Thesis (MScAgric)--Stellenbosch University, 1931. / ENGLISH ABSTRACT: This thesis is presented in partial fulfilment of the requirements for the degree of MSc. Agric in Entomology. In this work an attempt has been made to gather all the available literature on the family Pentatomidae and to work out keys where possible for the genera and species recorded in South Africa . The keys for the species in either the University Collection or those of the South Africa Museum did not present much difficulty as I had access to the latter through the courtesy of Dr gill and the museum Entomologist, Dr. A. J. Hesse. I especially wish to thank Dr. Hesse for his kind assistance in connection with this work. Where I had to rely on the meagre descriptions of some entomologists it has in a few cases been impossible for me to include some of species in the keys, but I have, however, incorporated the original descriptions of the species in this work. The writer hopes, that, with the aid of the drawings and the general descriptions, the keys will be of value for the correct determination of the members of this family. The Literature available on the South African Pentatomidae is very comprehensive and scattered through various publications, some of which are hardly obtainable . This is the first attempt which has been made in this country to co-ordinate the literature on this subject and it will doubtlessly prove of value to those entomologists who have not the time or the opportunity of working through the voluminous records on this interesting group. The work has been done under the direction of Dr. T. J. Potgieter, Professor of Entomology at the Stellenbosch-Elsenberg College of Agriculture of the University of Stellenbosch and I am greatly indebted to him for advice and the kindly way in which he assisted me.

Thesis (MSc (Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Ambient temperature plays a key role in insect-physiology, -population dynamics and ultimately -geographic distribution. Here, I investigate the survival of codling moth, Cydia pomonella (Linnaues) (Lepidoptera: Tortricidae), which is a pest of economic importance in pome fruit production, to a wide range of temperature treatments. In this thesis, I first explore how temperature affects the survival and limits to activity of codling moth and secondly investigate if thermal acclimation can improve field performance of moths used in sterile insect technique control programmes under ecologically relevant conditions. First, I found that absolute temperature as well as the duration of temperature exposure significantly affects adult C. pomonella survival. Lethal temperatures, explored between -20 °C to -5 °C and 32 °C to 47 °C over a range of durations, showed that 50% of the adult C. pomonella population killed at -12 °C and at 44 °C after 2 hrs for each treatment. At high temperatures a pretreatment at 37 °C for 1 hr dramatically improved survival at 43 °C for 2 hrs from 20% to 90% (p<0.0001). Furthermore, high temperature pre-treatments (37 °C for 1 hr) significantly improved low temperature survival at -9 °C for 2 hrs. In sum, my results suggest pronounced plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low temperature responses. Secondly, low-temperature acclimated laboratory-reared moths were recaptured in significantly higher numbers (d.f. = 2, χ2 = 53.13 p<0.001), by sex pheromone traps, under cooler conditions in the wild relative to warm-acclimated or non-acclimated moths. However, these improvements in low temperature performance in cold-acclimated moths came at a cost to performance under warmer conditions in the wild. This novel study demonstrates the importance of thermal history on C. pomonella survival and clear costs and benefits of thermal acclimation on field and laboratory performance, and thus, the potential utility of thermal pre-treatments for improved efficacy in the sterile insect technique programme for C. pomonella control under cooler, springtime conditions. Finally, on a global scale, this study highlights that low and high temperatures could play a role in CM adult survival through direct mortality and thus, may influence, or have influenced in the pest, population dynamics. / AFRIKAANSE OPSOMMING: Temperatuur speel ‘n belangrike rol in die fisiologie, populasiedinamika en geografiese verspreiding van insekte. In hierdie tesis ondersoek ek die rol van ‘n wye reeks temperature op die oorlewing van kodlingmot Cydia pomonella (Linnaues) (Lepidoptera: Tortricidae), ‘n sagtevrug pes-spesie van ekonomiese belang. Ek ondersoek hoofsaaklik die effek van temperatuur op die fisiologie en fiksheid van kodlingmot, asook die mate waartoe termiese akklimasie (‘n mate van aanpassing) die veldgedrag van die steriele insek beheer-metode (SIT), d.m.v. kodlingot, in relevante omgewingstemperature kan verbeter. Ek het (i) gevind dat die temperatuur en duur van die temperatuur toediening ‘n betekenisvolle toename in volwasse C. pomonella oorlewing tot gevolg het. In die deel van die studie is temperature tussen -20 °C en -5 °C and tussen 32 °C en 47 °C ondersoek oor ‘n reeks van 0.5, 1, 2, 3 en 4 ure van duur. In kort lei -12 °C en 44 °C vir 2 uur onderskeidelik tot die uitsterf van 50% van die volwasse C. pomonella populasie. Indien die motte vooraf gehou is by 37 °C vir ongeveer 1 uur, is oorlewing by 43 °C vir 2 ure betekenisvol verbeter van 20% tot 90% (p<0.0001). Hoër temperatuur vooraf-blootstellings (akklimasie), by 37 °C vir 1 uur, het daartoe gelei dat lae temperatuur lae-temperatuur-oorlewings by -9 °C vir 2 ure betekenisvol verbeter het. Oor die algemeen het die resultate gedui dat hoër akute temperatuurstoleransie in C. pomonella bestaan, maar beperkte akute lae-temperatuur reaksies bestaan. Verder het lae-temperatuur akklimasie (laboratorium geteelde) motte ‘n betekenisvolle hoër getal hervangste deur geslagsferomone in koeler omgewings opgelewer (v.i. = 2, χ2 = 53.13, p<0.001) in vergelyking met warmer-temperatuur geakklimatiseerder motte. Hierdie verbeteringe in laetemperatuur reaksies vanaf lea-temperatuur akklimasie groepe is teen ‘n koste teen warmer reaksie-toestande in die natuur geïs. Hierdie eersdaagse studie demonstreer die belang van historiese temperatuur op die oorlewing van C. pomonella. Die kostes- en voordele van termiese akklimasie op veld- en laboratoriumpopulasie reaksies en die potensiële gebruik daarvan in die verbetering van steriele insek tegniek programme, onder koeler omstandighede, is uitgelig. Laastens, beklemtoon hierdie studie die belangrikheid van temperatuur as bepalende faktor van kodlingmot-oorlewing en die invloed daarvan op die vrugte-pes populasiedinamika.

Thesis (MScConsEcol)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Decision-making in conservation should be efficient and effective as time and resources are typically limited. Conservation planning is one process by which stakeholders collaboratively make decisions when attempting to ensure the persistence of biodiversity. Spatial prioritization is the activity of applying quantitative data to spatial analysis to select locations for conservation investment and is a distinct process within conservation planning. The use of experts in spatial prioritization, and more generally in conservation planning, is widely accepted and advocated, but there is no general operational model for how best to involve them. Acceptable standards of practice in selecting experts and in applying specific techniques for eliciting expert knowledge need to be developed and tested in different contexts to ensure robust and defensible results of spatial prioritization processes. Although experts and expert knowledge have limitations, including them in spatial prioritization can produce many benefits, such as increased robustness of decisions and time and cost savings. Timeous, decisive, cost-efficient and robust decision-making is essential when attempting to stem the continued loss of biodiversity across the world. Although widely used, very little research has been conducted into the role of experts in spatial prioritization processes. In this research, the role and use of experts and expert knowledge in spatial prioritization was explored through the following processes: 1) a review of the peer-reviewed literature examining the role, and different types, of experts included in spatial prioritization studies (Chapter 2) to identify the patterns of their involvement; 2) a study examining the process and the differences between individual and group expert outputs and outcomes produced from a typical spatial prioritization workshop to provide a baseline against which experts might be identified for future involvement (Chapter 3); and 3) a study examining the knowledge of local community and land management experts and their ability to predict private landowners self-reported attitudes towards conservation, willingness to partner with organizations and behavior relating to conservation, aimed to test if expert knowledge might replace interviews when mapping conservation opportunity (Chapter 4). The main findings of this research are, firstly, that experts primarily contributed to spatial prioritization through mapping of species, habitats and ecosystems (that can be input into spatial prioritization analyses), and specifically also the selection of areas important for implementing conservation action (e.g., priority conservation areas). Secondly, individual experts contributed different expertise to the spatial prioritization processes in which they were involved, sometimes despite being considered experts in the same field. Individual experts differed to each other in the knowledge they contributed, decisions they made, and in the information content and its spatial representation. Groups of experts collaborating to produce the same information were more effective at capturing expert knowledge than individuals. Thirdly, when seeking to map human and social data to inform the mapping of conservation opportunity, experts were unable to reliably score private landowner's attitudes towards conservation, willingness to partner with organizations and behavior relating to conservation. Experts were able though, to provide accurate knowledge on the general attitudes of landowners, the context of the area in which the research was conducted, and the challenges that landowners in the area face. Collectively, this research can be used to inform the development of standards of best practice to ensure the most effective and cost efficient approach to integrating spatial prioritization software with expert knowledge. / AFRIKAANSE OPSOMMING: Besluitneming in bewaring moet doeltreffend en effektief wees omdat tyd en hulpbronne skaars is. Bewaringsbeplanning is een proses waardeur aandeelhouers gesamentlik besluite kan neem wanneer hul poog om die voortbestaan van biodiversiteit te verseker. Ruimtelike prioritisering verwys na die proses waar kwantitatiewe data toegepas word op ruimtelike analise om areas vir bewaringsbelegging te selekteer. Dit is 'n afsonderlike proses binne bewaringsbeplanning. Die gebruik van deskundiges in die bepaling van ruimtelike prioritisering en meer algemene bewaringsbeplanning word wyd aanvaar en bepleit maar daar is geen algemene operationele model wat bepaal hoe om hul ten beste in te sluit nie. Aanvaarbare standaarde in die praktyk van die seleksie van kundiges en die aanwending van spesifieke tegnieke om kundige kennisstelsels uit te lok moet ontwikkel en getoets word in verskillende kontekste om robuuste en verdedigbare resultate te verseker. Daar is baie voordele verbonde aan die gebruik van deskundiges en kundige kennisstelsels, ten spyte van hul beperkings. Voordele sluit onder andere tyd- en kostebesparings in. Tydige, beslissende, koste-effektiewe en robuuste besluitneming is noodsaaklik wanneer daar gepoog word om die voortdurende wêreldwye verlies aan biodiversiteit te stuit. Al word hul algemeen gebruik is daar nog baie min navorsing gedoen oor die rol van kundiges tydens die proses van ruimtelike prioritisering. Die rol en gebruik van kundiges en kundige kennisstelsels in die bepaling van ruimtelike prioritisering is deur die volgende prosesse ondersoek: 1) 'n Oorsig van portuurbeoordeelde literatuur wat die rol van en verskillende tipes kuniges wat in ruimtelike prioritisering studies ingesluit word, bestudeer (Hoofstuk 2) ten einde die patrone van hul betrokkenheid te identifiseer; 2) 'n studie wat die proses en verskille tussen die insette en uitkomste van individuele en groepe kundiges, soos geproduseer by 'n tipiese ruimtelike prioritisering werkwinkel, bestudeer ten einde 'n grondlyn daar te stel waarteen kundiges vir toekomstige betrokkenheid geïdentifiseer kan word (Hoostuk 3); en 3) 'n bestudering van die kennis van plaaslike gemeenskaps- en grondbestuur kundiges en hul vermoë om privaat grondeienaars se selfgerapporteerde houdings teenoor bewaring, hul bereidwilligheid om met organisasies saam te werk en gedrag wat verband hou met bewaring te voorspel om te toets of kundige kennis onderhoude sal kan vervang tydens die kartering van bewaringsmoontlikhede (Hoofstuk 4). Die vernaamste bevindinge van hierdie navorsing is, ten eerste, dat kundiges se primêre bydrae tot ruimtelike prioritisering plaasvind deur die kartering van spesies, habitats en ekosisteme (wat alles in ruimtelike prioritisering analise vervat kan word), en meer bepaald die seleksie van areas wat belangrik is vir die implementering van bewaringsaksie (bv. prioriteit bewaringsareas). Tweedens, individuele kundiges se bydrae tot die ruimtelike prioritisering prosesse waar hul betrokke was, het verskil, selfs waar hul as kundiges in dieselfde veld beskou word. Individuele kundiges het van mekaar verskil ten opsigte van die kennis wat hul bygedra het, die besluite wat hul geneem het, die inhoud van inligting en die ruimtelike voorstelling daarvan. Groepe kundiges wat saamwerk om dieselfde inligting op te lewer was meer effektief in die vaslegging van kundige kennis as individuele kundiges. Derdens, tydens die soeke na menslike en maatskaplike data om die kartering van bewaringsmoontlikhede in te lig was kundiges nie in staat is om 'n betroubare skatting van privaat grondeienaars se houdings teenoor bewaring, bereidwilligheid om saam met organisasies te werk en gedrag wat verband hou met bewaring te maak nie. Deskundiges kon egter akkurate kennis meedeel ten opsigte van die algemene houdings van grondeienaars, die konteks van die area van navorsing en die uitdagings wat grondeienaars in die spesifieke areas in die gesig staar. Hierdie navorsing kan gesamentlik gebruik word om die ontwikkeling van standaarde van beste praktyk vas te stel om die mees doeltreffende en koste-effektiewe benadering tot die integrasie van ruimtelike prioritisering sagteware met deskundige kennis te verseker.

Thesis (MScConEcol)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Reductionism, an approach to understanding complex systems based on reducing the system to its individual components and the interactions between these components, is the linear and rigid approach to traditional management and research that allows us to understand complicated systems. Yet its application to complex systems has likely added to the degradation of social-ecological systems. In recognition of this, there is currently a shift to holism: the concept that a system is greater than the sum of its components and that the system has emergent properties that are only present through the complex interactions of the whole system. The inclusion of this natural complexity within social-ecological systems is thought to promote resilience – the ability of a system to absorb shock and thus promote sustainability. However, these concepts are largely theoretical and few examples exist that demonstrate ways of transferring them to pragmatic land management. Holistic ManagementTM (HM) could potentially be such a working example. It is a decision-making framework that provides a holistic context for the adaptive management of natural resources. However, limited peer-reviewed research has been applied to this potential to promote sustainability. Thus the current study aimed to address this apparent gap by determining if HM land managers were a distinct group from non-HM (NHM) land managers in regards to their management practices and if HM land managers had a greater adaptive capacity (the management of resilience) than non-HM land managers. The study was conducted in a community of livestock farmers in the arid rangelands of the Karoo, South Africa. Data were mainly gathered through face-to-face interviews with land managers – including 20 self-defined HM land managers and 20 self-defined NHM land managers. To compare the reported management approaches of land managers, two scoring systems were developed. The HM Adoption Index measured the extent to which participants were aligned with key principles and practices of HM (including having a holistic goal, testing decisions, applying the Holistic Planned Grazing, demonstrating continuous learning and innovation). The Adaptive Capacity Index measured the extent to which participants demonstrated key traits of adaptive capacity as identified from the literature. In addition, participants were also asked to describe the strategies they apply to deal with local livestock farming challenges including parasite control, predation management and drought management. A significant difference was found between HM and NHM land managers for both the HM Adoption Index and Adaptive Capacity Index (p<0.01). The majority of HM land managers adopted ―true holistic and ―adaptive management practices (80%) while NHM land managers were mostly ―semi holistic and ―coping (65%). HM land managers also notably tended to report more innovative and environmentally aware methods in dealing with farming challenges and were more likely to be part of study groups which build social capital and promote social learning. Results imply that HM provides a framework that introduces holistic principles to land management, making the holistic context and resilience accessible to individual managers for practical day-to-day decision-making. / AFRIKAANSE OPSOMMING: Reduksie, 'n benadering om komplekse sisteme te verstaan deur om die sisteme te besnoei tot sy individuele komponente en interaksies tussen die komponente, is die liniêre en rigiede benadering tot tradisionele bestuur en navorsing. Dit laat ons toe om komplekse sisteme te verstaan. Tog het die toepassing van reduksie op komplekse sisteme waarskynlik bygedra tot die degradasie van sosiaal-ekologiese sisteme. In herkenning van laasgenoemde is daar tans 'n skuif na holisme: die konsep dat 'n sisteem groter is as die somtotaal van al sy komponente en dat die sisteem voortkomende eienskappe het wat net navorekom deur die komplekse interaksies van die sisteem. Die insluiting van die natuurlike kompleksiteit binne sosiaal-ekologiese sisteme bevorder moontlik weerstandigheid; die vermoë van 'n sisteem om 'n skok te absorbeer en so volhoubaarheid te bevorder. Hierdie konsepte is egter meestal teoreties en min voorbeelde bestaan wat metodes demonstreer om die konsepte oor te dra na pragmatiese grondbestuur. Holistiese BestuurTM (HB) kan moontlik so 'n werkende voorbeeld wees. Dit is 'n raamwerk vir besluitvorming wat 'n holistiese konteks verskaf vir die aanpasbare bestuur van natuurlike hulpbronne. Daar is min eweknie-hersiende navorsing wat HB se potensiaal om volhoubaarheid te bevorder ondersoek. Dus het die huidige studie beoog om die gaping aan te spreek deur te bepaal of HB praktiseerders onderskei kan word van 'n groep van nie-HB (NHB) praktiseerders in terme van bestuurspraktyke en of HB praktiseerders 'n groter aanpasbaarheid (die bestuur van weerstandigheid) toon as NHB praktiseerders. Die studie het plaasgevind in 'n gemeenskap van veeboere in die dorre veld van die Karoo, Suid Afrika. Data was versamel deur aangesig tot aangesig onderhoude met grondbestuurders; 20 self-geïdentifiseerde HB praktiseerders en 20 self-geïdentifiseerde NHB praktiseerders. Twee puntestelsels is ontwikkel om die gerapporteerde benaderings van grondbestuurders te vergelyk. Die HB Toepassing Puntelys het gemeet tot watter mate 'n deelnemer inskakel met die kern beginsels van HB (insluitend om 'n holistiese doelwit te hê, om besluite te toets, om Holistiese Beplande BewydingTM toe te pas en om 'n voortsetting van leer en innovasie te demonstreer). Die Aanpasbaarheid Puntelys het gemeet tot watter mate 'n deelnemer die kern kenmerke van aanpasbaarheid, soos geïdentifiseer in literatuur, demonstreer. Bykomend was deelnemers ook gevra om die strategieë te beskryf wat hulle toepas om die uitdagings van plaaslike veeboerdery tegemoed te kom insluitend die beheer van parasiete, die bestuur van roofdiere en die bestuur tydens droogtes. 'n Betekenisvolle verskil was gevind tussen HB en NHB praktiseerders vir die HB Toepassing Puntelys en die Aanpasbaarheid Puntelys (p<0.01). Die meederheid van HB praktiseerders het ―ware holistiese en ―aanpasbare praktyke toegepas (80%) terwyl NHB praktiseerders se metodes meestal ―semi-holisties en ―korttermyn probleem hantering was (65%). HB praktiseerders het ook 'n waarneembare neiging gehad om innoverende en omgewingsbewuste metodes te rapporteer in verband met veeboerdery uitdagings en was meer waarskynlik deel van 'n studie groep wat sosiale kapitaal gebou en sosiale leer bevorder het. Die resultate het aangedui dat HB 'n raamwerk voorsien wat holistiese beginsels oordra na grondbestuur en so die holistiese konteks en weerstandigheid toeganklik maak vir die individuele bestuurder vir daaglikse praktiese besluitneming en toepassing.

Thesis (MScConEcol)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Soil respiration (Rs) is a major component of CO2 emissions and the global carbon balance. In the context of global change it of interest to understand seasonal patterns of RS in fynbos riparian ecosystems, particularly in invaded-riparian ecotones of these Mediterranean type ecosystems (MTE's) in the Western Cape, South Africa. Riparian ecotones are three dimensional transitional zones that provide multiple ecosystem services and functions and they act as the linkage between terrestrial and aquatic ecosystems where key ecological and geomorphological processes occur. Riparian ecotones are highly prone to disturbance, and because of this reason are also vulnerable to invasion by invasive alien plants (IAPs), notably Acacia species. Invasion by IAPs is considered one of the major threats to global change and biodiversity causing extensive ecological, economical, and social impacts. In south-western Cape, more than two thirds of the riparian environment is invaded to some extent, IAPs replacing the well adapted native species along river systems. In particular, impact of IAPs on soil respiration (Rs) may be relevant, with consequences for ecosystem function and services. Clearing of invaded riparian zones initiated by the Working for Water program has been a successful in eradicating alien plants within riparian areas even though recovery after alien clearing is lagging at many sites, and knowledge on repair of ecosystem function is lacking. Various studies have generated knowledge on carbon cycling and Rs in forests, savanna, grasslands, tundra and Mediterranean shrublands, but little is known about Rs in riparian zones, and even less about soil CO2 efflux in invaded riparian fynbos riparian ecotones. The objective of this study was to contribute to a better understanding and quantifying the effect and impact of IAPs on carbon cycling between and across riparian ecotones with different invasion status: natural, invaded, and cleared. The study areas were located in the south-western Cape and measurements of Rs, soil temperature, soil moisture, root mass, litter mass, and soil properties were carried out in riparian soils of the mountain and transitional stream longitudinal river sections, and uplands fynbos areas of six different perennial river systems. In each site, four to five transects were laid out with one sampling site of each landscape position (wet bank, dry bank, and terrestrial areas) giving a total of 12 to 15 samples per site. Soil respiration measurements were taken over a period of two years, and were done seasonally. Results from this study showed that Rs was different among seasons with highest soil respiration rates in summer. Soil CO2 efflux increased in response to warm and dry conditions during summer, while seasonal soil CO2 efflux declined in autumn and winter in response to wet and cold soil conditions. The large increase in soil CO2 efflux response to warm and dry periods when temperature was 25 to 30 °C over all riparian sites and was highest in invaded sites compared to the natural and cleared sites. A significant difference was found between sites with different statuses with invaded sites leading seasonal Rs rates. Natural and cleared sites did not differ significantly in their CO2 efflux rates, suggesting that clearing of IAPs may put invaded ecosystems on a trajectory of restoration. There were also differences in terms of landscape positions; dry banks zones of the invaded sites had higher rates compared to wet banks and the uplands areas. Our results further suggest that roots are the most important component of overall Rs rates, rather than microbial respiration. When we incubated soils minus roots, little difference was evident, either when viewing the results by invasion status or by landscape position, which suggest that inherent soil differences in terms of microbial respiration were not different. We also use a trenching approach to further investigate this, and though we found Rs to decline significantly, trends later suggest that decomposition of fine and course roots likely obscured the decline in overall Rs due to root respiration. Overall, our results showed that clearing of invaded riparian zones will likely lead to successful restoration of soil functioning in terms of C cycling. Clearing of Acacia-invaded riparian ecotones will likely lead to a decline in root density, and which removes a major component of overall Rs. These results make the investigation of the C balance of invaded riparian ecotones and terrestrial areas critical in order to assess their contribution to regional C cycles. / AFRIKAANSE OPSOMMING: Grondrespirasie (Rs) is 'n belangrike komponent van CO2 uitstroming en die globale koolstofbalans. Binne die konteks van globale verandering is dit van groot belang om die seisoenale patrone van Rs in fynbos oewer ekosisteme, veral in indringer-oewer ekotone, in die Meditereense tipe ekosisteme (MTE's) in die Wes- Kaap, Suid- Afrika te verstaan. Oewerekotone is drie-dimensioneel oorgangssones wat veelvuldige ekosisteem dienste en funksies verskaf. Hulle dien as die verbinding tussen terrestriële en water-ekosisteme waar kern ekologiese en geomorfologiese prosesse plaasvind. Oewerekotone is hoogs vatbaar vir versteuringe, en as gevolg van hierdie rede, is hul ook kwesbaar vir indringing deur indringer plante (IAPs), veral Acacia spesies. Indringing deur IAPs word beskou as een van die groot bedreigings tot en met globale verandering en biodiversiteit, wat ekstensiewe ekologiese, ekonomiese, en sosiale impakte veroorsaak. In die suid- westelike Kaap word meer as twee derdes van die oeweromgewing tot 'n mate binnegedring. IAPs vervang die goed aangepaste inheemse spesies langs riviersisteme. Die impak van IAPs, spesifiek op grondrespirasie mag substansieël wees, met gevolge vir ekosisteem funksies en dienste. Opruiming van hierdie spesifieke oewer sones, geinisieer deur die Working for Water program, was suksesvol in die uitroeing van indringer plante binne oewer areas. Alhoewel herstel na indringer opruiming op baie terreine agter is, is kennis oor die herstel van ekosisteemfunksies gebrekkig. Verskeie studies het kennis ontwikkel oor koolstofsiklisering en Rs in woude, savanna, graslande, tundra en Meditereense struiklande, maar daar is minimale informasie oor oewersones,en nog minder oor grond CO2 uitstroming in indringer oewer fynbos en oewer ekotone. Die doel van hierdie studie is om 'n bydrae te lewer koolstofsiklisering beter te verstaan, en die impak van IAPs op koolstofsiklisering te kwantifiseer tussen en oor oewerekotone met verkillende indringer statusse: natuurlik, binnegedring en skoongemaak. Die studie areas was geleë in die suid- westelike Kaap, en maatstawe van Rs, grond temperature, grondvogtigheid, wortelmassa, plantafvalmassa, en grondeienskappe is uitgevoer in oewergrond van die berg en transisionele stroom longitudinale rivier seksies, asook terrestriële fynbos areas van ses verskillende standhoudende riviersisteme. In elke area is vier tot vyf transekte uitgelê met een monsternemingsarea van elke landskapsposisie (nat bank, droë bank en terrestriële areas) met 'n totaal van 12 tot 15 monsters per area. Grondrespirasie maatstawe is geneem oor 'n periode van twee jaar, en is seisoenaal uitgevoer. Resultate van die studie het getoon dat Rs verkil het tussen seisoene, met die hoogste grondrespirasietempo in die somer. Grond CO2 uitstroming het toegeneem in reaksie op warm en droë kondisies gedurende somer, terwyl seisoenale grond CO2 uitstroming afgeneem het in herfs en winter in reaksie op nat en koue grond kondisies. Die grootste toename in grond CO2 uitstroming was in reaksie op warm en droë periodes wanneer temperature gewissel het tussen 25 tot 30˚C oor alle oewersones, en was die hoogste in binnegedringde sones, vergeleke met die natuurlike en skoongemaakte terreine. 'n Beduidende verskil is gevind tussen terreine met verskillende statusse in CO2 uitstromingskoerse‚ 'n aanduiding dat opruiming van IAPs binnegedringde ekosisteme op 'n trajek van restorasie plaas. Daar was ook verskille in terme van landskapsposisies; droë bank sones van die binnegedringde terreine het hoër tempos gehad, vergeleke met die nat bank en die hoogland areas. Ons resultate dui verder aan dat wortels, eerder as mikrobiologiese respirasie, die mees belangrike komponente van Rs koerse uitmaak. Toe ons grond minus wortels inkubeer, is min verskille opgemerk, as gekyk word na die resultate deur indringer status of landskapsposisie, wat toon dit dat inherente grondveskille in terme van mikrobiologiese respirasie nie verskillend is nie. Ons het verder ook 'n sloot-benadering gebruik om verdere ondersoek hierop in te stel, en alhoewel ons bevind dat Rs aansienlik afgeneem het, dui neigings later aan dat afbraak van fyn en growwe wortels die afname in gehele Rs as gevolg van wortel respirasie waarskynlik verdoesel. Ons resultate dui daarop dat opruiming van binngedringde oewers klaarblyklik sal lei tot suksesvolle restorasie van grondfunksionering in terme van C siklisering. Opruiming van Acacia- binnegedringde oewer ekotone sal vermoedelik lei tot 'n afname in worteldigtheid, en wat 'n belangrike komponent van die gehele Rs kan verwyder. Hierdie resultate maak die ondersoek van die C balans van binngedringde oewer ekotone en terrestriële areas krities, om sodoende hulle bydrae tot streeksgewyse C siklusse te asseseer.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Plant-parasitic nematodes, consisting of a wide range of species, can cause severe economic losses in most agricultural food crops. Meloidogyne spp. (root-knot nematodes), Criconemoides xenoplax (ring nematode), Xiphinema index (dagger nematode) and Pratylenchus spp. (lesion nematodes) are some of the economically important plant-parasitic nematodes that pose a threat to viticulture and other perennial crops in South Africa. Worldwide there is ever-increasing pressure on pre-plant synthetic soil fumigants and post-plant nematicides. For sustainable nematode management, it is important to have a holistic approach; taking into consideration cultural, biological and chemical options as part of an integrated management approach. Biofumigation has the potential to fit into such an integrated management system and previous research indicates the positive response on soil-borne diseases, nematodes and weeds. Biofumigation occurs where certain plant species, containing glucosinolates (GSL) in the vacuole of the plant cells, come into contact (after cell maceration), with the enzyme myrosinase (MYR) situated in the cytoplasm of the cell, to form active compounds such as isothiocyanate (ITC). When this green manure is applied to infested soil, the ITC has the potential to have a direct suppressive effect on the soil-borne pathogens and there is also an indirect effect that can be expected after green manure soil amendment, because microbial activity is enhanced in the soil. Brassicas are known to possess GSL and MYR in their cells and thus have the potential to be utilized as biofumigation crops. There are, however, differences in the potential within the Brassicaceae family, based on different types and concentrations of GSL present in the different species. To ensure effective biofumigation it is important to use the correct brassica species and have a good understanding of the factors that have a positive impact on the biofumigation action. Laboratory bioassays were done to determine the potential of different cover crops to suppress Meloidogyne javanica and C. xenoplax, when applied as a green manure. The cover crops used for the bioassays included Oats (Avena sativa cv. Pallinup), White mustard (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) and Nemat (Eruca sativa cv. Nemat). The plant material was cut into small pieces and mixed with sterilised soil inoculated with either M. javanica or C. xenoplax. Results from the bioassays showed a significant suppression of M. javanica by the three biofumigation species: White mustard, Caliente 199 and Nemat. These results supported previous research, indicating the nematode suppressing effect due to the biofumigation action of certain brassica crops. Canola did not have the same suppressing impact on the M. javanica and gave comparable results to the control, indicating that Canola is not a good biofumigation crop for M. javanica suppression. In terms of biofumigation effect oats did not differ significantly from the control or the three brassicas: White mustard, Caliente 199 and Nemat. In the bioassays done for C. xenoplax no significant differences were found between the green manure treatments and the control. These results indicate that the different crops tested, including the three well known biofumigation crops, did not suppress the C. xenoplax at the applied biomass concentrations used in the bioassay. Crops can also be classified according to their host status for certain plant parasitic nematodes. Crop host trials were conducted to determine the crop host status of the five different cover crops, to M. javanica and C. xenoplax. The crops were planted in sterilised soil, inoculated with the latter plant-parasitic nematodes and left for 60 days, after which, a root gall index analysis was done for M. javanica and for 85 or 92 days after which C. xenoplax was extracted from the soil. All the crops evaluated had a significantly lower root gall index for M. javanica than the control. Nemat and Oats was classified as poor hosts for M. javanica. A visual inspection of the root systems of all the crops was performed to determine whether M. javanica managed to complete its lifecycle in the different root systems. On all root systems, M. javanica managed to form root galls and produce egg masses, from which (J2) juveniles emerged. This indicates that M. javanica did complete its lifecycle in the different root systems of the crops evaluated and that all the cover crops acted as hosts. The expression of the gall symptoms were, however, less severe on Nemat and Oats, compared to the others. In the C. xenoplax crop host trials, all except the Nemat treatment showed a significant difference, compared to the Tomato treatment, with lower C. xenoplax numbers being present in the other crops. The nematode numbers in the different crops, compared well with the control (only inoculated soil), indicating that the crops did not stimulate the reproduction of C. xenoplax. Canola had the lowest numbers of C. xenoplax present after the growing cycle and Caliente 199 also showed a declining trend. In South Africa, the use of annual cover crops in vineyards is an established soil cultivation practice. In a field study, Oats, White mustard, Canola, Caliente 199 and Nemat were established in a vineyard as cover crops for three growing seasons (2009/10, 2010/11, 2011/12), and evaluated for their biofumigation impact, as well as their host impact on the suppression of certain economically important plant-parasitic nematodes. Two cover crop management practices, namely mechanical incorporation (MC) into the top soil and chemical removal of the cover crop (CC) were applied to the different cover crops. Nematode samples were taken in the work row and in the vine row at different times to determine the nematode status. These periods were April/May, before planting the cover crops, as well as 0, 15, 30 and 60 days after the management practices were performed. The crop biomass, measured as dry matter production (DMP) in tons/ha, differed significantly between the different crops, but also showed substantial increases during the three cover crop growing seasons for most crops. During the three consecutive seasons, Canola (CC) and Caliente 199 (CC) showed a constant reduction in the C. xenoplax population in the vine row based on the 60 day analysis. This trend was also observed for the total plant-parasitic nematode population in the vine row for the three seasons, based on 60 day analysis. The same trend took place during the three-year trial period for all the different sampling periods (0, 15, 30 and 60 days). The results can be attributed to the host status of these crops and not primarily because of the biofumigation effect. Both the Canola (CC) and the Caliente (CC) had a substantial increase in DMP during the three growing seasons that might have played a role in this trend. White mustard (CC and MC) showed a significant increase in the C. xenoplax population in the vine row, over the three year period, based on the 60 day analysis. The same trend was found Nemat (CC) and weeds and nematicide (CC) measured at the same period. A positive result from the Meloidogyne sp. analysis was that there was no significant increase in the Meloidogyne sp. in the vine row during the three growing seasons based on the 60 day analysis. This trend was seen in all the different treatments. The results from this study opens the possibility to apply these cover crops as part of a crop rotation programme without expecting an increase in the Meloidogyne sp. population to occur in the vine row through time. / AFRIKAANSE OPSOMMING: Plantparasitiese nematodes, wat bestaan uit 'n wye verskeidenheid van spesies, kan lei tot ernstige ekonomiese verliese in die meeste landbou gewasse. Meloidogyne spp. (knopwortel nematode), Criconemoides xenoplax (ring nematode), Xiphinema index (dolk nematode) en Pratylenchus spp. (letsel nematode) is van dié belangrikste plantparasitiese nematodes wat 'n bedreiging inhou vir wingerd en ander meerjarige gewasse in Suid-Afrika. Wêreldwyd is daar tans toenemende druk op die uitfasering van voor-plant chemiese grondberoking middels en so ook op nauitplant nematisiede. Vir volhoubare nematode bestuur, is dit belangrik om 'n holistiese benadering te volg, in ag genome kulturele, biologiese en chemiese maatreëls as deel van 'n geïntegreerde benadering. Bioberoking het die potensiaal om deel uit te maak van so 'n geïntegreerde benadering en baie vorige navorsing bevestig hierdie positiewe reaksie, in terme van onderdrukking, wat bioberoking op grond-gedraagde siektes, nematodes en onkruid kan hê. Bioberoking kan beskryf word as die reaksie, wat plaasvind wanneer glukosinolaat (GSL), wat teenwoordig is in die vakuool van die plantselle, in kontak kom met die ensiem mirosinase (MYR), nadat selbreking plaasgevind het en die aktiewe verbinding isothiosianaat (ITC) en ander sekondêre metaboliete gevorm word. Wanneer hierdie groen plantmateriaal in die grond ingewerk word, kan ʼn direkte onderdrukkings effek, as gevolg van die ITC, asook ʼn indirekte onderdrukkings effek as gevolg van die stimulasie van mikrobe aktiwiteit, verwag word. Brassica gewasse is bekend daarvoor dat daar GSL en MYR in die plantselle teenwoordig is en hulle besit dus die potensiaal om ITC te vorm. Daar is egter verskille in hierdie potensiaal binne die Brassicaceae familie, wat gebaseer is op verskillende tipes en konsentrasies GSL. Die keuse van ʼn brassica spesie is dus belangrik, tesame met ʼn verskeidenheid van ander faktore, om optimale bioberoking te verseker. Laboratorium biotoetse is gedoen om die bioberokings effek van verskillende dekgewasse op Meloidogyne javanica en C. xenoplax, wanneer dit aangewend word as groenbemesting, te bevestig. Die dekgewasse wat gebruik is sluit in: Hawer (Avena sativa cv. Pallinup), Wit mosterd (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) en Nemat (Eruca sativa cv. Nemat). Die plantmateriaal is fyn opgesny en ingewerk in gesteriliseerde grond wat met onderskeidelik M. javanica en C. xenoplax geïnokuleer is. Resultate van die biotoetse vir M. javanica toon dat die drie gewasse; Wit mosterd, Caliente 199 en Nemat, wat alombekend is vir hul bioberoking potensiaal, ʼn betekenisvolle onderdrukkings op M. javanica tot gevolg gehad het. Hierdie biotoetse ondersteun vorige navorsing, waar effektiewe onderdrukking van sekere Meloidogyne spesies as gevolg van bioberoking verkry is. Die resultate dui ook aan dat Canola nie ʼn goeie opsie is vir effektiewe bioberoking om M. javanica onderdrukking te verkry nie. Die Hawer behandeling het nie betekenisvol van die kontrole of van die ander bioberokings gewasse verskil nie. Daar is geen betekenisvolle verskille verkry tussen die kontrole en die ander gewasse tydens die C. xenoplax biotoetse nie. Die resultate dui aan dat die dekgewasse, insluitende die drie bekende bioberokings gewasse, nie C. xenoplax onderdruk teen die toegediende biomassa konsentrasies nie. Gewasse kan ook geklassifiseer word op grond van hul gasheer status vir sekere nematode. Gasheer toetse is gedoen om die gasheer status van die verskillende dekgewasse vir M. javanica en C. xenoplax te bepaal. Dieselfde vyf verskillende dekgewasse is geplant in grond, wat vooraf onderskeidelik met M. javanica en C. xenoplax geïnokuleer is. Plante is gelos om vir `n spesifieke periode te groei waarna ʼn galindeks evaluasie is gedoen om die gasheer status vir M. javanica te bepaal en ʼn nematode ontleding gedoen is om die gasheer status vir C. xenoplax te bepaal. In die M. javanica gasheer toetse was die galindeks van al die gewasse betekenisvol laer as die kontrole. Nemat kan geklassifiseer word as ʼn swak gasheer vir M. javanica en het betekenisvol minder galle as al die ander gewasse, behalwe die Hawer, waarvan dit nie betekenisvol verskil het nie. Nemat pas dus goed in ʼn dekgewas program waar die doel is om die M. javanica populasie te onderdruk tydens die groei van die gewas. ʼn Visuele inspeksie van die wortelstelsels is ook gedoen ten einde te bepaal of die lewensiklus van M. javanica voltooi is. Wortelgalle en eiersakkies was teenwoordig in die wortels van al die verskillende gewasse en larwes het uit die eiers uitgebroei. Dit dui aan dat M. javanica daarin geslaag het om sy lewenssiklus op al die dekgewasse suksesvol te voltooi. Daar was aansienlik minder eiersakke by Nemat en Hawer; wat hul swak gasheer status bevestig. In die biotoetse vir die gasheerstatus van C. xenoplax het al die gewasse, behalwe Nemat, betekenisvol laer C. xenoplax getalle, in vergelyking met die Tamatie behandeling, tot gevolg gehad. Die nematode getalle was soortgelyk aan die kontrole (slegs geïnokuleerde grond), waar geen gewas in medium geplant is nie, en dui dus aan dat die getalle op die verskillende gewasse nie vermeerder het nie. Die Canola behandeling het die laagste C. xenoplax getalle gehad, gevolg deur Caliente 199. Hierdie gewasse toon dus die meeste potensiaal om aangewend te word in 'n rotasie stelsel of dekgewas program, waar die doel is om die C. xenoplax populasie te onderdruk. In Suid-Afrika is die aanwending van spesifieke eenjarige gewasse, as dekgewasse in wingerde, reeds ʼn standaard praktyk met verskeie voordele. In veldproewe oor ʼn tydperk van drie jaar (2009/10, 2010/11, 2011/12) is Hawer, Wit mosterd, Canola, Caliente 199 en Nemat aangeplant as dekgewasse in ʼn wingerd proefperseel. Die doel van die veldproewe was om die effek van dekgewasse op die plantparasitiese nematodes, wanneer dit aangewend word as bioberokings gewasse, te bepaal. Die gasheer status van die gewasse is ook ondersoek om te bepaal wat die effek sal wees op die nematode getalle. Twee dekgewas bestuurspraktyke is toegepas; meganiese inwerk van die dekgewasse in die bogrond (MC) en chemiese beheer van die dekgewasse (CC) en nematode monsters is op verskillende tye in die werksry en in die wingerdry geneem. Hierdie periodes sluit in April/Mei, voor die vestiging van die dekgewasse en 0, 15, 30 en 60 dae nadat die bestuurspraktyk toegepas is. Die dekgewas se biomassa produksie is, op grond van die droë massa produksie (DMP), in ton/ha gemeet, wat betekenisvol verskil het vir die verskillende dekgewas. Daar het ook `n duidelike toename in DMP plaasgevind oor die drie seisoene vir meeste gewasse. Gedurende die drie jaar periode het die Canola (CC) en Caliente 199 behandelings, gemeet 60 dae na die bestuurspraktyk, ʼn konstante afname getoon in die C. xenoplax in die wingerd ry. Dieselfde tendens het ook voorgekom gedurende hierdie periode in die totale plantparasitiese nematodes teenwoordig in die wingerd ry. Daar is ook ʼn geleidelike afnemende tendens in die C. xenoplax in die wingerd ry, oor die verskillende periodes 0, 15, 30 en 60 dae vir die drie opeenvolgende seisoene, waargeneem. Hierdie resultate kan primêr toegeskryf word aan die gasheer status van die dekgewasse, wat in die gasheer proewe as swak gashere vir C. xenoplax aangetoon is. Nog ʼn faktor wat hier ʼn rol speel is die feit dat beide die Canola (CC) en die Caliente 199 (CC) ʼn toename in DMP van meer as 2 ton, gedurende die drie jaar periode, gehad het; wat op sigself ook ʼn bydraende rol kon speel. Wit mosterd (CC en MC) het oor die drie seisoene ʼn betekenisvolle verhoging in die C. xenoplax populasie tot gevolg gehad, gebaseer op die 60 dae ontleding. Dieselfde tendens is ook opgemerk vir die ander behandelings, onder andere Nemat (CC) en die onkruid en aalwurmdoder (CC) behandeling. ʼn Baie positiewe resultaat na afloop van die drie seisoene is die feit dat daar nie ʼn betekenisvolle verhoging in die Meloidogyne sp. populasie in die wingerdry, op grond van die 60 dae onledings, plaasgevind het nie. Dit was ook die geval vir al die ander behandelings. Hierdie resultate ondersteun die moontlikheid om hierdie bioberokings gewasse deel te maak van ʼn geïntegreerde dekgewas benadering, sonder om in die proses die Meloidogyne sp. in die wingerd ry te verhoog.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The export of South African fruit to some of its biggest international markets may be rejected if the phytosanitary pest, Phlyctinus callosus (Coleoptera: Curculionidae) is found in fruit consignments. An alternative to methyl bromide fumigation is needed and one of the most promising of the alternative treatments is phytosanitary irradiation as it is environmentally friendly, does not leave residues on food or in the environment and it is effective against a wide variety of insects. Field-collected weevils were treated with five doses of gamma irradiation (5, 10, 20, 40 and 80 Gy) and the fecundity and fertility of mating crosses of treated males and females with treated and untreated individuals of the opposite sex, were determined to evaluate the effect on P. callosus reproductive ability post-treatment. Results indicated that irradiation treatment did not affect fecundity, but fertility was significantly affected, decreasing as the irradiation dose increased. Females were more susceptible to the irradiation treatment than males, and after treatment with 80 Gy, eggs laid by females and mated with either treated or untreated males, did not hatch. A generic dose of 400 Gy for all insect pests except tephritid fruit flies and pupae and adult Lepidoptera is currently approved by USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) for use on certain commodities. Results from the present study support the development of a species-specific dose for P. callosus, as well as the development of a group generic dose for the Curculionidae that is lower than 400 Gy. Effective phytosanitary irradiation treatments are only feasible if the treatment does not adversely affect fruit quality and the marketability of export fruit. Therefore, an investigation of the effects of irradiation disinfestations treatments on the quality of the new pluot cultivar, ‘Flavor Fall’ was made. Packed cartons were treated with three doses of gamma irradiation: 400 Gy, 900 Gy and 1400 Gy. After treatment fruit underwent a PD 7 dual temperature cold storage regime for 42 days and a shelf-life simulation for 7 days. The impact of insect-proof bags, sometimes required by importing countries to keep insects off packaged fruit, was also investigated. Respiration rate of the fruit was measured throughout and fruit quality evaluations were done after cold storage and after shelf-life. The results indicated that quality parameters measured at the end of cold storage, which would be after the fruit arrives at the export markets, were above the minimum standards for overseas markets. Gel breakdown was unacceptably high after the higher temperature exposure of shelf-life for fruit treated with the 900 and 1400 Gy doses. The insect-proof bags reduced shrivel, but resulted in higher incidence of gel breakdown. The use of irradiation, together with the use of the insect-proof bag, has potential as an alternative postharvest mitigation treatment for plums. Lastly, an investigation into potential rearing methods for P. callosus, including recommendation for the future, was made as the availability of a sustainable rearing method that ensures a consistent supply of high quality P. callosus adults would enable continuous research with greater numbers of this pest. The information generated in this study provides a greater understanding of the radiation biology of, not only this curculionid species, but the Curculionidae as a group, and is valuable in advancing the development of alternative postharvest control measures against this phytosanitary pest. / AFRIKAANSE OPSOMMING: Suid Afrikaanse vrugte uitvoere na van die grootste internasionale markte mag weg gewys word as die fitosanitêre pes, Phlyctinus callosus (Coleoptera: Curculionidae) in die versending gevind word. ‘n Alternatief vir metiel bromied beroking word benodig en een van die mees belowende alternatiewe behandelings is fitosanitêre bestraling aangesien dit omgewings vriendelik is, nie residue op kos of in die omgewing los nie, en effektief is teen ‘n wye verskeidenheid van insekte. Veldversamelde kalanders is behandel met vyf dosisse gamma bestraling (5, 10, 20, 40 en 80 Gy) waarna die vrugbaarheid van paringskruisings bepaal is deur kruisings tussen behandelde manlike en vroulike kalanders met behandelde en nie-behandelde individue van die teenoorgestelde geslag te maak, en so die na-behandelings effek op die voortplantings vermoeë van P. callosus te evalueer. Die resultate het getoon dat die bestralings behandeling geen invloed gehad het op die hoeveelheid eiers wat gelê is nie, maar dat die uitbroei van eiers aanduidend geaffekteer is deur die behandeling. Die hoeveelheid eiers wat uitgebroei het, het minder geraak soos die bestralings behandeling toegeneem het. Vroulike kalanders was meer sensitief vir die behandeling en na 80 Gy, of hul gekruis is met behandelde of niebehandelde mannetjies, het geen eiers uitgebroei nie. ‘n Generiese dosis van 400 Gy vir alle insekte, uitsluitend tephritiese vrugte vlieë en papies en volwasse Lepidoptera is huidiglik goedgekeur deur die USDA-APHIS (United States Department of Agriculture – Animal and Plant Health Inspection Services) vir sekere kommoditeite. Die resultate van die huidige studie ondersteun die ontwikkeling van ‘n spesie-spesifieke dosis vir P. callosus, so ook die ontwikkeling van ‘n generiese groep dosis vir Curculionidae wat laer as 400 Gy is. Effektiewe fitosanitêre bestralings behandeling is slegs moontlik indien die behandelings dosis nie nadelig vir vrugkwaliteit en die bemarking van uitvoer vrugte is nie. Dus is die effek wat bestralings bestryding behandeling op die kwaliteit van ‘n nuwe pluot kultivar, ‘Flavor Fall’ ondersoek. Vrugte verpak in kartonne is met drie dosisse gamma bestraling behandel: 400 Gy, 900 Gy en 1400 Gy. Na behandeling is die vrugte deur ‘n PD 7 dubbel temperatuur koelopbergings regime van 42 dae en rak-lewe simulasie vir 7 dae gesit. Die impak van insek-bestande sakke wat insekte van die verpakte vrugte weg hou en soms deur invoerende lande ‘n vereiste is, is ook ondersoek. Respirasie tempo van die vrugte is getoets en vrugkwaliteit evaluasies is gedoen na koelopberging en rak-lewe. Die resultate het getoon dat die kwaliteits maatstawwe wat getoets is na koelopberging (wat tipies is wanneer die vrugte by die uitvoer mark arriveer), almal bo die minimum standaarde van die uitvoer markte was. Gel-afbraak was onaanvaarbaar hoog na blootstelling aan die hoër temperature tydens rak-lewe vir vrugte wat behandel is met 900 en 1400 Gy. Die insek-bestande sakke het verrimpeling verminder, maar die voorkoms van gel-afbraak vermeerder. Die gebruik van bestraling, tesame met die insek-bestande sakke, het potensiaal as alternatiewe na-oes behandeling vir pruime. Laastens is ‘n ondersoek ingestel vir moontlike teeltegnieke vir P. callosus en aanbevelings gemaak vir toekomstike studies. Die beskikbaarheid van ‘n volhoubare teeltegniek wat konstante, hoë kwaliteit P. colossus individue verskaf sal aaneenlopende navorsing met groter getalle van die pes moontlik maak. Die inligting wat deur hierdie studie gegenereer is help om die bestralings biologie, nie net van hierdie curculionid spesie nie, maar die Curculionidae as ‘n groep te verstaan, en is kosbaar in die bevordering van ontwikkeling van alternatiewe na-oes beheer meganismes teen hierdie fitosanitêre pes.

Thesis (MScConsEcol)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Apis mellifera, the honeybee, is regarded as the most crucial insect pollinator to South African agriculture as it is the only managed pollinator used in the pollination of commercial agricultural crops. Essential to sustaining managed honeybees is the supply of adequate and sustainable forage resources upon which managed honeybee colonies can forage throughout the year. In most instances agricultural pollination services are only required for a brief period of the year, and consequently managed honeybee colonies need to be sustained on a variety of alternate forage resources for the remaining months of the year. As an essential resource in maintaining managed honeybee colonies, honeybee forage can subsequently be linked to the maintenance of agricultural crop pollination. Exotic honeybee forage species have always been an important part of managed honeybee foraging patterns, however recent pressure to control exotic plant species in South Africa has put this type of honeybee forage under threat. This studies’ first aim was focused on identifying the historic honeybee forage use pattern in South Africa, thereby identifying which forage species have maintained managed beekeeping up until this point. A comprehensive literature review of the South African Bee Journal, dating back to the journals first publication in the 1910’s documented both the exotic and indigenous forage species that have sustained the beekeeper industry in the past. Significance ratings of individual species were determined according to the number of times a species was cited in the literature throughout the review period. Although indigenous species where cited in the literature, the predominately used forage species was found to be exotic, highlighting the role these species played in the development of South African beekeeping. Secondly, this study identifies and highlights the current honeybee forage usage pattern in South Africa. By means of a country wide honeybee forage questionnaire, honeybee forage usage patterns were determined based on forage species usage by beekeepers in different provincial regions. Important forage species were highlighted in each region on the basis of number of colonies using individual forage species. In addition to identifying current forage usage, this questionnaire was able to help estimate the number of managed honeybee colonies in South Africa at present, given that census data is not yet available. Even though there is currently a greater awareness and usage of indigenous forage species, it remains that the predominantly used forage source are exotic forage species. Whilst there appears to be a movement and awareness towards the use of indigenous forage species across South Africa, forage species usage patterns have not shift dramatically in the last century. In order to fulfill their foraging requirements, managed honeybee colonies remain heavily dependent on exotic species, especially that of Eucalyptus and certain agricultural crop species. The removal of Eucalyptus should thus just be done in sensitive environments, while all woodlots should be demarcated and managed to ensure continued forage availability. In turn growers of forage crops should be made aware of their contribution to provincial honeybee forage resources. / AFRIKAANSE OPSOMMING: Apis mellifera, die heuningby, word beskou as die belangrikste insek bestuiwer vir kommersiële boerdery in Suid Afrika, aangesien dit die enigste bestuurde bestuiwer is wat vir kommersiële landbou-gewasse gebruik word. Die beskikbaarheid van voldoende en volhoubare voedselbronne vir bestuurde heuningby kolonies is noodsaaklik vir hul voortbestaan. Bestuiwing deur hierdie insekte is in die meeste gevalle net nodig vir ʼn kort tydperk elke jaar, dus benodig bestuurde heuningby kolonies ʼn verskeidenheid van alternatiewe voedselbronne vir die oorblywende maande. Heuningby voedselbronne is noodsaaklik vir die handhawing van heuningby kolonies, en dus kan die beskikbaarheid van hierdie bronne gekoppel word aan die onderhouding van landbougewas bestuiwing. Uitheemse heuningby voedsel spesies is belangrik vir die voortbestaan van die heuningby, maar ’n toename in uitheemse plant spesies bestuur bedreig hierdie heuningby voedselbronne. Die eerste doel van hierdie studie was om die historiese heuningby voer gebruik patrone in Suid Afrika te identifiseer, om vas te stel watter plant spesies tot nou toe belangrik was vir byboerdery. ʼn Omvattende literatuuroorsig van die South African Bee Journal, vanaf die eerste publikasie in die 1910’s, het bevestig watter inheemse en uitheemse spesies belangrik was vir die voortbestaan van byboerdery in die verlede. Betekenis gradering van individuele spesies was bepaal volgens die aantal kere wat ʼn spesies aangehaal is in die literatuur binne die oorsigtydperk. Alhoewel inheemse plant spesies aangehaal was in die literatuur, was die meerderheid van die spesies uitheems. Dit dui dus die belangrikheid van uitheemse spesies aan vir die ontwikkeling en voortbestaan van Suid Afrikaanse byboerdery. Die tweede doel van hierdie studie was om die huidige kos soek patrone van die heuningby in Suid Afrika aan te wys. Die heuningby voer gebruik patrone is bepaal deur ʼn landwye vraelys, wat die voedselbron spesies van byeboere in die verskillende provinsies ondersoek het. Belangrike voedselbron spesies in elke streek was uitgelig in terme van die aantal by kolonies wat daardie spesie gebruik. Hierdie vraelys was ook gebruik om vas te stel hoeveel bestuurde heuningby kolonies daar tans in Suid Afrika is, aangesien sensus data nog nie beskikbaar is nie. Alhoewel daar tans ʼn groter bewustheid is van die gebruik van inheemse spesies as ʼn voedselbron, word uitheemse spesies steeds die meeste gebruik. In die laaste eeu was daar nie ʼn dramatiese verskuiwing vanaf uitheemse na inheemse spesies nie, ten spyte van die toeneemde bewustheid. Ten einde hul voedsel vereistes te voldoen, bly bestuurde heuningby kolonies afhanklik van uitheemse spesies, veral Eucalyptus spesies en sekere landbou-gewasse. Eucalyptus moet net in sensitiewe omgewings verwyder word, en bebosde gebiede moet afgebaken en bestuur word om te verseker dat hul as volhoubare voedselbronne beskikbaar bly. Verder moet produsente van gewasse wat byeboere kan gebruik bewus gemaak word van hul bydrae tot die voedselbronne van bestuurde heuningbye in hul streek.

Thesis (MScConsEcol)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Rûens Silcrete Renosterveld (RSR) is a critically endangered vegetation type in the Overberg region of the Western Cape Province of South Africa. In the last few centuries about 80% of it has been severely transformed by agriculture. The RSR contains many unique and rare plants species, and has very high conservation value. It is recommended that all remaining areas of this vegetation type should be conserved. However, very few of these areas are formally conserved and most are on farms where they are used for grazing of domestic livestock. The RSR appears to be sensitive to overgrazing and to grazing at a time of the year when it is sensitive to major change. This study examined the effects different grazing regimes had on the RSR vegetation on farms in Buffeljagsrivier, a small farming community in the Eastern Overberg. Different methods were used to compare vegetation structure and composition, of heavily-, medium- and under-grazed areas. Information on the biodiversity in RSR areas was found to be scarce, with almost nothing known of the invertebrates. In this study a comprehensive checklist of plants and vertebrates in the study area was compiled. An insect order/family list and separate species lists of Lepidoptera and Orthoptera were also compiled. The insects were recorded by using different collecting and observation methods. A study was also made of the major plant/animal interactions occurring in the area. For this study, the focus was mainly on interactions with two dominant woody plants, Acacia karroo and Searsia glauca. Other interactions were also noted. Different grazing regimes affected both structure and plant composition in the different grazing camps. Some plant species were found to be more dominant in heavily-grazed areas and some more in under-grazed areas. Heterogeneity in grazing pressure of the camps contributes to make the whole area more diverse and may have enabled the high biodiversity to persist in the area. More than 400 indigenous plant species were recorded in the study area of which more than 30 plant species were found to be of conservation concern. 37 % of the overall species are endemic to the Cape Floristic Region. The study area contained 127 geophyte species. This is 51 % of all the known geophyte species that occur in the Langeberg Centre. A new plant species, Haworthia groenewaldii, was discovered in the study area. Overall, 214 insect families in 23 insect orders were also found in the study area. A total of 103 Lepidoptera species was recorded. About five moth species are possibly new to science and still need to be scientifically described. Some plants and insects were recorded beyond their known geographical ranges. Twelve different frog, 22 reptile, 30 mammal and 122 bird species were found to occur in the study area. Nineteen insect species from 14 insect families in four orders associated with Acacia karroo trees were found in the study area. Thirty-four insect species from 25 families, in six orders, were found to be interacting with Searsia glauca trees. Sixty one bird species were associated with A. karroo and 42 with S. glauca. Other interactions that were observed included caterpillars feeding on host plants. For the Lepidoptera list, the possible plant species on which the juveniles feed was also investigated. This study unequivocally showed that this geographical area has a very high overall biodiversity that needs to be conserved. It also found that grazing can affect the composition distribution and combination of this biodiversity. Much research is still to be done on plant/invertebrate interactions in the RSR. This study provides a baseline for further research on future actions to conserve this unusual and special area in terms of invertebrate biodiversity especially for generations to come. / AFRIKAANSE OPSOMMING: Rûens Silkreet Renosterveld (RSR) is ʼn Kritiek Bedreigde veld soort,in die Overbergstreek van die Wes-Kaap Provinsie van Suid-Afrika. Omtrent 80% van RSR is uitgeroei deur landbouprakteike van die afgelopetwee eeue. RSR bevat baie unieke en skaars plant spesies en het dus ʼn baie hoë bewaringswaarde. Dit word aanbeveel dat alle gebiede wat die tipe plantegroei bevat, bewaar behoort te word. Baie min van die oorblywende RSR word formeel beskerm en die grootste gedeeltes wat nog oor is, kom voor op plase waar dit vir weiding ingespan word. Die veld soort is skynbaarbaie sensitief vir oorbeweiding, asook vir beweiding in die verkeerde seisoen. Hierdie studie het na die uitwerking van verskillende weidingsmetodes op natuurlike veld op aangrensende plase in Buffeljagsrivier, ʼn klein plaasgemeenskap in die Oostlike Overberg, gekyk. Verskillende metodes was gebruik om die plantegroei se samestelling en struktuur van ʼn lae, middelmatige en oorbeweide gebiede met mekaar te vergelyk. Inligting oor die biodiversiteit van RSR, veral oor invertebrate, was moeilik om in die hande te kry. Spesies lyste so volledig as moontlik was in die studie vir al die vertebrate en plante opgestel. Lyste is ook opgestel vir alle insek ordes en families, wat in die studiegebied versamel is. Daar is ook aparte lyste opgestel vir alle Lepidoptera en Orthoptera, in die studiegebied. Verskillende metodes was gebruik om insekte te versamel en te monitor. Die interaksies tussen plante en diere, wat voorkom in die studie gebied, is ook bestudeer Twee plantsoorte, Acacia karroo en Searsia glauca, is uitgesonder en so veel moontlik biologiese interaksies is opgeteken. Ander interaksies was ook aangeteken soos hulle in die veld aangetref is. Die studiegebied het meer as 400 plant spesiesbevat. Van die was meer as dertig van bewaringsbelang. Sewe-en-dertig persent van die plante wat aangeteken is, is endemies tot die Kaapse Plant Koningryk. Daar is altesaam 127 bolplant spesies gevind wat net meer as die helfte van alle bolplant species wat vir die Langeberg Kern aangeteken is. Haworthia groenewaldii is ʼn nuwe plant spesies wat in die studie gebied ontdek is. In die studie area is 214 insek families in 23 insek ordes opgeteken. Van die is 103 Lepidoptera species (waarvan vyf moontlike nuwe spesies is) aangeteken in die studiegebied. Negentien insek spesies van 14 insek families in vier ordes het interaksies met A. karroo getoon. Interaksies tussen vier-en-dertig insek spesies van 25 insek families in sesordes het met S. glauca getoon Een-en-sestig voël spesies was geassosieerd met A. karroo en 42 met S. glauca. Ander interaksies watgewaar is, sluit ruspes op voedselplante in. Twaalf verskillende paddas, 22 soorte reptiele, 30 soorte soögdiere en 122 soorte voëls was ook in die studie gebied aangeteken. Uit die huidige studie is dit duidelik dat die gebied ʼn baie hoë biodiversiteit besit wat beskerm moet word. Daar is ook bevind dat weiding die samestelling en struktuur van RSR kan beïnvloed. Verdere studies oor die plant/dier interaksies in RSR behoort gedoen te word en hopelik dien die huidige studie as ʼnbegin vir verdere navorsing oor hoe ons die unieke veld soort vir die nageslag kan bewaar.

Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / The mutual association between honeydew foraging ants and vine mealybugs in vineyards is detrimental to the biological control of the vine mealybug Planococcus ficus (Signoret). This study investigated the relationship between ants, vine mealybugs and their parasitoids to improve biological control of the vine mealybug. The investigation was carried out during two consecutive growing seasons (2005-2006 and 2006-2007) in two major wine grape growing areas of the Western Cape Province, Simondium (two farms) and Breede River Valley (one farm). A presence – absence cluster sampling system was used on a biweekly basis throughout both growing seasons from October to February on each of the farms. Additionally, yellow delta traps with vine mealybug pheromone, were used to catch parasitoids in vineyards. Prior to harvest, economic damage to grape bunches was assessed using a 0-3 damage rating index. Three ant species, Anoplolepis steingroeveri (Forel), Crematogaster peringueyi Emery and Linepithema humile (Mayr) foraged mainly on vine stems during both seasons, relative to other plant parts. Vine mealybugs of all stages were found on all sampling dates. Three species of primary parasitoids attacked the vine mealybug, including Anagyrus sp. near pseudococci (Girault), Coccidoxenoides perminutus (Timberlake) and Leptomastix dactylopii Howard. Bunch damage was significantly different between seasons in the Breede River Valley but not in Simondium. There was a negative linear relationship between ants and parasitoid activity in all vineyards. Spatial Analysis by Distance IndicEs (SADIE) was used to analyse spatial distribution of ants and parasitoids and ArcView, with its extension, Spatial Analyst, were used to map the gap, patch and local association indices where significant association and disassociation occurred. A significant association was found between C. peringueyi and parasitoids and L. humile and parasitoids. There was a significant disassociation between L. humile and C. peringueyi and between A. steingroeveri and C. peringueyi indicating interspecific hostility.