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

GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH-AFRICA FOR EXPORT Gawie van der Merwe

2025|2026

All rights reserved. No part of this publication may be reproduced, distributed or transmitted in any form or by any means without the prior written permission of the publisher, except in the case of brief citations in critical reviews and certain other non-commercial uses permitted by copyright. Requests for permission should be addressed to the publisher at info@satgi.co.za. Information may only be published with acknowledgement of the source.

About the author

Gawie van der Merwe was born in Worcester and grew up on a wine-grape farm. He completed his BScHons in Viticulture at Stellenbosch University in 1973. The following year, he began his career at the Nietvoorbij Research Institute for Viticulture and Oenology (the precursor to the ARC Infruitec-Nietvoorbij) in Stellenbosch. From 1988–2009, Van der Merwe served as a technical adviser for table grapes at Capespan. During this time, he obtained his M Inst Agrar (Agricultural Extension) from the University of Pretoria. Since 2009, Van der Merwe has been an independent technical adviser. He consults to table-grape growers and marketers in all the main South African production regions, as well as in Namibia and internationally. He can be contacted at vandermerwe.gawie@gmail.com.

Guidelines for the preparation of table grapes for export 2021/2022

Guidelines for the preparation of table grapes for export

by Gawie van der Merwe

2012

Guidelines for the preparation of table grapes for export 2021/2022

GUIDELINES FOR THE PREPARATION OF TABLE GRAPES FOR EXPORT 2019/2020

South African Table Grape Industry (SATI) 63 Main Street | Paarl 7646 Western Cape | South Africa

Tel: +27 21 863 0366 Fax: + 27 21 863 0339 Email: info@satgi.co.za Web: www.satgi.co.za

SATIonline

@sati_sa

2012

2016/17

2021/22

GUIDELINES FOR THE PREPARATION OF TABLE GRAPES FOR EXPORT 2014 / 2015

2019/2020 GUIDELINES

SOUTH AFRICAN TABLE GRAPE INDUSTRY (SATI) 63 Main Street | Paarl 7646 Western Cape | South Africa

FOR THE PREPARATION OF TABLE GRAPES FOR EXPORT

Tel: +27 21 863 0366 Fax: + 27 21 863 0339 Email: info@satgi.co.za Web: www.satgi.co.za

SATIonline

@sati_sa

2014/15

2019/20

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

1

Contents

Preface......................................................................................................................................................................... 4 Introduction.................................................................................................................................................................. 5 The principles of pruning...........................................................................................................................................12 The development of a grape berry........................................................................................................................17 Vigour norms..............................................................................................................................................................19 Table-grape cultivation throughout the year........................................................................................................21 White seedless 26 1. Arrafifteen (Arra Sweeties™) .................................................................................................................... 28 2. Arrathirtythree (Arra Honey Pop ™ ). ........................................................................................................ 30 3. Grapaes (Early Sweet ® )............................................................................................................................. 32 4. IFG Ten (Sweet Globe™) . ......................................................................................................................... 34 5. IFG Eleven (Sugar Crisp™) ........................................................................................................................ 36 6. Prime ® .......................................................................................................................................................... 38 7. Regal Seedless...........................................................................................................................................40 8. Sheegene 2 (Timpson™ )........................................................................................................................... 42 9. Sheegene 21 (Ivory™ )............................................................................................................................... 44 10. Sugraone (Superior Seedless ® )................................................................................................................. 46 11. Sugrathirtyfive (AUTUMNCRISP ® )............................................................................................................... 48 12. Sundance Seedless. .................................................................................................................................. 50 13. Thompson Seedless (Sultanina)................................................................................................................52 Red seedless 54 1. Arratwentynine (Arra Passion Fire ™ ). ...................................................................................................... 56 2. Crimson Seedless.......................................................................................................................................58 3. Evans Delight™ . ......................................................................................................................................... 60 4. Flame Seedless...........................................................................................................................................62 5. IFG 68-175 (Sweet Celebration™) . .......................................................................................................... 64 6. Joybells ® ...................................................................................................................................................... 66 7. Ralli Seedless™ ........................................................................................................................................... 68 8. Sheegene 13 (Timco™ )............................................................................................................................. 70 9. Sheegene 20 (Allison ™) ............................................................................................................................ 72 10. Starlight ® ...................................................................................................................................................... 74 11. Sugrafiftythree (Ruby Rush™) ................................................................................................................... 76 12. Sugranineteen (Scarlotta Seedless ® )....................................................................................................... 78 13. Tawny Seedless ® ......................................................................................................................................... 80 Black seedless 82 1. IFG Seventeen (Sweet Joy™) ................................................................................................................... 84 2. Sugrasixteen (Sable Seedless ® ). ............................................................................................................... 86 3. Sugrathirteen (Midnight Beauty ® )............................................................................................................ 88 4. Sugrathirtyfour (Adora Seedless ® )............................................................................................................ 90 Red seeded 92 1. African Delight™ ........................................................................................................................................ 94 2. Red Globe..................................................................................................................................................96 Tables Table 1..................................................................................................................................................................13 Table 2..................................................................................................................................................................18 Table 3..................................................................................................................................................................98 Table 4................................................................................................................................................................102

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

Preface

It is necessary to update this book regularly as new cultivars are introduced and the techniques for existing cultivars are refined. The production of export table grapes of acceptable quality is specialised and labour intensive. Nowadays, no table-grape cultivar can be cultivated successfully without performing specific manipulations at the right time. These manipulations must be carried out precisely and effectively to obtain good results. Labour is the table-grape grower’s single most significant expense and increases every year. Consequently, techniques must be continually adapted and developed to reduce labour costs for bunch preparation and eliminate unnecessary manipulations. These guidelines were compiled to promote the maximum production of Class 1 export grapes per hectare. There is a balance between quality, price, and pack-out percentage. The higher the fruit quality, the better the expected price. However, when growers attempt to pack as many bunches as possible into export cartons, the average quality of the fruit starts to drop, and so does the expected price. There will come a point where the additional cartons no longer compensate for the lower quality and price. Growers need to decide for themselves where they fit into this model. To the best of our knowledge, the recommendations in this book yield the best results. These methods have been tested in practice. We acknowledge the contributions of cultivar breeders and owners, growers who have experimented themselves, and researchers.

The information on patented cultivars was obtained from cultivar breeders and owners. Although every effort was made to ensure that the information is correct, allowing growers to obtain the best results, the author and publishers accept no liability for any losses resulting from the application or non-application of these guidelines. Growers should consult their technical advisers before implementing any recommendations from this book.

Changes since the previous edition l The cultivar-specific

information is summarised. l Only the most important cultivars are included. l A section on the principles of pruning has been added. l The development of a grape berry is described. l The physiology of berry shatter is discussed.

Please read the introduction carefully. Some concepts have evolved, and new information has been introduced.

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

Introduction

To meet market requirements, growers must apply specific manipulations during the spring and summer. Some cultivars need more manipulations than others, but there are no cultivars that can be marketed for export in their natural state. It is necessary to explain specific terminology before discussing cultivars individually. Shoot thinning This involves the manual removal of unnecessary and infertile shoots, typically at a shoot length of 20–30 cm. Removal of lateral shoots Lateral shoots between the base of the main shoot and the bunch are removed. As this is labour-intensive, only prominent shoots are removed, and only up to the bunches. Don’t overdo this. Research has shown that lateral shoots contribute to the manufacture of carbohydrates that are translocated to nearby bunches. Tipping of shoots This involves the manual removal of 2–5 cm of the growth tip of a shoot, resulting in improved set and more fertile buds. Tipping is usually done just before or during flowering. Topping This is the removal of the top 15–25 cm of a shoot, including the growth tip, by cutting with secateurs or a scythe, or by swiping with a length of wire. Topping is more drastic than tipping. As with tipping, topping aims to improve set, berry size, and fertility. It is also done after set and véraison to enhance light penetration in the middle of the row. If bud break is very uneven, dominant shoots must sometimes be tipped or topped early to allow weaker shoots to catch up. Tipping is usually performed when dominant shoots are 15–20 cm long. Dominant shoots with bunches can also be topped one to two nodes above the bunch. Dominant shoots without bunches should be entirely removed. Removal of extra tendrils and lateral bunches Tendrils and small lateral bunches sometimes develop on the central axis above the shoulders of a bunch. The tendrils are known as anchors, and the removal of these tendrils or small bunches is also referred to as anchoring. When not removed in time, the tendrils can entangle the bunch. The tendrils can be a nuisance, especially in Crimson Seedless and Sugranineteen (Scarlotta Seedless ® ). Shouldering This is the pinching back of the top two laterals of a bunch, typically before flowering, to enhance set in the upper part of the bunch. Sometimes only a small part of the lateral is removed, and sometimes a larger part, up to half of it.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 5

Tipping of bunches This involves manually removing the bottom (± 5 cm) part of the bunch to improve the set, especially in the lower part of the bunch. Tipping is usually done just before or during flowering. Shortening This is the final shortening of the bunches to the desired length, achieved by cutting off the unwanted portion. Shortening is usually done just after set. Different measurements apply, for example, the length of snipping scissors, a cigarette lighter, or a hand’s breadth. Sometimes the bunch is shortened to a number of laterals. The modern trend in the table-grape industry is to aim for an optimal number of berries per bunch for a given cultivar (Table 3). See page 98. Shatter or abortion Shatter refers to the abortion and dropping of flowers or small berries (2–5 mm) just after flowering during set. The cultivars that are most prone to shatter are Alphonse Lavallée, Sugrathirteen (Midnight Beauty ® ), Sugrathirtyfour (Adora Seedless ® ) and IFG Ten (Sweet Globe™). A tendency to shatter is likely to be genetic. Experience with Alphonse Lavallée 30–40 years ago suggested that levels of carbohydrates and other nutrients during flowering and setting played an important role. The number of bunches per vine is also important. When there are too many bunches, plant growth regulators such as cytokinins and auxins are diluted, and levels in any given bunch are not high enough to prevent shatter. By removing bunches, growers can increase the available carbohydrates, nutrients, and plant growth regulators per bunch, and therefore the opportunity for berries to set. Set has been extensively researched in Alphonse Lavallée. The resulting recommendations for improved set apply to other cultivars and are summarised below. Before flowering Retain one bunch per shoot. Reducing bunches increases the carbohydrate levels in the remaining bunches. Leaving all the bunches, especially in very fertile cultivars, risks excessive shatter. At 5% flowering Remove leaves around bunches and shoulder bunches, especially large bunches. At this stage, the basal leaves don’t contribute much to carbohydrate levels through photosynthesis. Making bunches smaller elevates the carbohydrate levels in the remaining parts of the bunches. At 10% flowering Top shoots. Actively growing shoots compete with bunches for available carbohydrates and nutrients. The severity of topping is determined by vigour and temperature. The more vigorous the plants and the warmer the weather, the bigger the section that should be topped. At 50%–80% flowering Vines can be girdled at 50%–80% flowering in extreme conditions (high temperatures and vigorous growth). By interrupting the phloem, the downward flow of carbohydrates is stopped, which increases the carbohydrate levels in the bunch zone. Since the research on Alphonse Lavallée, plant growth regulators such as cytokinins have become available. These can enhance set when applied at 1-2 ppm during 50%–80% flowering. However, note that cytokinins are not registered for this use in South Africa. Cytokinins only promote set when applied preventively. It doesn’t reduce shatter when used at a berry size of 3–4 mm (set). Cytokinins have disadvantages when used during flowering. Small shot berries may remain, and berries become rounder. Colour development may also be adversely affected.

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

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

The thinning process can take up to five days to complete. Therefore, the decision about which gibberellic acid concentration to apply should be informed by the temperature forecast for the five days after the planned thinning date. Don’t remove leaves before the thinning application. The gibberellic acid doesn’t necessarily need to come into direct contact with the bunches, but it’s essential to wet the vines thoroughly. The application details for each cultivar were selected to provide the best outcome. Prime ® , Grapaes (Early Sweet ® ), Sugraone (Superior Seedless ® ), Sugratwelve (Coachella Seedless ® ) and Ralli Seedless™ are genetically predisposed to shot berries (incompletely fertilised berries), so the dose and timing have been calibrated to abort shot berries during set. The thinning application must occur during set, after petal fall, when the ovaries are 2–3 mm in diameter. Trimming Bunches are trimmed to obtain the desired shape. Trimming is typically performed in conjunction with thinning and involves the removal of points and abnormally protruding laterals. Bunches should weigh 500–800 g. A looser bunch of 400–500 g is preferred for punnets. Bunch removal or crop control Bunch removal is the term growers use to refer to the process for optimising the crop load per vine for a given cultivar. The correct crop load is essential for the eventual success of table-grape production. Unwanted bunches should ideally be removed as soon as possible after set, leaving only the optimal number of bunches. These remaining bunches receive the greatest benefit from a smaller crop at an early stage and can develop larger berries with better colour and taste. In practice, it may be challenging to determine which bunches will develop the best shape when assessing them just after set. Therefore, bunches are usually only removed when berries are 5–7 mm in diameter. A preliminary bunch removal before flowering is recommended to improve set in some fertile cultivars, such as Sugrathirteen (Midnight Beauty®) and IFG Ten (Sweet Globe™). Too many bunches can dilute carbohydrate and nutrient levels, thereby increasing the likelihood of excessive shatter. The golden rule is to allow only one bunch per shoot to flower. The recommendation is to have the crop load plus 25% bunches in flower. Leaf removal (leaf pulling) Removing some of the lower leaves on a shoot will improve air circulation and light penetration, prevent chafing of berries, and facilitate better penetration of plant growth regulators and crop protection products. Vine leaves begin contributing carbohydrates when they are approximately one-third of their final size. They photosynthesise maximally when they are fully grown. Thereafter, photosynthesis declines over the following approximately 90 days, until the leaf no longer contributes carbohydrates. Therefore, the contribution of leaves in different positions on shoots to photosynthesis changes during the season. At véraison, the leaves on the middle third of the shoots contribute the most to carbohydrate accumulation.

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

Bunch spacing This is the arrangement and spacing of bunches on the canopy to prevent chafing. Flower and set Grapevine flowers are covered with fused petals that form the calyptra (Figure 1). The calyptra is pushed off when the flower opens. The five stamens (male) and stigma, style, and ovary (female) lie underneath. The pollen grain lands on the stigma and grows through the style to reach the ovary, which then develops into the grape berry.

FIGURE 1. The parts of a grapevine flower.

Flowering is the stage when the calyptra has dropped off and the stamens are visible (Figure 2). Set is the stage when the stamens have dropped off and only the ovary remains. The ovary is then 2–3 mm in diameter.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 9

FIGURE 2. Grapevine flowers, of which some still have calyptras and others show five stamens. Credit: Gawie van der Merwe.

Gibberellic acid Gibberellic acid is a naturally occurring growth regulator in plants. The gibberellic acid used in grapevines is called GA 3 . Gibberellic acid stimulates cell enlargement. When low doses are applied during full bloom, it promotes the artificial thinning of bunches (page 7). When high doses are applied at a berry diameter of 6–8 mm or later, it causes berry enlargement. The formation of fertile buds on new green shoots of the current season (initiation and differentiation) occurs from flowering and set until approximately 10 weeks after flowering. Complete coverage with gibberellic acid during initiation and the first phases of differentiation can compromise fertility, especially when doses exceed the recommended dose (see cultivar-specific guidelines and product labels). Electrostatic spray pumps can be used to spray for berry enlargement without negatively impacting fertility. Gibberellic acid must be applied under slow-drying conditions. Excessively high doses of gibberellic acid can negatively affect table-grape shelf life. In his research, Prof. Zoffoli of Chile found that the cuticle thins more when more gibberellic acid is applied. The cuticle is a thin, waxy layer on the epidermis. It protects the berry. When gibberellic acid is applied under nets, the dose should be reduced by approximately 30%, because the vines react much better under nets. A regular dose could, therefore, result in berries becoming too large.

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

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

The principles of pruning

Why prune? Pruning is the start of the new season. In table grapes, unlike in wine grapes, precision pruning is vital. Pruning is the first phase of crop control. A vineyard that isn’t pruned develops shoots, but the shoots grow weakly and break bud unevenly due to competition. Therefore, many bunches are carried on weak shoots. The result is smaller berries, delayed ripening, poor colour, and, worst of all, poor shelf life. The aim of pruning is to carry bunches on vigorous shoots and to ensure bunches are spread evenly over the entire bearing surface. In table grapes, bunches mustn’t be in contact with each other. Avoid gaps in the canopy where canes don’t cover the surface. Ideally, all shoots bearing bunches must be equally vigorous and approximately 80–120 cm long at flowering. Bunches shouldn’t be carried on shoots that are shorter than 50 cm, as these bunches take longer to develop sugars and colour, their cells break down, and the result is browning and poor shelf life. The timing of pruning determines the harvest date. The period between pruning and harvest varies by region and cultivar, but the average is approximately 142 days. This can be considerably shorter in very warm and early regions or with early cultivars. In subtropical areas (15° North or South of the equator), such as parts of Peru, Brazil, and India, grapevines do not enter dormancy. So, the time of harvest is regulated by adjusting the pruning date and other manipulations. Definitions of bearers Grapevines bear on one-year-old wood on two-year-old wood. A spur or short bearer has two buds. Don’t count the collar buds around the base of the cane. A half-long bearer has 6–8 buds. When applying a half-long-bearer system, leave a short bearer near the base of each half-long bearer. The short bearer is for renewal in the following season. A long bearer or cane has 12–14 buds. When applying a long-bearer system, leave a short bearer near the base of each long bearer. The short bearer is for renewal in the following season.

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

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

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

Canes usually start bleeding about two weeks before bud break. When canes bleed, pruning cuts must be made so that the sap runs away from the buds, as continuous wetting can lead to botrytis infections and rotting of buds. This is especially true of upright spurs. Don’t make the pruning cut too far from the bud. Canes have spongy marrow in the middle, which is interrupted by a diaphragm at each bud. Therefore, canes can’t dry out. Instead, rain can accumulate in long sections of marrow, leading to botrytis infections that can kill buds. This is again especially true for upright spurs in winter rainfall areas. By tying canes down, apical dominance is lifted and bud break improved (Figure 3).

FIGURE 4. Canes in South Africa. Note the length and thickness of the canes. Credit: Gawie van der Merwe.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 15

Average buds per vine = 58.2 Average buds per m 2 = 10.8

Average bud break % = 88.1% Average bunches per bud = 0.48

FIGURE 5. The average bud fertility of Crimson Seedless at four farms and in 31 randomly chosen vines in the Worcester region during the 2006 season. Credit: Gawie van der Merwe.

Figure 5 illustrates the fertility of Crimson Seedless. Bud position one is the first (lowest) bud on the cane. The chart shows that the best option for Crimson Seedless is half-long bearers with 6–8 buds and a bud load of 12–15 buds per m 2 of vineyard surface. The greatest fertility is between bud positions 4 and 9. The average fertility of Crimson Seedless is about 0.5 bunches per bud.

The development of a grape berry

Grape berries develop according to a double sigmoidal curve (Figure 6). There is an initial steep increase in berry size from set to véraison, followed by a slight flattening in the curve. Then there is another steep increase until harvest. The cell division phase, which determines the number of cells per berry, occurs from set until approximately 21 days after set. Thereafter, the berry grows primarily through cell enlargement. The first growth phase is crucial for determining the final berry size. If berry size is below average during this phase, it is impossible to catch up and ultimately achieve the optimal berry size. Actions such as bunch thinning, girdling, enlargement using gibberellic acid, and bunch removal and shortening during the first phase influence the final product.

Figure 6. The development of a grape berry. Credit: Gawie van der Merwe.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 17

TABLE 2. Extrapolation of the final berry diameter from the present berry diameter. The percentage by which the berry diameter can increase until harvest is given in brackets. Current size (mm) 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Stage when measured

Expected berry diameter at harvest

Before véraison (+ 30%)

15.6 16.9 18.2 19.5 20.8 22.1 23.4 24.7 26.0 27.3 28.6 29.9 31.2 32.5 33.8 35.1 36.4

5% véraison (+ 25%)

15.0 16.3 17.5 18.8 20.0 21.3 22.5 23.8 25.0 26.3 27.5 28.8 30.0 31.3 32.5 33.8 35.0

10% véraison (+ 20%)

14.4 15.6 16.8 18.0 19.2 20.4 21.6 22.8 24.0 25.2 26.4 27.6 28.8 30.0 31.2 32.4 33.6

20% véraison (+ 15%)

13.8 15.0 16.1 17.3 18.4 19.6 20.7 21.9 23.0 24.2 25.3 26.5 27.6 28.8 29.9 31.1 32.2

50% véraison (+ 10%)

13.2 14.3 15.4 16.5 17.6 18.7 19.8 20.9 22.0 23.1 24.2 25.3 26.4 27.5 28.6 29.7 30.8

80% véraison (+ 5%)

12.6 13.7 14.7 15.8 16.8 17.9 18.9 20.0 21.0 22.1 23.1 24.2 25.2 26.3 27.3 28.4 29.4

Vigour norms

The following norms apply to vigour evaluation between véraison and harvest. The amount of sunlight penetrating the trellis and canopy should be estimated at midday, when the sun is at its highest point. Poor vigour Final shoot length 50–80 cm.

Average shoot diameter is less than 8 mm. Short internodes (less than 5 cm on average). Shoot tips are poorly hardened off. No active growth tips after 10 mm berry diameter. Light green leaves.

The shade pattern on the ground beneath the trellis consists of more than 50% sun patches. Determine whether poor vigour is due to physical or chemical soil limitations, excessive or insufficient soil moisture, or soil-borne pests such as phylloxera, nematodes, or margarodes. Moderate vigour Final shoot length 80–100 cm. Average shoot diameter 10–12 mm No active growth tip at véraison. Ideal vigour Final shoot length 110–150 cm. 20%–30% active growth tips at véraison. 10–12 leaves per bunch. The shade pattern on the ground beneath the trellis consists of 20% sun patches. Only light topping and cutting back are required. High vigour Shoots longer than 150 cm. More than 50% active growth tips after véraison. Growth tips curl strongly, and shoots have a strong tendril and long petioles. The third tendril from the top can be pulled past the growth tip. Yellow leaves resulting from insufficient light. Black and red grapes colour poorly. Tendency to sparse bunches. Poor fertility. Risk of decay. The shade pattern on the ground beneath the trellis consists of less than 20% sun patches. Topping is needed 2–3 times during the season.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 19

Excessive vigour Long, thick canes (up to 5 m long).

Strong lateral shoot development and a large second crop. Strong tendril development. The tendril grows past the growth tip. Large, dark green basal leaves that turn yellow later.

Bluegreen bunches with poor taste. Sparse bunches at high risk of decay.

There are few or no sun patches beneath the trellis. The vineyard must be cut back every 2–3 weeks.

Table-grape cultivation throughout the year

This annual programme aims to provide an overview of table-grape cultivation throughout the season. Grapevines are perennial, deciduous crops grown in diverse climates. Therefore, the year has been divided into 17 phenological stages. Leaf drop (Autumn) The vine enters dormancy for the coming winter. The following can be done after leaf drop: • Start with preliminary pruning. • Control couch grass before winter starts. • Sow cover crops. Sowing from mid-March to mid-May is recommended for the Western Cape, depending on the region and the type of cover crop. Sowing from mid-March is recommended for summer-rainfall areas. These recommendations are linked to the optimal soil temperatures (10–18°C) for seed germination. Sowing too late, when the soil is too cold, is detrimental to the cover crop stand, as germination will be poor. In summer rainfall areas, cover crops must be irrigated. • Remove loose bark for effective girdling and mealy bug control. Winter The vines are dormant. Do the following: • Maintain trellis systems by replacing poles where necessary and tensioning wires. Inspect anchors. • Erect trellis systems for young vineyards. • Assemble cartons when it rains. • Control mealy bugs. Treatments can be repeated for severe infestations. Only treat infested vines. • Control ants with spot applications where nests are observed. • Control snails. • Carry out the final pruning on the appropriate date and with the appropriate method. • Tie canes down. • Treat buds with a rest-breaking agent where applicable. • Train young vineyards that grew sufficiently in the previous season (cordon arm diameter more than 8 mm or thicker than a pencil). Vines that didn’t grow sufficiently should be cut back to two buds above the graft union. • Prune 2 nd leaf vines as late as possible to improve bud break. Young vines have fewer reserves, resulting in poorer bud break. • Follow a weed-control programme later in winter.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 21

Just before bud swell Vines are emerging from dormancy to begin a new growth season. Root growth starts as soon as soil temperatures rise above 10 °C, which may be before bud break. When roots become active, positive root pressure causes sap flow that is visible at pruning cuts — the canes bleed. • Monitor soil moisture and irrigate if necessary. • Apply chemical mealy bug control. Pay attention to withdrawal periods. • Control stubborn weeds with systemic herbicides. • Remove scion roots and ensure graft unions are not covered in soil. Bud swell Treat for bud mites, dead arm disease (phomopsis), and anthracnose. 1–2 cm shoot length • Treat for dead arm disease, anthracnose, and bacterial blight. Should copper treatment be considered, be careful to avoid damaging vines when spraying in cold, wet weather. 5 cm shoot length • Follow up on treatments for powdery mildew, dead arm disease, and anthracnose. • Apply the first nitrogen fertilisation if necessary. The recommendation for vineyards with normal vigour is 40 kg/ha. Use a nitrate-containing product that vines can respond to quickly. 10 cm shoot length • Treat for powdery mildew, bacterial blight, dead arm disease, bud mites, and downy mildew. • Control snails. 14 days after 10 cm shoot length • Treat for powdery mildew, downy mildew, bud mites and weevils. Use the softest products for the latter two. • Apply trace elements if necessary. • Remove all shoots and lateral shoots in young vineyards, except for a main shoot growing toward the wire and an extra shoot, which is topped. 40–50 cm shoot length • Start with low concentrations (1.0%) of low-biuret urea to boost vigour in weak growers. Also apply to cultivars with compact bunches and poor vigour, where chemical thinning isn’t successful. Applications are usually weekly, but can be increased to twice per week if necessary. At 1.0% it can be sprayed with other products, but at 1.5% it must be sprayed on its own. • Only remove those leaves that directly touch the bunches. Shoot removal is crucial for determining fertility in the upcoming season. Do this judiciously! • Remove all double shoots, retaining the shoot with the best bunch. Remove all shoots without bunches, inferior shoots, and poorly positioned shoots. • Only remove strongly growing laterals from the base of the green shoot up to the bunch if necessary. • Adapt the shoot-removal programme to the cultivar. • Treat for powdery mildew and downy mildew.

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

• Apply trace elements if necessary. • In cultivars and vineyards with low fertility, vigorous shoots without bunches, located close to the trunk, can be cut back to two or three internodes. Lateral shoots will develop that may be more fertile than the primary shoot. It’s essential to do this early. Once the canopy becomes dense, the lateral shoots develop poorly. Just before flowering to flowering Only some aspects are mentioned below. Refer to the cultivar descriptions for more details. • Ensure optimal irrigation. • Tip or top vineyards that struggle to set. • Thin appropriate cultivars with gibberellic acid. • Girdle to improve set. Girdling at this stage can lead to the formation of shot berries. Ensure that vines suffer no moisture stress before and during the girdling process. • Control crop load on fertile cultivars before flowering by only leaving one bunch per shoot. • Remove the tendrils from flower bunches, especially on Crimson Seedless and Sugranineteen (Scarlotta Seedless ® ), where they can entangle the bunches. • Treat for powdery mildew, downy mildew and botrytis. • Treat thrips and weevils with softer products. Thrips survive on citrus, seed onions, lucerne, cover crops, and weeds. They move into the vines to feed on pollen as soon as the calyptras drop. Thrips damage the ovary, causing characteristic corky lesions on berries. Some cultivars are more sensitive to thrips damage. • Secure shoots. • Foliar applications of low concentrations (1.0%) of low-biuret urea give good results in cultivars with compact bunches that don’t respond to thinning with gibberellic acid. Just after flowering (berry set) • Apply the second nitrogen fertilisation. Be careful not to apply too much nitrogen after set in very early cultivars. Excessive nitrogen in the berries at harvest can promote decay. • Do the first crop load adjustment as soon as the bunches have set, and those that have set optimally can be distinguished. • Girdle applicable vineyards when the berry diameter is 4–5 mm. This will improve berry size and attachment. Avoid moisture stress before and during the girdling process. • Treat appropriate cultivars with gibberellic acid for berry enlargement. • Remove leaves that touch bunches. • Treat for botrytis, powdery mildew, and downy mildew. • Apply magnesium for berry stem necrosis if necessary. 6–8 mm berry diameter (pea berry) • Final crop load management. Supervision is crucial, as crop load management significantly impacts crop quality. • Do the first snipping out on appropriate cultivars. • Continue with bunch shaping as described for individual cultivars. • Keep the window in the canopy open. The optimal width is roughly 50 cm.

• Treat for botrytis, powdery mildew and downy mildew. • Apply magnesium for berry stem necrosis if necessary. • Arrange bunches and remove leaves around them.

SATI GUIDELINES FOR THE PREPARATION OF TABLE GRAPES IN SOUTH AFRICA FOR EXPORT 23