Diagnosing stem and head frost damage in cereals

All winter grains susceptible to frost. Wheat is more susceptible then barley at flowering, but it is not known if barley and wheat have different frost susceptibilities during grain fill. The order of susceptibility for cereals is (most to least); triticale, wheat, barley, cereal rye and oats.

Image 1: Frost damage at booting vs healthy head
Image 2: Frost damage of the peduncle showing a pale green ring
Frost affected anthers are white and distorted banana shaped) turning a dull brown colour
Image 4: Frost affected ovaries turn a dull brown colour and are spongy when squeezed. A frost affected stigma takes on a crumpled appearance
Image 5: Unfrosted to frosted grain comparision
Frosted barley head - floret sterility can be determined by raising the head so the sun is behind it. Light comes through florets where grain is absent.
Image 7: Frost damaged oat head showing aborted floret damage
Peel back the husk to inspect the condition of the floral organs in the head

Where does it occur?

Temperature
Temperature
Wet conditions
Wet conditions
  • This can depend on crop type, stage of development and if canopy is wet. It also depends on how low the temperature gets and for how long. Frost is a three stage response, with damage increasing for each stage.
  • 1. Cold damage: occurs when plants are exposed to temperature less than 10°C down to -2°C. If this occurs during pollen development (Z39-45) it can cause spikelet damage.
  • 2. Desiccation damage: when ice formation occurs on the outside of the leaves at temperatures from 0°C to -2°C. Moisture is drawn from the leaves leaving them dry and brittle, subsequently dying at the tips.
  • 3. Freezing damage: usually occurs at temperatures below -2°C when there is rapid ice nucleation and ice crystals form within the leaves. The ice crystals physically rupture cell walls and membranes within the cells causing physical damage. Damage can be seen once thawed as dark green water soaked areas, 10 days after a frost bleached heads might be evident.
  • A canopy that is wet from a light shower of rain is often more prone to frost damage. This is because rain contains ice nucleators such as bacteria or dust. These ice nucleators raise the freezing point of water. As a result, a slightly wet canopy may get frosted at warmer temperatures compared to a dry canopy.
  • Position in the landscape influences temperature variations and the severity of frost damage, with low lying areas more likely to experience cooler temperatures for longer.

Management strategies

  • A comprehensive frost management strategy needs to be part of annual farm planning. It should include pre-season, in-season and post frost event management tactics.
  • 1. Identify frost prone paddocks – with topographic, electromagnetic, yield maps and paddock history.
  • 2. Consider enterprise in a zone – cropping/sheep balance.
  • 3. Review nutrient management – targeted nitrogen, potassium, copper inputs.
  • 4. Modify soil heat bank – stubble levels, crop canopy.
  • 5. Select appropriate crops – oats, barley, wheat, canola.
  • 6. Manipulate flowering times – stage sowing time, mix long and short season varieties.
  • 7. Fine tune cultivar selection – wheat, barley susceptibility during flowering.

How can it be monitored?

  • When: Inspect crops when they are between ear-emergence and grain-fill, and when the temperature drops below 2°C (screen temperature). Damage is usually most evident 7-10 days after a suspected frost event.
  • Where: Examine the crop in more susceptible lower parts of the landscape first and if the crop is damaged proceed to higher ground.
  • How: Walk through the crop and examine a whole plant every 10-20 paces.
  • If the head has not emerged from the boot, check that the head has not been damaged. You will need to carefully dissect the plant from the top down to find the head of the plant.
  • If the crop has flowered, open the florets to check if the grain is developing (Image 8).
  • After a frost event, tag a few heads with tape and note the stage of grain fill. Return a week later to determine if grain development and grain filling is continuing.

Further information

The GRDC - Managing frost risk Tips and Tactics [1]

Links
[1] https://grdc.com.au/Resources/Factsheets/2016/02/Managing-frost-risk-Northern-Southern-and-Western-Regions

Source URL: https://www.agric.wa.gov.au/mycrop/diagnosing-stem-and-head-frost-damage-cereals
This print version was generated at 9:29pm on the 5th of May, 2024.
The original document was last revised at Tue, 08/01/2019 - 12:58pm

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Important disclaimer

The Chief Executive Officer of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.