Coastal Regions Of South Africa Research Articles

Comparative Bioactive Compounds and Mineral Properties of South African and Lesotho Artemisia afra (Jacq.) Genotypes.

Artemisia afra is a plant that grows in the northern, central, and coastal regions of South Africa, as well as in neighboring countries such as Eswatini and Lesotho. These phytochemicals can be used as active compounds in plant-based medicine. Therefore, it is important to determine how plant minerals and phytochemicals, particularly bioactive compounds, are affected by the geolocation in which they grow. This study aimed to evaluate the mineral and phytochemical properties of A. afra genotypes in the southern regions of Africa. Leaf samples of A. afra genotypes were collected from Lesotho, in Mohale's Hoek and Roma. In South Africa, leaf samples were collected in Wepener and Hobhouse, and 80 plants were randomly selected for phytochemical and mineral analyses. This study reveals that phosphorus, calcium, potassium, iron, and zinc loaded positively to the first principal component, while copper loaded positively to the second principal component with variabilities of 29.95% and 21.12%, respectively. Furthermore, both the Mohale's Hoek and Hobhouse genotypes exhibited relatively high levels of ascorbic acid, phenolic compounds, flavonoids, and tannins. It is worth noting that genotypes from Roma and Wepener showed higher levels of foliar magnesium. Thus, the Mohale's Hoek and Hobhouse genotypes could be recommended for their better phytochemical contents.

Long-term Effects of Irrigation with Treated Municipal Wastewater on Soil Chemical and Physical Responses in Commercial Vineyards in the Coastal Region of South Africa

The prolonged drought in the Western Cape province of South Africa in recent years has been particularly detrimental to the wine industry. Water restrictions imposed by authorities and the limited supply of fresh water that can be stored, have emphasisedthe need for alternative water sources for vineyard irrigation. Treated municipal wastewater has been used successfully as an alternative source of irrigation water in other countries. A long-term trial was conducted in commercial vineyards in the Coastal region of South Africa to assess the impact of treated municipal wastewater irrigation on vineyards. Cabernet Sauvignon and Sauvignon blanc grapevines were irrigated using treated municipal wastewater from the Potsdam wastewater treatment works for 11 years. Grapevines were either rainfed (RF), irrigated with treated municipal wastewater via a single dripper line (SLD), or received twice the volume of wastewater via a double dripper line (DLD). Irrigation using treated municipal wastewater increased soil pH(KCl), the electrical conductivity of the saturated extract (ECe) and Cl-. Substantial amounts of Na+ and K+ accumulated in the topsoil due to irrigation with treated municipal wastewater. These soil K+ increases could have a negative effect on wine colour stability should the levels of soil K+ be such that they are absorbed excessively by grapevines. The near-saturation hydraulic conductivity (Kns) at the surface of the soil could be related to the ECe in the topsoil. The results represent specific in-field situations in three commercial vineyards under one set of climatic conditions.

Fruits of the city: The nature, nurture and future of urban foraging

Abstract Urban foraging is a global informal phenomenon which has been investigated in the Global North more than other parts of the world. Characterising the nature of urban foraging in the Global South is imperative given the rapid urbanisation and sustainable development priorities in the region. In this study, we interviewed 80 urban foragers in four cities in the eastern coastal region of South Africa, with an aim to understand the nature of urban foraging in a developing nation context. We asked foragers about their initiation to and motivations for foraging, their logistics, yields and associated activities, descriptions of their foraging grounds, and if and how they had changed, and what they envisage as an ideal future for foraging. Many foragers started foraging in their childhood, in the company of friends and family, and, as in the Global North, regarded it as a cultural and recreational activity. Foraging was mostly done within a 5‐km radius of home, on a weekly or fortnightly basis, and very few foragers processed or sold their foraged products. Unlike the Global North, formal green spaces were not foraged in, and were perceived to be poorly provisioned in urban planning. Forests and roadsides were equally used by the foragers, and very few had been discouraged from foraging. Most foragers were enthusiastic about the possibility of more people foraging, having designated spaces for foraging, and foraging‐based businesses such as processed products and ecotourism. We recommend that policymakers and land managers recognise and encourage foraging as a potentially sustainable use for stewardship of urban green spaces. To this end, we list the main wild edible fruit species used by foragers in the area, which could be planted in public spaces. We also suggest harnessing foragers' knowledge of useful species and spaces to develop green spaces and foraging‐based supply chains. Read the free Plain Language Summary for this article on the Journal blog.

Sugarcane cultivar genetic gains for coastal agro-ecological regions of South Africa

Cultivar genetic gains quantify the increase in productivity from release of cultivars and measure genetic improvements from plant breeding. The objectives of this study were to evaluate the genetic gains from sugarcane coastal cultivars and evaluate their contribution to productivity. Data were derived from replicated plant breeding and post-release variety evaluation trials conducted by the South Africa Sugarcane Research Institute (SASRI) from 1996 to 2020. There were significant cultivar differences for cane yield, sucrose content, sugar yield, fibre % and purity %. Significant analyses of cultivar by location, cultivar by crop-year and cultivar by location by crop-year indicate further optimisation of cultivar disposition is needed to increase productivity. Cultivar genetic gains were found for cane yield (0.19–0.48 t ha−1), sucrose content (0.01–0.02%), sugar yield (0.03–0.07 t ha−1 per year), fibre % cane (0.04–0.06%) and purity % (0.02–0.04%), highlighting the increased yield and quality from genetic improvement. The best cultivars produced 8–22% higher sugar yields than popular cultivars indicating that planting high yield cultivars did increase yields. Sugar cane production declined at a slower rate than area planted, also showing the benefit of high yield cultivars. Increasing the area planted to new, higher yielding cultivars will increase sugar yields for coastal regions of South Africa.

Effect of Irrigation with Treated Municipal Wastewater on Vitis vinifera L. cvs. Cabernet Sauvignon and Sauvignon blanc in Commercial Vineyards in the Coastal Region of South Africa - Vegetative Growth, Yield and Juice Characteristics

Effect of Irrigation with Treated Municipal Wastewater on Vitis vinifera L. cvs. Cabernet Sauvignon and Sauvignon blanc in Commercial Vineyards in the Coastal Region of South Africa - Vegetative Growth, Yield and Juice Characteristics

Thermal physiology of Tropical House Geckos (Hemidactylus mabouia) in a cool temperate region of South Africa.

ABSTRACT Temperature profoundly influences the functioning of ectotherms and understanding the thermal biology of invasive species affords valuable insights regarding the suitability of different habitats. Yet, this remains an understudied aspect in the field of invasion biology. Here, we investigated the thermal physiology of the highly invasive Tropical House Gecko (Hemidactylus mabouia) in a coastal region of South Africa. The study site is near to the southernmost extent of the species’ distribution and we expected the physiology of individuals at the study site to differ compared to that of individuals inhabiting tropical regions. Relative to tropical geckos, we observed a decrease of 3.4°C in preferred body temperature (Tpref) to 24.0 °C, which was likely driven by selection for improved functioning within the cooler temperate climate. However, the lower (CTmin) and upper (CTmax) critical thermal limits were higher in geckos at the study site. CTmin was similar between sexes at 11.9 °C, whereas males had a higher CTmax by ≈ 1.9 °C reaching 39.7 °C. A broader tolerance range is typical of a highly variable climate, and we presume that the increase in CTmax allows geckos to better cope with occasional high temperatures. Further, sex-specific differences are uncommon in reptiles, but our study supports claims of improved heat tolerance in male geckos, argued to be related to their aggressive and territorial behaviour. The results also support claims that tropical geckos are more adaptable than previously thought, allowing them to invade new areas. Thereafter, their aggressive behaviour, dietary flexibility and year-round activity likely provides house geckos with a competitive advantage over some native reptiles.

An Assessment of Treated Municipal Wastewater Used for Irrigation of Grapevines with Respect to Water Quality and Nutrient Load Assessment of TMW for vineyard irrigation

The impact of treated municipal wastewater (TMW) irrigation on soil and grapevines was assessed under field conditions in vineyards in the Coastal region of South Africa. Grapevines were irrigated using TMW from the City of Cape Town uninterruptedly over a period of 11 years. Grapevines were either rain fed, irrigated with TMW via a single dripper line, or received twice the volume via double dripper lines. The quality of the TMW used for vineyard irrigation was acceptable, and below the minimum criteria stipulated by the General Authorisations to irrigate up to 500 m3 per day in terms of pH, ECw and SAR. Mean Na+ concentration in the TMW exceeded the critical value of 100 mg/ℓ for irrigating grapevines in South Africa. The Cl- levels in the TMW were well below the threshold value of 700 mg/ℓ at which toxicity in grapevines might occur. Consistently high P concentrations measured in the TMW could lead to the formation of algal blooms in water storage facilities and bio-fouling of irrigation equipment. The low N content in the TMW could not supply the annual N requirement of grapevines. The annual amount of P applied via the single dripper lines was slightly below grapevine requirements, whereas double the TMW irrigation applied excessive amounts of P. Amounts of K+ applied via TMW irrigation was in excess of annual grapevine requirements, which could affect wine quality negatively. The amount of Ca2+ and Mg2+ applied via the TMW also exceeded annual grapevine requirements.

Predicting the number of fruits and the seed biomass of Trichilia emetica (Vahl.) in the eastern coastal region of South Africa

Trichilia emetica is a coastal fruit tree species from sub-Saharan Africa that has a potential for commercial harvest for its edible and useful seed oils. However, the prediction of its fruit and seed yields is necessary to plan a profitable harvest. This study aims to calibrate allometric equations that predict the amount of fruits and the biomass of seeds of T. emetica. A total of 35 trees were selected based on seven classes of the diameter at breast height (DBH) in the Umkhanyakude district. The trees were measured during fruit maturation period. The measurements included the DBH, the canopy diameter, and the total height. Fruits were counted on each tree using randomized branch sampling technique. Twelve fruits were harvested per tree and were brought to the laboratory for the determination of biomass. Six allometric models were identified and fitted to the data using ordinary least squares method. The Akaike information criterion (AIC) was used to select the best-fit models. The results suggested that simple linear models, basing solely on DBH (in cm), were the best predictors of both the number of fruits on the trees (NF) and the fresh seed biomass (SB; in kg) of T. emetica. The exponential forms of the best-fit general models were: (1) NF = 375.364 × DBH1.009; and (2) SB = 1.858 × DBH1.009. The prediction tests of these models indicated that the errors were large when predicting the fruit number and the seed biomass of smaller trees (DBH ≤ 20 cm) and bigger trees (DBH ≥ 30 cm). For medium-size trees (20 cm < DBH < 30 cm), the error was small. On the other hand, tree size category models developed in this study improved statistically the accuracy of predictions. The findings recommend the use of the fitted tree size category equations.

Optimal design of wind-powered hydrogen refuelling station for some selected cities of South Africa

The transport sector is considered as one of the sectors producing high carbon emissions worldwide due to the use of fossil fuels. Hydrogen is a non-toxic energy carrier that could serve as a good alternative to fossil fuels. The use of hydrogen vehicles could help reduce carbon emissions thereby cutting down on greenhouse gases and environmental pollution. This could largely be achieved when hydrogen is produced from renewable energy sources and is easily accessible through a widespread network of hydrogen refuelling stations. In this study, the techno-economic assessment was performed for a wind-powered hydrogen refuelling station in seven cities of South Africa. The aim is to determine the optimum configuration of a hydrogen refuelling station powered by wind energy resources for each of the cities as well as to determine their economic viability and carbon emission reduction capability. The stations were designed to cater for 25 hydrogen vehicles every day, each with a 5 kg tank capacity. The results show that a wind-powered hydrogen refuelling station is viable in South Africa with the cost of hydrogen production ranging from 6.34 $/kg to 8.97 $/kg. These costs are competitive when compared to other costs of hydrogen production around the world. The cities located in the coastal region of South Africa are more promising for siting wind powered-hydrogen refuelling station compared to the cities located on the mainland. The hydrogen refuelling stations could reduce the CO2 and CO emissions by 73.95 tons and 0.133 tons per annum, respectively.

Chemical characterisation of Pelargonium sidoides root based on LC-QToF-MS non-target screening strategies.

Pelargonium sidoides is a member of the Geraniaceae family and it originates from the coastal regions of South Africa. In the last decades, Pelargonium sidoides root has been subjected to several surveys due to the assertion of its health benefits, such as the relief of symptoms of acute bronchitis, common cold and acute rhinosinusitis. Many studies have been conducted to reveal its naturally occurring bioactive chemicals, yet no wide-scope chemical characterisation strategies have been done using mass spectrometry. This research aimed to comprehensively characterise the chemical profile of Pelargonium sidoides root via high-resolution mass spectrometry. The Pelargonium sidoides root was extracted by a mixture of methanol: water in the proportion of 80:20. The extraction procedure included vortexing, shaking as well as the use of an ultrasound sonication bath under 40°C. After centrifugation, the supernatant was evaporated to dryness. The dry residue was reconstituted with a mixture of methanol/water (50:50, v/v), filtered and injected into an ultra-high-pressure liquid chromatography-quadruple time-of-flight mass spectrometer. Overall, 33 compounds were identified in the root using suspect and non-target screening. These compounds were originated from different classes of compounds such as amino acids, phenolic acids, α-hydroxy-acids, vitamins, polyphenols, flavonoids, coumarins, coumarins glucosides, coumarin sulphates and nucleotides. Quantitative results were provided for the identified compounds, where their reference standards were available. Some important compounds were elucidated, belonging to different classes of compounds such as antioxidants (coumarins and phenolic compounds), amino acids, nucleotides and vitamins revealing the importance of the bioactive content of this root.

Relative performance of coppice versus seedlings of 16 eucalypt taxa over two rotations in northern coastal Zululand, South Africa

From the 1980s, Eucalyptus grandis × E. camaldulensis (GC) and E. grandis × E. urophylla (GU) were planted as alternatives to E. grandis for improved productivity in the Zululand coastal regions of South Africa. Although these hybrid combinations provided a degree of drought and/or disease tolerance together with the ability to regenerate the stand via the management of coppice growth, there was the need to test better-suited species for the drier, northern parts of coastal Zululand. Species, provenances and inter-specific hybrid clones of the genera Eucalyptus, Corymbia, Acacia and Casuarina were tested as alternatives to GC and GU in four site × species trials over one rotation (1996 to 2006). Although E. longirostrata, Corymbia henryi, C. citriodora subsp. variegata and E. argophloia showed promise as alternatives to GC and GU, their coppicing ability remained unknown. To determine this, one of the trials (Palm Ridge) was re-implemented and managed for regeneration via coppice over a second rotation (2R). Coppicing ability, growth and susceptibility to pests and disease data were compared for the 16 species at Palm Ridge over the two successive rotations (1R — planted = 8.9 years; 2R — coppiced = 8.2 years). Except for E. argophloia and one E. camaldulensis provenance, all treatments had equivalent, or improved stem stocking in 2R relative to 1R (trial mean: 1R = 1 174 stems ha-1; 2R = 1 288 stems ha−1). The two commercial hybrid clones had the highest volumes in both the 1R (GU = 174 m3 ha−1; GC 163 m3 ha−1) and 2R (GU = 149 m3 ha−1; GC 124 m3 ha−1) rotations. The mean annual volume increments (MAI in m3 ha−1 y−1) were not significantly different between rotations (1R = 10.74 m3 ha−1 y−1; 2R = 9.95 m3 ha−1 y−1), nor were there any significant rotation × treatment interactions indicating that the treatments performed in a similar manner over both rotations. Although there were differences among provenances within taxa, these were not as great as the differences amongst the taxa tested: GC/GC > C. citriodora subsp. variegata > E. logirostrata > C. henryi, with E. tereticornis, E. camaldulensis, E. argophloia and E. watsoniana not performing well over both rotations. Despite the higher rainfall recorded over 2R (837 mm y−1) relative to 1R (765 mm y−1), the incidence of pests and diseases that was not recorded in 1R most likely contributed to the reduced growth of the coppiced trees. Most notable of these were Leptocybe invasa on the GC, E. tereticornis and E. camaldulensis treatments, Botryosphaeria spp. on all but the Corymbia treatments, kino on the Corymbia treatments, and Coniothyrium spp on the GU treatment. Relative to the two commercial hybrid clones (GC and GU), E. longirostrata, and C. henryi were the most promising of the alternative species tested over both rotations (planted and coppiced), with C. citriodora subsp. variegata also showing promise. Although all treatments were affected by pest(s) or disease(s), some of the species showed resistance and provenances within species tolerance, indicating the potential for selection for a reduction in biotic risk.

Urban foraging: Land management policy, perspectives, and potential.

Gathering of uncultivated food from green spaces, also known as foraging, is observed in urban areas across the world, but the literature focuses predominantly on the global north. Our study examines the existing urban land management structure and its approach to urban foraging in the eastern coastal region of South Africa. Through interviews with municipal officials in nine cities, we identified different stakeholders and their roles in urban green space management. We then used network analysis to represent interactions and influence of these stakeholders, and environmental worldviews to determine organisational and perceptual barriers to and enablers of foraging in urban green spaces. The policy on urban green space management, as well as land managers themselves are amenable to the concept of foraging in public spaces. Lack of knowledge on wild indigenous species and sustainable offtake, ambiguous, coarse, or lacking policy, and normative views of pristine nature may hinder foraging. We recommend pathways for policy and stakeholder partnerships to incorporate sustainable foraging in their biodiversity conservation and land stewardship strategies.

Salt marsh at the tip of Africa: Patterns, processes and changes in response to climate change

This study developed a conceptual understanding of climate change responses of salt marsh in open and closed estuaries and outlined changes in terms of implications for ecosystem services. Changes in salt marsh cover in South Africa were described in relation to prevailing pressures. Salt marshes occur in the sheltered estuaries distributed along the ~3000 km coastline. Supratidal salt marsh occurs at elevation greater than 1.5 m amsl and are dominant in the cool temperate (5328.28 ha) and intertidal salt marsh in the warm temperate region (2093.31 ha). Although small in total extent (14 955 ha), salt marshes play a central role in biodiversity conservation because they provide critical habitat for migratory fish and birds. Approximately 43% of salt marsh habitat has been lost due to encroaching development and agriculture from the 1930s to 2018. In addition, salinisation and desiccation resulting from upstream freshwater abstraction reduces freshwater inflow, which extends periods of mouth closure in temporarily closed estuaries causing inundation and flooding of salt marsh. Predicting the combined effects of multiple stressors (increase in storm surges, floods, droughts and reduced river flow) is critical to conserve these important habitats. Research and monitoring to understand salt marsh responses is ongoing because the interface between the subtropical and warm temperate coastal regions of South Africa is expected to be affected by mangrove range expansion. This study is globally relevant as little is known about southern hemisphere salt marshes in Africa and data are needed for comparative purposes.

Multi-season RapidEye imagery improves the classification of wetland and dryland communities in a subtropical coastal region

Remote sensing is considered a valuable tool for monitoring the impacts of global change on vegetation species composition, condition and distribution. Multi-season imagery has been shown to improve the classification of vegetation communities though the contribution of the winter season in multi-seasonal classifications remains to be assessed. The capability of multi-season images of RapidEye, a new generation high spatial resolution (5 m) space-borne sensor containing an additional red-edge band, was evaluated for the classification of several wetland and dryland communities. RapidEye images were obtained for four seasons (winter, spring, summer and autumn) between 2011 and 2012 for a subtropical coastal region of South Africa. The separability of nine wetland and dryland communities was assessed for each season using the Partial Least Square Random Forest (PLS-RF) algorithm. The four-seasons approach yielded a higher overall classification accuracy (OA = 86 ± 2.8%) when compared to using any single-season classification. The highest single-season accuracies were obtained in spring (80 ± 2.9%), summer (80 ± 3.1%), and autumn (79 ± 3.4%) compared to the winter (66 ± 3.1%). A three-season combination of autumn, winter and spring yielded the highest average OA (86 ± 3.1%), maximised the user’s accuracies and minimised the number of comparable pairs confused. The inclusion of indices in the classification scenarios showed a minor (±1 percentage points) difference in the average overall and user’s accuracies compared to the classification results where only bands were used. The red-edge band of RapidEye increased the overall and average user’s accuracy for most of the scenarios by 2–6 percentage points and thus contributed to the separability of communities which are dominated by evergreen tree species.

Implications of geographical range changes and resultant sympatry for three Accipiter hawks on the Cape Peninsula, South Africa

Some invasive species are known to compete with and even displace indigenous species. Two Accipiter species historically indigenous to eastern South Africa have colonised the Cape Peninsula in the south-west of the country and have become sympatric with a third local Accipiter species. We investigated the changes in the occurrence reporting rates of all three species on the Cape Peninsula between 1982 and 2018 using data from the Atlas of the Birds of the Southwestern Cape and from the two data collection periods of the Southern African Bird Atlas Project (SABAP1 and 2). We found that the Black Sparrowhawk Accipiter melanoleucus has become more abundant and that the African Goshawk A. tachiro and the historically local Rufous-breasted Sparrowhawk A. rufiventris have declined since the invasion of the Cape Peninsula by Black Sparrowhawks, suggesting that the latter species has outcompeted and at least partially displaced the other two species. Although that may be the case, since the three species seem to have relatively stabilised population sizes after 2010 this could suggest progressive resource partitioning with a level of ecological isolation following the initial dominance interactions. Since the westward expansion of the ranges of the Black Sparrowhawk and the African Goshawk along the southern coastal region of South Africa were most likely facilitated by anthropogenic alteration of the landscape ultimately leading to the sympatry of the three species on the Cape Peninsula, we suggest that this is therefore a case of indirect human-caused alien invasion.

Subcutaneous merocercoids of Clistobothrium sp. in two Cape fur seals (Arctocephalus pusillus pusillus).

Fur seals represent intermediate hosts of the cestode Clistobothrium. Large sharks are definitive hosts for these parasites. Two female, 25– and 27-year-old fur seals, caught in the 1980s at the South African coast, were examined pathomorphologically. Both animals showed multifocal, up to 1 cm in diameter large cavities of the thoracic and abdominal subcutaneous adipose tissue containing intraluminal metacestodes of tapeworms, which were surrounded by a locally extensive, pyogranulomatous panniculitis. The metacestodes (merocercoids) of one fur seal were isolated from the subcutaneous adipose tissue and characterized morphologically and for the first time from this host by molecular techniques. The morphometric data corresponded with ‘delphini'-morphotype merocercoids, but the sequence of the partial 28S ribosomal RNA gene identified them as conspecific with merocercoids of the morphotype ‘grimaldii’. These merocercoid types are morphologically Type XV metacestodes of marine tapeworms and represent different species of Clistobothrium. Sequence data were generated for 18S, ITS1, 5.8S, ITS2, partial 28S ribosomal DNA and partial mitochondrial cox1 gene and phylogenetic analysis of 18S rRNA and partial 28S rRNA genes identified the fur seal merocercoids as Clistobothrium species. However, it cannot yet be assigned to species level because of limited molecular data from adult stages. Most likely, both fur seals were infected as juveniles in their original habitat, the coastal regions of South Africa. The metacestode infection is probably an incidental finding, however, there is a chronic inflammatory reaction next to the subcutaneous merocercoids. It is noteworthy, that the merocercoids remain in a potentially infective stage even after more than 20 years.

Water Status,Vegetative Growth and Yield Responses of Vitis vinifera L. cvs. Sauvignon blanc and Chenin blanc to Timing of Irrigation during Berry Ripening in the Coastal Region of South Africa

The effects of additional irrigation during berry ripening on water relations, growth and yield in Sauvignon blanc and Chenin blanc grapevines were investigated. In all treatments the grapevines were irrigated when berries reached pea size in December. One treatment received no further irrigation until after harvest. All of the remaining treatments received a second irrigation at veraison. Except for a single treatment, which was not irrigated during ripening, these treatments received a third irrigation at either 14, 21, 28 or 31 days after veraison. The six treatments were applied in a field trial carried out in the Stellenbosch district of the coastal winegrowing region of South Africa over consecutive seasons, between 1990 and 1993. Irrigation at pea size berries and at pea size berries plus veraison increased leaf water potential, but did not affect vegetative growth and yield in either cultivar. Relative to a single application at pea size berries, irrigation at pea size, at veraison and during ripening increased berry size in both cultivars, though not consistently, over the three seasons. However, this result must be viewed in terms of the fact that qualitative assessments of root development and distribution have revealed that effective soil preparation contributes to well-developed root systems. Results confirmed that these root systems could sustain vegetative growth and yield where a single irrigation was applied at pea size berries compared with additional irrigations applied at veraison and during ripening. Irrigation applied at, and after, veraison resulted in yield losses of both cultivars when rainfall favoured Botrytis cinerea infection.

Juice and Wine Quality Responses of Vitis vinifera L. cvs. Sauvignon blanc and Chenin blanc to Timing of Irrigation during Berry Ripening in the Coastal Region of South Africa

The effects of additional irrigation during berry ripening on juice and wine quality in Sauvignon blanc and Chenin blanc grapevines were investigated. In all treatments the grapevines were irrigated when berries reached pea size in December. One treatment received no further irrigation until after harvest. All of the remaining treatments received a second irrigation at veraison. Except for a single treatment, which was not irrigated during ripening, these treatments received a third irrigation either 14, 21, 28 or 31 days after veraison. The six treatments were applied in a field trial carried out in the Stellenbosch district of the Coastal winegrowing region of South Africa over consecutive seasons, between 1990 and 1993. Irrigation during berry ripening decreased the N concentration in the juice of both cultivars, but increased the P and Ca concentrations in the juice, though only in Sauvignon blanc. In neither cultivar were the juice K and Mg concentrations affected by irrigation during the ripening period. The irrigation treatments did not affect sugar concentration in Sauvignon blanc grapes. In contrast, sugar concentrations in Chenin blanc grapes that were irrigated 28 days after veraison were lower than in grapes that were irrigated at pea size. Irrigation applied 21 days and 28 days after veraison resulted in higher total titratable acidity in the juice of both cultivars. Irrigation applied 31 days after veraison, i.e. three days before harvest, raised juice pH in Chenin blanc grapes relative to grapevines that received a single irrigation at pea size. Although not consistent over seasons, irrigation applied during the later stages of ripening had negative effects on fresh vegetative aroma (green pepper, herbaceous or green cut grass flavours) and fullness of Sauvignon blanc wines. Similarly, irrigation during the middle stages of ripening reduced the fermentation character (guava flavour) and fullness of Chenin blanc wines, though not in all seasons. Overall, irrigation during berry ripening tended to reduce wine quality in both cultivars.

The effect of cow-level factors on colostrum quality, passive immunity and health of neonatal calves in a pasture-based dairy operation

A study of 95 cows (19 primiparous and 76 multiparous) and their offspring was performed on a pasture-based dairy in the coastal region of South Africa. Collected data included weight changes during the dry period, colostrum immunoglobulin G (IgG) and calf serum IgG at 24–48 h after birth. Colostrum and serum IgG concentrations were measured using radial immunodiffusion and colostrum was regarded as having adequate IgG concentration if the amount was ≥50 g/L. Calf serum IgG concentration of ≥10 g/L was considered an adequate transfer of passive immunity. The median (range in parentheses) colostrum quality for cows with weight loss during the dry period was 23.1 g/L (9.0, 108.1) compared with 61.9 g/L (10.9, 200.0) in cows without weight loss. The median serum IgG of calves from cows with weight loss was 9.9 g/L (0.5, 44.6) compared with 14.0 g/L (0.5, 76.3) in calves from cows that did not lose weight during the dry period. Cows experiencing weight loss were four times more likely to have colostrum with lower concentrations of IgG (OR = 0.25; 95% CI, 0.07–0.88; P = 0.030). Lactation number was also significantly associated with colostrum IgG concentration (P &lt; 0.001), with younger cows tending to have higher IgG concentrations. Failure of passive transfer did not have a significant effect on any calf-health or production variables measured in the study. The effect of dry-cow feeding on colostrum IgG concentration is poorly understood and inadequate pasture management could have an impact on colostrum quality in pasture-based dairy herds.

Assessing and managing the threat posed by Epipremnum aureum in South Africa

The predictive success of risk assessments is still largely a function of invasiveness elsewhere. Therefore, species that are invasive elsewhere should be prioritised for management, and where possible eradicated. We set out to investigate the threat posed by the alien climber Epipremnum aureum (Araceae) and assess techniques for controlling the spread of the species in South Africa. Epipremnum aureum is highly invasive in Hawaii and Sri Lanka, and has recently been considered as a potential invader in South Africa. However, no study has examined the invasion dynamics of the species. We mapped the species' current distribution in South Africa, modelled its potential distribution globally, and explored control methods. We only recorded the species in the KwaZulu-Natal province of South Africa, comprising 78 naturalized populations and 321 cultivated populations. Delimitation surveys of the naturalized populations revealed ~187,000 plants over ~3ha. Several of these populations comprised plants as tall as the trees they were growing on, and were often found flourishing in dump sites, along roadsides or as a result of escaping cultivation. Species distribution models showed that E. aureum has a high probability of expanding its current range primarily along the coastal regions of South Africa and into neighbouring countries on Africa's eastern seaboard. Due to the invasion threat of the species, we recommend that all plants outside cultivation be removed. To achieve this, we found that applying herbicides to freshly cut stems significantly reduced plant growth. Given the species' limited dispersal ability and effective chemical control methods, we propose that E. aureum should be listed as category 3 under NEM:BA A&IS regulations, i.e. naturalized populations need to be managed, it cannot be propagated or sold in future, but current garden plantings may remain.