Chromolaena odorata (L.) King and Robinson (chromolaena, triffid weed) (Asteraceae: Eupatorieae) is one of the most problematic weeds in the subtropical northeastern parts of South Africa. Calycomyza eupatorivora Spencer (Diptera: Agromyzidae) was introduced as a biological control agent for the control of this weed. No study has yet been done to quantify field populations of C. eupatorivora since its establishment in 2003. The aim of this study was therefore to measure aspects of the field population and laboratory behaviour of C. eupatorivora on C. odorata. The first objective was to determine the percentage leaf area mined by larvae of C. eupatorivora on C. odorata plants exposed to three densities of mated flies, and also to determine the number of mines produced by these different densities, and their distribution on the plant. It also attempts to determine the relationship between chromolaena leaf quality and usage by C. eupatorivora. The maximum percentage of leaf area damaged was 37.5% for one of the trials involving five pairs of flies. Mean percentage leaf area damaged was slightly higher with five (28.5%) than ten pairs (22.0%) of adults and was lowest with one pair (6.5%), but these differences were not significant. In relation to the mean number of mines per plant, five and ten pairs of flies caused slightly more mines than one pair. The other significantly different parameter was number of leaves mined per plant, which was higher for five pairs. Within a plant, C. eupatorivora probably selects a subset of leaves with certain chemical and physical characteristics for oviposition since certain leaves were left unmined while others received multiple eggs. Percentage water content did not differ between mined and unmined leaves, but clear patterns were shown by acid detergent lignin which was higher in unmined leaves and nonstructural carbohydrates which were much higher in mined leaves. It is likely that leaf age plays a role in its suitability. The second objective was to quantify C. eupatorivora infestation levels, by counting and examining larval leaf mines, on C. odorata in the field at four times ('seasons' - September, December, March and July) over a 12-month period, and at three study sites that each included two habitats, viz. open and shady. At each of these six sampling sites, line transects were laid out and plants/branches sampled along them. Both plant/branch height and the number of leaves increased between September and March, and plants in the open habitats were taller and had more leaves than those in the shaded habitats. At the third site, the shady habitat supported taller plants with more leaves compared to the same habitat at the other sites. There was a steep increase in the number of C. eupatorivora mines from December to March. The mean number of mines, both total and in relation to leaves available, was highest in March, and was higher in the shaded habitats compared to the open habitats. The mean number of mines per damaged leaf was slightly higher in December compared to the other seasons, and was also higher in the open than the shaded habitats. Mean larval mortality was high (70%) in September but decreased to 32% in December, and increased again in late summer. The overall levels of mining by C. eupatorivora were low, with less than 5% of leaves sampled having mines. Taken together, the laboratory and field trials suggest that C. eupatorivora is restricted to a subset of the leaves of C. odorata for its development; that the field population is unable to make full use of the resource of young, palatable leaves that develop in early- to mid-summer because it only becomes large in late summer; and that the high mortality rate of young larvae negatively affects both the population of the fly and the level of damage to the plant. Given that these results were obtained in an area where the population of C. eupatorivora is relatively high, it is unlikely that the fly is having anything more than a negligible effect on C. odorata in South Africa at present. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Scrapter Lepeletier de Saint-Fargeau & Audinet-Serville, 1828 (Hymenoptera: Aculeatea: Anthophila: Colletidae) is a genus of solitary bees largely endemic to southern Africa. This dissertation investigated the phylogenetic systematics of the genus. Eleven new species of Scrapter are described, principally from the Succulent Karoo biome of South Africa, bringing the total number of species in the genus to 42. An updated dichotomous key to facilitate identification is provided. The previously unknown females of S. albifumus Eardley and S. amplispinatus Eardley are also described. The genus is recorded from outside southern Africa for the first time with the collection of S. nitidus (Friese) in Kenya. This constitutes a significant range extension of the genus. The taxonomic status of five species described by Cockerell in 1944, and subsequently overlooked, is addressed. They are all found to be synonyms of other Scrapter species, except one, which is found to be a Ctenoplectrina species (Apidae: Apinae: Ctenoplectrini). The new synonymies are: S. subincertus Cockerell = S. niger Lepeletier de Saint-Fargeau & Audinet-Serville; S. brunneipennis Cockerell = S. niger Lepeletier de Saint-Fargeau & Audinet-Serville; S. merescens Cockerell = S. leonis Cockerell; S. sinophilus Cockerell = S. algoensis (Friese). Scrapter ugandica Cockerell becomes Ctenoplectrina ugandica (Cockerell) as a new combination. Investigation of selected morphological features (e.g. postmentum, facial fovea, galea) revealed much diversity in Scrapter. The monophyly of Scrapter is not supported by unambiguous apomorphies, but is defensible by the congruence of various qualitative characters (e.g. premental fovea, T2 fovea, hindleg and sternal scopa in [females], two submarginal cells). A cladistic analysis using 25 morphological characters recovered numerous most parsimonious trees under both equal- and successive-weighting. To aid in resolution, several taxa known from only one sex or from very limited material, and with many unknown states, were deleted from the matrix. Analysis using this reduced matrix under equal- and successive-weighting resulted in better resolution, although with low consistency index values. Several subclades were common to both cladograms, and likely represent monophyla. The low consistency indices and general lack of unique synapomorphies upholding these subclades, however, dictated against making any classificatory re-arrangements. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Eldana saccharina Walker (Lepidoptera: Pyralidae) is an indigenous insect widely distributed throughout Sub-Saharan Africa that is a major pest of sugarcane in southern Africa. Studies have shown that populations from West Africa have distinct behavioural differences compared to populations from eastern and southern Africa. In addition, the parasitoid guilds attacking populations in these regions are markedly different. This marked behavioural and parasitoid guild variation evoked a hypothesis of genetic diversification. To evaluate this hypothesis a project on the phylogeography of E. saccharina was initiated. The project was planned to include sampling of as many regions as possible in its known range in Africa, to obtain specimens of E. saccharina for genetic analysis. When these surveys were initiated in Ethiopia, it was found that there was no published literature available on the occurrence of stem borers in Ethiopian sugarcane. It was thus clear that no stalk borer/parasitoid surveys had been completed in either sugarcane or any large grass and sedge indigenous hosts in Ethiopia. The study was thus expanded beyond the investigation of only the genetic diversity of E. saccharina, to include area-wide surveys to determine ecological aspects of the borer complex in suspected host plants, including sugarcane, in Ethiopia. In this way the host plant range and distribution of E. saccharina and other sugarcane borers in Ethiopia in particular could be determined, samples for a larger phylogeography project could be collected, and the insect's impact on sugarcane could be assessed. Quantified area-wide surveys of the sugarcane estates and small-scale farmer fields of Ethiopia were conducted between December 2003 and February 2004. The surveys verified the presence of four lepidopteran stem borer species on Ethiopian sugarcane. These were Chilo partellus Swinhoe (Lepidoptera: Crambidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae), Busseola fusca Fuller (Lepidoptera: Noctuidae) and Busseola phaia Bowden (Lepidoptera: Noctuidae). The surveys indicated that Busseola species are the major and most widely distributed sugarcane stem borers in sugarcane farms of Ethiopia. Over 70% of the peasant sugarcane fields visited were infested by these borers, with the highest levels of infestation (35% and 50%) being in the northern and western part of the country, respectively. Busseola was also the predominant stem borer of sugarcane in two of the three estates (Wonji and Finchawa). Chilo partellus and S.calamistis were recovered in very low numbers at all the commercial estates and from peasant farms in the western part of Ethiopia. However, C. partellus was the predominant sugarcane stem borer in lowland areas of northern, southern and eastern parts of the country. Eldana saccharina was recovered from large sedges in waterways of Metehara and Wonji sugar estates in the central part of the country, and sedges growing around lakes in northern and southern Ethiopia, but not from sugarcane anywhere in Ethiopia. The phylogeographic study conducted on E. saccharina populations from eleven countries of Africa clearly showed the population structure of the insect within the continent. Five hundred and two base pairs of the mitochondrial DNA (mtDNA), corresponding to the Cytochrome Oxidase subunit I (COl) region, were sequenced to clarify phylogenetic relationships between geographically distant populations from eastern, northern, southern and western Africa. Results revealed that E. saccharina is separated into four major populations corresponding to their geographical location, i.e. West African, Rift Valley and two southern African populations. Sequence divergence between the four populations ranged from 1% to 4.98%. The molecular data are congruent with an isolation by distance pattern except for some of the specimens from eastern and southern Africa where geographically close populations are genetically distant from each other. Geographical features such as the Rift Valley and large water bodies in the continent seem to have a considerable impact on the genetic diversity in E. saccharina. Identification of field-collected stem borer specimens was done using classical taxonomic techniques, except for Busseola spp. where DNA barcoding was used. As field-collected larval material of Busseola died before reaching the adult stage, identification of species using adult morphology was not possible. 'Sequence divergence in the COl gene was used as a tool to identify the species of Busseola attacking Ethiopian sugarcane. Partial COl sequences from Ethiopian specimens were compared with sequences of already identified noctuid species from the East African region. Results of the sequence analysis indicated that the Busseola species complex in Ethiopian sugarcane comprised B. fusca and B. phaia. Sequence divergences between Ethiopian Busseola species was as high as 5.0 %, whereas divergences within species were less than 1% in both species identified. Several larval parasitoids, bacterial and fungal diseases of stem boring caterpillars were also recorded in Ethiopian sugarcane. Amongst these was Cotesia flavipes Cameron (Hymenoptera: Braconidae). This exotic parasitoid has been introduced into several African countries for the control of C. partellus in maize and sorghum, but had never been released in Ethiopia. To investigate the origin of C. flavipes in Ethiopian sugarcane, molecular analyses were conducted on Ethiopian specimens from sugarcane and specimens of C. flavipes from different countries of Africa released from the Kenyan laboratory colony, again using COl sequences. Results of the analysis revealed that the C. flavipes population that had established in sugarcane fields of Ethiopia was similar to the south east Asian populations released against C. partellus in maize in other parts of Africa, and different from other populations of this species, providing evidence that the Ethiopian C. flavipes is likely to be a descendant of the original Pakistani population that was released in different parts of Africa. The study reveals the importance of lepidopteran stem borers in sugarcane production in Ethiopia and highlights the role of molecular methods in species identification and determining phylogenetic relationships. More importantly, this study establishes the continental phylogeographical pattern of the indigenous moth, E. saccharina. The impact of geological events, geographic barriers and cropping systems on the evolution, distribution and abundance of stem borers are discussed. Future areas of research for understanding more about the phylogeographic relationships of E. saccharina and management of stem borers are discussed. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Solanum mauritianum (bugweed, woolly nightshade) is a perennial tree native to South America that has invaded many countries including South Africa and New Zealand. In South Africa, after 143 years of naturalization, the plant is ranked as the country‟s sixth worst weed and has invaded 1.76 million ha. Invaded areas include agricultural lands, forest plantations, water courses and conservation areas, especially in the eastern higher rainfall regions. The success of the spread of this weed is due to its production of very high numbers of bird-dispersed seeds. Since conventional control methods are unsustainable in the long term, the weed has been targeted for classical biological control since 1984. Following exploration work in its native range, biological control experts recommended that agents that are able to limit the weed‟s reproductive potential would help to manage the spread and invasiveness of this weed. Anthonomous santacruzi, a flower-feeding weevil found throughout the native range of the weed, was imported and tested between 1998 and 2002. Following approval for its release in South Africa in 2007, a new colony was imported and propagated at the University of KwaZulu-Natal Pietermaritzburg. This study was initiated to investigate aspects that could influence the release and establishment of this agent. Three aspects were investigated namely: (1) reassessing the weevil's host range to confirm that the new colony is not different from the colony tested originally and to assess the risks associated with the release of the weevil in New Zealand; (2) surveying the arthropods associated with S. mauritianum in the field to identify groups of predators that could interfere with the establishment of the weevils as well as to investigate, through laboratory-based trials using spiders as surrogate, the impact of these predators on the survival and proliferation of the weevils; and (3) propagation and release of the weevil and monitoring of its establishment. Host-specificity tests revealed that the host range of new colony is not different from that of the originally tested culture. In no-choice trials, the weevils fed and reproduced on some non-target Solanaceae species but reverted back to S. mauritianum in the choice tests. Although the risks for releasing the weevils in New Zealand were calculated to be very low, additional evidence is needed to demonstrate this conclusively. Future research to provide this evidence includes open-field trials complemented with a chemical ecology study, to resolve the case of two species, a New Zealand native and South African native, which have shown higher risks in comparison to the other tested species. For arthropods associated with S. mauritianum in the field, Araneae (especially Thomisidae), Thysanoptera, Hemiptera (especially Miridae) and Hymenoptera (especially Formicidae) were identified as generalist predators that could interfere with the establishment of A. santacruzi. However, their numbers in the field appear to be too low to provide a major threat. Also, laboratory trials using spiders as a surrogate suggested that A. santacruzi populations can survive and reproduce in the presence of such predators. The weevils were released at four sites in KwaZulu-Natal and monitoring of three of these has confirmed establishment at the warmest site along the South Coast but not at the coldest site in the Midlands. Further releases in the province are intended to complement these promising results, while additional studies are intended to facilitate the weevil's release in New Zealand. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Larvae of Pareuchaetes insulata were released in South Africa for the biological control of the invasive weed Chromolaena odorata. Pareuchaetes insulata has proved to be a difficult agent to establish in the field in South Africa, for various possible reasons. Populations collected from Florida and Jamaica (their aboriginal home) were released separately at several sites each in South Africa, but only one population (Florida) was definitely established. It is possible that adults from this established population interbred with adults from the Jamaican population released at nearby sites. The aims of this study were to determine whether there were any differences in biology between the two populations and whether hybridization affected the fitness of either. Trials involved: (i) pure-breeding of both Florida (F) and Jamaica (J) populations; (ii) cross-breeding of the two populations and; (iii) back-crossing of the hybrids with the parent populations. The fitness of these populations was determined by measuring adult longevity and fecundity, egg viability, and larval development and survival rates. The F population was superior to the J population in most of parameters measured, including fecundity. Hybridization of these populations reduced the fitness of the F population. It is unknown whether these differences in fitness reflect differences in their native regions, laboratory cultures or response to South African C. odorata. It appears that different populations of P. insulata have different levels of fitness, and that hybridization negatively affects the fitness of stronger populations. The lower fitness of the J population may have reduced its likelihood of establishing successfully, and even reduced the fitness of the established F population where the populations came into contact. These results caution that the possible consequences of mixing different genotypes of a biocontrol agent species should be properly investigated prior to their release in the same country. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Alien trees, Pinus spp. and Eucalyptus spp., affect ants negatively in the Cape Floristic Region (CFR), a global biodiversity hotspot in South Africa. They reduce ant abundance and species richness, thus also changing ant assemblage structure. This is alarming, because almost 1300 species of plant species in the CFR are dispersed by certain indigenous ants, and thus there is concern for an indirect effect on indigenous plant assemblages. One of the most impacting ant species on seed dispersal is the invasive Argentine ant (Linepithema humile (Mayr)), which discards seeds outside its nest, where they do not germinate. Ten sites, on Vergelegen Wine Estate, were selected to explore these effects of alien plants. These varied from invaded to non-invaded sites. Each site consisted of six sampling points, which in turn consisted of four pitfall traps left out for seven days, during December 2005, February 2006, May 2006 and September 2006. Forty species of ant were sampled, and various analyses used to illustrate the comparative effects of plant invasion. All analytical methods showed that invasive alien plants had a significant impact on the abundance and richness of the ant species assemblage, by creating a dense canopy cover that changed the abiotic environment of the epigaeic ants’ habitat. Furthermore, increased alien tree invasion correlated significantly with Argentine ant abundances. The Argentine ant displaced Pheidole capensis and Camponotus spp., while it decreased the abundances of commonly-occurring indigenous ants, such as Lepisiota capensis and Plagiolepis spp. Displacement by the Argentine ant may be a result of indirect competition for food resources. The effects of invasive aliens are synergistic in that there is a cascade effects from initial plant invasions to subsequent animal invasion. / AFRIKAANSE OPSOMMING: Indringer bome, Pinus en Eucalyptus, affekteer miere op negatiewe wyse in die Kaap Florsitiese Streek (KFR), ‘n area in Suid Afrika van belang t.o.v. globale biodiversiteit. Hierdie uitheemse indringer bome verminder hulle hoeveelheid en spesies rykheid. Die bogenoemde is kommerwekkend omdat meer as 1300 plant spesies in the KFR versprei word deur miere. Die verandering in hoeveelheid en versameling van inheemse miere kan dus ernstige implikasies hê op die saad verspreiding van inheemse plant spesies. Een van die mees verwoestende effekte op saad verspreiding is veroorsaak deur die indringer Argentynse mier (Linepithema humile (Mayr)), wat sade neer werp buite hulle neste, waar hulle nie suksesvol kan ontkiem nie. Tien monsterings-tereine was geselekteer om die bogenoemde effekte te ondersoek op Vergelegen Landgoed. Hierdie het afgewissel van indringer tot skoon tereine. Elke terrein is op ses versamelings-plekke gemonster, met vier pitvalle, wat oopgelê het vir sewe dae gedurende Desember 2005, Februarie 2006, Mei 2006 en September 2006. 40 spesies van miere was gemonster. Indringer plante het ‚n betekenisvolle impak gehad het op die hoeveelheid en rykheid van die mier gemeenskappe, deur die skepping van ‚n dig baldakyn wat die abiotiese omgewing van die miere se habitat verander het. Die vermeerdering van indringer plante veroorsaak die vermeerdering van Argentyne miere. Kanonieke Mede-Respons Analise illustreer dat die Argentynse mier Pheidole capensis en Camponotus spp. verplaas het, terwyl dit ander inheemse mier getalle verminder het, soos Lepisiota capensis en Plagiolepis spp. Die verplasing deur die Argentynse mier mag die resultaat wees van indirekte wedywering vir hulpbronne. Die effekte van indringer species is dus sinergisties deur dat ‚n kaskade effek ontstaan vanaf plant tot dier indringer spesies.

Parthenium hysterophorus (Asteraceae), classified as an emerging weed in South Africa, has become abundant throughout large parts of southern and eastern Africa. In South Africa it has invaded areas in KwaZulu-Natal, Mpumalanga, the North West Province and Limpopo. A biological control programme against parthenium weed was launched in South Africa in 2003, based on the success achieved in Australia. Zygogramma bicolorata, a leaf-feeding beetle native to Mexico, was imported into South Africa via Central Queensland, Australia where it was released in the 1980s. This thesis examines aspects of the thermal physiology of Z. bicolorata which, in conjunction with its native and exotic geographical distribution, was used to predict the potential distribution of the agent in South Africa, in relation to climate. To determine Z. bicolorata’s physiological capability, several physiological parameters were examined for mechanistic modelling purposes. These parameters included the beetle’s lethal thermal limits, critical thermal limits, lethal humidities (Chapter 2) and developmental rate at constant temperatures (Chapter 3). In Chapter 4, these physiological parameters were entered into the dynamic modelling program CLIMEX (CLIMEX programme ver. 2, CSIRO Entomology ©) and a map of the areas that are acceptable for the establishment of Z. bicolorata was produced. The CLIMEX model predicted that most of South Africa is favourable for the establishment of the beetle, except in the west of the country and in the north of Lesotho, extending into South Africa. All areas in which parthenium currently occurs were predicted to be very favourable for Z. bicolorata establishment and proliferation. Optimal release sites aimed at initial establishment were earmarked at three areas in the northeastern part of South Africa (Jozini, Ndumu Game Reserve and along the road from Swaziland to Mozambique). It is concluded that Z. bicolorata is climatically suited to South Africa, increasing the likelihood that populations will establish and proliferate when released. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.