Guidelines for the preparation of table grapes in SA for export 2025/2026_ND

Apply during slow-drying conditions. A dye can be added to show whether all canes have been thoroughly wetted. Potassium nitrate (KNO 3 ) at 6% can be applied to achieve more even bud break, but it will not advance the harvest date. It must be sprayed at bud swell or when the first buds open, or both. It’s a safe product and won’t damage young leaves. Practical considerations In practice, manipulations are often combined. The vigour of a vineyard determines which manipulations are done. An excessively vigorous vineyard tends to have sparse bunches due to poor set. The more vigorous the vineyard, the sparser the bunches, and the more drastic the manipulations that are needed. Cultivars that are sensitive to pruning too early include Prime ® , Grapaes (Early Sweet ® ), Starlight ® , Red Globe, Thompson Seedless, Sheegene 21 (Ivory™) and Sugrasixteen (Sable Seedless ® ). Pruning too early results in poor, uneven bud break and small bunches without shoulders. Young vineyards (2 nd and 3 rd leaf) must be pruned later because they have low reserves due to high vigour and because they also sometimes continue growing late into the season. Longer canes don’t help in infertile vineyards. The longer these bearers are, the weaker their bud break will be. Limit the bearers to ten buds, and leave more bearers to increase the bud load to 25 buds per m 2 . In infertile vineyards, side shoots can also be used as bearers if they are thick enough, or as stubs with one bud if they’re not strong enough. However, they must be at least 7 mm in diameter and hardened off. The stubs always break bud, which stimulates the axillary bud to break, thereby increasing the chances of obtaining a bunch.

FIGURE 3. Canes in Chile. Note the length and thickness of the canes. Tying canes down improves bud break at the base. Credit: Gawie van der Merwe.

14 SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT