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

Cytokinin Cytokinin is a plant growth regulator that occurs naturally in plants and promotes cell division. Synthetic cytokinin can be used in combination with gibberellic acid to increase berry size. Cytokinin is a powerful compound that yields impressive results even at low concentrations (1–3 ppm). It also makes berries rounder. White grapes remain greener in colour, which could be advantageous for some markets. Overdosing cytokinin can delay harvest and negatively impact the development of taste and colour. On white grapes, high concentrations of cytokinins can cause the development of corky lenticels (dead stomata), also known as fly spot. Climate plays a role in this condition. Cytokinin at concentrations of 0.5–1.5 ppm during flowering can help improve set in cultivars with a tendency to shatter, for example, Sugrathirteen (Midnight Beauty®) and IFG Ten (Sweet Globe™). Note that cytokinin is not registered for this use in South Africa. Ethephon Ethephon releases ethylene, which accelerates the ripening process. It’s used to improve the colour of red and black cultivars. Ethephon is applied at the first signs of colour in very early cultivars and slightly later (5% colour) in later cultivars. To ensure that ethephon has broken down to acceptable levels, as required in some markets, it must be applied very early in early cultivars. Ensure thorough wetting and use under slow-drying conditions. Keep the maximum residue limits of markets in mind when spraying. When applied at high doses in warm areas in the autumn, ethephon will defoliate vines. Note that ethephon is not registered for this use in South Africa. Abscisic acid Abscisic acid is a plant growth regulator that is registered for colour improvement in table grapes. It also has a thinning effect when applied during flowering. Summary The ideal table-grape vineyard must have only 5%–10% active growth tips at harvest. Overly vigorous vineyards have 60%–70% active growth tips at harvest. Growth tips that curl indicate excessive vigour. The ideal canopy shouldn’t be thicker than 50 cm (with a maximum of four layers of leaves). The canopy must allow about 20% of the sunlight to pass through during the middle of the day. A strip at least 30 cm wide at the top of the trellis should allow the sun to pass through completely. In very vigorous vineyards, girdling and topping of shoots before flowering, as well as shouldering and tipping of bunches, may be needed to improve set. Vines should never be exposed to drought stress during flowering and girdling. The guidelines for individual cultivars apply to a vineyard with normal vigour under normal climatic conditions. If a vineyard is very vigorous, it may require manipulations that differ from the usual recommendations. Every grower should, therefore, assess each block on its own merit and make the necessary adjustments. It’s impossible to provide a general recipe that will work everywhere. Growers must also be willing to experiment on a small scale on their own farms.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 11