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

Girdling Girdling refers to cutting through the living bark around the vine, using a special knife or small saw. A strip of living bark is removed. Sometimes a single cut is made to the hardwood using an ordinary knife, especially for late girdling. Girdling is done to improve set or obtain larger berries after set. It also strengthens berry attachment. In general, girdling produces impressive results, with berry enlargement of 25% or more. The effectiveness of girdling with a knife at véraison to improve the colour of red and black grapes varies among cultivars. Girdling is sometimes combined with other manipulations. It’s a practice that’s here to stay, and most producers currently apply it. The following practical tips will improve the results: • Remove old bark before cutting. • Ensure that cuts completely circle the trunk. • Don’t cut too shallow or deep. • Don’t make cuts too close together, as the wounds will struggle to heal. • Don’t girdle young or weak vines or wines that are less than 30 mm in diameter. • Don’t girdle vines that are under any stress. • Don’t girdle vines too late or twice in the same season. • Disinfect girdling equipment after every vine if bacterial blight is a risk. • Service the girdling equipment regularly. • Each cultivar has its own recipe for girdling. Refer to the discussion of individual cultivars for details. Thinning or snipping out By hand The berries and laterals on bunches are thinned to prevent the bunch from becoming too compact. Thinning is usually done when berries are 10–15 mm in diameter, just before bunch closure. By snipping out laterals or parts of laterals, the task is performed faster than by snipping out individual berries. However, it must be done carefully so as not to ruin the shape of the bunch through cutting gaps, especially at the shoulders. Depending on the cultivar, the third, fifth, seventh, and ninth lateral can be removed, or only the fifth, seventh, and ninth can be removed. The laterals are counted from the top to the bottom. Sometimes, the laterals are lifted and the bottom berries are snipped off, rather than removing the entire lateral. Ideally, no more than 3–4 berries per cluster should remain after thinning. Bunches are felt to ensure that thinning is sufficient. It should usually be possible to insert the fingers to the central axis after thinning. Note that berries can increase in size by up to 30% from just before véraison until harvest. Sometimes it’s only necessary to cut a path in the bottom third of the bunch, working by feel to check that the bunch has been thinned enough. Small berries are snipped out immediately afterwards. No further snipping is done. This method is quick and saves labour. With gibberellic acid Refer to the section on gibberellic acid (page 10) and the discussion of individual cultivars. Some cultivars can be thinned with a low dose of gibberellic acid during flower and at the start of set. The principle is that the gibberellic acid stimulates shoot growth at a critical stage. The actively growing shoot competes with the bunches for available carbohydrates and nutrients, resulting in the abortion of flowers and berries. For gibberellic acid to function effectively, strong growth (minimum shoot length of 80 cm at flowering) and enough heat (maximum temperatures above 25°C and minimum temperatures above 15°C) are needed.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 7