Effect of Spring Frost on Emerging Crops

Submitted by Anastasia Kubinec, Manitoba Agriculture

Originally posted May 8th and 30th, 2015…..re-post May 13, 2016 and now May 27, 2019.

Don’t assume because there is frost (or snow) on the ground, that your emerging crop in dead!

With the drop in temperatures in the past couple of days, there are a few things to keep in mind if the mercury dips below 0°C. The temperature is the instigator for causing frost, but whether it is -0.1°C or -4°C the damage inflicted is highly influenced on these other factors:

  1. Duration
    • Short 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 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 frost is 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 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

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.


Have a follow-up question?

Spring Options for Applying Nitrogen Fertilizer in 2017

With the wet conditions and delayed harvest experienced in parts of Manitoba in fall 2016, very few farmers were able to complete their fall fertilization program.  Since early seeding is important for optimizing crop yield, producers will be looking for ways to apply their N requirements efficiently without delaying the seeding operation.  In addition, soil reserves of N are variable and margins between crop revenue and input costs are modest; therefore, optimizing nitrogen fertilizer use efficiency is important.  To achieve these objectives for a spring fertilization program will require use of a 4R nutrient stewardship strategy:  applying the right rate of the right fertilizer source, with the right placement and at the right time to minimize losses of fertilizer N to the environment and optimize the crop’s access to the fertilizer.

For more detailed information, see the on-line factsheet at http://www.gov.mb.ca/agriculture/crops/seasonal-reports/pubs/spring-n-options-17.pdf

Submitted by John Heard, Crop Nutrition Specialist, MB Ag

Have a follow-up question?

Getting the Facts on Fusarium Head Blight

Fusarium head blight, or FHB, is a major disease that wheat and other cereal producers deal with each year to varying levels. The conditions in 2016 were conducive for infection in both winter and spring wheat as well as other cereal crops (symptoms were observed in both barley and oats). While 2016 was not the worse year on record for FHB in Manitoba (see post on FHB survey results), levels across the prairies were amongst the highest they have been in recent years.

Manitoba Agriculture has partnered with Alberta Agriculture and Forestry and the Saskatchewan Ministry of Agriculture to develop a Q & A series “Getting the Facts on Fusarium Head Blight”. This series will address FHB issues producers faced in the 2016 season as well as issues they are facing regarding infected seed. The answers provided will be a combined effort of the provincial disease specialists with input from researchers at Agriculture and Agri-Food Canada, the University of Saskatchewan, and the University of Manitoba.

If you have a question you would like to see addressed please submit via Crop Chatter or contact your provincial disease specialist.

Submitted by

Holly Derksen, Field Crop Pathologist, Manitoba Agriculture

Barbara Ziesman, Provincial Specialist, Plant Disease, Saskatchewan Ministry of Agriculture

Michael Harding, Research Scientist, Plant Pathology, Alberta Agriculture & Forestry

Have a follow-up question?

Canadian Grain Commission’s Harvest Sample Program


Photo Credit: Canadian Grain Commission

Mitchell Japp, the Provincial Cereal Crops Specialist with the Saskatchewan Ministry of Agriculture, recently wrote an article on the Canadian Grain Commission’s Harvest Sample Program – what it is, how to request a sample kit in order to submit a harvest sample, and getting results.  The complete article is available here: Harvest Sample Program.

The CGC is providing a valuable service to individual farmers and industry with the Harvest Sample Program, but it takes participation for it to work.  I would encourage Crop Chatter subscribers to click on the link and read Mitchell’s article!


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

For more information, visit the Canadian Grain Commission page.
Have a follow-up question?

Manitoba Insect & Disease Update – Issue 10: July 20, 2016

The Manitoba Insect and Disease Update is now posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-report-2016-07-20.html

Some highlights from the update:


  • Pea aphid levels are still a concern in some pea fields, although many fields will be getting to the stage where management would no longer be economical.
  • Aphid levels have dropped in many cereal fields where previously levels had been increasing. High levels of natural enemies have been noted in some of these fields, and some intense rains may have also contributed.
  • In some areas of Central and Southwest Manitoba, greater than 90% of the wheat midge are expected to have emerged. In many areas of Manitoba about 50 to 90% of wheat midge are expected to have emerged. A reminder that wheat that has already produced anthers is no longer susceptible to feeding by wheat midge. Even if adults are still active in these more advanced fields, the larvae will not feed on the grain.
  • Egg masses of European corn corer are starting to be noted in some fields of corn. So far there are no reports of high levels, but now is the time to be checking fields for the egg masses.

Figure 1. Egg masses of European corn borer.

Plant Pathogens:

  • Some infections of blackleg in canola and fusarium head blight in cereals have been reported.
  • A few cases of loose smut in barley were also reported.
  • Two positive identifications of Goss’s Wilt in corn were made. The positive identifications were made based on immunostrips and/or polymerase chain reaction (PCR) assays.

Submitted by: John Gavloski, Entomologist & Pratisara Bajracharya, Field Crop Pathologist, Manitoba Agriculture

Manitoba Agriculture website: www.manitoba.ca/agriculture
Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture


Have a follow-up question?

The Potential Impact of Spring Frost on Winter Wheat

With the forecasted cooler overnight temperatures, here is a refresher on the potential impact spring frost can have on winter wheat crops in Manitoba. (Hopefully, we won’t have a need for this post!).  Currently, winter wheat acres range in development from tillering to stem elongation.

For winter wheat at tillering stage, plants can withstand very low temperatures for a period of time (-11°C for less than 2 hours). Frost damaged winter wheat at this stage will have leaf chlorosis and necrotic leaf tips. However, the effect on yield will be slight.

For winter wheat at jointing stage (stem elongation), plants can tolerate temperatures of -4°C for less than 2 hours.  Frost injury symptoms could include a dead leaf appearing in the whorl if the growing point was damaged, leaf yellowing or burning, or splitting or bending of the lower stem.  The impact to yield can range from moderate to severe, and lodging can also occur later in the season if stems were damaged.

For winter wheat at the boot stage, plants can tolerate temperatures of -2°C for less than 2 hours.  Frost injury symptoms in winter wheat (or even fall rye) can include spikes being trapped inside the boot and they may not emerge normally, spikes may emerge but may remain yellow or even white (sometimes only portions of the head may be impacted), awns may be twisted and you may see floret sterility resulting in poor kernel set and low grain yield.

In 2012, we did see winter wheat crops impacted by frost.  A frost event occurred May 30 when some winter wheat acres were at the early flag emergence stage.  When the spikes started to emerge, injury symptoms were noted.  In the photo below (taken by Ingrid Kristjanson, MAFRD),  you will note frost injury symptoms of twisted awns and incomplete kernel set.

Frost damaged winter wheat - ingrid

Frost Damaged Winter Wheat; Frost was Recorded May 30 at Early Flag Leaf Stage (2012) – Photo by Ingrid Kristjanson, Manitoba Agriculture

In Manitoba Agriculture’s June 3, 2015 webinar (available on YouTube at http://youtu.be/UDa3uWMmZzg), I covered some of the basics of frost injury symptoms in winter cereal crops and what to look for in terms of recovery.

For more information on frost damage in winter cereals and other crop types, please refer to Manitoba Agriculture’s Spring Frost Damage Bulletin.

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

Have a follow-up question?

Will my early seeded wheat survive the forecasted cold snap?

With the forecasted cool temperatures, perhaps a quick refresher is needed for the potential impact on Manitoba’s spring cereal crops.

Spring cereals such as wheat, barley and oats are very tolerant to temperatures as low as -6°C since the growing point is below the soil surface until the 5 leaf stage to jointing.  In the May 21, 2015 NDSU Crop & Pest Report, Joel Ransom who is the Extension Agronomist for Cereal Crops, wrote there is “variation for tolerance between crops, however. In general terms for the cereals grown in ND (and provided they are at the same stage of development), tolerance to freezing temperatures can be ranked in the following order: winter rye (most tolerant to frost) > winter wheat > oats > barley > wheat > corn (least tolerant).”

Frost damaged spring cereals will have wilted, dark green and discolored leaves and will become necrotic at the leaf tips within 1 or 2 days after freezing. However, new leaf growth (normal green color) from the growing point should follow within 2-3 days. However, it can be upwards of 5 days if growing conditions remain cool after the frost event.

Fortunately, majority of emerged spring wheat, oats and barley acres in Manitoba are in the 1 to 3 leaf stages of development where the growing point is still below ground and therefore protected from the cool air temperatures.

For cereal acres that have recently been planted, but haven’t emerged, there is often concern cold and freezing temperatures can kill sprouted seed. In a 2015 article by Jochum Weirsma (University of Minnesota), he reports “literature has shown that sprouted wheat and young seedling will likely survive temperatures in the low twenties (20F = -6.7C).  A quick first check of the color of radicle (first root) and coleoptile (first leaf) is the first step: a white and firm radicle and coleoptile will indicate that the sprout is not damaged by frost after the seed has been allowed to thaw out. A second test to determine viability of seed is to dig up seed and bring it home, place it between moist paper towels, and keep it at room temperature.  If the seed is viable the sprouts should start to grow within 24 hours.”

And remember, temperature and crop type are only two factors that play a role in determining the impact of spring frosts – duration of temperatures, other weather conditions, soil moisture and residue cover can also have an impact.

More additional information on frost damage, refer to Manitoba Agriculture’s Spring Frost Damage Bulletin or the Crop Chatter post Effect of Spring Frost on Emerging Crops.

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

Have a follow-up question?

Safe Rates of Seed Placed Fertilizer – Cereals & Canola

A reminder that if seedbeds turn dry, the safety margin shrinks when applying seed placed fertilizer.  Seedburn can result from ammonia toxicity and/or salt content of fertilizers.

For nitrogen, our Soil Fertility Guide provided safe guidelines for seed placed urea on cereals and canola across a range of soil types and seed-fertilizer configurations.  With the increased popularity of narrow seed and fertilizer spreads with disk drills, the safe rates are reduced.  For example, safe urea rates for cereals vary from 10 to 25 lb N/ac going from sand to clay soil using disk openers on 6” row spacing.  These guidelines are for moist soil and should be reduced by 50% if seedbed moisture is lower when weather is hot and windy.

The safe rates of seed placed phosphorus depends on the crop, with cereals being quite tolerant compared to soybeans, dry beans and canola.  With a disk drill as described above, cereals can tolerate 50 to 60 lb P2O5/ac as mono ammonium phosphate while rates would be 20 lbs/ac for canola and less for beans.   If there greater seedbed utilization (i.e. narrower rows or a wider seedrow with less fertilizer concentration) rates could be more liberal.

More on these safe rates of fertilizer is posted on Manitoba Agriculture’s website at: http://www.gov.mb.ca/agriculture/crops/soil-fertility/print,safe-rates-of-seed-placed-phosphorus-for-manitoba–narrow-row-and-row-crops.html

Submitted by:  John Heard, Crop Nutrition Specialist, Manitoba Agriculture

Have a follow-up question?

Don’t Rely Solely on Your Grain Loss Monitor – Estimating Harvest Losses in Cereals

It is harvest time in Manitoba. Since final yields aren’t determined until the crop is in the bin, attention now has to be focused on the harvest operation. Grain loss at harvesting time is a direct loss of income. The more grain saved, the greater the returns. The following information comes from 2 articles: ‘Grain Harvest Losses’ by V. Hofman with edits by Dr. J Wiersma & T. Allrich (University of Minnesota) and ‘Estimating Harvest Loss’ by G. Carlson & D. Clay (South Dakota State University).

Grain harvest losses result from shattering of the standing grain, shattering during windrowing (swathing) or direct combining, picking up the swath with the combine, and threshing, separating and cleaning within the combine. Estimates of acceptable losses for small grains such as wheat, barley and oats are placed at 3% of total yield (total yield equals harvested yield plus harvest losses).

It is usually very difficult to reduce total losses below 1 to 2% so the operator must decide on the value of the crop, the cost of combining and the time available for combining or climate conditions. Some harvest loss is unavoidable in order to get harvesting done in the time available with an end goal of cleaned harvested grain.

Estimating Harvest Losses.  Advancements in engineering have greatly improved harvest operations. Combines have various types of monitoring equipment available, including grain loss monitors, to help alert the operator to any potential problems.  A grain loss monitor is a good guide in selecting travel speed for varying conditions such as size of windrow and moisture conditions. A grain loss monitor must be calibrated to provide an acceptable grain loss reading. If the combine is used on different crops, the monitors are not only useful in limiting maximum speeds and losses, but can be used to properly feed the combine for optimum capacity.

However, a grain loss monitor is not a substitute for careful machine adjustments and good old fashioned monitoring, i.e. getting out of the combine to estimate losses. Or even better, when your local retail agronomist comes out with cold beverages, put him/her to work to estimate harvest losses.

A simple and rough estimate of grain loss requires the use of a one-foot square frame. A rough estimate of how much grain is left behind in a harvested field can be done with a few simple steps:

  1. Pick a typical area of the field after the combine has passed.
  2. Place a 1 ft by 1 ft (inside dimension) box on the ground and count the kernels found within the box. To improve accuracy, three counts (one behind the left side of the header, one behind the centre of the combine, and one behind the right side of the combine) are better.
  3. A one (1) bushel per acre loss equates to 20 wheat kernels/ft2, 14 barley kernels/ft2 and 10 oat kernels/ft2. Keep in mind that this is a ‘fudge factor’ but for the purpose of rough field estimation is an adequate estimate. There are more accurate ways to estimate harvest losses which take into consideration the width of windrower cut and combine cylinder.

If losses are on the high end, some investigation is warranted to try and identify the source of loss.  Is the crop shattering prior to the arrival of the combine (do the above steps before harvest to determine this)? Are there header losses? Or are the losses due to less than perfect threshing/separation of grain within the combine?  Finding the answer may help to adjust the harvest operation and maximize the amount of grain going into the bin!

Good luck with Harvest 2015.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD


Have a follow-up question?

Thinking about Reseeding Cereals? Read this First.

I have been receiving a few calls on producers considering reseeding poor barley stands, or concerned about their cereal crops in general. So I thought I would take this chance to review some key points producers and agronomists should think about if considering reseeding their cereal acres. A lot of the information is derived from a great article by North Dakota State University staff titled “Replanting or Late Planting Crops” (Publication A-934; Revised). I have included some of that information and added Manitoba-specific data and comments.

Why are some cereal fields impacted? Many producers were able to start seeding their cereal crops early in 2015. However, slow and/or uneven emergence was noted in many fields due to cool soil temperatures, dry soil conditions (in some areas of the province) and below normal temperatures following emergence. The slow growth was further complicated by excessive rainfall, wind, snow and frost over May Long weekend, and then another frost event on May 30. Not only do these conditions bring with it concern for erratic crop emergence and poor plant stand establishment, it can also promote a number of seeding diseases and root rots.

The Main Question to Answer. At the end of the day, producers must try and answer the question “Will which result in greater net return – keeping the original stand or replanting to the same/different crop?”.

The final decision should be backed by sound agronomic and economic information as well as taking into consideration AgriInsurance coverage and contracts. Agronomic information to consider should include: level of injury, crop uniformity and overall plant health of the original stand, alternate crop choices if reseeding, and management practices related to crop growth and development for either the original stand or the replanted crop. Producers and their agronomists should accurately assess all these factors in order to make an informed decision. I realize that is a lot of information to gather. Perhaps it is easy to think of it in a few steps.

Step 1: Evaluate original crop stand and yield potential. The best possible evaluation of the surviving stand is needed because the critical yield comparison ultimately will be between the original stand versus the replanted stand with a later than optimum planting date.  Remember, you need to allow time for crop to recover from injury prior to assessing plant stands!

To accurately evaluate the existing stand, stand counts should be taken at random from several areas of the field. For more information read the article “Doing Plant Stand Counts in Your Cereals”: http://cropchatter.com/doing-plant-counts-in-your-cereals/.  Typically for cereals, minimum stand levels that should be considered acceptable before reseeding is done ranges from 8 to 14 plants per square foot (NDSU). During early growth stages, most cereal crops can sustain some stand loss without experiencing significant yield reduction due to increased tillering. Keep in mind barley and oats typically tiller more than spring wheat.

However, the minimum stands stated is assuming plant stands are relatively uniform in distribution; what can complicate this assessment is the damage in fields can be distributed randomly throughout the field.

In addition to the direct effect of stand reduction, indirect effects of crop injury, such as increased weed competition and increased disease potential, should be considered. Damaged crops usually grow slowly until they have recovered, which provides the potential for greater weed competition.

Step 2: Evaluate yield potential & agronomics of replanted crop options. Crops replanted later in the season almost always will yield less than those planted at an optimum time. Figure 1 shows the yield potential of various crop types as seeding moves into June in Manitoba.

Figure 1: Percent Average Yield from 2005-2013 for Manitoba Crops Planted in Week/Month as Reported to MASC


Not only yield potential should be considered however. A short growing season increases risk of damage by fall frost affecting both yield and quality of the replanted crop. Increased risk of high daytime temperatures can also affect crop development. For example, there is increased risk of the crop flowering when daytime temperatures are high which can increase probability of floret abortion.

Delayed seeding may also increase potential of yield loss due to disease and insects. MAFRD articles Crop Choices in a Late Planting Scenario and Mitigating Risks Associated with Delayed Seeding will provide additional information to producers.

Step 3: Determine Reseeding Costs. Comparison of the estimated yield of the original stand with expected yield of the replanted crop minus any costs associated with reseeding must be considered.

The decision to reseed ultimately must be made by comparing the economics of the original plant stand with that of a replanted crop. This can be subjective and each case must be considered individually in terms of time of year, alternate crop choices, previous herbicide use, crop economics, AgriInsurance coverage and contracts, and other related factors.  If a producer has AgriInsurance, it is recommended they contact their MASC agent prior to terminating a field and replanting.

Once again, I’d like to acknowledge information from NDSU’s article “Replanting or Late Planting Crops” (Publication A-934; Revised).

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist

Have a follow-up question?