Widespread frost was reported across much of Saskatchewan (other than the southwest) and western Manitoba this morning. However, growers should not consider swathing canola until a field assessment can be done.
The amount of frost damage is dependent on various factors including crop stage, degree and length of frost, relative humidity, and presence of rain or dew.
To determine when to swath after a frost, check the extent of damage 2-3 days after the frost. Frost damage will be evident on the outside of the pods, which will often show a white, speckled appearance (caused by ruptured cell walls leaking fluid). Immature and watery seeds will start to leak their inner fluid, and begin to shrivel. The outside of the seeds will begin to turn dark green, instead of a light-medium green. If the majority of the seeds remain turgid, delay swathing to allow for further seed maturity. If the pods are severely damaged and are beginning to desiccate, swath during periods of dew or high humidity to reduce the amount of pod shelling and pod drop.
Severe frost after flowering can result in significant yield reductions and grade loss. The amount of fall frost damage to canola depends on its stage of maturity. Dry, mature seeds can be frozen with little or no effect on seed quality and viability. However, seeds with moisture content of 20% or more will suffer frost injury. Generally, the higher the seed moisture content, the greater the chance of frost injury. A frost of –3°C is enough to kill immature seeds containing 50 to 60% moisture while those with less than 20% moisture will normally escape damage. Frost does not damage all seeds to the same degree since the canola plant flowers progressively from the lower to the upper parts of stems.
Frost that results in green seed is the major cause of downgrading in canola. Green seed occurs due to a failure of the seed to complete the normal chemical processes involved in "degreening." Even a light frost can fix the green colour, preventing additional chlorophyll clearing, regardless of how favourable the following weather conditions. Sub-lethal frosts from 0 to 1°C can disrupt the biological enzyme system that breaks down chlorophyll in seed nearing maturity. Frost damaged seed dries down or desiccates very rapidly. Once seed moisture content is down to about 20%, the biochemical activities within the seed have slowed to a very low level so that little or no further enzyme chlorophyll clearing can take place.
Growers considering swathing early to avoid damage from future frosts need to remember that swathing should be done at least 2-3 days (depending on temperature) before the anticipated frost. This will allow the seeds to dry down and raise their solute level sufficiently, and be less likely to be damaged.
Direct questions regarding this overall report
to John Mayko, Agronomic Research & Extension
Manager with the Canola Council of Canada at maykoj@canola-council.org
or ph/fax: 780-764-2593.
For specific questions regarding
regional issues associated with this report, consult
one of the following Canola Council of Canada
regional agronomists or provincial oilseed specialists;
For specific questions regarding regional issues associated with this report, please consult one of the following Canola Council of Canada regional agronomists or provincial oilseed specialists;
Derwyn Hammond, Agronomist,
Manitoba,
hammondd@canola-council.org,
204-729-9011
Rob Park, Manitoba Agriculture
& Food,
rpark@gov.mb.ca,
204-745-5665
David Vanthuyne, Agronomist,
Eastern Saskatchewan,
vanthuyd@canola-council.org,
306-782-7799
David Blais, Agronomist, Western
Saskatchewan,
blaisd@canola-council.org,
306-895-2122
Jim Bessel, Senior Agronomist,
Northeastern Saskatchewan,
besselj@canola-council.org,
306-373-6771
Bill Greuel, Saskatchewan Agriculture,
Food & Rural Revitalization,
wgreuel@agr.gov.sk.ca,
306-787-2756
Doug Moisey, Agronomist, Central
Alberta,
moiseyd@canola-council.org,
780-645-3624
Christine Mardell, Agronomist,
Peace River Region,
mardellc@canola-council.org,
780-518-1513
Nancy Muchka-Dahl, Agronomist,
Southern Alberta,
muchkan@canola-council.org,,
403-625-3406
Murray Hartman, Alberta Agriculture,
Food & Rural Development,
murray.hartman@gov.ab.ca,
403-782-8024
Kerry Clark, BC Ministry of
Agriculture, Food & Fisheries,
Kerry.Clark@gems9.gov.bc.ca,
250-787-3213
The Canola Watch Report provides just-in-time information on canola production to growers and industry. Contributors to the Canola Agronomy Network are: Manitoba Agriculture & Food; Manitoba Canola Growers Association; Agricore United; Cargill; Saskatchewan Wheat Pool; United Farmers of Alberta; Saskatchewan Agriculture, Food & Rural Revitalization; Saskatchewan Canola Growers Association; Saskatchewan Canola Development Commission; Alberta Agriculture, Food & Rural Development; Alberta Canola Producers Commission; BC Ministry of Agriculture; Food & Fisheries; and the Canola Council of Canada.