Management of Spring-Frost in Grapes

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Management of Spring-Frost in Grapes

After yesterdays (4/10/2020) cold night, please assess the abundance and severity of potential frost damage in your vineyard and manage accordingly. Be aware that some damage will probably show with some delay.

How to assess cold damage?

Bud injury

  • If no bud break has occurred: Sacrifice approx. 30-60 buds/acre on already pruned vines and assess for dead tissue. If you haven’t pruned, assess 30-60 buds/acre which will be retained (on a VSP: the first 2-3 buds on a spur). Please watch this video to learn how to assess bud damage!
  • Please read this article.
  • Please also see this presentation (pdf) for more information on how to assess bud cold injury.

Trunk Injury

  • Trunk injury can occur without directly visible symptoms. Results are weak growth in the following seasons.
  • Phloem can be injured, but no splitting may have occurred. Please see this article.
  • Trunk/Cane splitting is a very severe cold injury and requires attention
  • If Trunk/Cane splitting remains unattended, Crown gall and trunk disease are often the result, leading to expensive losses in subsequent years.

Damage of shoots

  • Frost damage may not be immediately noticeable. Symptoms on shoots may appear more clearly after a few days.
  • Shoots show the typical browning and wilting effects. For IMAGES of shoot frost injury, please visit the Ontario GrapeIPM website.
  • Young succulent shoots will wilt once the frost thaws, but older more hardened shoots will take a few days to show symptoms.
  • In the case of a severe frost (when all green shoots are killed back to the cordon), let the vines re-shoot and grow out (from dormant bud) the season.
  • If incomplete kill of shoots occurs, no action might be the best approach (see below). If damaged shoots are not removed, a proliferation of lateral shoots may result.

How to manage cold injury

Most grape varieties have fruitful secondary buds which will produce 50-70% of a full crop. Maximizing crop loads after cold injury may lead to less crop the coming year, depending on severity and type of damage.

No action

  • Bud injury: No action might be the best approach. However, damage needs to be assessed for crop prediction.
  • Trunk/Cane injury: If visible trunk injury is seen, please go to: Removing damaged material. Not removing damaged canes/trunk can lead to severe problems in following seasons.
  • Shoot injury: Once the vines reach a certain stage (E-L 15, see the E-L scale), taking no action is the best approach. However, no actions means: There is increased risk of disease due to the dead material retained.

Removing damaged material

  • Bud injury: Before E-L 12, buds can be rubbed off to force the growth of secondary buds. However, it is unclear of this will have an advantage over no action.
  • Trunk/Cane injury: If visible damage, trunks/canes need to be removed. Can be removed at the end of season, depending on overall health of trunk. Keeping injured trunks and canes in the vineyard over several seasons will cause large problems with crown gall and trunk diseases.
  • Moderate shoot injury: Cutting the tops off the green shoots stimulates bursting of secondary buds lower down. However, this is not recommended:  extra lateral growth that can be an issue, and late ripening, secondary crop can cause issues at harvest.
  • Severe shoot injury: Removing all shoots back to the cordon may be considered only if E-L 12 or lower and if higher quality pruning material for next season is desired. Yields in this season will be less than no action! The later the shoot removal is conducted, the greater the reduction in bud fruitfulness for the following season.

Some useful resources:

Cornell University: Anatomy of Winter Injury

Shoot Cold Injury: What to do?

Modified Lorenz System

Images and article on shoot frost injury

Cornell video on assessing bud cold damage (YouTube)

Article on bud and trunk cold damage 

NC State Presentation on Assessing Bud Cold Damage