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

Bud load Bud load refers to the optimal number of buds per vine or per m 2 of vineyard surface area. The South African wine industry started with guidelines for bud load. The South African table grape industry, after several trials from 2004 to 2006, developed guidelines that have stood the test of time and are now considered accurate. The recommended bud load for different pruning systems is given in Table 1. TABLE 1. Guidelines for bud load for different pruning systems. Pruning system Recommended number of buds per cane Recommended number of buds per m 2 vineyard area Expected average bud break %

Spurs

2

8–10

100 plus

Half-long bearers

6–8

12–15

75–80

Canes

12–14

20–25

50–65

It is clear that the bud-break percentage decreases with increasing bud numbers. Therefore, it makes no sense to have longer and longer bearers. It is better to have more bearers with 12 buds than fewer bearers with 20 buds. The longer the bearer, the weaker and more uneven its bud break. Fertility in terms of bunches per vine is the product of the bud-break percentage and the fertility of the canes where bud break occurs. If bud break is 10% less, there will be 10% fewer bunches than planned. The fertility of a grapevine bud is expressed as bunches per bud. For example, if the average fertility of Thompson Seedless is 0.5 bunches per bud, this means that a bud has a 50% chance of developing a bunch. General pruning tips Use only well-lignified, dark brown or red canes as bearers. These canes have high sugar and starch reserves. Avoid pale or light grey canes that are low in reserves. Avoid canes with abnormally long internodes in the middle. These canes have grown too vigorously and may have depleted their reserves. Prune to ensure that bunches are evenly distributed across the entire bearing surface. Use bearers of the optimal thickness (10–14 mm). For Sugraone (Superior Seedless ® ), Sugratwelve (Coachella Seedless ® ) and Ralli Seedless™, the optimal thickness is 12–14 mm. For Thompson Seedless and Crimson Seedless, it is 10–12 mm. Spurs shouldn’t be thinner than 8 mm. Winter pruning can be completed in two steps (preliminary or clean pruning followed by final pruning) or in one step (only final pruning). Preliminary pruning is done to facilitate final pruning. During preliminary pruning, all canes that are not going to be used for bearers are removed. Preliminary pruning should be done when at least 80% of the leaves have dropped. During final pruning (short pruning), canes are cut back to the correct number of buds. The final pruning date is crucial, as it can impact the percentage and uniformity of bud break. Rest breaking Hydrogen cyanamide applied at 2.5% six weeks before the expected bud-break date is recommended for advancing the harvest. For a stronger and more even bud break, 5% hydrogen cyanamide can be applied 3–4 weeks before the expected bud-break date. The combined effect of pruning and hydrogen cyanamide is necessary for optimal rest breaking. Please read the label attentively and use it with care. Hydrogen cyanamide is phytotoxic and will scorch any green tissues.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 13