Scielo RSS <![CDATA[South African Journal of Enology and Viticulture]]> vol. 43 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Insecticide Efficacy Against Trimen's False Tiger Moth, <i>Agoma trimenii </i>(Lepidoptera: Agaristidae)</b>]]> Trimen's false tiger moth, Agoma trimenii (Lepidoptera: Agaristidae), has developed pest status in vineyards in the Northern Cape and Groblersdal areas of South Africa, and an integrated pest management system is required. The objective of this study was to test the susceptibility of A. trimenii larvae to three commercial products (Delegate®WG, Steward®150 EC and three doses of DiPel® DF). Bioassay tests using all three products, and semi-field trials to test the potential of DiPel® DF against A. trimenii larvae, applied at different water volumes (50 g/1 000 L/ha and 50 g/1 430 L/ha) were performed. The residual activity of DiPel® DF, when applied at different water volumes, was investigated daily. Delegate® WG, Steward®150 EC and the recommended dose of DiPel® DF showed 100% larval mortality within seven days. Delegate® WG and the recommended dose of DiPel® DF proved to be the fastest acting products. The product label recommended dose of DiPel® DF (0.25 g/500 mL distilled water) proved the most effective dose (in comparison to halved and doubled dosages) and showed 100% mortality five days after application. Increasing the water volume per ha of a spray application of DiPel® DF for the same application area, showed no significant increase in larval mortality. A reduction in insecticidal activity for DiPel® DF applied at both water volumes was seen between leaves picked four days after spraying and leaves picked five days after spraying, and no mortality was observed after day 6. To help improve efficacy, attention should be given to increasing spray coverage and residual activity of DiPel® DF, as well as using all tested products within an integrated pest management system. <![CDATA[<b>Mitigation and Adaptation Practices to the Impact of Climate Change on Wine Grape Production, with Special Reference to the South African Context</b>]]> In South Africa, environmentally and socio-economically sustainable wine grape production is promoted by governmental and private initiatives. All the initiatives contribute to establishing a scientifically based response strategy of agro-systems to ensure sustainable production under future expected climate conditions. South African wine grape producers would probably have to cultivate their grapevines under higher atmospheric CO2 levels and in warmer, mostly drier, conditions. Due to the projected increase in climatic variability, an effort must be made to improve the resilience of vines against these environmental conditions. Whole-vine functioning and balances should be considered when adjustments are made to current long and short term cultivation practices. All practices should be aimed at promoting the development of a deep, dense and buffered root system that is able to support a well-developed canopy with optimal microclimate that would sustain a high yield of good quality. Mitigation and adaptation strategies would most likely have to be region specific, and small scale terroir data, (which should include both climate and terrain/soil information) may play a critical role in decision-making. <![CDATA[<b>Attempted Identification of Causal Constituents of Pink Discolouration in White Wines</b>]]> The pinking phenomenon has been known in the wine world for the past 50 years. The phenomenon occurs when a white wine turns pink under certain conditions. Since then, a Portuguese study found malvidin-3-O-glucoside in Siria grapes making a connection to anthocyanin as the causing agent. Control (K), naturally pinked (NP) and pink induced (PI) Sauvignon blanc wine samples were analysed by LC-MS and WineScanTM (Fourier Transform Infrared - FTIR) after Solid Phase Extraction. The monomeric anthocyanins were analysed by a pH differential method, and CieLab was used to differentiate colour differences between the control and pinked samples. It was found that malvidin-3-O-glucoside was below the threshold values to facilitate pinking in Sauvignon blanc wines. Petunidin-3-O-glucoside showed a slight peak in the LC-MS analysis, and together with the malvidin-3-O-glucoside, the potential to pink the white wines increased. FTIR results showed that phenols and anthocyanins absorption could not be distinguished and that there were possibly other compounds involved in the pinking of white wines. Analysis by CieLab expressed the PI wines as a darker pink colour than the control wine and the absorbency value at 500 nm was at least three times higher for PI than the control, showing the aggressive oxidative nature of H2O2 on wine. <![CDATA[<b>The Influence of Micro-oxygenation on the Long-term Ageing Ability of Pinot noir Wine</b>]]> In this study, Pinot noir wines were bottle aged for 12 and 18 months after micro-oxygenation (MOX) applied before or after malolactic fermentation (MLF) at two doses (10.8 and 52.4 mg/L/month). After ageing, a greater decrease in the total SO2 concentration was found in wines with the higher MOX dosage, demonstrating a long-term impact of higher oxygen exposure on wines' SO2 requirement. Meanwhile, a negative impact of MOX on wine colour development occurred over time, resulting in a large loss of colour measures (i.e., 420 nm for brown hues, 520 nm for red colour, SO2 resistant pigments, and colour intensity), which was greater with the early oxygen exposure. This was linked to a significantly lower content of large polymeric pigments in MOX treatments. Tannin concentration was, in the end, not affected by the MOX treatments. However, regarding tannin composition, considerably higher (-)-epicatechin extension units but much lower (-)-epicatechin terminal units were found with MOX treatments. In addition, a significant reduction of tannin trihydroxylation (%Tri-OH) but a higher galloylation (%Galloyl) and mean degree of tannin polymerisation (mDP) remained in wines with MOX, indicating a long-term negative influence on astringency intensity. <![CDATA[<b>Dry Matter Accumulation, Seasonal Uptake and Partitioning of Mineral Nutrients by <i>Vitis vinifera </i>L. <i>cv. </i>Sultanina Grapevines in the Lower Orange River Region of South Africa - A Preliminary Investigation</b>]]> Table grapes are harvested from November until early February in the Orange River Region of South Africa, where a functional leaf canopy is present for up to six months of post-harvest. Seasonal uptake and partitioning of mineral nutrients by 'Sultanina' grapevines in this long-season area were quantified in a preliminary investigation. Entire grapevines growing on two different soil types were sampled during the growing season. On sandy soil, further from the river, grapevine vigour was not excessive; however, on the fertile alluvial soil vigour was higher with active post-harvest re-growth. At budbreak, reserve N played an important role on the sandy soil, while it was less important on the alluvial one. During the post-harvest period, 34.3% of the annual N-requirement was absorbed by grapevines cultivated on sandy soil at post-harvest, while only 17.0% was absorbed on the alluvial soil. Approximately 4.0 kg N was utilized for the production of one ton of fresh grapes. A major fraction of the annual P-requirement (41.9%) was absorbed post-harvest by grapevines on the sandy soil. Grapevines on alluvial soil absorbed more P at pre-harvest; however, P was somehow lost post-harvest. Comparable amounts of K and Mg were absorbed by both selections of grapevines. Sandy soil grapevines absorbed K and Mg at post-harvest, while a net loss occurred for those of alluvial soil. Calcium utilized by sandy soil grapevines was less than half that utilized by those of alluvial soil. The seasonal absorption pattern of Ca was comparable for both soils. Results suggest that that seasonal uptake and partitioning of mineral nutrients are affected by soil type and grapevine vigour. <![CDATA[<b>Technological Advances in Winery Wastewater Treatment: A Comprehensive Review</b>]]> The commercial production of wine is directly linked to the use of large amounts of fresh water coupled with the generation of copious amounts of wastewater containing significant amounts of organic and inorganic substances. The impact of this waste stream on the environment has required the wine industry to implement certain protocols in wastewater management to comply with respective effluent discharge regulations as set out by local authorities. Reduced accessibility to good quality water resources in recent years has forced wineries to consider more efficient wastewater management strategies to improve water recovery and re-use, thereby promoting more sustainable wine production and minimizing the impact on stressed water resources. This review presents a comprehensive overview of established and emerging, physicochemical, biological, advanced oxidation and hybrid wastewater treatment technologies specifically applicable to the wine producing industry. Herein, winery wastewater composition and treatment techniques, environmental implications, knowledge gaps, technological operational challenges, alternative disposal and recycling options of treated winery wastewater are critically evaluated. <![CDATA[<b>Is <i>Haplothrips clarisetis </i>Priesner (Thysanoptera: Tubulifera) an Economic Threat to Table Grapes in the Lower Orange River Production Region of South Africa?</b>]]> Table grape producers and consultants in the Lower Orange River region, Northern Cape province, have been reporting conspicuous, fairly large, black thrips on new growth and inflorescences early in the growing season in recent years. These thrips were identified as Haplothrips clarisetis Priesner and H. nigricornis Bagnall, both indigenous species widely distributed in South Africa and Africa. The aim of this investigation was to determine if H. clarisetis causes any damage to table grapes and if it poses an economic threat to the industry in the Northern Cape province. Inspections were conducted over two seasons during flowering and fruit set, prior to and after harvest in four vineyards near Augrabies (28.7630 S, 20.5668 E) and four in the Blouputs Valley (28.4631 S, 20.0789 E) where Haplothrips had previously been reported. Developing inflorescences, bunches, leaves and shoot tips were inspected for the presence of Haplothrips and for any signs of feeding damage. Very few thrips were found and no signs of feeding were observed. Adult H. clarisetis were collected from flowering grape bunches and from flowers of Osteospermum microcarpum (Asteraceae) and Mesembryanthemum crystallinum (Aizoaceae) growing wild adjacent to the vineyards and confined on grapevine flowering bunches, leaves and a single shoot tip. Daily inspections showed no signs of feeding damage on the shoot tip, leaves or inflorescences and thrips did not survive for more than three days on average. We therefore conclude that H. clarisetis does not pose an economic threat to table grapes in the Lower Orange River region. <![CDATA[<b>Data-driven Determination of Disease Markers' Threshold Values in Rot-affected Wine Grapes</b>]]> Grapevine bunch rot is detrimental to grape and wine quality. Traditionally, detecting and quantifying the severity of rot infection is executed visually. This study aimed at defining local, area-specific threshold values of rot-associated disease markers. This is a first step towards making informed decisions about the quality of grapes delivered at winery intake. Viticulturists visually assessed on-vine rot infection in nine white wine grape cultivars. Results showed that severity ratings were consistent between assessors. Chemical analyses of the grape must from these assessed samples were done. Multiple factor analysis (MFA) showed that rot severity was positively correlated with glycerol, alcohol, gluconic acid and acetic acid concentrations. As severity increased, gluconic acid, glycerol, alcohol, Brix, acetic acid and total titratable acidity (TA) concentrations also increased. Following the probability chosen for sensitivity and specificity, grape rot indicators' threshold values in white grape must are as follow: Alcohol > 0.10 %v/v; acetic acid > 0.17 g/L; glycerol > 0.79 g/L; gluconic acid > 0.99 g/L; TA > 8.86 g/L. Statistical determined threshold values differentiating between rot-affected and healthy grape must, would eliminate the subjectivity and bias associated with visual assessments.