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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How Many Days Until My Grain Corn Reaches Maturity?

The 2016 season has seen normal to above normal accumulation of corn heat units (CHU), with a range of 95 to 117% of normal from May 1st to August 14th: Percent of Normal Accumulated Corn Heat Units. So as we inch closer to September, producers start to wonder when their grain corn may reach physiological maturity (R6).  At this stage, kernels have reached maximum dry matter accumulation and kernel moisture can range between 30 to 35% (but can vary by hybrid and environment).  But more importantly, at physiological maturity the grain corn crop will be safe from a killing frost.

The following table was modified slightly from the original table found in NDSU’s Crop & Pest Report August 8, 2013.  The table relates calendar days to corn kernel development and yield in general terms.

Table 1: Relationship between corn growth stages and calendar days to maturity, yield loss, and other kernel characteristics

Days to Maturity Grain Corn

Source: NDSU Crop & Pest Report – August 8, 2013

The ranges listed are fairly large in order to take into account variances in temperature (climate) and the relative maturities of the hybrids grown (genetics).   It is also important to remember that the various plant stages and the duration of those stages can also be influenced by soil fertility, cultural practices (plant populations) and water availability (dry conditions can hasten maturity).

Source:  NDSU Crop & Pest Report August 8, 2013

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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Why am I seeing Tillers in my Corn?

I have been receiving a few calls over the season regarding tillering in corn. So I figured a Crop Chatter post based on an article I wrote back in 2005 would be good to answer some questions. Is it only due to plant populations? What could be other causes? What effect will tillering have on crop growth and yield potential?

What are Tillers? And What Causes Them?  Tillers are lateral branches that form at below ground nodes. Although tiller buds form at each below ground node, the number of tillers that develop is determined by plant population and spacing, soil fertility, early season growing conditions, and the genetic background of the hybrid.

  • Plant Population: Many hybrids will take advantage of available soil nutrients and moisture by forming one or more tillers where stands are thin in the row or at the ends of rows. However, excessive tillering may indicate problems with stand density and distribution. If tillering is associated with row gaps and less than optimal plant populations, these are the conditions which need to be corrected to ensure optimal yields.
  • Soil Fertility: Tillers are most likely to develop when soil fertility and moisture supplies are ample during the first few weeks of the growing season. They are usually visible by the 6-leaf stage of development.
  • Genetics: Hybrids with a strong tillering trait may form one or more tillers on every plant even at relatively high populations if the environment is favorable early in the growing season. If a particular hybrid shows excellent yield potential and also produces extensive tillering under some growing conditions, it should not be avoided.
  • Weather Conditions: Hail, frost, and flooding injury that destroy or damage the growing point early in the growing season can also result in tiller development and non-productive plants.

What is the Effect on Yield Potential? When farmers see extensive tillering in their corn hybrids, they often express concern that the tillering will have a detrimental effect of crop performance (that the tillers will “suck” nutrients from the main plant and thereby reduce yields). As a result, tillers are often referred to a “suckers”. However, research has shown that tillers usually have little influence on grain yields and what effects they do have are generally beneficial. Recent studies have found that there is little movement of plant sugars between the main plant and tillers before tasselling.

After silking and during grain fill, substantial amounts of plant sugars may move from earless tillers to ears on the main plant. When there are ears on both the tiller (often called ‘tassel-ears’) and the main plant, little movement of plant sugars occurs. The main plant and tillers act independently, each receiving sugars from their own leaves. The ‘tassel-ears’ that tillers may produce, therefore have no impact on the ear development of the main plant as was once thought and don’t contribute to yield.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, 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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Seeing Tall Plants in Your Semi-Dwarf Wheat?

Originally published July 24, 2015

If the differences in height are sporadic throughout the field, i.e. the odd plant here and there, it is probably one of three things causing these ‘tall-types’:

  1. a result if seed of another variety was inadvertently comingled with the variety you think you have (through cleaning of equipment, bins, harvest, etc.).
  2. a variety that is segregating for plant height – is less common but in extreme growing conditions can bring differences in plant height that previously had gone unnoticed.
  3. with introduction of semi-dwarf genes (Rht1), it’s been noticed that in certain lines and genetic backgrounds a number of tall plants would appear at a low frequency from one generation to the next generation.  Fancy terms is some plants become aneuploids, meaning individual progeny has one or more chromosome missing or extra.  Monosomic deletions, i.e. plants missing one chromosome, are most commonly encountered. Because Rht1 act as a suppressor of height, their reduced dosage as in monosomics, produces plants taller than in the euploid condition.If seed is saved, half the plants derived from these tall-types should revert back to the original variety, while the other half of the plants will be the taller-types again.

There is a very good article in the 2015 Saskatchewan Seed Guide (page 20) further explaining these ‘tall types’ in semi-dwarf wheat:

Submitted by: Pam de Rocquigny, Provincial Cereal Crops 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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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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Historically, what has been seeding progress prior to May 1st?

Some producers have started their 2016 seeding operations, with spring wheat being seeded and from what I’ve heard a few acres of corn as well.  With some seeding done, I’ve been asked the question: “What has been seeding progress prior to May 1st in Manitoba in recent years?”.

Producers who participate in AgriInsurance provides seeding date information to Manitoba Agricultural Services Corporation (MASC).  This dataset provides us a historical perspective of when seeding has taken place in the past.

In Table 1, cumulative seeding progress prior to May 1st for six crop types is provided.  A five year (2010-2014) average cumulative seeding progress is noted, along with what was seeded prior to May 1st in 2015. Please note that data is for final insured crop in the ground.

Table 1:  Seeding progress in Manitoba prior to May 1st.

Historical Planting Progress prior to May 1st

Data Source:  Manitoba Agricultural Services Corporation (MASC)

What the table doesn’t show is the wide range of seeding progress prior to May 1st over the past few years.  If we look at seeding progress for red spring wheat in Manitoba, we’ve seen less than 1% of acres seeded prior to May 1st (2009, 2011, 2013 and 2014) but as many as 65% of acres (2010) planted in April.

Look for future updates to historical seeding progress as we enter May!

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Follow Manitoba Agriculture on Twitter (@MBGovAg) to receive updates on seeding progress through the weekly Manitoba Crop Report.
The weekly crop report is also available at Manitoba Crop Report.


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Fall Fertilizer Decisions Based on Soil Temperatures



Growers should be monitoring soil temperatures to guide fall nitrogen management.  Provincial weather station soil temperatures are posted at:

The principle of fall fertilization is generally to delay applications until soils have cooled so microbial activity is curtailed.  That way less of the stable ammonium form-N (NH4+,) that is held on clay and OM, is converted to nitrate (NO3-) which can leach or denitrify.

The rate of nitrification of banded N to nitrate is illustrated in the following table from


Table 1. Nitrification rates of ammonia to nitrate form-N from banded urea (calculated from Tiessen et al, 20031).

Average soil temperature at band depth Days for 50% conversion to nitrate Days for 100% conversion to nitrate
1 oC

5 oC

10 oC

15 oC

20 oC












So as soils cool and eventually freeze, the microbial activity is reduced such that ammonium-N is retained in its stable form.  If one chooses to apply nitrogen before Mother Nature provides cool soil – they may consider using one of several enhanced efficiency fertilizers – N-Serve, eNtrench, ESN or SuperU. 

Submitted by: John Heard, Soil Fertility Specialist

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