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:

Southwest/Northwest Regions:

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

Central/Easter/Interlake:  Southwest/Northwest:

Another useful application of the data gathered by the network for rainfall can be found at Rain Watch



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Moving Beyond Purpling Leaves to Necrosis

There are reports coming from the Northwest Region of Manitoba (Grandview, Dauphin, Ste. Rose) where flag leaves on some wheat plants are turning a purple color, then bronze, and then becomes necrotic. In severe cases, the flag leaf has dropped off entirely.  Tissue samples have been sent into various labs with the diagnosis being physiological.  The good news is all the remaining leaves under the flag are in perfect condition

In an earlier post on Crop Chatter – Seeing Purpling Leaves in Wheat? – we reviewed the basics of why we see purpling plants.  However, in previous years we have seen that in severe cases, the flag leaf has become necrotic and sometimes dropped off, much like what is being reported in the Northwest.  Unfortunately, since it is physiological in nature, there isn’t much to be done. 

Of course, the next question is what will be the impact to yield if the flag leaf has become necrotic and/or dropped off.  In previous years when this has occurred, we haven’t heard any news of a significant yield reduction, which is good news.  However, we don’t have any firm data to say either way.   Everyone knows the importance of the flag leaf in yield determination, so one would expect there would be some impact. 

If we use the following table illustrating yield loss due to impact of rust on the flag leaf, we can see that the greater impact to yield occurs at flowering and when majority of the flag leaf is impacted.  As the crop matures the importance of the flag leaf diminishes as yield has largely been determined (with the exception of some kernel weight added during the grain filling process). This table is only a guideline however as yield loss is only estimated and growing conditions the remainder of the growing season will shape final yield.  As previously mentioned, all the remaining leaves on the affected plants are in perfect condition which will help with grain filling for the rest of the season.

Special thanks to Kathy for reporting what is happening in the Northwest Region!

Submitted by:  Pam de Rocquigny, MAFRI Cereal Crops Specialist

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Seeing Purpling Leaves / Stems in Wheat?

At a recent field tour, I was asked to explain why a particular spring wheat plant had a purple stem.

Over the past few years, Manitoba Agriculture’s Crop Diagnostic Lab and the Crop Industry Branch has received samples of wheat plants with a distinct purple coloration on its stems and in other cases, the leaves as well.  Similar symptoms were first reported in 2009 on leaves of KANE wheat (see photo below).  Since 2009, this purpling has been seen sporadically, usually on the leaves, and not only in KANE but also in the varieties of Unity VB, Glenn, AC Barrie, WR859 CL and Carberry.

Purpling of Leaves – cvr KANE
Photo taken by: A. Sirski (2009)

So what is the purpling?  Essentially it is a physiological response of the plant to abnormal stress conditions, such as low temperatures, drought, or a combination of hot and humid weather. Under stressful growing conditions, sugars can build up in the plant.  Within these sugars, there are purple anthocyanin pigments which then produces the color change.

It is also possible other plant parts such as stems (see photo below) and glumes can exhibit this purple coloration and in these cases it is called melanism (see Melanism in Wheat).

Purpling of Stems in Spring Wheat (2016) cropped

Purple Stems in Spring Wheat at MCVET Portage Site (Photo by P. de Rocquigny, 2016)

Purpling of leaves or melanism may be more prevalent in certain varieties as anthocyanin production can be a genetic.  It has been noted in literature the American varieties Amidon and Butte has exhibited this purpling.  Amidon is a parent of the variety McKenzie, which is a parent of KANE.  So this stress response of KANE that we starting seeing in 2009 and 2010 may be traceable back to Amidon.

Is there any impact to yield?  In the United States and here in Manitoba, this purpling has not caused any noticeable yield losses. However, keep in mind there could be other explanations to the color change.  If you think there could be more going on than just a physiological plant response, rule out phosphorous deficiency and viral diseases such as barley yellow dwarf that could also cause purpling of leaves or stems.

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

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Seeing Leaf Tip Burn in Your Cereal Fields?

Manitoba Agriculture’s Crop Diagnostic Lab receives several spring wheat samples over the growing season.

This post is from June 2013 where the lab had received samples showing symptoms where leaf tips are yellowing and necrotic.  Rejean Picard with Manitoba Agriculture in Somerset, submitted this photo from a field in his area.  He noted the symptoms appeared with the warmer temperatures and was evident in localized areas of several fields.

Leaf Tip Burn/Necrosis in Wheat
Photo by Rejean Picard, Manitoba Agriculture, Somerset

Mardi Desjardins, the former Crop Diagnostic Specialist, had seen similar symptoms in previous seasons when environmental conditions have caused rapid moisture loss from the leaves, i.e. windy weather combined with warm/hot temperatures.   The result is leaf tip burn or necrosis.

Wind and/or high temperature can result in injury of leaf tips of small grains
Credit: Photo Library of Manitoba Agriculture’s Crop Diagnostic Lab Reports (2009)

Note that leaf tip burn caused by wind and/or hot temperature injury can appear similar to the damage of contact herbicides, fungal diseases, viral diseases (BYDV), foliar fertilizer burn or soil salinity.  However, with wind and/or hot temperatures, damage is often limited to the newest, just emerging, leaf tips.  Back in 2013, most reports in Manitoba indicated symptoms were on the flag leaf, with one case where symptoms also appeared on the penultimate leaf.

In the United States, the severity of leaf tip necrosis has been noted to be dependent on both the growing conditions during flag leaf emergence and the variety.

Unfortunately, there is little information reported in the literature whether this type of damage causes any yield losses.

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

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Assessing Crops After Heavy Rains

Compiled by the Staff at Crop Industry Branch, Manitoba Agriculture

Some areas of Manitoba received heavy rainfall recently, resulting in the question “What is the extent of crop damage from the heavy rains?”  There is no quick answer unfortunately.  Field by field assessments over the coming days will give a better idea of what impact the rains had on crop development and plant stands. The following link can provide an idea of what is potentially occurring and how to monitor fields to assess for damage and recovery.

What is the Extent of Crop Damage from the Heavy Rains – Updated May 2016


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Avoid Herbicide Injury in 2013

Cool periods in May and June 2012 played havoc with some herbicide applications, leading to injury in normally tolerant crops.  Examples from last season include group 1, 2 and/or 4 injury in wheat and barley and group 2, 9 and/or 10 injury in canola. 

Crop tolerance to certain herbicides or herbicide groups allows for selective, post-emergent weed control.  Tolerance is achieved by metabolism or deactivation of herbicide molecules within the plant.  The process of deactivation requires that plants are actively growing and not stressed.

All crops have a minimum temperature above which plants are able to carry out normal functions for growth (e.g. photosynthesis, metabolism, etc.).  This temperature is often referred to as ‘base temperature’ and is used to calculate heat unit accumulation (e.g. GDDs) for individual crops (Table 1).  Base temperature is not the same as freezing point.

Table 1. Base Temperatures for Select Manitoba Crops

Crop Base Temperature (°C)*
Canola 0 – 5
Cereals 0 – 4.5
Corn 6 – 10
Flax 4
Potato 5 – 7
Soybean, beans 5 – 8
Sunflower 5 – 8

It’s important to note that, while we use common base temperatures for certain crops, actual base temperature depends on crop variety, growth stage and cold-hardening.

Given the above, herbicides should be applied when day time temperature is ≥ 10°C to ensure optimal crop tolerance.  This will also result in better weed control.  MAFRI also recommends producers:

  • Aim for day time temperatures of ≥ 10°C on the day of application and for 2 days after application
  • Apply herbicides earlier in the day if night time temperature is expected to be below 10°C
  • Refer to the product label for specific instructions regarding herbicide application and environmental conditions

Submitted by:  Jeanette Gaultier, MAFRI Pesticides – Minor Use & Regulatory Specialist

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