It’s Probably Not Giant Hogweed

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.

Information on identification of cow parsnip and giant hogweed is available from 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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Quick Tips – Effective Post-Emergent Weed Control in Conventional Soybeans

If you have only grown glyphosate tolerant soybeans in the past, the move to conventional soybeans can offer up new challenges in regards to weed control. Good weed control is critical for maximizing yield.  Here are a few quick tips:

    • Remember!! You can’t apply post-emergent glyphosate – Unlike glyphosate-tolerant soybeans, conventional soybeans are not a clean-up crop for weedy fields. They are a crop that needs to be planted in fields that have already been cleaned up.
    • Get in touch with your weed spectrum – If you have not done so already, determine what weeds are present or likely to be present in your conventional soybean fields. Are the herbicides you intend to use going to control the weed spectrum you have identified? A mismatch between weed spectrum and herbicides used is a frequent cause of weed control problems in conventional soybean fields.
    • Did you take advantage of pre-emergent weed control opportunities? If so, how is that working? – The advent of pre-emergent soil applied residual products has been a benefit to weed control in conventional soybeans. If this is a tool you decide to use, it is important to assess its effectiveness before you do post-emergent applications to ensure that weeds you are assuming have been dealt with have been controlled.
    • Amp up the Aggression!! Early and thorough weed control is key – Important regardless of the type of soybean you are growing. Research has demonstrated the critical weed free period for soybeans is emergence to the third trifoliate, where the removal of weeds provides the greatest protection of yield potential. Be timely with control and selective with products that may provide some residual control for an extended weed free period.
  • Know your crop growth stage, know your weed growth stageKnowing your crop and weed growth stages as you time herbicide applications is very important in conventional soybean production. Most of the herbicides available have tighter application windows than glyphosate

 

  • Overgrown weeds are less susceptible to herbicides – this can lead to growers dishing out more money on higher cost options that might not work due to size of plants. Please take note that some herbicides can cause crop damage if they are used at the wrong growth stage. In this competitive fight for yield, you don’t want to set back your crop.

 

 

  • Assess the effectiveness of herbicide applications and adjust your plan – Fields should be scouted after each herbicide application to assess effectiveness. If weeds have shown up that the previous herbicide would not have controlled, you might have to change products for your next application or add extra herbicide passé. Were the weeds that you expected to be controlled, actually controlled? Don’t assume that you have dealt with target weeds until you see the evidence. These post-spraying inspections are key opportunities to detect the development of herbicide resistant weeds before they get out of hand.
  • Weed control in conventional soybeans is going to cost more – Seed may be cheaper, but the cost of an effective weed control program in conventional soybeans is almost always more expensive than in glyphosate-tolerant production. But remember, poor weed control remains the #1 threat to maximizing yield and profit in conventional soybeans. Weed control is a key point of investment in this crop and there are no shortcuts if the weed control situation demands action.
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Post-Emergent Weed Control in Xtend Soybeans – Slow Down and Be Careful

The future of side by side soybean fields using different herbicides is here with Xtend soybeans commercially available in 2017.  Having more herbicide tools to combat the herbicide resistant weeds is important, but careful use is critical, to prevent crop damage and stay friends with our neighbors. Here are a few things to consider:

  • Non Xtend soybeans (and other crops) are easily damaged by dicamba – dicamba on sensitive crops always causes crop damage with very dramatic looking symptoms. As glyphosate -tolerant soybeans made up the majority of acres in the past and usually only sprayed with glyphosate, drift went unnoticed. The addition of Xtend soybeans to the cropping mix will be a reawakening to anyone who has gotten careless.
  • Should your pre-emergent application have been the one that included dicamba? – preferred timing for dicamba containing herbicides for use on Xtend soybeans is pre-emergent. Research has demonstrated the critical weed-free period in soybeans is emergence to the third trifoliate, early weed removal provides the greatest yield potential. Additionally, dicamba provides residual control for some weed species during that critical period. Another important point is, chances of application mistakes like drift on sensitive crops are greatly reduced during pre-emergent applications.
  • Only use herbicides specifically designed for the Xtend system – do not tank mix dicamba and glyphosate that you might have on hand in an attempt to make “homemade” herbicide for Xtend soybeans. The herbicide manufactured is designed specifically for use in Xtend soybeans, with reduced levels of volatilization, to prevent herbicide drift. Keep in mind the reports on the U.S. experience in 2016.  Homemade concoctions are a very bad idea, plain and simple.
  • The label is your friend…follow it! – the labels contain important information that will help minimize chances of accidental herbicide drift onto susceptible crops. Key points include:
    • Use nozzles delivering extremely coarse to ultra coarse spray droplets (volume median diameter of 450 microns or more) as defined by ASABE standard S572.1 and as shown in the nozzle manufacturer’s catalog.
    • Do not apply:
      • when risk of severe temperature fall in the night;
      • under high humidity, temperatures above 30oC, or fog conditions, to prevent drift to sensitive crops;
      • when wind is blowing toward a nearby sensitive crop;
      • when winds are below 3 km/h or above 15 km/h.

Source: Guide to Field Crop Protection 2017 p. 163

  • All soybeans look alike – know what field you are in – there is no way to visually discern between the different types of soybeans. When in doubt, make sure that the applicator is in the right field. Herbicides specifically designed for the Xtend system applied to Roundup Ready or conventional soybeans will cause significant crop damage. Additionally, knowing the types of soybeans in the adjacent fields is important to indicate increased risk for off target crop damage. Remember, dry beans look like soybeans from far enough away….never make assumptions.
  • Sprayer cleanout requires careful attention – If producers are growing two or more types of soybeans on their farms, careful consideration has to be given to sprayer cleanout as they move between soybean fields. Even a small amount of dicamba will serve as a contaminant in the next spray load being applied, causing significant damage. Especially if you have only grown Roundup Ready soybeans in the past, recognize that the situation has gotten more complicated.
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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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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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When to Roll Your Soybeans

Most growers will roll their beans shortly after seeding in order to prevent stones from entering the combine at harvest time and to make harvesting easier and quicker. On dry springs when soil conditions could lead to soil drifting a grower can wait and roll there beans after they are up and are at the first trifoliate stage..

When rolling after emergence

  1. Do not roll at the Hook Stage- This is when beans are first emerging.
  2. Do not roll in the morning wait until air temperature are around 25C before you start to roll to avoid damage to the plants.
  3. Check for damaged plants to ensure plants are not breaking off.
  4. If damage is too sever wait for a warmer day.

 

The attached video outlines some of the reminders about rolling beans.

Soybean School West: Why Rolling Matters & Timing it Right

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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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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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Crop Germination – What Soil Temperatures are Needed?

Soil temperature drives germination and seedling emergence, so how cold is too cold?  What is your soil temperature at your targeted seeding depth….today? Finally, when should you be measuring the soil temperature?

The following are the minimum temperatures needed for germination to begin in various crops.  These values should be regarded as approximate, since germination depends on factors other than just temperature.  But, if soils are too cool, germination will be delayed and cause uneven or poor seedling emergence.

 

Crop Temperature     (°C)
Wheat 4
Barley 3
Oats 5
Corn 10
Canola 5
Flax 9
Sunflower 6
Edible Beans 10
Peas 4
Soybeans 10

Sources: North Dakota State University Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

Getting an accurate measure on soil temperature

Determine how deep you will be seeding. Then place your soil thermometer at the targeted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm).  Average the two readings to determine the average soil temperature. The recommendation is to take readings for two to three days to establish a multiple day average and to measure at a number of locations in the field, to account for field variability.

Still not sure and short on time?  See the soil temperature data for various locations across Manitoba from the MB Ag-Weather Program: https://www.gov.mb.ca/agriculture/weather/soil-temperature.html.  This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!

 

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