considered to be -4 to -5° C for 6 or more hours, as this low temperature for the extended period is required to penetrate the thick layer in the back of the sunflower head and start the dry down process.  See attached bulletin for more details:

http://www.gov.mb.ca/agriculture/crops/production/pubs/frost-sunflowers.pdf

Visit www.canadasunflower.com for more updates on all sunflower issues

Visit Manitoba Agriculture http://www.gov.mb.ca/agriculture/crops/ for more frost information for other crop types

Submitted by Anastasia Kubinec, Manager – Crop Industry Development, Manitoba Agriculture

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