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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Waterhemp Now a Manitoba Weed

Can you identify the plants in the two pots below?

waterhemp-and-redroot-pigweed

The plants on the right are redroot pigweed (Amaranthus retroflexus); the plants on the left are waterhemp (Amaranthus tuberculatus).

Unfortunately, the need to distinguish between these closely related weed species has become a reality for Manitoba producers and agronomists since waterhemp was found in the province in the fall of 2016. Suspect plant specimen collected from a soybean field in the RM of Taché was verified as waterhemp by staff with the Agriculture and Agri-Food Canada Collection of Vascular plants in Ottawa.  Waterhemp occurs in neighbouring states and provinces, including Minnesota, North Dakota and Ontario.

Both species thrive in agricultural fields where they compete with crops for nutrients, moisture and light. Waterhemp has no hairs on its stem or leaves, which can be used to distinguish it from redroot pigweed when plants are small.  The lack of hairs give waterhemp leaves a ‘glossy’ look unlike that of the ‘dull’ green leaves of redroot pigweed.  Also, waterhemp leaves are lanceolate in shape (longer than they are wide) compared to the more ovate leaves of redroot pigweed.  Colour is not a reliable identifying characteristic since both species can be green, red or variations of the two colours.

Mature waterhemp plants tend to be more branched than redroot pigweed. And unlike redroot pigweed, which has male and female flowers on the same plant, waterhemp has separate male and female plants.  Waterhemp inflorescence are long, slender and vary in colour compared with the compact, prickly inflorescence of redroot pigweed.  Like most pigweeds, waterhemp is a prolific seed producer with up to a million seeds per plant (under ideal conditions).

Waterhemp populations resistant to group 2, group 9 (glyphosate) and group 2+9 exist throughout the US, including Minnesota and North Dakota, and in Ontario. Seed from one of the plants found in Manitoba have been sent to Ontario for resistance testing.

Information on waterhemp will be added to Manitoba Agriculture’s weeds webpage shortly (http://www.gov.mb.ca/agriculture/crops/weeds/) and will be included at the Weed Seedling Identification Day (hosted by the Manitoba Weed Supervisors Association).  Manitoba Agriculture staff will conduct a waterhemp surveillance program in and around the RM of Taché in 2017.

Additional information on waterhemp is available at: http://www.extension.purdue.edu/extmedia/BP/gwc-13.pdf (excluding herbicide recommendations).

waterhemp-tone-ag-consulting

Photo: Waterhemp in Manitoba, Tone Ag Consulting

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture

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ANNUAL OR WINTER ANNUAL?

Fall is the most effective time to manage certain weed species. The recommendations seem clear-cut:  winter annuals = fall herbicide application/tillage; annuals = no fall management.  But figuring out the life cycle of the weeds in your field this fall is the catch……

Bromes, cleavers, chickweed, night-flowering catchfly, narrow-leaved hawk’s-beard, shepherd’s-purse and stinkweed are all facultative winter annuals, meaning that they can germinate in either the fall or the spring depending on environmental conditions.  These weeds are often best managed in the fall, if populations warrant it.  In general, waiting until about this time of year maximizes fall-germinating flushes of winter annuals.  If using a herbicide, consider weed stage and the weather forecast, prior to application.

The problem is, given the right conditions – like the long falls and mild winters we’ve had the last few years –several of our annual weed species can also successfully overwinter:

Biennial wormwood – Despite its name, biennial wormwood behaves like an annual in agricultural fields.  When scouting, estimate the average growth stage of biennial wormwood populations in a field.  If the majority of the plants have already set seed, a fall herbicide application won’t help.  An application may be worthwhile only if there is a large flush of biennial wormwood that haven’t set seed and are less than ~3 inches tall.  Herbicide tank-mixes containing glyphosate + group 4 are more effective than glyphosate + group 2 on this weed.

Round-leaved mallow (RLM) – This annual weed can act as either a winter annual or a short-lived perennial, although it is more sensitive to freezing than our common winter annuals.  Mild winters in 2015 & 2016 provided the right conditions for RLM to overwinter, allowing it to become (even more) problematic in certain fields over the last few growing seasons.  Long range forecasters are predicting a harsh winter across the prairies this year, which should control RLM.  However, if you have little faith in forecasts and decide to apply a herbicide, glyphosate mixed with either Distinct or DyVel DSp has activity on this weed.

IMG_20150915_081215

Round-leaved mallow post-harvest


Stork’s bill –
Like biennial wormwood, stork’s bill tends to be predominantly an annual in Manitoba.  If this is a problem weed for you, scout affected fields to determine average weed stage.  Again, if most of your stork’s bill has set seed you’re better off working on a plan for next year.  Stork’s bill, especially larger plants, is relatively tolerant of many herbicides.  If you decide to apply a herbicide because of stork’s bill this fall, glyphosate + group 2 or glyphosate + group 2 + group 4 on weeds up to the 4 to 6 leaf stage is probably your best bet.

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture

Information on more weeds and their life cycles is available at: www.gov.mb.ca/agriculture/crops/weeds/
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Staging Cleavers

Herbicides work best when weeds are small. Period.  Exclamation mark.  You get the gist…

There’s perhaps no better example of this than cleavers. Take a quick flip through the Guide to Field Crop Protection and you’ll notice that most herbicides with activity on cleavers only guarantee control/suppression of this weed when applied between the 1 to 4 whorl stage. Although this staging is most common, application timing may be limited to as few as 2 whorls or extend up to the 8 whorl stage, depending on the product.  There are also herbicides that are somewhat ambiguous as to cleavers staging but research and experience have shown that, when it comes to herbicide application to cleavers, the smaller the better.

It makes sense then that a recent question on CropTalk Westman was: ‘How do you stage cleavers?’

Whorled leaves, one of cleavers most distinctive features, results in a herbicide application staging unique to this weed. Staging cleavers is similar to other weeds with a few simple tweaks:

  1. Find the main stem. Identifying the main stem is an important step in staging crops and weeds. But this is often easier said than done with cleavers because of its creeping habit and similar sized branches. If you can’t find the main stem, just be sure to pick the stem with the highest number of whorls present.
  2. Don’t count the cotyledons. Only the true leaves count when staging plants. The cotyledons of cleavers are oval to oblong with a notch at the tip and are easy to distinguish from the true leaves.
  3. Each whorl counts. Unlike most other weeds, cleavers have a whorled leaf arrangement, with each whorl having ~4 to 8 leaves (usually 6). In this case, simply count each whorl along the main stem rather than each leaf (see figure & example below).

staging cleavers figure

Actualy photo staging cleavesrs

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture 

Find the 2016 Guide to Field Crop Protection online: www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp
Register for CropTalk Westman 2016 Here
Register for Crop Talk Eastman 2016 Here

 

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GOT JIMSONWEED?

According to reports from across the Prairies, you’re not alone. In Manitoba, the weed has been found in fields from Swan River down through the south-central region.

Jimsonweed (Datura stramonium) is an annual broadleaf with white/off-white trumpet-like flowers on stalks that can grow over 5 feet tall. It reproduces by seed that is contained in spiny pods (see Figure 1). This weed isn’t new to the Province but it’s only occasionally a problem. Although seed contamination is being considered, it’s just as likely that warm temperatures and less competitive crop stands contributed to increased germination and establishment of existing weed seeds.

Jimsonweed seed pod

Jimsonweed seed pod

Recommendations for Control:

Crop Rotation: Jimsonweed is not overly vigorous, so rotating to competitive crops like cereals or canola will help with control. The weed tends to be a bigger issue in less competitive and later season crops, including corn and soybean.

Herbicides: Although Jimsonweed doesn’t show up on many product labels there are lots of pre- and post-emergent herbicides that should provide control including glyphosate, glufosinate and various group 2’s, 4’s 6’s, 14’s and 27’s (www.msu.edu/~zandstra/Weed-Chem/jimsonweed-Chem.htm**; 0= no activity, 1= good to excellent, 2= fair to good). **Only use labelled applications of herbicides registered by Health Canada.

Application timing: Like most weeds, herbicides are most effective on Jimsonweed when it’s small. Because it’s a later germinating weed, it might be ‘missed’ by early herbicide applications but be too large for some later herbicide applications.

Rouging or cutting: Hand-pulling or cutting Jimsonweed before it sets seed is also an option, depending on the number of plants and their distribution in the field. Seed growers may need to put this option into play this fall since Jimsonweed is a prohibited noxious weed seed under the Weed Seeds Order (http://laws-lois.justice.gc.ca/eng/regulations/SOR-2005-220/page-2.html#h-4). Jimsonweed seed can be similar in size to canola.

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, MAFRD

Visit MAFRD Crop webpage for more current topics: www.gov.mb.ca/agriculture/crops/seasonal-reports/current-crop-topics.html#agronomy

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Crop Biosecurity and the Roles We Play

Submitted by Anastasia Kubinec, MAFRD Oilseed Crop Specialist
Reduction of pest movement in crops, is good business for everyone involved.  Though producers are responsible for their operations, others working on agricultural lands have also have the responsibility to reduce pest movement, introduction or increase of pest populations (ex: weed, insect, disease, nematode, etc.), as these all can have long-term negative effects on farm productivity.
  • Assess risks associated with your operation for pest introduction and movement around farm.
  • Develop protocols to reduce the potential of pest introduction and spread between fields and properties.
  • Implement protocols and management practices in your operation.
  • Communicate with other groups working on your property about your protocols and expectations.

For Agricultural Retail, Custom Equipment Operators and Service Provider Industries

  • Develop and implement protocols that pertain to the activities and services you conduct on producers fields.
    • equipment cleaning between fields
    • avoid equipment traffic on fields during wet conditions
    • increased communication with clients on their expectations
  • Communicate and educate clients and industry about biosecurity and the threat that pest movement represents to Manitoba crop production.

For Energy, Construction, Water Management, Transportation Industry and Municipal Work on Agricultural Land

  • Develop and implement protocols to prevent pest movement and establishment to other fields and properties.  Protocols could include:
    • equipment cleaning between fields
    • avoid equipment traffic on fields during wet conditions
    • increased communication with clients on their expectations
  • Communicate and educate clients and industry about biosecurity and the threat that pest movement represents to Manitoba crop production.

For Private and Public Agronomists

  • Conduct field surveys for crop pests, publically reporting on current pest levels and the discovery of new pest.
  • Provide consultation, extension information and training on how to identify and control pests.
  • Educate the agriculture industry, oil industry and general public about biosecurity and the threat of pest introduction, multiplication and movement .
  • Educate agricultural retail industry, environmental companies, tile drainage/water management, custom applicators, petroleum, construction and transportation industries, and landscaping companies about equipment sanitation requirements and pest spread within and between fields and municipalities.

For Agricultural Researchers

  • Assess the risks associated with your activities for pest introduction and movement between fields where research is occurring.
  • Develop protocols to reduce the potential of pest introduction and spread between fields and properties
    • cleaning equipment between fields
    • training on non-target pest identification
  • Communicate with the producer cooperator or field station manager about their biosecurity expectations, discussing the management activities to be implemented.
    • Discuss protocols with staff so they understand the expectations.
  • Provide consultation, extension and training on pest identification and management with researchers, other government bodies, industry and producers.
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Options for Managing Drowned Out Spots

The following is from an article by Tom Peters, Extension Sugarbeet Agronomist with NDSU & U of MN, published in  North Dakota State University CROP & PEST REPORT July 10, 2014 Issue, with a Manitoba perspective by Pam de Rocquigny, Manitoba Agriculture Provincial Cereal Crops Specialist

If you take a drive across Manitoba, you’ll notice the impact of excessive moisture on crops.  Symptoms of excess moisture can include crop yellowing, hastened crop development such as premature bolting in canola, stunted growth, and in extreme cases crop death in drowned out areas.

What options do producers have to manage these drowned out spots?  Producers should continue to actively manage these areas of fields since they are a perfect environment for weeds to grow without crop competition and potentially will produce tremendous numbers of weed seeds. Left unattended, these spots could dramatically impact weed management strategies for future crops in future years.

So what options does a producer have? Some questions to consider are whether you can reach these spots with equipment such as a rotary mower or a sprayer and what will effectively control the weeds?

  • Mowing is a good option, but in all likelihood, affected areas in fields will need to be mowed on 10 to 14 day intervals to prevent weed seed production.
  • Spray the drowned-out areas of the fields as if you were managing a crop if you are still spraying the field for weeds (if the drowned out spots have dried enough for a sprayer pass of course). If you are spraying only the affected areas, be sure to consider the crop around the drowned out spots to prevent damage to the surviving crop.  And keep in mind any potential crop rotation restrictions to next year’s cropping plans with the product you are using.
  • A third possibility is to plant the drowned-out areas of the field to a cover crop such as a cereal, once again if the area is dry enough to allow a seeder to pass. Cover crops will use excess water in soils and will compete with weeds for light and thus may limit germination and emergence of weeds.
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What is Purslane Speedwell and How Do I Control It?

The following picture was received last week for identification. 

 photo

If you have seen this weed and not sure what it is, it is  purslane speedwell (Veronica peregrina L.).  It is a member of Figwort family (another weed from this family is yellow toadflax).

Purslane speedwell characteristics:

  • annual weed 
  • reproduces only by seed
  • Stems are erect and much branched at the base
  • stems have fleshy texture and fine sticky hairs
  • leaves also have fleshy texture
  • flowers are small 4 lobed and whitish in color
  • the plant flowers from mid-May to July 

 

Purslane speedwell has been found at some locations in Manitoba and more commonly in winter cereals. It is also found in gardens, lawns, roadsides and other non-agricultural areas.

 

Unfortunately there is not much information available to control this weed. The USDA Weed Control Compendium mentions poor control from the commonly used group 4 herbicides like 2,4-D, MCPA, Dicamba, etc. No information regarding the efficacy of glyphosate on this weed. The other tough to control weeds in the Figwort family include Dalmatian and yellow toadflax and common mullein.

 

Submitted by Nasir Shaikh, MAFRD Weed Specialist

Want to submit a picture – submit to [email protected]

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Warm Soil Means Fast Emergence….So Go Scout!

With most soil temperatures across Manitoba averaging over 10C, and the good soil moisture, crops planted are emerging quickly!

So, great news, but what this means is it is time to get out and start scouting!

Things to look for are:

  1. Emergence, plant stands, patterns in field – this can indicate if seeds planted evenly, but can also you could indicate early issues like cutworms, soil-borne disease and herbicide residue injury.
  2. Weeds species, numbers and size – if you crop is coming up this fast, so are the weeds!  Targetting the weeds when they are small and knowing the species so you can choose the right product and the right will really help with the control.  Make sure those little yield-robbbers don’t get to use the sun, moisture and fertilizer instead of your crop.
  3. Insects – cutworms were mentioned before, but more look more specifically for the damage on the plants if you can’t see the insect, as that can help with identification.  Are leaves clipped off leaves at or above the soil vs. chewed with ‘shot-gun’ hole marks in leaves.  Keep in mind the economic thresholds for control!
  4. Other funny stuff ?  Keep these in mind too when out scouting and mark down spots (or GPS tag) to monitor as the days go on to see how they progress, sometimes it takes a couple of days before things become obvious.  When in doubt give the Crops Knowledge Centre a call at 204-745-5663.

Submitted by: Anastasia Kubinec, Oilseed Crop Specialist, MAFRD Crops Knowledge Centre.

Resources:

MAFRD Guide to Crop Protection: http://www.gov.mb.ca/agriculture/crops/guides-and-publications/index.html#gfcp

Weed Identification: http://www.gov.mb.ca/agriculture/crops/weeds/

Insect Identification: http://www.gov.mb.ca/agriculture/crops/insects/index.html

 

 

 

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