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 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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Manitoba Weed Update

Despite rainy and windy conditions, early post-emergent herbicide applications are nearing completion in most crops. Emergence of cool season annual weeds was relatively unaffected by earlier cool, dry conditions while emergence of warm season annual weeds was delayed, resulting in herbicide staging issues for some producers.  Emergence of warm season annuals, like redroot pigweed and barnyard grass, is now well underway due to recent rainfall.

Weed Identification:

Weed identification form: www.gov.mb.ca/agriculture/crops/crop-diagnostic-services/.  Weeds submitted to Manitoba Agriculture for identification in the previous week include:

Black nightshade:

Black nightshade (Solanum nigrum) is a warm season annual problematic in potato, dry bean and soybean production.  What to look for: small seedlings with pointed ovate cotyledons, currently in the cotyledon to early true leaf stage (see picture submitted to MB Ag).

Galinsoga species:

Hairy galinsoga (Galinsoga quadriradiata) and smallflower galinsoga (Galinsoga parviflora) are annual species also referred to as ‘quickweed’ based on their ability to set seed within only weeks after emerging.  What to look for: toothed, opposite leaves and ‘club’ shaped cotyledons (see picture submitted to MB Ag).

Oak-leaved goosefoot:

Of the various goosefoot species coming in for identification, oak-leaved goosefoot (Chenopodium glaucum) has been the most common.  What to look for: goosefoot shaped leaf, often with distinct yellow-green veins.  Stems may be red and green to red.  Typically grows more prostrate than lamb’s-quarters.  Oak-leaved goosefoot does especially well in wet and/or saline areas.

Weed Management Issues:

Manitoba Agriculture staff have begun to receive herbicide drift complaints and are providing advice accordingly. Talking to the applicator should always be the first step in a suspected drift incident.  Herbicides involved in the drift complaints to date include glyphosate, group 2 and group 4 herbicides.

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Don’t Overlook Group 2 Herbicide Resistance

You’ve probably read about media dubbed ‘superweeds’ like glyphosate-resistant palmer amaranth and giant ragweed. Glyphosate-resistant weeds often earn this distinction because they are viewed as a greater management hardship for producers than weeds resistant to other herbicide mechanisms of actions (MOAs).  And maybe rightly so.  Farmers dealing with glyphosate resistant weeds elsewhere in the world have been reduced to tillage and hand rouging for weed control in some crops.

But, while glyphosate use dominates the Roundup Ready corn, soybean and/or cotton rotation in the US, group 2 herbicides play an (equally?) important role in our more diversified cropping system. For example, group 2 herbicides are used in crops like alfalfa, corn, dry beans, field pea, potato, soybean, sunflower, and in Clearfield and other group 2-tolerant crops.  These herbicides are also a popular choice for group 1-resistant grassy weed control in cereals.

The point of this article isn’t to downplay the importance of glyphosate resistance but to elevate consideration of group 2 resistance. In Manitoba, over 10 weed species are known to have biotypes resistant to group 2 herbicides.  And herbicide-resistant weed surveys led by AAFC indicate that the prevalence of certain species is increasing (Figure 1).

Figure 1: Prevalence of group 2 resistance in Manitoba in 2003 and 2008 as a percent of the weed species population surveyed (Beckie et al).

 

The following practices can help reduce the risk of developing herbicide resistant weeds and/or managing existing resistant weed populations:

  • Diversifying your crop rotation;
  • Using multiple herbicide MOAs effective on target weeds (e.g. herbicide ‘layering’, tank mixing);
  • Practising good basic agronomy (variety selection, seeding rates, etc.);
  • Judicial use of tillage.

If you suspect group 2 resistance in a weed species on your farm, it’s best to verify this by herbicide-resistance testing. Unfortunately there‘s no quick method – seed from the suspect population needs to be allowed to mature and collected.  Samples can be submitted to AgQuest for testing in Manitoba.

In my opinion, knowing if you have group 2 resistance and assessing your risk factors is worth it. Because while glyphosate resistance is grabbing headlines, group 2 resistance may be quietly growing in your fields.

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Blackleg in Canola – to spray or not to spray?

Things to consider:

  1. Crop rotation – the tighter the rotation the higher the risk of blackleg
  2. Historic levels of blackleg in that field – have you experienced yield loss from blackleg?
  3. Weather forecast – infection requires free moisture (light-moderate rainfall, not soil saturation)
  4. Presence of inoculum –can you see leaf lesions on first true leaves? or pseudothecia present on canola stubble?
  5. Yield potential – what is your target yield, return on investment expected?

If you have made the decision to spray, what else do you need to know?

  1. Application timing – apply at the 2 to 4 leaf stage, later applications are not as effective at reducing disease.
  2. Fungicide type – strobilurin fungicides (Group 11) are more effective at reducing disease than triazoles (Group 3). For more information on what products are registered for blackleg management, see the MB Guide to Field Crop Protection http://www.gov.mb.ca/agriculture/crops/guides-and-publications/pubs/crop-protection-guide-disease.pdf.
  3. Yield increase….not guaranteed – while strobilurin fungicides applied at the 2 to 4 leaf stage did significantly reduce the severity of the disease, yield bumps were only observed when a susceptible cultivar was grown.

 

 

 

Reference: Liu, C. 2014. Evaluation of fungicides for management of blackleg disease on canola and QoI-fungicide resistance in Leptosphaeria maculans in Western Canada. Master of Science Thesis. University of Manitoba. 172 pp.

 

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What is Waterpod?

Waterpod is:

  1. an annual weed occasionally found in agricultural fields;
  2. a mobile irrigation system; or
  3. a one person submarine?

 

 

If you chose a), you’d be right. Waterpod (Ellisia nyctelea L.) is an annual broadleaf plant native to Manitoba.  It’s often found in shaded, wooded areas but can also thrive in ditches and agricultural fields.  Our wet soils and cool spring must have provided ideal conditions for waterpod emergence as it’s being found in abundance in fields across the province.

The good news is waterpod isn’t much of agricultural pest.  Although it’s an annual, it emerges and flowers early and usually dies off in June.  It’s also very susceptible to glyphosate and most other burn-off and post-emergent herbicides.

Identifying characteristics:

  • oval cotyledons with a flat top;
  • deeply lobed and hairy leaves;
  • small, white 5-petaled flowers.

 

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How Can I Reduce Fertilizer Losses in Dry Spring Soils?

Dry spring weather is great for seeding but may play havoc with some fertilizer applications and losses.

1.Seedplaced fertilizer – Where seedbed moisture is low or when weather is hot and windy, reduce the rates of seedplaced nitrogen  by approximately 50 per cent. Table 7 of the Manitoba Soil Fertility Guide  http://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-fertility-guide/nitrogen.html indicates safe rates of seedplaced urea under different soil texture, moisture and seedbed utilization conditions.  But as conditions dry, these rates should be reduced accordingly.

2.Surface applied urea or urea-forms (like UAN solution 28-0-0) – are vulnerable to volatilization losses.  The soil and environmental factors increasing risk of loss are well known and include:moist soil conditions, followed by rapid drying

  • high wind velocity
  • warm soil temperatures
  • high soil pH (> pH 7.5)
  • high lime content in surface soil
  • coarse soil texture (sandy)
  • low organic matter content
  • high amount of surface residue (Zero Till)

Volatilization losses can be reduced with dribble placement of UAN versus broadcast applications and the use of an urease inhibitor.  The active ingredient NBPT used in Agrotain Ultra is now marketed by a number of companies.  To expect the same level of protection as Agrotain Ultra, ensure the application rate is similar, since formulation strength and recommended rates differ among suppliers.  Agrotain Ultra contains 27% NBPT with an application rate of 3.1 l/tonne urea or 1.6 l/tonne UAN.

3. Last year the lack of rainfall through much of May left surface applied nitrogen stranded at the surface.  If possible, a portion of the crops nitrogen for cereals and canola should be in-soil placed.  In season applications should be targeted prior to stem elongation of cereals and bolting of canola.

 

 

 

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Manitoba Ag Weather Network

Manitoba Agriculture has a number of weather stations across the province that measure air/soil temperature, soil moisture, wind direction and speed.  For local information please visit

Central/East/Interlake Regions: http://www.gov.mb.ca/agriculture/weather/current-conditions-summary1.html

Southwest/Northwest Regions: http://www.gov.mb.ca/agriculture/weather/current-conditions-summary2.html

Previous Day on Highs/Lows and Average Soil Temperature at:

Central/Easter/Interlake:http://www.gov.mb.ca/agriculture/weather/yesterdays-summary1.html  Southwest/Northwest: http://www.gov.mb.ca/agriculture/weather/yesterdays-summary2.html

Another useful application of the data gathered by the network for rainfall can be found at Rain Watch http://www.gov.mb.ca/agriculture/weather/rain-watch.html

 

 

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Seeding for Target Plant Stands, not lbs/ac

Seed can be an expensive input, but a poor crop stand can be lost profit.  To maximize your seed, still get the stand needed to optimize yield, start calculating the real seeding rate needed for the plant stand desired and not gauging seeding rate by lbs/ac or bu/ac.

The following are the standard recommendations for FINAL plant stand, not what you are putting in the ground. Germination, TKW and mortality are very important to use in the equation to determine actual seeds/ac to plant.  For example, if you assume your germination is 96% and its only 85% and conditions turn cold and wet (increasing mortality), you may have a lot thinner stand than you anticipated (which could mean a harder time controlling weeds).

                    Grain Crops                               Oilseed Crops                   Pulse Crops        
Barley Wheat Oat Corn Canola Sunflower Flax Peas Soybean Dry Bean*
Plants/ft2 22-25 23-28 18-23 7-14 37-56 7-9
 Plants/ac (1000s) 26-30 18-22 180-210 85-100
Mortality Rates (%) 10-15 10-15 10-15 10-15 20-60 10 40-50 5-15 5-10 5-10

*Navy Bean = pinto beans on lower end and navy bean require higher plant stands

Source:  Manitoba Agriculture, Canola Council of Canada, Flax Council of Canada, Ontario Ministry of Agriculture, Food and Rural Affairs

 Seeding Rate (lbs/ac) = target plant stand/ft2 x TKW (g) / % expected seed survival x 10                       

 e.g. FLAX Seeding Rate= 45 plants/ft2 x  5g (TKW) / ((88% germination x (1- 40% mortality)) X 10 = 43 lbs/ac

Other information

Wheat – http://www.gov.mb.ca/agriculture/crops/production/print,aiming-for-higher-wheat-yields.html

Using 1000 Kernel Weight for Calculating Seeding Rates – http://www1.agric.gov.ab.ca/%24department/deptdocs.nsf/all/agdex81

Canola – http://www.canolacouncil.org/canola-encyclopedia/crop-establishment/seeding-rate/

Optimizing Plant Establishment – http://www.gov.mb.ca/agriculture/crops/production/pubs/optimizing-stand-establishment-in-less-than-optimal-conditions.pdf

 

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Seed Placed Fertilizer – Safe Rates

A reminder that if seedbeds turn dry, the safety margin shrinks when applying seed placed fertilizer.  Seedburn can result from ammonia toxicity and/or salt content of fertilizers.

For nitrogen, our Soil Fertility Guide provided safe guidelines for seed placed urea on cereals and canola across a range of soil types and seed-fertilizer configurations.  With the increased popularity of narrow seed and fertilizer spreads with disk drills, the safe rates are reduced.  For example, safe urea rates for cereals vary from 10 to 25 lb N/ac going from sand to clay soil using disk openers on 6” row spacing.  These guidelines are for moist soil and should be reduced by 50% if seedbed moisture is lower when weather is hot and windy.

The safe rates of seed placed phosphorus depends on the crop, with cereals being quite tolerant compared to soybeans, dry beans and canola.  With a disk drill as described above, cereals can tolerate 50 to 60 lb P2O5/ac as mono ammonium phosphate while rates would be 20 lbs/ac for canola and less for beans.   If there greater seedbed utilization (i.e. narrower rows or a wider seedrow with less fertilizer concentration) rates could be more liberal.

More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at: http://www.gov.mb.ca/agriculture/crops/soil-fertility/print,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html

 

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