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Ministry of Agriculture, Food and Rural Affairs

WINTER INJURY

Identification
Bud

  • Uneven bud break or lack of bud break on canes in the spring
  • Development of weaker secondary buds which start development 10 to 14 days after primary bud break
  • Collection of canes during the dormant period and performing bud sections to assess for survival (dead buds will be brown/black while healthy buds will be green)

Trunk

  • Large cracks or splits that may leak visible sap near the ground or snow line
  • Large numbers of suckers develop at base of vine
  • Buds break and shoots develop then collapse when vine undergoes water stress (often at bloom and shortly afterwards) or
  • Crown gall may develop with symptoms (gall formation) appearing the year or two after winter injury occurs

Often Confused With
Viral diseases

Herbicide Injury

Biology

Buds and cambial tissue are the most sensitive to cold damage. Frequently the damage is observed first in low-lying areas of the vineyard or where natural airflow is restricted. Vines that did not mature properly the previous year (excessive vigour, excessive crop, highly shaded canopies, stressed due to drought or excess moisture, pest injury, etc) are more likely to have injury than healthy balanced vines.  

Bud injury may be detected while vines are still dormant by collecting canes and sectioning buds. It is important that the canes be allowed to warm to above freezing temperatures for 24 to 48 hours after the injury even so that oxidation (browning) of the damaged buds is easily visible.  Cambium injury in the trunk (and other permanent wood such as cordons) is visible soon after the tissue thaws. Often trunk injury is most easily found near the ground or snow line.

Period of Activity
After winters with extremely cold temperatures or during late dormancy (February/March) when deacclimation vines are exposed to sudden low temperatures.

Scouting Notes
Injury will usually be more common in low spots in the vineyard, areas of vines stress or where natural air movement is restricted resulting in areas where cold stagnant air accumulates.

No winter damage to buds Dead primary bud, live secondary and tertiary buds Dead primary and secondary buds Winter damage to Sauvignon Blanc Winter damage to Merlot Winter damage to Vidal Winter damage to Merlot Click to enlarge.