Canola seedlings can with stand a considerable frost (-5 to -8 0 C) if plants have become acclimatized following a few days of cold temperatures. However, canola seedlings growing under warm conditions will be tender, and can be killed by even a few degrees below zero. Ice crystals will form on the leaf surface before they form within cells causing damage.
Prior to taking any action, wait four to five days to assess any damage.
- Check the growing point at the centre of the leaf rosettes for green colour. Although the cotyledons or other leaves may be black, re-growth can occur in 4-10 days depending on weather conditions.
- Assess stand survival prior to making application of any weed control product. Allow a minimum of 1-2 days for plants to recover before applying any product. If frost damage to canola plants is significant, wait at least 4-5 days to assess survival and for new growth to emerge. Plants that have new leaf area are better able to handle (metabolize) the herbicide, even if they are herbicide tolerant. Herbicide activity on weeds will be improved when application is made to weeds that have resumed growth. Liberty works best when applied during the heat of the day.
- Check fields for flea beetle activity. Action threshold is 25% leaf feeding damage.
For further information on assessing frost damaged canola, refer to Canola Council resources on spring frost damage.