Summer Rainfall Areas Research Articles

The South African Pollen Monitoring Network: Insights from 2years of national aerospora sampling (2019-2021).

Pollen monitoring has been discontinuously undertaken in South Africa, a country with high biodiversity, a seasonal rainfall gradient, and nine biomes from arid to subtropical. The South African Pollen Monitoring Network was set up in 2019 to conduct the first long-term national aerospora monitoring across multiple biomes, providing weekly reports to allergy sufferers and healthcare providers. Daily airborne pollen concentrations were measured from August 2019 to August 2021 in seven cities across South Africa. Updated pollen calendars were created for the major pollen types (>3%), the average Annual Pollen Index over 12 months was calculated, and the results were compared to available historical data. The main pollen types were from exotic vegetation. The most abundant taxa were Poaceae, Cupressaceae, Moraceae and Buddleja. The pollen season start, peak and end varied widely according to the biome and suite of pollen taxa. The main tree season started in the last week of August, peaked in September and ended in early December. Grass seasons followed rainfall patterns: September-January and January-April for summer and winter rainfall areas, respectively. Major urban centres, for example, Johannesburg and Pretoria in the same biome with similar rainfall, showed substantive differences in pollen taxa and abundance. Some major differences in pollen spectra were detected compared with historical data. However, we are cognisant that we are describing only 2years of data that may be skewed by short-term weather patterns. Differences in pollen spectra and concentrations were noted across biomes and between geographically close urban centres. Comparison with historical data suggests pollen spectra and seasons may be changing due to anthropogenic climate change and landscaping. These data stress the importance of regional and continuous pollen monitoring for informed care of pollinosis.

Palaeoclimatic niche modelling reveals the phylogeographic history of the South African shrew Myosorex varius and the colonisation route of the genus Myosorex (Mammalia, Soricidae) from East Africa

Myosorex varius is a South African generalist shrew, which has been found to consist of several genetic clades across its range. A northern clade inhabits the more mesic, summer-rainfall areas of grassland and savannah in the east of South Africa. A southern clade occupies areas of fynbos in the south, and can be further divided into a western subclade occupying winter-rainfall areas and an eastern subclade occupying areas with aseasonal rainfall. Non-South-African members of the African genus Myosorex primarily are limited to isolated montane habitats along the East African Rift System. Here, we used palaeoclimatic niche modelling to examine the effects of Pliocene and Pleistocene climate change on the distributions of M. varius, its clades and the genus as a whole. Results indicate that repeated cycles of range expansion during glacial periods and fragmentation during interglacials are responsible for current phylogeographic patterns within M. varius. Based on their close alignment with rainfall zones and lack of genetic mixing despite areas of contact, it is likely that these (sub)clades are locally adapted to their respective areas. Earlier climatic fluctuations allowed the genus to ‘island hop’ south from East Africa along the East African Rift System, expanding in range during cooler periods and retreating to montane refugia during warmer periods. Areas currently occupied by Myosorex species largely correspond with predicted montane refugia that have allowed them to survive previous warm periods.

Out of the Palaearctic: the Helophorus water beetles of the Afrotropical Region (Coleoptera: Helophoridae)

Helophorus Fabricius, 1775 (Coleoptera: Hydrophiloidea: Helophoridae) is an old and largely Holarctic genus of beetles, with most extant diversity concentrated in the Palae­arctic. As with a number of primarily northern temperate lineages, the genus has colonised the Afrotropical Region, with species described from the Ethiopian Highlands and southern Africa. Here, the Afrotropical Helophorus fauna is revised, based on a study of all primary types and additional material, including extensive recent collections from South Africa. The known Afrotropical fauna is shown to be comprised of six species, only three of which were previously described: H. aethiopicus Régimbart, 1907, from southern highland areas of Ethiopia, H. aethiops J. Balfour-Browne, 1954 known from summer and year-round rainfall areas of South Africa and Namibia and H. cooperi Orchymont, 1948, stat. nov., described as a subspecies of H. aethiopicus and still only known from the type locality in Ethiopia. To these, three new species are added: H. brumopluvialis sp. nov., widespread in winter rainfall areas of the Western and Northern Cape Provinces of South Africa, H. nyandaruaensis sp. nov. from mountains of the East African Rift in Kenya and H. simiensis sp. nov. from the Simien Mountains of northern Ethiopia. All species are (re)described in detail and illustrated with high-resolution photos. Known distributions are mapped and a key to species provided. It is suggested that the two South African species may have speciated allochronically, due to seasonal shifts in life cycle associated with the development of the winter rainfall regime in the Cape during the Plio-Pleistocene. Helophorus are hypothesised to have colonised the Afrotropics on at least two occasions from separate Palaearctic ancestors.

Impacts of Agroclimatic Variability on Maize Production in the Setsoto Municipality in the Free State Province, South Africa

The majority of people in South Africa eat maize, which is grown as a rain-fed crop in the summer rainfall areas of the country, as their staple food. The country is usually food secure except in drought years, which are expected to increase in severity and frequency. This study investigated the impacts of rainfall and minimum and maximum temperatures on maize yield in the Setsoto municipality of the Free State province of South Africa from 1985 to 2016. The variation of the agroclimatic variables, including the Palmer stress diversity index (PSDI), was investigated over the growing period (Oct–Apr) which varied across the four target stations (Clocolan, Senekal, Marquard and Ficksburg). The highest coefficients of variance (CV) recorded for the minimum and maximum temperatures and rainfall were 16.2%, 6.2% and 29% during the growing period. Non-parametric Mann Kendal and Sen’s slope estimator were used for the trend analysis. The result showed significant positive trends in minimum temperature across the stations except for Clocolan where a negative trend of 0.2 to 0.12 °C year−1 was observed. The maximum temperature increased significantly across all the stations by 0.04–0.05 °C year−1 during the growing period. The temperature effects were most noticeable in the months of November and February when leaf initiation and kernel filling occur, respectively. The changes in rainfall were significant only in Ficksburg in the month of January with a value of 2.34 mm year−1. Nevertheless, the rainfall showed a strong positive correlation with yield (r 0.46, p = < 0.05). The overall variation in maize production is explained by the contribution of the agroclimatic parameters; the minimum temperature (R2 0.13–0.152), maximum temperature (R2 0.214–0.432) and rainfall (R2 0.17–0.473) for the growing period across the stations during the study period. The PSDI showed dry years and wet years but with most of the years recording close to normal rainfall. An increase in both the minimum and maximum temperatures over time will have a negative impact on crop yield.

Citizen Science for the Prediction of Climate Extremes in South Africa and Namibia

Seasonal-to-interannual variations of rainfall over southern Africa, key to predicting extreme climatic events, are predictable over certain regions and during specific periods of the year. This predictability had been established by testing seasonal forecasts from models of varying complexity against official station rainfall records typically managed by weather services, as well as against gridded data sets compiled through a range of efforts. Members of the general public, including farmers, additionally have extended records of rainfall data, often as daily values spanning several decades, which are recorded and updated regularly at their farms and properties. In this paper, we show how seasonal forecast modelers may use site recorded farm rainfall records for the development of skillful forecast systems specific to the farm. Although the uptake of seasonal forecasts in areas with modest predictability such as southern Africa may be challenging, we will show that there is potential for financial gain and improved disaster risk farm management by co-developing with farmers forecast systems based on a combination of state-of-the-art climate models and farm rainfall data. This study investigates the predictability of seasonal rainfall extremes at five commercial farms in southern Africa, four of which are in the austral summer rainfall areas, while one is located in the winter rainfall area of the southwestern Cape. We furthermore calculate a measure of cumulative profits at each farm, assuming a “fair odds” return on investments made according to forecast probabilities. The farmers are presented with hindcasts (re-forecasts) at their farms, and potential financial implications if the hindcasts were used in decision-making. They subsequently described how they would use forecasts for their farm, based on their own data.

Inoculum Dynamics and Infection of Citrus Fruit by Phyllosticta citricarpa.

Citrus black spot, caused by Phyllosticta citricarpa, is characterized by fruit blemishes and premature fruit drop, resulting in significant economic losses in summer rainfall areas. The pathogen forms both conidia and ascospores during its life cycle. However, the occurrence of these spores and their contributions to infection of fruit in field conditions are not well understood. Our research using direct leaf litter monitoring and volumetric spore trapping in Queensland orchards revealed that pseudothecia and ascospores in leaf litter as well as trapped ascospores had low abundance, while pycnidia and conidia were highly abundant. Both P. citricarpa and endophytic Phyllosticta spp. were identified, with P. citricarpa being dominant. In replicated field trials, we determined that infection of Imperial mandarin fruit by P. citricarpa occurred from fruit set until week 20 of fruit development, with the key infection events taking place between weeks 4 and 16 in Queensland subtropical conditions. These results demonstrate that protecting fruit during weeks 4 to 16 significantly reduced P. citricarpa infection. We found no significant correlation between the disease incidence in fruit and P. citricarpa conidial abundance in leaf litter or ascospore abundance measured by volumetric spore trapping. Therefore, it is suggested that inoculum sources in the tree canopy other than those detected by spore trapping and direct leaf litter monitoring may play a major role in the epidemiology of citrus black spot. Improved knowledge regarding epidemiology of P. citricarpa and an understanding of propagules causing infection may aid in development of more effective disease management strategies.

Modeling the Distribution of the Invasive Alien Cycad Aulacaspis Scale in Africa Under Current and Future Climate Scenarios.

The cycad aulacaspis scale, Aulacaspis yasumatsui Takagi (Hemiptera: Coccoidea: Diaspididae), is native to Southeast Asia but an invasive pest of the gymnosperm order Cycadales in many parts of the world. Aulacaspis yasumatsui was recently reported on the cycad genus Encephalartos in South Africa and is currently categorized as a 'prohibited terrestrial invertebrate' in the invasive species legislation, National Environmental Management: Biodiversity Act, 2004 (NEM:BA). Encephalartos is endemic to Africa, and 11 species are listed as critically endangered and four species as endangered. Seeing the limited distribution of A. yasumatsui in South Africa and only one unconfirmed record from the Ivory Coast, understanding the potential distribution range is essential for control and management. Here we model the potential distribution of A. yasumatsui under current and future climate scenarios in Africa, with a focus on South Africa. Future climatic scenarios were simulated using a bio-climatic software, CLIMEX. The model indicates that, under the current climatic scenario, all 17 African countries possessing Encephalartos are susceptible to A. yasumatsui establishment. However, under climatic change, the suitability decreases for large parts of Africa. In South Africa, 93% of the winter rainfall areas, and 90% of the temperate, summer rainfall areas are suitable for A. yasumatsui establishment. In this study, we highlight the urgent need for regulation, management, and research on A. yasumatsui in African countries with native cycads.

An isotopic test of the seasonal migration hypothesis for large grazing ungulates inhabiting the Palaeo-Agulhas Plain

The Greater Cape Floristic Region of South Africa was critical to the evolution of early modern humans (Homo sapiens) during the Pleistocene. The now submerged continental shelf formed its own ecosystem, the Palaeo-Agulhas Plain (PAP), where early humans lived and foraged. Grazing animals living on the plain might have migrated east and west tracking seasonally varying rains—a hypothesis tested here by examining δ13C and δ18O of serially-drilled teeth from seven ungulate genera: Alcelaphus, Connochaetes, Antidorcus, Redunca, Damaliscus, and Hippotragus. Modern observations and paleoecological reconstructions indicate that summer rainfall areas to the east have more C4 grasses while the winter rainfall areas to the west have more C3 grasses, and that summer and winter rains differ in δ18O. Thus, we analyze δ13C and δ18O preserved in herbivore teeth from the site of PP30 (a hyena den dating to ∼151 ka) to infer diet and water source throughout tooth formation. On a generic level, none of the samples exhibit δ13C or δ18O values that differ significantly from a taxon that likely foraged locally through the year (Southern reedbuck, Redunca arundium). Overall, results indicate that the PAP could support herbivore populations year-round without substantial migration, providing an ecosystem ideal for human inhabitants.

Comparison of two remote sensing models for estimating evapotranspiration: algorithm evaluation and application in seasonally arid ecosystems in South Africa

Remote sensing tools are becoming increasingly important for providing spatial information on water use by different ecosystems. Despite significant advances in remote sensing based evapotranspiration (ET) models in recent years, important information gaps still exist on the accuracy of the models particularly in arid and semi-arid environments. In this study, we evaluated the Penman-Monteith based MOD16 and the modified Priestley-Taylor (PT-JPL) models at the daily time step against three measured ET datasets. We used data from two summer and one winter rainfall sites in South Africa. One site was dominated by native broad leaf and the other by fine leafed deciduous savanna tree species and C4 grasses. The third site was in the winter rainfall Cape region and had shrubby fynbos vegetation. Actual ET was measured using open-path eddy covariance systems at the summer rainfall sites while a surface energy balance system utilizing the large aperture boundary layer scintillometer was used in the Cape. Model performance varied between sites and between years with the worst estimates (R2<0.50 and RMSE>0.80 mm/d) observed during years with prolonged mid-summer dry spells in the summer rainfall areas. Sensitivity tests on MOD16 showed that the leaf area index, surface conductance and radiation budget parameters had the largest effect on simulated ET. MOD16 ET predictions were improved by: (1) reformulating the emissivity expressions in the net radiation equation; (2) incorporating representative surface conductance values; and (3) including a soil moisture stress function in the transpiration sub-model. Implementing these changes increased the accuracy of MOD16 daily ET predictions at all sites. However, similar adjustments to the PT-JPL model yielded minimal improvements. We conclude that the MOD16 ET model has the potential to accurately predict water use in arid environments provided soil water stress and accurate biome-specific parameters are incorporated.

Frost tolerance of various Pinus pure species and hybrids

Pinus species are widely planted by the South African forestry industry and are utilised for pulp, paper and saw timber products. Historically, Pinus patula Schiede ex Schltdl. et Cham. was the most widely planted commercial species in the summer rainfall area, but has come under severe threat due to the fungus Fusarium circinatum. Fusarium circinatum causes mortality in nurseries and in-field after establishment. Other Pinus species, such as P. tecunumanii F.Schwerdtf. ex Eguiluz et J.P.Perry and P. oocarpa Schiede ex Schltdl., have been crossed with P. patula to increase tolerance to F. circinatum and these hybrids have largely overcome the post-planting mortality problem. However, these hybrid-partner species are more prone to frost damage. This study reviewed laboratory screening techniques to assess the frost tolerance level of a range of Pinus pure species and hybrids. In vitro screening was done with the electrolyte leakage and whole-plant freezing techniques. Seedlings and rooted cuttings from a range of genotypes, supplied by Sappi, were tested in vitro at different target temperatures (−3, −6, −9 and −12 °C) to determine their relative frost tolerance. These genotypes included a range of Pinus pure species, four interspecific hybrids (P. patula × P. tecunumanii low elevation [LE], P. patula × P. tecunumanii high elevation [HE], P. elliottii Engelm. × P. caribaea Morelet), and a three-way cross (P. patula × (P. patula × P. oocarpa)). Results from this study indicated that the electrolyte leakage technique was a reliable method to determine frost tolerance under laboratory conditions, with similar pure species rankings as experienced under field conditions. The interspecific hybrids of P. patula × P. tecunumanii LE and HE ranked intermediate between the parental species and the P. patula × P. tecunumanii HE hybrid was more frost tolerant than the P. patula × P. tecunumanii LE hybrid.

Cherry production in South Africa: status quo and new initiatives

At present the main production area for cherries in South Africa is situated in the Western Cape Province, which represents about 50% of the total 262 ha that has been planted up to 2016. Previously, production centered around the Highveld region in the eastern Free State. The cherry production areas in the eastern Free State are situated at approximately 28°45’ latitude and 27°45’ longitude and 1650 m a.s.l. The Highveld region is part of the summer-rainfall area, with dry winters and below zero temperatures during winter nights. This decline in production in the Highveld region is mainly due to these adverse growing conditions. Production was also negatively affected by using the too dwarfing ‘Gisela 5’ rootstocks that were not suitable for the shallow and sandy soils. Older orchards on Mahaleb rootstock are still producing good average yields in harsh growing conditions. Current initiatives include the use of more yield efficient rootstocks like ‘Maxma 14’ and the low-chilling scion cultivars from the breeding programs in California, USA. The poor rootability of Mahaleb cuttings in the nursery and the shortages of in vitro propagated rootstocks like ‘Maxma 14’, also tempered the planting of new orchards. This problem was overcome by a mass importation of in vitro ‘Maxma 14’ from Italy, optimising the current availability of nursery trees to increase dramatically from 32,000 to 150,000 trees year-1. These new initiatives will have a positive effect increasing the number of ha in non-traditional cherry growing areas in South Africa, such as the Northern Province as well as in the warmer parts of the Western Cape Province.

Variations in the accumulation of three secondary metabolites in Euclea undulata Thunb. var. myrtina as a function of seasonal changes

Euclea undulata Thunb. var. myrtina is a widely distributed shrub in South Africa. The roots are used by traditional healers in the treatment of diabetes. Research indicated that the roots of this plant contain epicatechin and α-amyrin-3O-β-(5-hydroxy) ferulic acid, two secondary metabolites that show potential to treat diabetes. It was found that α-amyrin-3O-β-(5-hydroxy) ferulic acid inhibits α-glucosidase, while epicatechin lowers blood glucose levels. However, existing literature also indicated the presence of the naphthoquinone 7-methyl-juglone in the roots and due to its cytotoxic nature, 7-methyl-juglone poses a potential threat when E. undulata is used in the treatment of diabetes.In order to assist in the effective and safe use of this plant in the treatment of diabetes, this project aimed to determine whether the presence of these metabolites is seasonal. It further aimed to contribute to more sustainable harvesting methods by investigating stems and leaves in addition to roots for the presence of these secondary metabolites.Leaves, stems and roots were harvested from E. undulata plants in three different localities with different climatic conditions, with a specific focus on winter and summer rainfall regions. The plant material was air dried at room temperature and ground to a powder, which was subjected to NMR metabolomic analysis.Multivariate data analysis resulted in clustering of samples collected in the rainy and dry seasons for both winter and summer rainfall regions, as well as delineations between roots, stems and leaves due to their secondary metabolite contents. Clustering of samples in the rainy and dry seasons of the same plants was also observed with the OPLS-DA plots indicated clustering of samples harvested during the dry and rainy seasons.Results for the summer rainfall area indicate seasonal fluctuations in the levels of α-amyrin-3O-β-(5-hydroxy) ferulic acid in roots. It is also noteworthy that the roots always contain 7-methyl-juglone and only found in the leaves on the rainy season of the summer rainfall area. The stems can be harvested for α-amyrin-3O-β-(5-hydroxy) ferulic acid and the leaves for epicatechin in both seasons in the summer rainfall area. Results from the winter rainfall area indicate far less seasonal fluctuation. Most metabolites appear to be either present or absent in the respective organs regardless of season with the exception of epicatechin that is absent in the roots in the rainy season. Fluctuations were, however, detected in epicatechin levels in stems and 7-methyl-juglone levels in roots. From the results obtained it is evident that α-amyrin-3O-β-(5-hydroxy) ferulic acid occurs in roots, stems and leaves in the winter rainfall area and is independent of temperature whereas 7-methyl-juglone is present only in the roots. Leaves can replace the use of roots when harvested in a winter rainfall area irrespective of season as α-amyrin-3O-β-(5-hydroxy) ferulic acid and epicatechin are present and 7-methyl-juglone are absent.

Alternative pine hybrids and species to Pinus patula and P. radiata in South Africa and Swaziland

Through the collaborative efforts of companies affiliated with the International Program for Tree Improvement and Conservation (Camcore), a number of pine hybrids have been produced over the last decade. Many of these have been planted in trials across southern Africa that broadly represent winter and summer rainfall areas, with the latter ranging from warm to cold temperate sites. The five-year survival and growth of the hybrids and other pines in 12 of these trials were compared with Pinus radiata in the winter rainfall, and P. patula in the summer rainfall, regions where these species have been planted extensively. Except for the highest altitude site, where freezing conditions are common, the survival of most hybrids and tropical pines was better than P. patula or P. radiata. This was, in part, attributed to their improved tolerance to the pitch canker fungus, Fusarium circinatum, which was present in the nursery at the time of planting. In the winter rainfall area, the P. elliottii × P. caribaea hybrid, P. maximinoi and, surprisingly, the P. patula hybrids performed well. In the summer rainfall regions, hybrids with tropical parents such as P. caribaea, P. oocarpa and P. tecunumanii were more productive in the subtropical/warm temperate zone and, with increasing elevation, those hybrids crossed with P. patula performed relatively better. The P. patula × P. tecunumanii hybrid, particularly when crossed with low-elevation P. tecunumanii, performed exceptionally across most sites.

Phylogenetic position of a remarkable new fideliine bee from northern Chile (Hymenoptera: Megachilidae)

AbstractFideliine bees are an archaic group with a disjunct distribution mostly restricted to deserts of South America and South Africa. This group was previously thought to be more diverse in Africa than in South America, where only one genus (Neofidelia) comprising five species is known. Here we describe a species belonging to a second South American genus: Xenofidelia colorada Packer gen. et sp.n., from northern Chile. The species is illustrated and its phylogenetic position within Megachilidae is assessed using morphological, molecular and combined data. The 214 character morphological matrix includes 55 new characters with an additional 16 hitherto unexplored for megachilid phylogeny. The molecular dataset is based upon seven nuclear gene sequences, totalling 6439 bp, many of which are published for the first time for particular megachilid taxa. In all analyses, Xenofidelia was found as sister to Neofidelia (endemic to Chile and Peru). It differs from that genus most notably in its short mouthparts, absence of a glossal rod, unmodified female metabasitarsus and an elongate and horizontal dorsal surface of the metapostnotum. Morphological and combined data support a monophyletic Fideliinae (excluding Pararhophites), while molecular data alone failed to recover fideliine monophyly. Dating analyses suggest that Xenofidelia and Neofidelia diverged 34.3–40.6 Ma, indicating that New World fideliines were probably present in arid habitats of South America during the Eocene. This divergence time predates both the main orogenic events that resulted in the formation of the Andean mountains and the origin of hyperarid conditions in the Atacama Desert; it also corresponds to a period prior to the origin of the summer rainfall area in the far north of Chile where the new genus is found. These results support the view that arid habitats have been present continuously in South America since the Eocene.This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:EA69BB4A‐6F59‐4A15‐AB44‐2A8949E3CF8F.

The Effect of Three Rootstock Cultivars, Potassium Soil Applications and Foliar Sprays on Yield and Quality of Vitis vinifera L. cv. Ronelle in South Africa

The early black cultivar Ronelle is the major export table grape produced in the northern summer rainfall area of South Arica. In a rootstock trial at Roodeplaat near Pretoria, low yield, poor quality and low export mass as well as typical potassium (K) deficiency symptoms were observed for Ronelle grafted onto 110 Richter, despite K saturation percentages of 6,3% and 6,0% in the topsoil and subsoil respectively. The effect of 500 kg ha-1 and 1 000 kg ha-1 soil-applied K combined with a 0,02% foliar application of K was investigated for Ronelle grafted onto 110 R (V. rupestris x V. Berlandieri), 101-14 Mgt (Y. riparia x V. rupestris) and 143 B Mgt (v. riparia x V. vinifera). The K fertilizer treatments were applied only once, before budbreak. Three foliar sprays were applied annually, at two-week intervals, commencing at 15 cm shoot length. Results after two seasons showed that neither high levels of K fertilizer, nor K foliar sprays improved yield or quality of Ronelle on 110 R. The K content of leaves was not significantly affected by any of the K treatments. Leaf K levels of 110 R were significantly lower compared to those of 143 Mgt, but the leaf K content of all three graft combinations was above the minimum norm. Apparently there is no effective cure for established Ronelle/110 R vineyards with K deficiency problems and it is recommended that the Ronelle/110 R graft combination is not used in future.

Geographic variation in factors that influence timing of moult and breeding in waterfowl

Waterfowl flight-feather moult is expected to occur when energy is not needed for breeding and when a suitable safe habitat is available. Flight-feather regrowth is an energetically costly stage in the annual cycle of waterfowls. In this study, we tested the hypothesis that moult will coincide with the time of year when food and aquatic habitats are most abundant. We investigated how the timing of rainfall relates to the timing of breeding and flight-feather moult in five common southern African waterfowl at two sites in South Africa with opposite rainfall regimes (one summer, one winter). We then incorporated published data to compare and contrast the relative timing of breeding and moult in southern hemisphere (southern African and Australian) waterfowl with northern hemisphere (European and North American) species. Our results showed that southern African waterfowl breed in the wet season and moult during the dry season. Tadorna cana was an exception, breeding in the dry season and moulting during the wet season in the summer-rainfall area. There was also a long lag period between peak breeding and peak moult in southern hemisphere waterfowl species, the longest lag being that of birds in the summer-rainfall area. By comparison, northern hemisphere waterfowl species breed and moult during the warm season, with a shorter lag period between peak breeding and peak moult compared to southern hemisphere species. We concluded that waterfowl in southern Africa (with the exception of T. cana), southeast Australia, Europe and North America time their breeding period to coincide with peaks in the availability of both food and breeding sites. Northern hemisphere species moult where chances of predation are low, when temperatures are warm, and before food and aquatic habitats approach their winter minima. By contrast, southern hemisphere waterfowl delay the onset of moult until the dry season, opting to moult when both food and aquatic moulting habitats are scarce.

Scientific critique of the paper “Climatic distribution of citrus black spot caused by Phyllosticta citricarpa. A historical analysis of disease spread in South Africa” by Martínez-Minaya et al. (2015)

The global distribution of citrus black spot (CBS) disease, caused by Phyllosticta citricarpa, is climatically constrained, which is evident from its occurrence in citrus growing areas with warm, summer rainfall and its absence from areas with cooler, Mediterranean-type winter rainfall. Various epidemiological and modelling studies have supported this observation, predominantly estimating unsuitability for P. citricarpa in Mediterranean type climates, with no more than marginal suitability estimated at a few localities within some regions with Mediterranean type climates. The study by Martinez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015), describes an historic sequence of recorded CBS occurrence in parts of South Africa, conducts an autocorrelation analysis and a correlative analysis with Koppen-Geiger climate zones and makes observations about the occurrence of certain Koppen-Geiger climate zones in the European Union. The study suggests that significant portions of the European Union and the broader Mediterranean basin are climatically similar to warm, summer rainfall areas in South Africa where P. citricarpa persists and causes CBS disease and concludes that the potential distribution of P. citricarpa is less constrained by climatic factors than spatial contagion. However, in this critique we expose methodological shortcomings in the Martinez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015) study and conclude that the study grossly overestimated the extent of the geographical area that could support P. citricarpa, thereby rendering the findings scientifically unreliable.

Resistance of Haemonchus sp. to monepantel and reduced efficacy of a derquantel / abamectin combination confirmed in sheep in NSW, Australia

Early in 2015, sheep in a summer rainfall area of NSW, Australia, displayed signs of haemonchosis despite treatment with monepantel. A faecal egg count reduction test (FECRT) was performed on yearlings with natural field infections using various anthelmintics. Only a four-way combination drench achieved a reduction in faecal egg count (FEC) greater than 95%. The combination contained abamectin, albendazole, levamisole and closantel. Treatments with a derquantel/abamectin combination, monepantel and moxidectin reduced FECs by 93, 31, and 30% respectively. Sheep treated with abamectin displayed an increase in FEC of 22%. Larval differentiation counts conducted 10days post-treatment showed that 100% of survivors were Haemonchus sp. This result confirms for the first time monepantel resistant Haemonchus in sheep in NSW, and is amongst the first of the Australian cases in sheep not associated with goats. A second FECRT was performed using sheep from the moxidectin and abamectin treatment groups in the first FECRT. In this second FECRT, monepantel treatment reduced FECs by 51% and 29% in the sheep previously treated with moxidectin and abamectin respectively. This suggests monepantel, in combination with moxidectin, may give some control against severely abamectin resistant Haemonchus.

A Regional Stable Carbon Isotope Dendro-Climatology from the South African Summer Rainfall Area.

Carbon isotope analysis of four baobab (Adansonia digitata L.) trees from the Pafuri region of South Africa yielded a 1000-year proxy rainfall record. The Pafuri record age model was based on 17 radiocarbon dates, cross correlation of the climate record, and ring structures that were presumed to be annual for two of the trees. Here we present the analysis of five additional baobabs from the Mapungubwe region, approximately 200km west of Pafuri. The Mapungubwe chronology demonstrates that ring structures are not necessarily annually formed, and accordingly the Pafuri chronology is revised. Changes in intrinsic water-use efficiency indicate an active response by the trees to elevated atmospheric CO2, but this has little effect on the environmental signal. The revised Pafuri record, and the new Mapungubwe record correlate significantly with local rainfall. Both records confirm that the Medieval Warm Period was substantially wetter than present, and the Little Ice Age was the driest period in the last 1000 years. Although Mapungubwe is generally drier than Pafuri, both regions experience elevated rainfall peaking between AD 1570 and AD 1620 after which dry conditions persist in the Mapungubwe area until about AD 1840. Differences between the two records correlate with Agulhas Current sea-surface temperature variations suggesting east/west displacement of the temperate tropical trough system as an underlying mechanism. The Pafuri and Mapungubwe records are combined to provide a regional climate proxy record for the northern summer rainfall area of southern Africa.

Dough mixing characteristics measured by Mixsmart software as possible predictors of bread making quality in three production regions of South Africa

South Africa has three wheat production regions, the winter rainfall region where spring wheat is planted; the summer rainfall where winter and intermediate wheat is cultivated; and the irrigation region where spring wheat is grown. The aim of this study was to determine dough mixing characteristics as measured by Mixsmart® software in these three regions over seasons and locations, and to relate this to important quality characteristics. In the winter rainfall area Mixsmart characteristics were very poor predictors of baking quality, especially of loaf volume, flour protein content and wet gluten content. The best predictors of loaf volume in this region were flour protein content and wet gluten content, which were highly interrelated. In the irrigation area, midline peak value and midline right value were very good predictors of flour protein content, gluten content and loaf volume. Midline peak value was highly correlated with protein content in both the irrigation and summer rainfall areas and was a better predictor than peak time of baking quality. The ideal would be to select several parameters from the mixograph and use them in a multivariate statistical analysis to obtain a more accurate prediction of loaf volume in the irrigation and summer rainfall areas.