The May 30th frost had the potential to impact winter wheat and fall rye crops in Manitoba as some may have been in crop stages more sensitive to freezing temperatures. In MAFRD’s June 3 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. The more vulnerable growth stages are either the jointing (stem elongation) or boot stage of development.
For winter wheat at jointing stage, plants can tolerate temperatures of -4°C for less than 2 hours. In areas of Manitoba, these temperatures may have been achieved along with some acres at the jointing stage, but whether the duration was long enough is unclear so scouting will be important over the coming days/weeks. 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. There may have been limited acres at this growth stage for winter wheat. However, it is possible some fall rye acres were at the boot stage, and in many areas temperatures did fall below -2°C for more than 2 hours. Frost injury symptoms in either crop 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.
For more information on frost damage in winter cereals and other crop types, please refer to MAFRD’s Spring Frost Damage Bulletin.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD