The growth of embedded generation and portable electrical installations has led to an increased demand for low cost, flexible and reliable generator systems for military and commercial applications. An interior permanent magnet (IPM) machine has high power density due to its reluctance torque and magnetic torque components so it can produce a large constant power-speed range. However, an IPM machine needs demagnetizing current at high-speed during the flux-weakening region and thus develops an inverter shutdown problem in an uncontrolled generator mode operation. In order to overcome the disadvantages of the IPM machine, the permanent magnet assisted synchronous reluctance generator (PMa-SynRG) can be a good solution for low cost, high efficiency reliable generator systems. A PMa-SynRG can produce a high efficiency drive by utilizing the proper amount of magnet and reluctance torque. This work proposes a PMa-SynRG with two flux barriers and permanent magnets embedded in the second layer of the rotor. A neodymium magnet (NdFeB) was used as permanent magnets in the rotor to prevent demagnetization. Finding the minimum amount of magnet is one of the goals of the optimization process. The objectives of this work are to build an optimal design for the 3kW generator and an advanced power electronics converter for the PMa-SynRG drive system. In order to find the optimized 3kW machine, a Lumped Parameter Model (LPM) was used to achieve fast computation, and Differential Evolution Strategy (DES) was used to embed the LPM in an efficient numerical optimization routine to identify optimum designs. Finite Element Analysis (FEA) was used for test performance of optimum designs. On the basis of differences between LPM and FEA, model predictions were used to fine tune the LPM model. For new optimum design converges, numerical optimizations and iterations were performed to produce LPM and FEA predictions. For the drive system, the thyristor based, current-fed drive is much simpler and has lower power losses compared to the pulse width modulation (PWM) drive. Eliminating the requirement for self-controlled switches is a distinct advantage for lower cost. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG.

When users are searching for documents, they must sift through a collection of potentially relevant documents assessing, categorizing and prioritizing them based on the current task at hand, a process we refer to as document triage. Since users' time is precious, as much information as possible should be presented to them to aid the process of document triage. This thesis presents a simple visualization and a set of features that can help users in identifying information of interest. As a part of this thesis, the System Layer of the Visual Knowledge Builder (VKB) was developed as a tab strip container. Each of the tabs presents a different type of information about Web Documents. The types of information currently included in VKB are: a summary of the Web Document, keywords based on users' interests provided by the Interest Profile Manager (IPM), popular keywords from a social bookmarking site, metadata about the Web Document, a list of outgoing links of the Web Document, and the history of the Web Document. We performed a heuristic evaluation to assess the usefulness of the new visualization and features. During the evaluation, participants were asked to rate the usefulness of each of the new web document features over a scale of 1 to 7, where a value of 1 indicated strong disagreement, and 7 indicated strong agreement. Our results indicate that the document summary, the keywords from IPM, popular tags, and the history of the Web Document are expected to be most useful during the process of document triage.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Despite the easiness of adaptation to the climate of Brazil, pests the culture of the sugarcane faces a series of fitossanitary problem, such as the incidence, that diminish the production and the productivity, causing economic damage for the producers. The spittlebug Mahanarva fimbriolata (Stål, 1854) (Hemiptera: Cercopidae) is one of the main pests of the sugarcane not only in Alagoas as also in other states of Brazil. Currently, in result of the indiscriminate use of insecticides, the use of the Biological Control becomes necessary, which is not pollutant, it does not unbalance the environment and he is not toxic. In this way some plants of the State of Alagoas are using fungous entomopathogenic Metarhizium anisopliae (Metsch.) Sorokin, to reach the control of the spittlebug. This work had as objective to evaluate the efficiency of the Evidence® insecticide and two dosages of biological insecticide M. anisopliae in the control of the spittlebug. Two experiments had been conducted, in the cane-plantation region of the Plant Waterfall located in Maceió-AL, the period understood between July and September of 2006. Initially a population evaluation of nymphs and adults was carried through and the others to the 15, 30 and 45 days after the treatments. The application of the insecticides occurred in 19 of July and a reapplication of the biological insecticide in 22 of August. In experiment 1 the nymphs had been observed populations varying of 49 the 67 and the presence of adults of M. fimbriolata were not evidenced. The treatments had not differed between itself to the 5% for the test distribution free of Kruskal-Wallis, but the test of percentage of efficiency of Henderson and Tilton indicated for decreasing order of efficiency percentage the dosages, of 1,5L/ha of Evidence®, 20kg/ha of fungous and 10kg/ha of fungous with 72,48%, 62.35% and 24.76% respectively for nymphs; and 42.25%, 34.54% and 15.51% respectively for adults. In each area the test distribution free of Kruskal-Wallis was observed in accordance with that the numbers of nymphs had differed between the periods in all the treatments and that in the area dealt with Evidence® difference in the number of adults did not only occur 5% of significance. It had a high positive correlation between rainfall and amount of nymphs in the areas dealt with 20kg/ha to fungous and 1,5L/ha of Evidence®. In the area dealt with 10kg/ha to fungous and in the Control, an average correlation was observed. Also it was observed an average negative correlation between rainfall and amount of adults in the treated areas and Control. In experiment 2 the nymphs had been initially observed populations varying of 51 the 101. The presence of adults varying of 1 the 2 was evidenced, the treatments had not differed between itself to the level of 5% of significance for the test of Kruskal-Wallis, but the method of Henderson and Tilton indicated for decreasing order of efficiency percentage the dosages, of 1,5L/ha of Evidence®, 20kg/ha of fungous and 10kg/ha of fungous with 94,33%, 65.08% and 51.37% respectively for nymphs; e 93.33%, 70% and 50% respectively for adults. In each area it was observed for the test of Kruskal-Wallis that the number of nymphs between the periods did not only differ in the Control and that difference in the number of adults in treatment of 10 kg/ha of fungous the 5% of significance only occurred. In all the analyses were applied the Polynomial Regression so that if it could follow the development of the pest. To if analyzing the data they had been evidenced that it occurred a high positive correlation between rainfall and amount of nymphs in the areas dealt with 10 and 20 kg/ha to fungous and with 1,5L/ha of Evidence®, in the Control observed an average correlation. Also an average negative correlation between rainfall was observed and amount of adults of the areas dealt with 10 and 20kg/ha to fungous and Control, however, in the area dealt with 1,5L/ha of Evidence® got a negative correlation decrease. The total cost of the application of the Evidence® had been minor who of the other treatments, but is important to take in consideration the happened risks of the use of the pesticides. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Apesar da facilidade de adaptação ao clima do Brasil, a cultura da cana-de-açúcar, Saccharum officinarum L. (Poaceae), enfrenta uma série de problemas fitossanitários, que geram prejuízos para os produtores, destacando-se a cigarrinha-da-raiz, Mahanarva fimbriolata (Stål, 1854) (Hemiptera: Cercopidae), como uma das principais pragas não só em Alagoas como também em outros Estados do Brasil. Atualmente, em decorrência do uso indiscriminado de inseticidas, fazse necessário o uso do Controle Biológico, estratégia não-poluente, não-tóxica e que não desequilibra o meio ambiente. Considerando que, para controlar essa praga, algumas usinas de Alagoas vêm utilizando o fungo entomopatógeno Metarhizium anisopliae (Metsch.) Sorokin, através desse trabalho pretende-se avaliar a eficiência do inseticida químico Evidence® e do inseticida biológico M. anisopliae no controle da cigarrinha-da-raiz. Para tanto, conduziram-se dois experimentos, na região canavieira da Usina Cachoeira localizada no município de Maceió, Alagoas, entre julho e setembro de 2006. Antes da aplicação dos tratamentos foi realizada uma avaliação populacional de ninfas e de adultos. Depois foram feitas mais três, 15, 30 e 45 dias após os tratamentos (pulverização aérea em 19 de julho e em 22 de agosto). Foram utilizadas duas cultivares (SP813250, no experimento 1, e RB855035, no experimento 2). No experimento 1, foram observadas populações variando de 49 a 67 ninfas e não foi constatada a presença de adultos de M. fimbriolata. Os tratamentos não diferiram entre si a 5% pelo teste não paramétrico de Kruskal-Wallis, mas o teste de porcentagem de eficiência de Henderson e Tilton indicou por ordem decrescente de porcentagem de eficiência, as dosagens, de 1,5L/ha de Evidence®, 20kg/ha de fungo e 10kg/ha de fungo com 72,48%, 62,35% e 24,76% respectivamente para ninfas; e 42,25%, 34,54% e 15,51% respectivamente para adultos. Em cada área observou-se de acordo com o teste não paramétrico de Kruskal-Wallis que os números de ninfas diferiram entre os períodos em todos os tratamentos e que, somente na área tratada com Evidence® não ocorreu diferença no número de adultos a 5% de significância. Houve uma correlação positiva alta entre precipitação pluviométrica e quantidade de ninfas nas áreas tratadas com 20kg/ha de fungo e com 1,5L/ha de Evidence®. Na área tratada com 10kg/ha de fungo e na Testemunha, observouse uma correlação média. Também foi constatada uma correlação negativa média entre precipitação pluviométrica e quantidade de adultos nas áreas tratadas e Testemunha. No experimento 2 inicialmente foram observadas populações variando de 51 a 101 ninfas. Foi verificada a presença de adultos variando de 1 a 2. Os tratamentos não diferiram entre si ao nível de 5% de significância pelo teste de Kruskal-Wallis, mas o método de Henderson e Tilton indicou por ordem decrescente de porcentagem de eficiência as dosagens de 1,5L/ha de Evidence®, 20kg/ha de fungo e 10kg/ha de fungo com 94,33%, 65,08% e 51,37%, respectivamente para ninfas; e 93,33%, 70% e 50%, respectivamente para adultos. Em cada área observou-se pelo teste de Kruskal-Wallis que o número de ninfas entre os períodos só não diferiu na Testemunha e que somente ocorreu diferença no número de adultos no tratamento 10 kg de fungo/ha a 5% de significância. Em todas as análises foi aplicada a Regressão Polinomial para que se pudesse acompanhar o desenvolvimento da praga. Ao se analisar os dados constatou-se que ocorreu uma correlação positiva alta entre Precipitação Pluviométrica e quantidade de ninfas nas áreas tratadas com 10 e 20 kg/ha de fungo e com 1,5L/ha de Evidence® e na Testemunha observou-se uma correlação média. Foi também observada uma correlação negativa média entre precipitação pluviométrica e quantidade de adultos nas áreas tratadas com 10 e 20kg/ha de fungo e Testemunha; porém, na área tratada com 1,5L/ha de Evidence® obteve-se uma correlação negativa baixa. Os custos totais da aplicação do Evidence® foram menores que o dos outros tratamentos, mas é importante levar-se em consideração os riscos advindos da utilização do agrotóxico.

Doctor of Philosophy / Department of Entomology / Brian P. McCornack / Timely enactment of insect pest management and incursion mitigation protocols requires development of time-sensitive monitoring approaches. Numerous passive monitoring methods exist (e.g., insect traps), which offer an efficient solution to monitoring for pests across large geographic regions. However, given the number of different monitoring tools, from specific (e.g., pheromone lures) to general (e.g., sticky cards), there is a need to develop protocols for deploying methods to effectively and efficiently monitor for a multitude of potential pests. The non-random movement of the Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), toward several visual, chemical, and tactile cues, makes it a suitable study organism to examine new sensor technologies and deployment strategies that can be tailored for monitoring specific pests. Therefore, the objective was to understand Hessian fly behavior toward new sensor technologies (i.e., light emitting diodes (LEDs) and laser displays) to develop monitoring and deployment strategies. A series of laboratory experiments and trials were conducted to understand how the Hessian fly reacts to the technologies and how environmental factors may affect the insect’s response. Hessian fly pupae distribution within commercial wheat fields was also analyzed to determine deployment of monitoring strategies. Laboratory experiments demonstrated Hessian fly attraction to green spectrum (502 and 525 nm) light (LEDs), that response increased with light intensity (16 W/m2), and that they responded in the presence of wheat odor and the Hessian fly female sex-pheromone, but, response was reduced under ambient light. These laboratory experiments can be used to build a more targeted approach for Hessian fly monitoring by utilizing the appropriate light wavelength and intensity with pheromone and wheat odor to attract both sexes, and mitigating exposure to ambient light. Together this information suggested that light could be used with natural cues to increase attraction. Therefore, a light source (green laser display) was applied to a wheat microcosm, which resulted in greater oviposition in wheat covered by the laser display. Examination of Hessian fly pupal distribution within commercial wheat fields showed that proportion of wheat within a 1 km buffer of the field affected distribution between fields. This helps to inform deployment of monitoring strategies as it identified fields with a lower proportion of wheat within a 1 km buffer to be at higher risk Hessian fly infestation, and therefore monitoring efforts should be focused on those fields. Together this work demonstrates Hessian fly behavior toward new sensor technologies, how those technologies interact with environmental cues, and how environmental composition affects pupal distribution. Collectively this information will enable cheaper, more accurate and more efficient monitoring of this destructive pest.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-09-28T20:40:41Z No. of bitstreams: 2 Dissertação - Fernando Augusto dos Santos - 2016.pdf: 3948267 bytes, checksum: 689aba9aeb9345dc8d0c4cd99daa4626 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-30T12:16:13Z (GMT) No. of bitstreams: 2 Dissertação - Fernando Augusto dos Santos - 2016.pdf: 3948267 bytes, checksum: 689aba9aeb9345dc8d0c4cd99daa4626 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-09-30T12:16:13Z (GMT). No. of bitstreams: 2 Dissertação - Fernando Augusto dos Santos - 2016.pdf: 3948267 bytes, checksum: 689aba9aeb9345dc8d0c4cd99daa4626 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-02-27 / Outro / This study analyzes the importance production costs knowledge for decision-making in adopting the technology of integrated pest management - IPM for sustainable and rational agricultural production. In order to identify key characteristics of farmers, this study applies a survey to a sample of irrigation farmers in the Cristalina-GO region (N = 60), in such a way that qualitative data are explored for the case of analytical categories. The analysis revealed that the farmers of the Cristalina-GO region aware of the importance of knowing the structure are agricultural production costs, the IPM is a useful technology, but of doubtful viability. There are strong reports that the producer needs more training, guidance and dissemination of more sustainable practices. Despite the provision in the IPM adoption, the attitude towards the risk of economic damage to crops has been mostly prioritized the agrochemical preventive control and somehow caused changes in the agro-ecosystem (myriad effects). The results suggest to consider rationality as the basis for decision making, and use IPM and other sustainable technologies to maximize profit by adding value to production; the spread of the IPM should be expanded. This study presents results for the direct questioning of farmers about their environmental awareness with background on its economic health. Open the question of the ac - tual non-use of IPM in everyday reasons. It shows that the irrigation farmers at Cristalina-GO dominate the preventive use of agrochemicals. / Este estudo traz a baila a importância do conhecimento dos custos de produção agrícola, para a tomada de decisão ao adotar a tecnologia do manejo integrado de pragas – MIP, por uma produção agrícola mais racional e sustentável. A fim de identificar importantes características dos produtores rurais, este estudo aplica um survey para uma amostra dos agricultores irrigantes da região de Cristalina-GO (N=60), de tal sorte que dados qualitativos são explorados para o atendimento de categorias analíticas. A análise revelou que o produtor rural da região de Cristalina-GO tem consciência da importância de conhecer sua estrutura de custos de produção agrícola, considera que o MIP é uma tecnologia útil, contudo de viabilidade duvidosa. Há sólidos registros de que o produtor necessita de mais treinamento, orientação e disseminação sobre práticas mais sustentáveis para a agricultura. Em que pese a disposição na ado - ção do MIP, a atitude diante do risco de dano econômico à lavoura tem sido, em sua maioria, priorizada através do controle preventivo agroquímico, que de certa forma tem provocado alteração no agroecossistema (myriad effects). Os resultados sugerem considerar a racionalidade como base para a tomada de decisão; utilizar o MIP e outras tecnologias sustentáveis de modo a maximizar o lucro com a redução dos custos de produção; ampliar a disseminação da tecnologia MIP. Este estudo apresenta resultados referentes ao questionamento direto do produtor rural sobre sua consciência ambiental com pano de fundo sobre seu desenvolvimento econômico. Abre-se a a discussão sobre os reais motivos do não-uso do MIP cotidianamente. Apresenta que para os produtores rurais irrigantes de Cristalina-GO adotam predominantemente o uso preventivo de agroquímicos na lavoura.

O parasitoide Ageniaspis citricola Logvinovskaya é o principal agente de controle biológico do minador-dos-citros Phyllocnistis citrella Stainton. No entanto, com a detecção do huanglongbing houve um aumento no uso de inseticidas nos pomares cítricos e não se conhece seus efeitos à A. citricola. Desta maneira, estudou-se o efeito letal de cinco inseticidas e a persistência aos 3, 7, 10, 17 e 24 dias após a pulverização em mudas de citros mantidas em casa de vegetação ao parasitoide A. citricola, nas dosagens especificadas (g i.a. L-1): imidacloprido 0,04 (Provado&reg; 200 SC), clorpirifós 0,72 (Lorsban&reg; 480 BR), bifentrina 0,02 (Talstar&reg; 100 EC), beta-ciflutrina 0,0125 (Turbo&reg; 50 EC), abamectina 0,0054 (Vertimec&reg;), bem como o efeito subletal no parasitismo em fêmeas expostas por 24 horas aos resíduos de abamectina. Imidacloprido, clorpirifós, bifentrina e beta-ciflutina foram considerados nocivos para adultos de A. citricola (M > 75%), enquanto que, abamectina foi considerado inócuo (M < 25%). Com base na duração do efeito nocivo, clorpirifós e beta-ciflutrina foram considerados de vida curta (< 5 dias), enquanto que, imidacloprido foi levemente persistente (5-15 dias) e bifentrina moderadamente persistente (16-30 dias). Abamectina não alterou a taxa de parasitismo de A. citricola, mas alterou substancialmente a razão sexual (0,11) quando comparado ao tratamento controle (0,5). Os resultados indicam que deve-se ter cautela em recomendar os produtos avaliados, observando-se o efeito residual daqueles produtos considerados nocivos à A. citricola, de forma a explorar a seletividade ecológica. Abamectina, embora inócua a adultos do parasitoide, pode levar a uma redução populacional de A. citricola, devendo-se realizar estudos de campo para elucidar essa questão. / Ageniaspis citricola Logvinovskaya is the main biological control agent of Phyllocnistis citrella Stainton. However, with the huanglongbing report, there was an increase in the use of insecticides in citrus orchards and the effects on A. citricola are not known. Thus, we studied the lethal effects of five insecticides and the persistence on 1, 3, 7, 10, 17 and 24 days post application in seedlings of citrus kept in greenhouse, using the specified dosages (g a.i. L-1): imidacloprid 0.04 (Provado&reg; 200 SC), chlorpyriphos 0.72 (Lorsban&reg; 48 BR), bifenthrin 0.02 (Talstar&reg; 10 EC), beta-cyfluthrin 0.0125 (Turbo&reg; 5 EC), abamectin 0.0054 (Vertimec&reg; 18 EC), as well as the sublethal effect on the parasitism by females exposed to residues of 24 hours of abamectin. Imidacloprid, chlorpyriphos, bifenthrin and beta-cyfluthrin were considered harmful to A. citricola (M > 75%) and abamectin were considered harmless (M < 25%). Chlorpyriphos and beta-cyfluthrin were considered of short life (< 5 days), imidacloprid slightly persistent (5-15 days) and bifenthrin moderately persistent (16-30 days). Abamectin did not affect the parasitism by A. citricola, but the sex ratio, with a sex ratio of 0.11 against 0.5 of the control. The results indicate that we must be careful to recommend the evaluated insecticides, observing the persistence of those classified as harmful to A. citricola, as a manner to explore the ecological selectivity. Even though considered harmless to adult parasitoids, abamectin can lead to population reduction of A. citricola, being necessary field studies to confirm that situation.

Orientador: Edson Luiz Baldin / Resumo: Embora o Brasil seja o segundo maior produtor de soja [Glycine max (L.) Merrill] do mundo, a produtividade desse grão é afetada diretamente pela incidência de insetos-praga. Dentre as pragas, os lepidópteros Chrysodeixis includens (Walker) e Spodoptera eridania (Stoll) (Noctuidae) têm causado danos expressivos nos últimos anos. As práticas de controle mais empregadas no manejo dessas pragas envolvem a aplicação de inseticidas sintéticos e o uso da tecnologia Bt. No entanto, a movimentação larval dessas espécies pode comprometer essas estratégias, com impactos relevantes sobre o Manejo Integrado de Pragas (MIP) e o Manejo de Resistência de Insetos (MRI). Para a espécie S. eridania, existe um agravante, visto que a mesma apresenta baixa suscetibilidade à toxina Cry1Ac. Nesse sentido, esse estudo teve como objetivo caracterizar a movimentação de diferentes ínstares larvais dessas duas espécies e o possível impacto que esse comportamento tem sobre o MIP e MRI. Assim, foram realizados estudos de movimentação larval na planta e entre plantas em cultivares de soja Bt (TMG 7062 IPRO) e não Bt (TMG 7262 e 92Y83 “Pioneer”) em período reprodutivo sob condições de laboratório, casa de vegetação e campo. Nos estudos de movimentação na planta. Foram avaliadas a distribuição larval em três posições (superior, mediano e basal) das plantas e em diferentes períodos, além da permanência dos insetos sobre as plantas. Os estudos de movimentação larval entre plantas tiveram como objetivo caracteri... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Blackflies (Diptera: Simuliidae) are major pests in the livestock and labour-intensive farming systems along the major rivers in South Africa. At present, blackflies are controlled with the larvicide Bacillus thuringienses var. israelensis (B.t.i.). As part of establishing an environmentally friendly and cost-effective Integrated Pest Management (IPM) program against blackflies, investigations were initiated to support the present blackfly-control strategy in South Africa. Emphasis was placed on potential predators and parasites of the blackflies’ aquatic stages. Questionnaires were presented to livestock farmers along the Vaal and Orange Rivers to determine public views concerning blackfly annoyance. Furthermore, blackfly populations at thirteen sites along the Orange River, twelve along the Vaal River and one site along each of two tributaries to the Vaal River, namely the Riet and Harts Rivers, were monitored seasonally for one year. The abundance of the aquatic stages of blackflies and potential predators on stones and vegetation in the river was determined using the 10-point visual ranking system of Palmer (1994) and the South African Scoring system (SASS 5), respectively. The abundance of algae as well as other environmental factors, namely water flow, water temperature and turbidity, were also monitored. Farmers who were contacted along both the Vaal and Orange rivers indicated that they experience severe blackfly problems during the summer months and that the majority of farmers were not aware of any products available that could protect their animals against blackfly attacks. The farmers also indicated that they were willing to be involved in blackfly research to improve this situation. Blackfly larvae and pupae were found in high abundance in both the Vaal and Orange Rivers. Simulium chutteri was the most abundant species in the Orange River and S. adersi in the Vaal River. In both the Vaal and Orange Rivers there was no significant correlation between immature blackfly abundance and water flow and turbidity. Water temperature also played a role in the seasonal build-up of blackflies in the winter months. The three most abundant algae classes were Bacillariophyceae, Chlorophyceae and Cyanophyceae. Cyanophyceae was the only algae group that had a negative correlation with blackfly immature abundance in the Orange River; this was not statistically significant. There were no negative correlations in the Vaal River. In both the Vaal and Orange rivers, blackflies were infected with Mermithidae nematodes and Microspora protozoans. In the Vaal River, the infection prevalence in natural conditions was the highest for Microspora and in the Orange River the highest for Mermithidae. The most important families of blackfly predators identified were Hydropsychidae and Gyrinidae. Hydropsychidae was the only family recorded in high abundance but this predator had no effect on abundance of immature blackfly. Gyrinidae gave a negative correlation with immature blackfly abundance; however, this was not significant. The biological control agents identified in this research need to be evaluated further for use in an IPM approach with the current control system, B.t.i. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Veterinary Tropical Diseases / unrestricted