Use of pruning to revive cold injured grapevines



By Lucinda Heyns

The purpose of this study was to evaluate the potential of four different cordon renewal strategies to revive a 34-year-old, declining block of Merlot. The vineyard was cordon-trained and spur-pruned but continued exposure to freeze events resulted in gradual vine decline and reduced yields.

Project layout

Different pruning treatments were applied to a 34-year-old Merlot vineyard over three consecutive seasons:
  1. Cordon completely removed about 13 cm below cordon wire
  2. Three short canes were left per cordon and trained to the old cordon plus all other buds and spur positions were removed
  3. Cordon completely disbudded to encourage renewed spur positions
  4. Control: Standard spur pruning
Vine recovery was determined by measuring pruning weight, yield components and fruit composition.

Results

  • Retaining three canes resulted in higher average yields over a three year period, as well as cumulative yield, compared to the other treatments.
  • Complete cordon removal resulted in a uniform recovery, but the first year there was no yield and during the following two years, yields were intermediate. This is not ideal from an economic perspective.
  • Complete disbudding resulted in yields similar to the control. However, it also caused bushy growth in the first year, which increased canopy management costs.
  • Overall fruit composition remained similar in all four treatments.

Significance of the study:

Older vineyards where productivity starts to decline need to be replanted eventually, but establishment costs are high. This may be a method to delay replanting and the capital input costs associated with it, while still achieving economically viable yields.

Reference

Pruning approaches to revive col-injured Merlot grapevines: http://wawgg.org/files/documents/2017_AM/Lynn_Mills_2016_WAWGG_Pruning_approaches.pdf



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