Technical Yearbook 2024

frost damage of 1997. The higher cordons and increased bud load, in particular, were seen as a way to limit frost damage. They had to wait until 2019 for the theory to be tested (Photo 2). The result was that the vineyards recovered to such an extent within the same year, that crop losses were negligible. With the danger of spring frost damage in the Orange River posing a major problem every year, mechanical pruning can likewise play a significant role in lessening or limiting damage in this region. There are some producers who are already successfully applying mechanical pruning in the Orange River. The requirements are strong vigour, upright growing cultivars like Chenin blanc and Colombar, sufficient irrigation water and even soils. Many parts of the Orange River meet all the requirements and mechanical pruning can work very well. An example of such a vineyard can be seen in Photo 3. It is important to remember that these blocks form many but small bunches, which make mechanical harvesting necessary. An important requirement for mechanical pruning to be sustainable over the longer term is that the ‘box’ (seen from the side) should be cut at the same place every year. Older wood will thus be cut through, but new shoots are left on the inside which provide renewal (Photo 4). The latest research indicates that the incidence of trunk diseases (a major problem in the Orange River) is lower in mechanically pruned vineyards. Prof. Halleen, former senior researcher at the ARC Infruitec-Nietvoorbij, argues that the reason for this is fewer large cuts near the cordon in mechanically pruned vineyards. Where producers are less successful and struggle with the implementation of the system, it is mostly in cases where ‘mechanical’ pruning is done by hand. Pruners, in such cases, will almost automatically start to prune spurs and not cut through the older wood to keep the ‘box’ at the same size. Over time a build-up of bearers occurs, especially in

BRIAAN STIPP

PHOTO 2. Frost damage in Robertson (2019).

PHOTO 3. Chenin blanc successfully cultivated with mechanical pruning in the Orange River.

PHOTO 4. Shoots inside the ‘box’ create the opportunity for renewal in the system.

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TECHNICAL YEARBOOK 2024