Effect of Spring Frost on Emerging Crops

Submitted by Anastasia Kubinec, Manitoba Agriculture, Oilseeds Crop Specialist

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

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.


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Impact of Heavy Rains on Crops

Manitoba Agriculture has several factsheets on the impact of excess moisture on crop production.

For information on Seed And Seedling Survival In Flooded Conditions, please visit Manitoba Agriculture’s website at http://www.gov.mb.ca/agriculture/crops/production/seed-survival-flood-conditions.html.

Or download the following articles:

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

Managing Crops for Excess Water Stress– A detailed literature review by John Heard, Crop Nutrition Specialist, Manitoba Agriculture

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

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Top Winter Wheat Varieties in Manitoba – 2012

In 2012, there was 593,906 acres of commercial winter wheat seeded in Manitoba, as reported by producers for AgriInsurance purposes.

The variety CDC Falcon, at 68.0% of Manitoba’s commercial winter wheat acreage, was the most popular variety grown in Manitoba in 2012.  CDC Falcon has held the top spot in Manitoba since 2002.  Its popularity remains consistent in Manitoba due to its shorter stature, strong straw and good yield potential.  It was developed by the Plant Science Department, University of Saskatchewan and is distributed by SeCan.   CDC Falcon currently still belongs to the Canada Western Red Winter (CWRW) class but will transition to the Canada Western General Purpose (CWGP) class August 1, 2014.

Second spot goes to the variety CDC Buteo grown on 17.7% of Manitoba’s acreage.  CDC Buteo has held the second place spot since 2007 and this variety belongs to the CWRW class.  It was also developed by the Plant Science Department, University of Saskatchewan and is distributed by SeCan.

Third spot is held by CDC Ptarmigan at 4.2% of the acreage.  CDC Ptarmigan held the number four spot in 2011 and 2010.  This variety belongs to the CWGP class and is a soft white kernel type.  It was developed by the Plant Science Department, University of Saskatchewan and is distributed by Western Ag.

The varieties of McClintock (CWRW) and Peregrine (CWGP) round out the top 5 varieties grown in Manitoba in 2012.  The top 5 varieties were grown on 94.8% of winter wheat acres in Manitoba.

The remaining 5.2% of acres were seeded to 14 winter wheat varieties, including older varieties such as CDC Harrier, CDC Kestrel and CDC Raptor, and newer varieties such as Sunrise, Accipiter and Broadview.

With CDC Falcon still belonging to the CWRW class, CWRW varieties continue to be grown on a large percentage of acres in Manitoba.  In 2012, 88.8% of winter wheat acres were seeded to CWRW varieties as compared to 11.2% of acres that were seeded to CWGP varieties.  This may change substantially once CDC Falcon is moved from the CWRW class to the CWGP class as of August 1, 2014.

See attached figure illustrating the top winter wheat varieties grown in Manitoba in 2012:  Top Winter Wheat Varieties in Manitoba – 2012

Submitted by:  Pam de Rocquigny, MAFRI Cereal Crops Specialist

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