Winetech Technical Yearbook 2022

retraining, is that the internodes can become too long to assign the necessary spurs due to the vigorous growth. Timely flattening of shoots and topping actions are thus required to obtain shorter internodes. The shoot that will be used to form the new trunk, should preferably be located more than a hand’s length below the sawing wound. The uppermost shoot should therefore not necessarily be used to form the trunk. The wound will dry out like a pruning wound and this could also extend to dry out the new trunk, which will impede sap flow and result in a weak vine. The entire new trunk could possibly also die back. A mechanical harvester would also be able to snap such trunks easier in the area around the sawing wound. FACTORS TO TAKE INTO ACCOUNT The cordon wire will in most cases have to be cut and removed during the sawing back process, as it is usually not possible to remove the cordon arms from the intertwined cordon wire. A new

cordon wire is thus required and this also offers the opportunity to change the position of the cordon wire if desired. The vines will not bear grapes in the first growing season after sawing back and crop control will likely have to be performed on the first crop load in year two. Monitor the soil moisture status regularly during the first season after sawing back, as over-irrigation can easily occur due to the smaller canopy in comparison with the root system and subsequent lower water consumption. REFERENCE https://www.wineland.co.za/sawing-back-of-grapevines-for retraining/

For more information, contact Hennie Visser at henniev@vinpro.co.za.

2

3

PHOTO 2. One year after sawing back. This vine is in the same block as photo 1. Note that the shoot used for forming the trunk, is located very close to the sawing wound. The growth is significantly weaker than the vine on photo 1 and this can most likely be attributed to the sawing wound drying out all the way to the shoot, and impeded sap flow. It is therefore crucial to use a shoot that is located at least a hand’s length below the sawing wound to form the new trunk. PHOTO 3. The top shoot closest to the sawing wound was used for this trunk. This is not ideal as the wound can dry out, which impedes sap flow, and a mechanical harvester will also break this trunk easily. Note that there was also no space to attach the training string and it had to be fastened under the shoot forming the new trunk. On the photo it is evident that the string is already starting to strangle the trunk. PHOTO 4. Two years after sawing back. Note the good vine development. No dead or infertile vines are visible.

4

95

WINETECH TECHNICAL YEARBOOK 2022