Economics & Agronomics – Crop Management Decisions Need Both!

It’s an obvious statement to say successful farm management decisions need both agronomic and economic considerations. Farmers weigh out input cost versus the benefit to yield and quality of grain before making the decisions to buy and use new or additional products.

 Agronomy and economic crop management goes much beyond inputs. Consideration of crop rotation, Cost of Production, seeding date and weather indicators for disease all need to be considered. Within agronomic decisions there can be tools to estimate the economic impacts of different decisions. The ‘My Farm’, ‘Cost of Production’, ‘Canola Reseed Calculator’ and ‘Sclerotinia Treatment Decision Tool’ are all based on yield trends and agronomy to help make economic decisions easier.

See slideshow at

Submitted by Roy Arnott – Farm Business Management, Killarney and Anastasia Kubinec – Crops Branch, Carman.

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So we had a Frost on our Soybean, Now what?

The first step in accessing frost damage is asking how cold it was last night. A light frost of -1°C for short durations may clip off a few off the top leaves with no effect on yield. The concern begins when a killing frost at least -2°C occurs for an extended period of time. In this situation you will see frozen leaves and pods throughout the canopy.  This may cause quality issues and yield reduction if the crop has not reached full maturity.

See the latest MB Ag Weather latest frost map:

What growth stage are your beans at, see as a reference.

A killing frost at the R8 growth stage will see no yield or quality loss. The R8 stage is when the leaves have dropped off, all pods are brown, and seeds rattle within the pods when plants are shaken.

If however your beans are at the R7 growth stage, (which means one pod on the plant has reached its mature color), research has shown yield loss can range from 5-10 % dependent upon the severity of the frost. Quality issues in the way of green seed may also occur.

Finally, if your beans are at the R6 growth stage-(this is where pods containing a green seed that fills the pod cavity at one of the four uppermost nodes on main stem), yield losses can range from 20-30 %.  You will also have green seed issues which can also lead to marketing concerns.

There are a few areas in Manitoba where the beans are at the end of this R6 growth stage.  Most of the beans in Manitoba are at the R7-R8 growth stage. A light frost should not affect yield and quality for these beans. If beans were at the R6 growth stage and a hard frost occurred yield and quality losses would be noticeable.


Picture: Light frost damage on soybeans near Hamiota, 2016.

Photo from L.Grenkow, Manitoba Pulse Soybean Growers

Submitted by: Dennis Lange, Industry Development Specialist-Pulses, Manitoba Agriculture


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First ask yourself if you need to control the volunteer canola in your crop.  Research by Dr. Rob Gulden and graduate student Paul Gregoire at the University of Manitoba (U of M) showed that volunteer canola had little impact on soybean yield when there are less than:

  • 3 plants/m2 in solid seeded or narrow row soybean, or
  • 1.5 plants/m2 in wide row soybean.

Although economic thresholds (ET) such as these don’t consider seed return, this is generally not a concern for canola given it’s prevalence in our crop rotations.

If your volunteer canola populations exceed the ET, the U of M researchers also assessed the effectiveness of various post-emergent herbicides (Table 1).  Control of volunteer canola by the herbicides listed in table 1 are based on comparisons of treated research plots.  It’s unlikely that any of these options will provide full control of bolting or flowering volunteer canola.

Table 1: Ranking and application timing of volunteer canola herbicides in soybean

Vol Canola Control in Soybeans

*Will not control CLEARFIELD canola volunteers

**Registered in the Red River Valley only

Another consideration: use of these herbicides on larger volunteer canola may only set plants back, resulting in later flowering canola that may cause issues during soybean harvest.

Previous research by Dr. Gulden has shown that one of the best ways to manage volunteer canola is by limiting weed seedbank additions from canola harvest losses. Slower combine speeds while harvesting this year’s canola is a good way to reduce volunteer canola populations in future soybean stands.


Submitted by Dr. Jeanette Gaultier, Weed Specialist, Manitoba Agriculture

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‘Is my crop too stressed for herbicide application?’ has been a common question this week. As mentioned in an earlier post, recent wet weather has coincided with the window for post-emergent herbicide application in many crops.

The ability of a crop to ‘tolerate’ a herbicide application depends on its capability to metabolize or compartmentalize the active ingredient before it causes plant injury. This is the basis for herbicide selectivity.  Excess soil moisture reduces oxygen availability to the crop, which affects physiological processes like metabolism.  As such, water-stressed crops may not be able to effectively metabolize herbicides, resulting in crop injury.

What can you do reduce the risk of crop injury from herbicide application?

  • Check for new growth as an indicator that the crop has resumed physiological processes like photosynthesis and metabolism. If you don’t see any new growth in a stressed crop, wait 24 hours and re-assess.
  • Consider your herbicide choice. Some herbicides are more likely to result in injury to stressed crops than others. Group 2 herbicides, especially the more residual products, are an example. However, the risk of crop injury can also vary among chemistries within a herbicide group. For instance, pinoxaden may be a safer group 1 on stressed wheat than fenoxaprop.
  • What’s in your mix? Increasing the number of different products in your tank can overwhelm a stressed crop’s metabolic capabilities. Tank mixes that cause antagonism generally increase crop safety but also have decreased efficacy on weeds. Avoid using products that ‘heat up’ a tank mix, which can increase the risk of crop injury. Talk to your chem rep if you’re unsure; they may recommend different tank mixes or separate passes.
  • Wait until the end of the day. Applying herbicides in the evening can reduce their impact on a stressed crop, although research has shown that later-in-the-day herbicide applications can also be less efficacious. The trade off may be worth it since daytime temperatures over 27°C can add additional stress to the plants and can increase the activity of certain herbicides.
  • Check the forecast for rain. Trying to get a herbicide application on before a forecasted rain works for healthy crops but may not be the best strategy for stressed crops as addition rain may compound the problem. Besides additional stress, shallow, stressed crops roots can be impacted by herbicides moving into the root zone as well.
  • And finally, compare the risk of potential crop injury (i.e. how stressed is the crop, what proportion of the field is stressed, etc.) to the risk of yield loss due to weed pressure. If the stressed crop is limited to a few low spots in the field, it’s likely worth risking a few acres of injury to protect yield from weed competition. However, if most of the field is water-stressed, it might be worth moving on to a different field and returning after a day or two.

Submitted by Jeanette Gaultier (Weeds Specialist) and Ingrid Kristjanson (FPE Moris), Manitoba Agriculture.

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Wet field conditions across the province have many questioning the timeliness of their post-emergent herbicide application. Unfortunately, options are limited.  The stage of the crop and/or weeds dictate whether you  1) spray now and deal with the ruts later, or 2) hold off a few days in hopes of dryer weather.

Consider the following when prioritizing fields for herbicide application:

  • Crop and weed stage are critical. Applying herbicide(s) outside of the crop and/or weed stage indicated on the product label can result in crop injury and decreased herbicide efficacy. Be sure to check the condition of your crop before spraying, since stressed crops may be more susceptible to herbicide injury. The window for in-crop herbicide application varies by product and crop. Crops with relatively few herbicide options, like field peas, may have a small window of opportunity.
  • Crop competitiveness. The critical weed-free period indicates when and for how a crop needs to be kept weed-free to minimize yield loss. In general, the more competitive the crop, the shorter the critical weed free period. Therefore, your pre-seed burnoff, pre-plant or pre-emergent herbicide application may carry you further with competitive crops (e.g. cereals) compared to crops like soybean, corn or flax.
Picture3*Current University of Manitoba/Manitoba Pulse & Soybean Growers project to refine the critical weed-free period for soybean grown in MB.

  • Economic thresholds (ET). Thresholds can help determine if you need to apply an in-crop herbicide based on the density of a particular weed. For example, 6 to 16 plants/m2 of wild oat can result in less than 5% yield loss in spring wheat (actual ET depends on weed and crop staging; refer to page38 of the 2016 Guide to Field Crop Protection). Similar ETs exist for select grassy weeds in wheat, barley, canola, and flax, for kochia and biennial wormwood in sunflower and for volunteer canola in soybean (see below). The downside to weed ETs is that they are species specific and they don’t consider weed seed return to the weed seedbank.


A few other spray tips:

  • Don’t ‘save time’ by skimping on sprayer clean. Refer to the product label & page 15 of the Guide to Field Crop Protection for clean out instructions.
  • Check out SPRAYcast ( for a 3-day forecast of optimal spray times.

Happy herbiciding!

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

2016 Guide to Field Crop Protection:


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Manitoba Insect & Disease Update – May 18, 2016

  • Flea beetles are active and feeding on volunteer canola
  • Inquiries on soil borne insects and if they are feeding on crops,
    • Cutworms
    • Wireworms
    • Others insects that would not damage crops
Plant Pathogens: None of concern yet, scout as crops are emerging
Compiled by:
John Gavloski, Entomologist,  Phone: (204) 745-5668
Pratisara Bajracharya, Field Crop Pathologist, Phone: (204) 750-4248
To report observations on insects or plant pathogens that may be of interest or importance to farmers and agronomists in Manitoba, please send messages to the above contacts.
To be placed on an E-mail list so you will be notified immediately when new Manitoba Insect and Disease Updates are posted, please contact John Gavloski at the address or numbers listed above.
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Spring Frost or Late Snow and Emerged Canola – Time to Re-Seed?

Temperature is the instigator for causing frost, but damage inflicted and need to re-seed canola is highly influenced on these other factors:

  1. Duration
    • Short but LIGHT frost = < 2 hours,  may not cause much damage if frost is light (above -1 to -2°C), crop type and staging is tolerant, conditions wet and crop has become acclimatized.
    • Short and HARD frost = < 2 hours, but hard frost (lower than -2°C), crops like canola are more sensitive to longer frost vs. cereals, damage can be variable in field and across area.
    • Long frost = > 2 hours, whether light or hard the longer the negative temperatures the more time for damage to happen.  Tolerance by crop type varies.
  2. Other Environmental Conditions
    • Cloudy and wet – prior to a frost, cool temperatures slow plant growth and ‘hardens’ plants off, which will help them tolerate a frost.  Also wet soil helps buffer the cold air effects on the plants, as wet soils change temperature slower than dry soils.
    • Sunny and dry – The combination of a  dramatic drop in air temperatures when plants are actively growing then a brilliant sunny day after the frost event is where we have seen the most damage.  Scouting after the frost (24 and 48 hours) is very important though to assess extent and percentage of field injury.
    • Field trash cover – increased trash in fields was seen to increase frost damage on very susceptible crops in the 2009 June and May 30, 2015 frost
  3. Crop Type
    • Spring Cereals – more tolerant than other crops types, can tolerant to temperatures as low as -6°C as growing point below ground until the 5 leaf stage.
    • Winter Wheat – can withstand very low temperatures for a short period of time (-11°C for less than 2 hours) up until the tillering stage.
    • Corn – smaller then V5, will recover from light frost as growing point below ground. Leaves probably will be killed, but plants will recover if the growing point ok.
    • Oilseeds – environmental conditions impact frost severity on susceptible canola and flax cotyledons. Resiliency increases at the 3-4 leaf stage (canola) or 2nd whorl (flax).  Sunflowers are fairly tolerant  up to the V4 stage.
    • Pulses – peas are most tolerant, then soybean, edibles bean are very susceptible even before emergence.   Field pea crops are rarely lost to frost. Soybean are more sensitive, but the smaller the soybean plant the more tolerant they are  – from emergence to cotyledon can withstand short light frosts.

Scouting After a Frost (or Snow event)

Scouting should start 24 – 48 hours after the frost and continue for the 5 days following the frost event.  Look for leaves wilting, looking “water-soaked” or see “frost banding”.  Watch for new growth in the plant.  You do not want to see plants wilted and not perking back up or pinching off on the stem near the growing point (canola, flax, soybeans).  Also assess the area affected by frost, small areas or a few plants damaged are ok, as other plants emerged (or just emerging) will fill in those spaces.  Large dead areas may need to be re-seeded.

If in doubt of what look for, call your local agronomists, local FPE Specialist with Manitoba Agriculture or the Crop Industry Branch.

For more specific details on what actually occurs to plants with a frost and crop specific details and symptoms to look for (and how long after a frost to do assessment) see Manitoba Agriculture’s Spring Frost Damage Bulletin.

NEW RE-SEED Calculator developed by Manitoba Agriculture using historic data from MASC is another tool to help determine if re-seeding is finanacially the right decision, depending on plant stands and time of year see calculator at:

Submitted by Anastasia Kubinec, Manitoba Agriculture, Oilseeds Crop Specialist

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Soil Fumigants and Licensing for Application

Soil fumigants are pesticides that form a gas when applied to soil. Due to the toxicity of soil fumigants and the potential for gases to move from the soil to the air, soil fumigants are classified as restricted use pesticides.

Requirements for the use of soil fumigants include:
  • Soil fumigation license
  • A Fumigation Management Plan (FMP) for all soil fumigation applications
  • Mandatory Good Agricultural Practices (GAPs)
  • Notification of Application
  • Restrictions for workers re-entering treated areas
  • Buffer zones

Steps to obtaining a soil fumigation licence:

  1. Complete the Application for Pesticide Certification
  2. Write the exam
  3. Obtain general liability and pesticide drift insurance
  4. Apply for a licence

For more information on soil fumigation certification and licensing see and/or contact:

Anne Kirk, Pesticide Minor Use and Regulatory, Manitoba Agriculture
Phone: (204) 745-5663 , Email: [email protected]

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QU: Should I Be Worried About Stored Canola and Flax Spoiling on a 31C Day in May

Excellent question that we usually do not have to think about in early May!

As most grain is still cold in the bin and with the rapid increase in outside temperature, the potential for spoilage could still occur in stored canola and flax still in the bin from 2015 harvest.

If you think this might be an issues, check what is the seed moisture and the temperature is again. The 5C, 8.5% moisture canola in March had no risk of spoilage, but a 35C, 8.5% moisture canola does.  Flax is susceptible to spoilage as well, if the grain gets very warm in the bin and the moisture is over 8%.   If things are all good today, check in a couple of days again if the May heat wave continues and consider turning on the aeration fan and open up the bin hatch at the top of the bin to let humidity escape.

This question came in as a concern over the potential of condensation to form on the bin walls from the hot outside air hitting the cold grain in the bin.  Aeration could be used as a tool with the hot, but very dry air to warm the grain slowly and move some of the potential humidity out through the top vent or hatch.  Monitoring though is key and should continue until the grain is delivered to catch spoilage issues. A great resource on more about aeration and grain in storage can be found on the PAMI (Prairie Agricultural Machinery Institute) website and at the Canadian Grains Commission

Safe storage chart for canola and flax

Submitted by Anastasia Kubinec, Oilseed Crop Specialist, Manitoba Agriculture

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Understanding the 2015 Western Manitoba Soybean Adaptation Trial Table

The Western Manitoba Soybean Adaptation Trial table combines elements of both long term data and single site year data.

You start by using the long term data listed on the left half of the table to assemble a short list of varieties. Information includes Company Maturity Grouping, Variety Name, Yield % Check, Site Years Tested and Relative Days to Maturity +/- of Check. As you go down the table you will see that varieties are listed from earliest maturing near the top to later maturing near the bottom based on Relative Days to Maturity +/- of Check (23-10RY).  The Yield % Check and Site Years Tested should be used together when comparing the varieties.  The Site Years Tested represents the total number of locations a particular variety has been tested and the Yield % Check represents the yields of those varieties based on the number locations tested.

The right half of the table includes the 2015 Yield % of 23-10RY for five individual Western Manitoba sites and can help you refine your variety short list.  To assess real yield differences between any two varieties within a location using this table, start by looking at the LSD% at the bottom of the table. The LSD (Least Significant Difference) is the minimum difference required between any two varieties compared at the same site. For example, the LSD% for the Boissevain is 9% and yield for the check variety (23-10RY) has been set at 100%. Only varieties that yielded 109% or greater would be considered higher yielding than the check and only varieties that yielded 91% or less would be considered lower yielding than the check. Any other varieties are considered to be yielding the same as the check. We are not restricted to only comparisons with the check variety when using this single site year data.  Yield comparisons can be made between any two varieties at the same site using the LSD% for that site.  Caution should used when making variety decisions based on one year’s data. Using the long term data listed on the left half of the table will give you a better feel for how a variety performs over multiple site years.

Submitted by Dennis Lange, FPE Altona and Terry Buss, FPE Beausejour

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