Technical Yearbook 2023

2023 Technical Yearbook

Contents

VITICULTURE ............................................................. 6 Management of vine water stress through foliar treatment with microbial derivatives*.......................................................................7 Late pruning of the vine..........................................................................12 Manipulating Sauvignon blanc ripening through shoot trimming and crop reduction.................................................................15 Vineyard biodiversity – how to put it to work using cover crops......17 Winetech funds research towards improved Vitis planting material for the wine industry................................................................21 Seaweed-based biostimulants in Vitis vinifera L. wine cultivars – friend or foe?.........................................................................27 Chenin blanc – the versatile variety......................................................31 Soil compaction – the silent killer of conservation agriculture?........35 Managing for optimum root health.......................................................39 Winery wastewater for irrigation (Part 1): Irrigation application and water quality................................................44 Winery wastewater for irrigation (Part 2): Evaluation of catch crops on open land................................................47 Winery wastewater for irrigation (Part 3): Vineyard catch and cover crop responses.............................................50 Winery wastewater for irrigation (Part 4): Soil responses.................54 Winery wastewater for irrigation (Part 5): Grapevine and wine responses...............................................................58 OENOLOGY ..................................................................... 61 Effect of light exposure on bottled Sauvignon blanc wine..................62 Minerality in wine – understanding the concept and factors involved........................................................................................64 Fruit salad vs varnish – nitrogen sources and their impact on aroma production in wine....................................................66 Repurposing Sauvignon blanc fermentation gas for natural aroma enrichment......................................................................70 Wine in a can – rapid determination of a wine’s suitability for canning................................................................................................72 Micro-agglomeration and bioavailability of sterols – the revolutionary wine yeast protector: Faster yeast rehydration.....74 The significance of the H 2 S-C6 pathway for volatile thiol production..........................................................................80 RUBY™ – expressing thiols in red wine through an innovative yeast selection........................................................................82 PRACTICAL IN THE VINEYARD .......................................... 87 Underground irrigation at Alvi’s Drift...................................................88 Leafroll disease or deficiency symptom? ............................................... 91 Gen-Z interplanting project: preliminary results – Olifants River............................................................................................96 Manganese deficiencies ........................................................................... 98 The influence of climate change on the potassium, pH and total acidity of wines.......................................................................100

Collaboration to mitigate the risk of climate change.........................102 Recompaction of soil in existing vineyards – causes and upliftment methods............................................................105 Let nature work for you – employ winter weeds as cover crops......111 The effect of mountainous terrains on cold-unit accumulation .......114 PRACTICAL IN THE CELLAR . .................................................116 Filtration choices....................................................................................117 Preventing pinking during harvest......................................................118 The past, present and future of sulphur dioxide .................................120 Making a Top 10 Merlot – to cold soak or not...................................122 Bentonite and laccase – a doomed attraction.....................................124 The impact of cross-flow filtration on wine filterability ....................126 The trend of natural winemaking........................................................128 The pros and cons of pumping options for cellars.............................130 The ultrasonic sanitation of barrels.....................................................132 Barrel-to-barrel variation during red wine maturation.....................133 Maintaining barrels for longer use.......................................................134 Natural alternatives for sulphur dioxide . ............................................135 Factors that affect alcoholic fermentation ...........................................136 GENERAL ..........................................................................138 Confronting Climate change: Van Loveren shares their user experience feedback on the CCC carbon calculator ...................139 Outsmarting tomorrow.........................................................................145 Confronting Climate change: Wellington Wines shares their user experience feedback on the CCC carbon calculator ..................147 Uncertain times are a constant – be flexible and adaptable .............152 The value of healthy disagreements.....................................................154 Women add value – they have the power to create, nurture and transform...........................................................................155 Factors influencing knowledge uptake by practitioners – individual characteristics.......................................................................156 Factors influencing knowledge uptake by practitioners – characteristics of the knowledge source..............................................158 Factors influencing knowledge uptake by practitioners – characteristics of the knowledge..........................................................161 Factors influencing knowledge uptake by practitioners – the nature of the knowledge transfer channel....................................164 Confronting Climate change: Benchmark Report 2023 ...................166 Neethlingshof – a focus on knowledge development........................171 Confronting Cimate change: Villiera Wines shares their user experience feedback on the CCC carbon calculator ...........................172 Roodezandt RF – employer involvement establishes leaders..........177 La Bri – transfer of knowledge promotes positive self-esteem........178 Cellar Assistants’ Programme – information days and senior cellar assistants’ workshops add value....................................179

IMAGES COPYRIGHT: Individual authors, Shutterstock or WOSA library. DTP LAYOUT: Avant-Garde South Africa | 021 863 3165 | COVER IMAGE: Kevin Crause

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TECHNICAL YEARBOOK 2023

Authors / Contributors

Bennie Diedericks Soilution bennie@resalt.co.za

Gert Engelbrecht Vinpro gerte@vinpro.co.za Heinrich Schloms Vinpro heinrich@vinpro.co.za Hennie Visser Vinpro henniev@vinpro.co.za

Benoit Divol South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University divol@sun.ac.za

Bernard Mocke Laffort bernard.mocke@laffort.com Carien Coetzee Basic Wine carien@basicwine.co.za

Hanno van Schalkwyk Vinpro hanno@vinpro.co.za

Johan de Jager Vinpro johan@vinpro.co.za Karien O’Kennedy South Africa Wine karien@sawine.co.za

Carolyn Howell Soil and Water Science, ARC Infruitec-Nietvoorbij howellc@arc.agric.za

Charl Theron Private consultant vinofino@mweb.co.za

Lida Malandra Enartis lida.malandra@enartis.co.za Piet Loubser Lallemand ploubser@lallemand.com Prabashnie Ramouthar Nemlab prabashnie@nemlab.co.za

Eduard Hoffman Department of Soil Science, Stellenbosch University ehoffman@sun.ac.za Erna Blancquaert South African Grape and Wine Research Institute, Department of Viticulture and Oenology, Stellenbosch University ewitbooi@sun.ac.za

Santi Basson Private consultant santib@mweb.co.za

Etienne Terblanche Vinpro etienne@vinpro.co.za

Stephanie Midgley Western Cape Department Agriculture stephanie.midgley@westerncape.gov.za

Gabrielle Redelinghuys WinFieldUnited GRedelinghuys@WinFieldUnited.co.za

Gerhard Pietersen PathoSolutions gerhard@pathsol.co.za

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TECHNICAL YEARBOOK 2023

Foreword On 1 July 2023, South Africa Wine commenced operations as a non-profit organisation mandated by the South African wine and brandy industry to build resilience, foster transformation, and promote agility and competitiveness. Our primary mission, in close partnership with the government and other key stakeholders, is to champion the strategic objectives of the industry. Knowledge is as vital as the grapes themselves in the world of grape and wine production. One of South Africa Wine’s key focus areas is the communication of results of locally funded and international research. Using various knowledge transfer platforms, we aim to foster greater awareness of innovative possibilities that can help the industry navigate the complexities of modern grape growing and winemaking. One of our knowledge transfer channels is WineLand Magazine. In 2023, we published 49 technical articles covering topics such as vine water stress, winery wastewater for irrigation, root health, leafroll, minerality, yeast rehydration, ultrasonic sanitation of barrels, and many more. The Technical Yearbook combines all the technical articles published in WineLand in a calendar year in one book, serving as a comprehensive repository of technical knowledge related to viticulture and oenology. By consolidating a wealth of knowledge and expertise in viticulture and oenology into a single comprehensive resource, the yearbook is a vital tool for advancing the industry’s technical capabilities and fostering innovation. This repository of articles provides invaluable insights, best practices, and research findings that empower winegrowers, winemakers, and industry professionals to enhance quality, sustainability, and competitiveness in their operations. Moreover, by documenting and disseminating this wealth of information, the technical yearbook contributes to preserving and evolving South Africa’s rich winemaking heritage, ensuring its continued relevance and excellence in the global wine landscape. I sincerely hope that the 2023 Technical Yearbook will ignite a spark of curiosity and inspiration among you and empower you with the knowledge to create a more sustainable future for South African wine.

Karien O’Kennedy Knowledge Transfer Manager South Africa Wine – Research, Development and Innovation

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TECHNICAL YEARBOOK 2023

FOREWORD

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Viticulture 1

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JANUARY/FEBRUARY

Management of vine water stress through foliar treatment with microbial derivatives* By Lucia Giordano, Tommaso Frioni & Fabrizio Battista

An innovative microbial derivative has been developed to protect vines from the negative effects of water stress. The application of this product has been the subject of an in-depth study showing that the treatment enables faster and more effective osmotic regulation, limiting production and quality losses in increasingly frequent water stress situations. Vineyard water levels are a key aspect to be managed during the season to ensure a good vegetative-production balance and optimal production results. Against the backdrop of global warming, dry winters are rising, with a poor accumulation of soil water reserves. Spring and summer are characterised by frequent extreme events or intense rain events that bring no benefits to water balance in the vineyard.

moment for water shortage is between fruit set and veraison, during the grape’s vegetative growth phase. Water stress occurring when cell division and development processes are active impacts final yield much more than stresses of the same intensity occurring at veraison or post-veraison. Furthermore, loss of product caused by premature stress is irreversible, even if the amount of water replenished during the rest of the season increases. If water deficit is moderate and controlled in the final phase of ripening, it could also have positive effects on quality, especially for red grapes, whereas the first reaction of the plant to a substantial deficit is a slowdown in photosynthetic activity. When stress lasts several days, the stomata close and photosynthesis ceases, increasing leaf temperature as there is no transpiration thermoregulation. If these conditions continue for long periods, cell turgor is lost, with the accumulation of reactive oxidising species (mainly hydrogen peroxide) in the tissues, which is the cause of classic leaf yellowing and necrosis that can cause permanent damage to the photosynthesis system.

It is estimated that 99% of the water used by vines is transpired to allow photochemical and thermoregulation tissue processes. “Constitutional water”, namely water stored in the plant which is essential for maintaining the right cell turgor, is necessary for growth, stomata movement and root system functioning. With the same amount of rainfall, high temperatures increase vineyard evapotranspiration, and the incidence of water stress rises even in the wettest districts. The amount of

FIGURE 1 . Distribution of water needs during the vine’s vegetative cycle, with the total requirement being 100. Water stress during the fruit set-veraison period severely compromises seasonal production. Hence treatments with LalVigne ProHydro™ are recommended during this phase.

water required by the vine varies considerably during the different phenological phases (figure 1). This means that the consequences of water shortage differ considerably according to the development stage. The most delicate

* This article was first published in Italy in L’Enologo – Number 4, April 2022.

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How to fight water stress with a new foliar treatment A dual synergistic approach is required to manage extended or unpredictable water stress. On the one hand, planning of long-term strategies to be implemented during the planting phase; on the other, identifying flexible and timely techniques applicable during the season. The use of new natural foliar applications based on the action of specific microbial derivatives, such as inactivated yeasts and bacterial extracts, is a state-of-the-art cultivation strategy.

Specifically, LalVigne ProHydro™, based on the selected wine yeast derivative ( Saccharomyces cerevisiae ) and L-proline of natural origin ( Corynebacterium glutamicum ), was developed to improve vine response to water stress. Its preventive use achieves a dual action, ensuring high photosynthetic activity and avoiding excessive slowdown of basic plant metabolism, while preparing the plant to cope with water stress consequences. How the new foliar treatment works The water inside the plant moves, because of the negative water potential gradient, shifting from the soil to the atmosphere through roots, stems, shoots and leaves. In the event of water shortage, resources may be insufficient to ensure transpiration, photochemical reaction and cell turgor, three aspects that will be inhibited to varying degrees and dynamics. In these situations, the vine puts strategies in place to adapt to limiting conditions, such as increasing leaf angle and folding leaf margin, to escape exposure to direct light, or various chemical-physical rearrangements to regulate the water and biochemical balance of its tissues. These include the accumulation of proline, an osmotically active amino acid which, in the case of stress, is synthesised in chloroplasts and accumulated in the cytoplasm at concentrations equal to 10 times those of the pre-stress situation. Proline fosters osmotic adjustments necessary for maintaining cell turgor and draws water from the organelles with higher water potential. In addition, day-night proline turnover encourages reducing power (NADP+) accumulation and prevents the formation of reactive oxygen species, toxic molecules that cause yellowing and necrosis of stressed leaves. In 2020, potted Pinot noir vines were treated with LalVigne ProHydro™ and compared with an untreated control sample. From one day before treatment and at

PHOTO 1. Impact of water stress; even if water becomes available later, the plant is no longer able to recover pre stress photosynthesis rates. Extensive R&D conducted by Lallemand (patent pending) has led to the development of several specific formulations that can optimise vineyard performance in terms of improving tolerance to abiotic stresses (Giordano et al ., 2021) and phenolic and aromatic maturation (Pastore et al ., 2020).

FIGURE 2. Percentage of endogenous proline accumulation in response to treatment with LalVigne ProHydro™ at 1 kg/ha. A single treatment induced a constant accumulation of over 170% for the next 14 days, equal to a constant increase of 1.26 micromoles per day per g of weight.

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regular intervals after treatment, leaves were sampled, on which proline concentration was determined. After sampling, the leaves were cleaned with distilled water to remove any exogenous proline deposits so that only endogenous proline was measured (i.e., contained in leaf tissues). One hour after treatment, no significant differences between the treatments were observed. Starting from three days after treatment, the percentage variation of proline compared to pre-treatment levels gradually and steadily increased from +68% to +170% at 14 days from treatment, while untreated plants in the same period recorded a proline increase of 50%. This means that preventive treatment with LalVigne ProHydro™ prepares the plant for water stress and osmotic imbalances, with a priming effect that leads to earlier, more abundant proline biosynthesis. In addition to its osmolytic function, proline acts as a free radical scavenger, preventing permanent tissue damage caused by oxidising chemical species the vine produces when under stress. From a practical point of view, this translates into better use of the water resource for photochemical processes and thermoregulation, favouring preservation of low foliage temperature and more effective prevention of excess energy that causes yellowing and foliar abscission. Experimental trial set up Perugia University, in collaboration with Università Cattolica del Sacro Cuore (Piacenza), evaluated the use of LalVigne ProHydro™ on the physiological and production functions of seven-year-old vines ( cv. Sangiovese, clone

VCR30) grown in pots and artificially subjected to water stress conditions in a period of high temperatures.

PHOTO 2. Potted vines subjected to water stress. Left, untreated vines with evident chlorosis caused by water stress; right, vines treated when ripe with LalVigne ProHydro™, where no damage from water stress is evident.

FIGURE 3. Physiological parameters recorded in plants treated and not treated with LalVigne ProHydro™, indicated by the arrows at a dose of 1 kg/ha: plants always irrigated (A, C) and subjected to a period of pre-veraison water stress (B, D). A and B: photosynthesis and maximum air temperature; C and D: water use efficiency (WUE) calculated as the ratio between photosynthesis (Pn) and stomatal conductance (gs). *: indicates significant differences between control and treatment.

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Three foliar treatments of LalVigne ProHydro™ were applied at the equivalent dose of 1 kg/ha at these phenological stages: fruit set (19 June), pea-size (3 July), and cluster closure (17 July). Control vines were treated with water only at the same time point. All the plants were kept under full irrigation conditions (90% of pot capacity) for up to three days after the last treatment (20 July), when half of the vines from each sample were subjected to water stress, keeping maximum water capacity at 40%. On 8 August (a few days before veraison), 90% of maximum water availability was restored for all plants until the end of the season. Photosynthesis (Pn), stomatal conductance (gs), water use efficiency (WUE), photochemical efficiency of PSII (Fv/Fm), and chlorophyll content (SPAD units), as well as quantitative and compositional parameters of the grapes at harvest (12 September), were recorded. Results The data that emerged show how treatment with LalVigne ProHydro™ was able to limit the effects of water and heat stress during the year. From a climatic perspective, the study was conducted in a period with maximum temperatures (T max) above 35°C for over 22 days (figure 3A-B). It can be seen that regardless of the water regime implemented, all the plants in the trial were subjected to significant thermal stress during the season. The physiological data and, in particular, photosynthesis data show how, in response to the first and second treatment with LalVigne ProHydro™, there was increased photosynthesis compared to the untreated control. These differences decreased when lower temperatures were recorded on 15 July (figure 3A-B). In the samples not subjected to water stress, after the third treatment, following seven consecutive days with T max above 35°C, treated vines showed better photosynthesis than control vines (figure 3A). In the same period, with vines subjected to water stress, the treated plants showed a higher level of photosynthesis than the control, respectively +48% on 25

July (five days from the beginning of water stress) and +21% on 1 August (12 days of stress) (figure 3B). When full water volumes were restored, the treated plants responded promptly with a fast and consistent recovery of Pn (+56%) and WUE (+40%), which returned to pre-stress levels, while the untreated plants never recovered full photosynthetic rates (figure 3B-D). This suggests that during the stress period, the treated plants did not suffer permanent or irreversible damage to the photosynthesis system, as shown by the photochemical efficiency data evaluated through the Fv/Fm fluorescence ratio (figure 4A). This parameter has a threshold value of 0.65, below which there is an irreversible loss of efficiency of chloroplast photosystem II, evident as leaf yellowing, chlorosis and necrosis (photo 2), the result of hydrogen peroxide and other phytotoxic molecules accumulation under severe stress conditions. The plants treated with LalVigne ProHydro™ maintained a higher photochemical efficiency than the control, staying above the threshold value of 0.65 for the entire trial. Conversely, the control vines fell below this value, triggering chronic photoinhibition processes. No photoinhibition phenomena occurred in the irrigated plants, either in the treated or control plants (data not shown). In addition to rapidly recovering photosynthetic efficiency after the period of stress, the treated vines maintained their foliar system in activity longer, ensuring good photosynthesis levels until harvest. This observation is also confirmed by the higher content of chlorophyll found in the treated vines both during the hottest days in the irrigated trials (data not reported) and in those subjected to water stress (figure 4B). The better physiological performance of the treated vines allowed a better allocation of dry matter and reduction of grape dehydration phenomena, as shown by the average weight of the berries and yield per vine, higher than the control, both in the irrigated and in the stressed vines (table 1). At the same time, treatment supported sugar accumulation and concentration of polyphenols in plants subject to water stress (table 2).

TABLE 1. Production parameters recorded at harvest. Treatment with LalVigne ProHydro™ avoided losses due to dehydration enabling better average berry weight both in situations of good water supply and in situations of concomitant thermal and water stress. Different letters indicate statistically significant differences between treatments (p < 0.05). Sangiovese Average cluster weight (g) Berry weight (g) Yield (kg/vine) Irrigated control 210 b 1.29 b 1.68 b Irrigated ProHydro™ 256 a 1.55 a 2.05 a Control water stress 205 b 1.14 c 1.40 c ProHydro™ water stress 236 ab 1.36 b 1.65 b Conclusions

the natural biosynthesis of endogenous proline in the leaves, which allows a higher level of cell turgor and avoids the biosynthesis of phytotoxic molecules, such as hydrogen peroxide and other reactive oxygen species.

LalVigne ProHydro™ is a new microbial derivative capable of ensuring greater photosynthesis and fostering a faster plant recovery in case of water stress. The treatment stimulates

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TABLE 2. Grape composition at harvest. Treatment with LalVigne ProHydro™ enables good acidity to be maintained and sugar to be accumulated in the samples subjected to water and thermal stress, as well as allowing complete phenolic maturation. Different letters indicate statistically significant differences between treatments (p < 0.05).

Sugars (°Brix) 21.40 b 21.77 b 21.45 b 24.07 a

Titratable acidity (g/L)

Yield (kg/vine)

Sangiovese

pH

Irrigated control

5.80 c 7.12 a 6.40 b 6.70 ab

3.33 3.21 3.20 3.28

0.93 b 0.96 b 0.84 c 1.09 a

Irrigated ProHydro™ Control water stress ProHydro™ water stress

FIGURE 4 . Photochemical efficiency of the photosynthetic system (A) and chlorophyll content in SPAD units (B) of LalVigne ProHydro™ treated and control plants at times indicated by the arrows at a dose of 1 kg/ha in plants subjected to a period of pre-veraison water stress. The photochemical efficiency is calculated as the ratio between Fv fluorescence (difference between the minimum and maximum fluorescence) and Fm (maximum fluorescence); values below 0.65 indicate that the photosynthesis system suffered permanent damage. *: indicates significant differences between control and treated plants.

In this study, carried out in a semi-controlled environment in potted Sangiovese vines, it was shown that foliar treatments carried out between fruit set and veraison with LalVigne ProHydro™ can help to avoid production losses linked to water stress and, at the same time, maintain the accumulation of sugars and phenolic compounds. These effects are linked to the enhanced physiological performance of the treated plants when stressful conditions arise. The

treated plants do not suffer permanent damage to the photosynthetic system, allowing complete functional integrity of the foliage to be retained, with a greater allocation of photosynthates until harvest. These data confirm that the maximum effectiveness of LalVigne ProHydro™ is obtained with preventive treatments undertaken in the period in which water stress can severely compromise yield (fruit set veraison period). 

Reference https://www.wineland.co.za/management-of-vine-water-stress/

For more information, please contact Piet Loubser at ploubser@lallemand.com.

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MARCH

Late pruning of the vine By Alain Deloire & Anne Pellegrino

Republished with permission from IVES Technical Reviews , September 2022. DOI: https://doi.org/10.20870/IVES-TR.2022.7167.

Take note, this research was done in France (Northern Hemisphere), hence the seasons will differ from ours in South Africa (Southern Hemisphere). In the current climatic context, with milder winters leading to earlier budburst in most wine regions, vines are exposed to the risk of spring frosts for a longer period. Depending on the year, frost can lead to yield losses of between 20 and 100%, jeopardising the economic survival of wine estates. In addition, by destroying young shoots, spring frosts can impact the following season’s production, by reducing the number of canes available for pruning, for example. Late pruning is one method to combat spring frosts. 1,2 Why prune late? 1. To delay budburst and thus limit the impact of spring frosts in April (especially for early grape varieties) in temperate regions with mild winters. 2. To delay (in addition to budburst) the other phenological stages, namely flowering, veraison and ripening, and hence the harvest date. What basic workings of the vine need to be known for effective late pruning? We shall distinguish between pre- and post-budburst pruning. Pre-budburst pruning Pre-budburst pruning should be considered in relation to two key stages of the vine’s winter resting period: endodormancy (linked to physiological limitations) and ecodormancy (linked to climatic limitations). Ecodormancy is divided into two physiological sub-stages: before and during bleeding of the vine. 3,4 Pruning before bleeding has no impact on the phenological stages. Only pruning as from the time of bleeding can delay budburst, but without impact on the subsequent phenological stages. According to our results with Syrah (Mediterranean climate), the delay in budburst is approximately six days (to be adjusted for other grape varieties and climates).

Post-budburst pruning To practice post-budburst pruning, i.e. beyond mid budburst (when 30 - 50% of the latent buds have burst on winter canes not yet pruned, stage EL-4 on the Eichhorn & Lorenz scale), it is important to understand certain concepts related to the development and functioning of the vine, such as acrotony and the dynamics of changes in the carbon reserves of the canes, trunk and roots. 3 - Acrotony: on a vertically positioned winter cane, the top buds will develop first, inhibiting the development of latent buds at the base. Acrotony thus permits post budburst pruning of the vine. It is recommended to leave at least eight to 10 latent buds on a cane in case of pre pruning, so that acrotony can do its work effectively. - Vine reserves: the carbon reserves (starch, soluble sugars) and nitrogen reserves (amino acids, proteins) stored in the perennial organs (roots, trunk, canes) are called on at budburst to allow the growth of the young shoots (figure 1). According to Bates and other authors (2002), 5 up to 80% of the reserves are called on before the flowering stage. The reserves are then gradually built up again during the growth cycle, when the leaves become mostly autotrophic (at around the time of flowering). Justification of post-budburst pruning should be based on the pool of carbon reserves established the previous year and the quantity of carbon allocated to new shoots. 6 In this respect, the phyllochron (thermal time between the sequential emergence of leaves) can be used as an indicator of the post-budburst level of depletion of carbon reserves. Trials carried out on the Syrah cultivar have shown that herbaceous growth of berries (figure 2) and the onset of veraison (softening and colouring of the berries) (figure 3) are all the more delayed when pruning is carried out at advanced growth stages, i.e. from the bleeding stage (pre-budburst) to the three to five leaves separated stage (post-budburst). To complete the legend for figure 3, it is interesting to note that mid-veraison was around 31 July 2021 for the first two pruning dates and approximately 10 days later for pruning on 21 April 2021. The notable effect of the grape variety × climate × soil interaction on the shift in phenological stages should again be emphasised here.

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TECHNICAL YEARBOOK 2023

soil interaction on the shift in phenological stages should again be

emphasized here. runing mpact s with mately

(when uned, rstand of the arbon buds at the It is n case ) and ennial w the

FIGURE 1. (a) Post-budburst late pruning at the three to five leaves separated stage for the two or three latent buds at the top of the cane. (b) Longitudinal section of a node and (c) visualisation of starch in the ligneous parenchyma of the secondary xylem by Lugol’s Iodine staining. (d) and (e) Cross sections of the cane showing the tissues before and after Lugol’s Iodine staining. The presence of starch in the ray parenchyma of the secondary xylem is visible 15 days after the normal date of budburst.

Adjustment of the post-budburst pruning variety × environment” situation is t budburst (Figure 4), and possibly th without causing significant yield loss carbon reserves. What to take away abou vine Pre-budburst 1/ The most effective period for pruni the bleeding phase. Clearly, this rais related to the size of vineyard to be pr of labor. In this respect, mechanical p with its speedier implementation allowi 2/ The determination/prediction of th requires more research-experimentatio “grape variety/rootstock × temperatu interaction. Post-budburst The pruning period will depend on t interaction versus grape varieties (early hot) applying the concepts of acrotony reserves of the vine. Adjustment by wine region and by necessary (i.e. early or late varietie budburst occurs for them 7 .  as a function of pruning date (50% budburst on the control observed on 1 April 2020). 1) Pruning on 5 February 2020 at the ecodormancy stage and before bleeding. 2) Pruning on 13 March 2020 at the time of vine bleeding. 3) Post-budburst pruning on 9 April 2020. 4) Post budburst pruning on 7 May 2020. Adjustment of the post-budburst pru variety × environment” situation budburst (Figure 4), and possib without causing significant yield carbon reserves. What to take away ab vine Pre-budburst 1/ The most effective period for p the bleeding phase. Clearly, thi related to the size of vineyard to b of labor. In this respect, mechanic with its speedier implementation a 2/ The determination/prediction requires more research-experime “grape variety/rootstock × temp interaction. Post-budburst The pruning period will depend interaction versus grape varieties hot) applying the concepts of acr reserves of the vine. Adjustment by wine region and necessary (i.e. early or late va budburst occurs for them 7 .  FIGURE 3. Example of the effect of pruning dates on percentage veraison (colour of a population of 60 berries), the sugar concentration (°Brix) and the average fresh weight of the berries (g); the measurements were made on 21 July 2021. Three pruning dates are compared: pre-budburst in the endodormancy phase (21 December 2020); during bleeding (5 March 2021) and post budburst on 21 April 2021, when the un-pruned canes have developed young shoots at the two to four leaves separated stage (example of the Syrah cultivar, Institut Agro vineyard; study carried out on individual berries).

FIGURE 1. (a) Post-budburst late pruning at the 3-5 leaves separated stage for the 2 or 3 latent buds at the top of the cane. (b) Longitudinal section of a node and (c) visualization of starch in the ligneous parenchyma of the secondary xylem by Lugol’s Iodine staining. (d) and (e) Cross-sections of the cane showing the tissues before and after Lugol’s Iodine staining. The presence of starch in the ray parenchyma of the secondary xylem is visible 15 days after the normal date of budburst. FIGURE 2. Syrah bunches observed on 8 July 2020 and average berry weight

this article into English was offered to you by Moët Hennessy.

FIGURE 2. Syrah bunches observed on 8 July 2020 and average berry weight as a function of pruning date (50% budburst on the control observed on 1 April 2020). 1) pruning on 5 February 2020 at the ecodormancy stage and before bleeding; 2) pruning on 13 March 2020 at the time of vine bleeding; 3) post-budbust pruning on 9 April 2020; 4) post-budburst pruning on 7 May 2020.

FIGURE 2. Syrah bunches observed on 8 July 2020 and average berry weight as a function of pruning date (50% budburst on the control observed on 1 April 2020). 1) pruning on 5 February 2020 at the ecodormancy stage and before bleeding; 2) pruning on 13 March 2020 at the time of vine bleeding; 3) post-budbust pruning on 9 April 2020; 4) post-budburst pruning on 7 May 2020.

FIGURE 3. Example of the effect of pruning dates on percentage of veraison (color of a population of 60 berries), the sugar concentration (°Brix) and the average fresh weight of the berries (g); the measurements were made on 21 July 2021. Three pruning dates are compared: pre-budburst in the endodormancy phase (21 December 2020); during bleeding (5 March 2021) and post-budburst on

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TECHNICAL YEARBOOK 2023

of 60 berries), the sugar concentration (°Brix) and the average fresh weight of the berries (g); the measurements were made on 21 July 2021. Three pruning dates are compared: pre-budburst in the endodormancy phase (21 December 2020); during bleeding (5 March 2021) and post-budburst on 21 April 2021, when the un-pruned canes have developed young shoots at the 2-4 leaves separated stage (example of the Syrah cultivar, Institut Agro vineyard; study carried out on individual berries).

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FIGURE 4. (a) Syrah vine pruned during endodormancy. The start of budburst was observed at the end of March 2021 and the photo shows the stage of development of the latent buds of the spur as of 8 April; (b) example of a cane bearing 12 buds and not pruned on 8 April. The buds at the top of the cane have developed, inhibiting the budburst of at least 4 buds at the base. (c) on 21 April 2021, for the un-pruned vines, it is observed that only the latent buds at the top of the canes have developed, inhibiting the development of the buds at the base (d), which permits post-budburst late pruning. FIGURE 4. (a) Syrah vine pruned during endodormancy. The start of budburst was observed at the end of March 2021 and the photo shows the stage of development of the latent buds of the spur as of 8 April. (b) Example of a cane bearing 12 buds and not pruned on 8 April. The buds at the top of the cane have developed, inhibiting the budburst of at least four buds at the base. (c) On 21 April 2021, for the unpruned vines, it is observed that only the latent buds at the top of the canes have developed, inhibiting the development of the buds at the base (d), which permits post-budburst late pruning.

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Adjustment of the post-budburst pruning date according to the “grape variety × environment” situation is therefore necessary to delay budburst (figure 4), and possibly the other phenological stages, without causing significant yield losses due to exhaustion of the carbon reserves. What to take away about late pruning of the vine Pre-budburst 1. The most effective period for pruning to delay budburst is during the bleeding phase. Clearly, this raises the question of feasibility related to the size of vineyard to be pruned and the logistics in terms of labour. In this respect, mechanical pruning can be an advantage, with its speedier implementation allowing for late pruning. 2. The determination/prediction of the bleeding period

of the vine requires more research-experimentation and consideration of the “grape variety/rootstock × temperature × water status of the soil” interaction. Post-budburst The pruning period will depend on the “grape variety × climate” interaction versus grape varieties (early or late) and climate (cool or hot) applying the concepts of acrotony, phyllochron and the carbon reserves of the vine. Adjustment by wine region and by family of grape varieties is necessary, depending on how early budburst occurs for them. 7  References https://www.wineland.co.za/late-pruning-of-the-vine/

IVES Technical Reviews | September 2022

This work is licensed under

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Shutterstock

Manipulating Sauvignon blanc ripening through shoot trimming and crop reduction By Carien Coetzee

The effect of canopy management strategies on the berry composition and harvest dates of Sauvignon blanc was investigated in a study 1 performed by a New Zealand research group. Introduction The leaf area to fruit mass ratio is a source-sink ratio that may have an important influence on grape development and maturity during ripening. Both the leaf area, as well as the

fruit mass, can be manipulated through viticultural practices such as leaf/shoot removal and crop thinning. Materials and methods The study was conducted in a commercial vineyard in the Wairau Valley, Marlborough, New Zealand. Sauvignon blanc vines (clone MS) were used in this trial. The canopy management strategies included: 1. Trimming the shoots (no leaf removal in the bunch zone) to six or 12 main leaves per shoot, and/or 2. Removing bunches (0, 50 or 75% bunch removal). The canopy management strategies were applied either

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Other ripening markers Titratable acidity, pH and fresh berry weight were largely unaffected by the treatments. It is therefore possible to reduce the rate of TSS accumulation without altering the evolution of other ripening markers. However, the relative composition and relationship between the berry components must be considered when applying these ripening management strategies. Conclusion Canopy management practices such as shoot thinning, leaf removal, hedging and crop thinning are often used to modify the canopy for a specific target of shoot density, crop level, or cluster exposure. However, canopy management strategies such as leaf area reduction by trimming shoots and crop removal can also be successfully employed to adjust the rate of TSS accumulation, and therefore the timing of veraison and harvest dates. It is possible to manipulate the TSS accumulation using canopy management techniques without affecting other ripening markers such as titratable acidity and pH. The extent to which the reduction in leaf area and crop removal alters the source-sink ratio in grapevines and subsequently changes TSS accumulation rates post-veraison largely depends on the degree and timing of crop removal and/ or shoot trimming. The secondary effects of these canopy management strategies should be considered. For instance, shoot trimming early in the growing season could encourage lateral growth, causing the canopy density to increase. Under warmer climate conditions, delaying veraison and slowing TSS accumulation could help address logistical issues during compressed harvests. This information is also potentially important to counteract the effect of advanced phenology in response to increased temperature due to climate change or, conversely, to enable target TSS concentration to be reached in marginal environments with cooler climates. Abstract Canopy management strategies such as crop removal and leaf area reduction by shoot trimming can be successfully employed to adjust the ripening tempo of Sauvignon blanc resulting in modified veraison and harvest dates.  Reference https://www.wineland.co.za/manipulating-sauvignon blanc-ripening/

at fruitset or at veraison. The berry composition was monitored during regular intervals from pre-veraison to harvest and included total soluble solids concentration (TSS) (°Brix), pH, titratable acidity and fresh berry mass. Results Reducing the leaf area • Reducing the leaf area to six leaves at fruitset (0% crop removal) had the most significant influence on the ripening tempo resulting in delayed veraison (up to one week). • The rate of TSS accumulation of the six-leaf treatment was significantly slower than when the leaf area was reduced to 12 leaves (0% crop removal). • Reducing the leaf area at veraison also slowed the rate of TSS accumulation during maturation; however, the effect was not as pronounced as when the leaf area was reduced at fruitset. The two trimming regimes, therefore, resulted in very different ripening rates, with the effect being more pronounced when the canopy management strategy was applied at fruitset compared to at veraison. This would suggest that the earlier the trimming is applied, the greater the effect on the berry composition and ripening tempo. Care should be taken as the ability of the bunches to reach a targeted TSS concentration might be compromised in cases where severe trimming techniques were applied. Crop removal • Crop removal (either at fruitset or veraison) resulted in higher TSS concentrations at harvest compared to 0% crop removal. This effect was seen for the majority of the shoot trimming treatments. Therefore, crop removal accelerated the TSS accumulation rate regardless of the severity of trimming. Leaf area reduction vs crop removal Restricting potential carbohydrate sources (through shoot trimming) in Sauvignon blanc during post-flowering resulted in delayed veraison and maturation, while crop removal affected the evaluated parameters to a lesser extent. When the leaves were removed (six-leaf shoots) in combination with bunch removal (50% crop removal), a countereffect was observed, and the rate of TSS accumulation was similar compared to the 12-leaf shoots with 0% crop reduction.

For more information, contact Carien Coetzee at carien@basicwine.co.za.

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MAY

Vineyard biodiversity – how to put it to work using cover crops By Geoff Gurr, Jian Liu & Jason Smith

This article is republished from Grapegrower and Winemaker , Issue 705, October 2022, with permission from the authors and Grapegrower and Winemaker .

Vineyards usually have a groundcover made up of spontaneously growing grasses and broadleaved weeds or have bare earth, either directly under the vines or across the whole vineyard. Each of these options has problems. Bare earth increases the risk of soil erosion by wind and water run-off and can lead to poor soil structure. Conversely, a weedy groundcover uses valuable water and requires mowing to prevent excessive growth. If the weeds are too vigorous, they can block air flow and favour development of fungal diseases and frost damage. Reflecting this challenging situation, there has been growing interest both in Australia and overseas in the use of alternative types of groundcovers. That’s where cover crops come in. These can be thought of as form of groundcover that is deliberately established and often more actively managed than a spontaneous coverage of weedy plants. Cover crops can deliver a range of benefits in the vineyard. Early work in South Australia, for example, showed scope for weed control using under-vine cover crops. In 2021, Wine Australia awarded funds to a new project that aims to generate evidence-based guidelines for using a range of cover crop types to deliver multiple benefits to vineyards. Results from the first year of this project, run by Charles Sturt University, are the focus of this article. One feature of the new project is the use of laboratory studies to assess the benefits of a range of potential cover crop plants to parasitic wasps that attack light brown apple moth, one of the key vineyard pests in many districts. The caterpillars of this pest damage bunches and leave them more susceptible to infection by botrytis fungus, leading to bunch rot. Our work has focussed on minute Trichogramma wasps that lay their eggs in the pest’s eggs, ‘hijacking’ them so they give rise to more wasps rather than developing into damaging caterpillars. Whilst Trichogramma wasps are widely distributed in Australia, they live for only a few days unless able to feed on nectar. Unfortunately, nectar plants tend to be scarce in vineyards making them

inhospitable locations for effective biological control. Our laboratory research has identified a range of plant species that may remedy this problem by providing nectar that is suitable for use by Trichogramma wasps. One example is buckwheat which produces nectar that extends the lifespan of these tiny wasps and more than doubles their egg laying. Buckwheat can be grown as a mid-row cover crop in vineyards but is too tall (about 1 m) to be suitable for use directly under the vines. Here, another plant, alyssum, seems to have good scope as it grows to only a quarter of the height of buckwheat. Alternatives to these exotic plants include several native species that might be favoured in settings where the manager wished to soften their overall environmental impact and make the vineyard a setting where native invertebrates and small animals find harbour. But our screening of various options has revealed an important practical message. Some native plants, including Acacia and Kunzea species, appear to provide no benefit to Trichogramma. Fortunately, many other species do greatly boost egg laying by wasps. These include the prostrate growing species Grevillia lanigera , Myoporum parvifolium and Leptospermum ‘Pink Cascade’. Our laboratory tests

Geoff Gurr checking early season establishment of buckwheat sown as a mid-row cover crop.

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Buckwheat plants blooming mid-season and providing nectar to beneficial insects.

established under the vines. This was an exciting finding because those natives were established as small plants that took time to grow yet they were still delivering benefit in year one. By the end of the first season several, especially Dampiera and Myoporum, were aggressively covering more ground and out-competing the adjacent weeds but still retained their prostrate growth habit. This meant that they did not climb into the vine foliage and, at an average of less than 20 cm high, were considerably shorter than the weedy plants in the control plots in the trials which comprised the original groundcover. Those grassy and broadleaved weeds were typically around 50 cm high so much more likely to impede air flow through the vines and around bunches. We Key facts • Several native and non-native plant species have been identified as agronomically well suited for use as vineyard cover crops both mid-row and under vine; • Several species (including perennials) established and achieved significant levels of ground-coverage and competed well with weeds; • Several species exhibited a prostrate growth habit in vineyard settings to the extent that they were shorter than the weedy vegetation they replaced and thus can be assumed to improve air flow, so reducing frost risk and fungal disease severity; • Fruit bunch attack by light brown apple moth was greatly reduced by some cover crop treatments such as alyssum; • Both incidence and severity of botrytis bunch rot was reduced by some cover crop treatments, including alyssum, which suggests that reductions in the severity of light brown apple moth attack can have a knock-on effect in reducing the botrytis fungus infection within bunches.

Light brown apple moth: one of the key vineyard pests and for which cover crop can provide protection by attracting beneficial insects such as nectar-feeding Trichogramma wasps.

help inform which plants might be used as vineyard cover crops, as well as for selecting species suitable for ‘insectary plantings’ beside vineyards, and even help understand which native woody plants might be valuable in shelterbelts and the wider landscape. Vineyard trials So much for boffins playing with bugs in the lab; what actually happens in the field? Vineyard trials were conducted in 2021-22 in the Orange district to assess ease of establishment of various cover crop species and measure the benefits of each. An important finding from this season long trialling was that some of the plants that were shown to be useful to Trichogramma wasps in the laboratory led to reduced levels of field damage to bunches by light brown apple moth. In the case of alyssum established as under vine plots, for example, the numbers of damaged fruit bunches were reduced by two thirds at both the organically managed site (See Saw Wine’s Balmoral Vineyard) and a conventionally-managed site (Angullong Vineyard). Moreover, the alyssum cover crop led to lower numbers of fruit bunches affected by botrytis and, for those affected bunches, the severity of rot was reduced. Similar effects, though slightly less pronounced, were apparent when a mix of low-growing, perennial native plant species was

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