Dissertations / Theses on the topic 'Weed identification'

Adoption of a Site-Specific Weed Management System (SSWMS) can contribute to sustainable agriculture. Weed mapping is a crucial step in SSWMS, leads to saving herbicides and protecting environment by preventing repeated chemical applications. In this study, the feasibility of visible and near infrared spectroscopy to classify three problematic weed species and to identify glyphosate-resistant weeds was evaluated. The canopy temperature was also employed to identify the glyphosate-resistant weeds. Furthermore, the ability of UAS imagery to develop accurate weed map in early growing season was evaluated. A greenhouse experiment was conducted to classify waterhemp (Amaranthus rudis), kochia (Kochia scoparia), and lambsquartes (Chenopodium album) based on spectral signature. The Soft Independent Modeling of Class Analogy (SIMCA) method on NIR (920-2500 nm) and Vis/NIR (400-2500 nm) regions classified three different weed species with accuracy greater than 90 %. The discrimination power of different wavelengths indicated that 640, 676, and 730 nm from red and red-edge region, and 1078, 1435, 1490, and 1615 nm from the NIR region was the best wavelengths for weed species discrimination. While, wave 460, 490, 520 and 670 nm from Vis range, and 760, 790 nm from NIR region were the significant discriminative features for identifying glyphosate-resistant weeds. Random Forest was able to detect glyphosate-resistant weeds based on spectral weed indices with more than 95% accuracy. Analysis of thermal images indicated that the canopy temperature of glyphosate-resistant weeds was less than susceptible ones early after herbicide application. The test set validation results showed the support vector machine method could classify resistant weed species with accuracy greater than 95 %. Based on the stepwise method the best times for discrimination of kochia, and waterhemp resistant were 46 and 95 hours after glyphosate application, respectively. In addition, a field study was proposed on soybean field to identify weed species and glyphosate-resistant weeds using multispectral and thermal imagery. Results revealed that the object-based supervised classification method could classify weed species with greater than 90% accuracy in early growing season. Furthermore, the glyphosate-resistant kochia, waterhemp and ragweed were identified based on canopy temperature with 88%, 93% and 92% accuracy, respectively.

Bibliography: leaves 124-136. This thesis gives an overview of factors used in weed risk assessments and explores the disparity between the measured high accuracy rate of the weed risk assessment system (WRA) as implemented in Australia and the pessimistic assessments of some workers about the possibility of predicting the weed potential of plant species imported in the future. The accuracy of the WRA may not be as high as previously thought, and it varies with weed definition and taxonomic groups. Cluster analysis and comparative analysis by independent contrasts were employed to determine the value of individual biological and ecological questions on the WRA questionnaire. Results showed that some WRA questions could be deleted from the questionnaire and the scores for others weighted differently. The WRA is not a reliable predictor of weeds when it is considered in the context of the base-rate probability of an introduced plant becoming weedy in Australia. As a result a far greater number on non-weeds will be placed on the prohibited imported list than was initially expected.

Modern agriculture encounters several challenges these days. There is a vital need for spatial data about plant and weed distributions. Obtaining accurate knowledge of the plants and weeds distribution in the field with manual methods are time-consuming. In this research, image processing programs were developed from the unmanned aerial vehicle (UAV) digital images to obtain the plant-stand count and weed identification and mapping in the field. Algorithms using pixel-march with search-hands criterion for the plant-stand count and shape-based features for weed identification were developed. Results were found to be accurate in the cropped UAV stitched images (>99 %) in manual image-based validation. User-friendly message windows, labeled images, textual results, and distribution maps were produced as outputs. The outcomes of this study will enable farmers to determine the plant and weed distributions in the field and will be helpful in deploying precision agriculture measures.
Cannayen, Igathinathane
Flores, Joao Paulo

The management of weeds in agriculture is a time consuming and expensive activity, including in Australia where the predominant strategy is blanket spraying of herbicides. This approach wastes herbicide by applying it in areas where there are no weeds. Discrimination of different plant species can be performed based on the spectral reflectance of the leaves. This thesis describes the development of a sensor for automatic spot spraying of weeds within crop rows. The sensor records the relative intensity of reflected light in three narrow wavebands using lasers as an illumination source. A prototype weed sensor which had been previously developed was evaluated and redesigned to improve its plant discrimination performance. A line scan image sensor replacement was chosen which reduced the noise in the recorded spectral reflectance properties. The switching speed of the laser sources was increased by replacing the laser drivers. The optical properties of the light source were improved to provide a more uniform illumination across the viewing area of the sensor. A new opto-mechanical system was designed and constructed with the required robustness to operate the weed sensor in outdoor conditions. Independent operation of the sensor was made possible by the development of hardware and software for an embedded controller which operated the opto-electronic components and performed plant discrimination. The first revised prototype was capable of detecting plants at a speed of 10 km/h in outdoor conditions with the sensor attached to a quad bike. However, it was not capable of discriminating different plants. The final prototype included a line scan sensor with increased dynamic range and pixel resolution as well as improved stability of the output laser power. These changes improved the measurement of spectral reflectance properties of plants and provided reliable discrimination of three different broadleaved plants using only three narrow wavelength bands. A field trial with the final prototype demonstrated successful discrimination of these three different plants at 5 km/h when a shroud was used to block ambient light. A survey of spectral reflectance of four crops (sugarcane, cotton, wheat and sorghum) and the weeds growing amongst these crops was conducted to determine the potential for use of the prototype weed sensor to control spot-spraying of herbicides. Visible reflectance spectra were recorded from individual leaves using a fibre spectrometer throughout the growing season for each crop. A discriminant analysis was conducted based on six narrow wavebands extracted from leaf level spectral reflectance measured with a spectrometer. The analysis showed the potential to discriminate cotton and sugarcane from

This thesis reports the design and control of the ??GreenWeeder??, a non-herbicidal autonomous weeding robot, in order to autonomously track crop rows for weeding through electrocution in the inter-row space. The four wheel mobile robot platform was designed and built with a motorised Ackerman steering system allowing the robot to steer up to 30 degree left and right. It was also equipped with an electronically geared rear wheel drive, a pair of stereo cameras, a SICK LMS-291 laser range finder to localize itself with respect to the crop rows, a GPS system for obtaining the robot position in the field and a long-range communication system for tele-supervision by operators. The first prototype of the robot electrocution system was also designed and constructed to ignite 22kV electrical arcs to destroy weeds. Its operation was tested in the research field of the University of Sydney and the results of this experiment were analysed to improve the efficiency of this first prototype. An improved prototype of the electrocution system was then constructed and attached to a cradle extending out at the back of the mobile robot platform. The testing of this improved prototype was conducted at Lansdowne farm, a research field of the University of Sydney. After the construction of the robot platform, the robot control was considered with the demands for robot localization with respect to crop rows, an autonomously tracking control system and a manual control mode in order to take the robot to transportation vehicles. Firstly, the robot localization was accomplished by utilizing SICK LMS-291 laser range finder sensor for the sensing and perception of the robot. Secondly, the robot control system was developed with a PID controller, a second order model of the robot system and a first order filter. The PID controller is in the standard form with the filtered derivative and the PI part being in automatic reset configuration. The second order model was identified using Matlab System Identification toolbox based on the robot kinematic analysis. The first order filter is utilized for filtering out the lateral deviations of the robot with respect to the crop rows received from the SICK laser sensor. A Simulink simulation model of the robot control system was also built in order to fine-tune PID and filter parameters. Thirdly, the manual control mode of the robot was produced. In this mode, a joystick can be attached to a notebook to wirelessly drive the robot around or it can be plugged into a USB port at the back of the robot to drive it without the notebook. After the robot control was implemented and simulated, some experiments were conducted with the robot autonomously tracking a strip of reflective tape mimicking a crop row stuck into the ground of a laboratory. Depending on distances from the row assigned to the controller, the robot tried to keep those distances away from the row. The results showed the lateral errors of the robot with respect to the row were approximately 4.5 cm which were sufficient for our current agricultural application.

Un projet visant à identifier des mycoherbicides pour lutter contre les adventices a été initié entre l’UMR Agroécologie de Dijon et la société DE SANGOSSE® (Agen). Trois volets ont structuré ce projet à l’issue d’une collecte de prélèvement de 475 plantes représentatives de 23 espèces d’adventices symptomatiques et asymptomatiques en Bourgogne et en Beauce. Le 1er volet reposait sur une approche de type metabarcoding (technologie Illumina), pour évaluer et comparer la diversité des communautés fongiques endophytes des plantes symptomatiques et asymptomatiques. 542 genres fongiques ont ainsi été identifiés. Des taxons associés aux plantes symptomatiques ont été identifiés. Parmi ceux-ci, certains sont des pathogènes connus, d’autres non et ils constituent des pistes à exploiter pour la recherche de candidats mycoherbicides. Le deuxième volet repose sur une approche conventionnelle de microbiologie et pathologie. Une collection de 194 champignons associés aux symptômes des adventices a été constituée. La pathogénicité de ces isolats a été testée grâce à une série de screenings de plus en plus sélectifs qui ont abouti à la sélection de cinq souches, identifiées par séquençage de l’ITS ou d’autres marqueurs taxonomiques. Une souche appartient à l’espèce Boeremia exigua var exigua, une autre à l’espèce Alternaria alternata, deux appartiennent à l’espèce A. penicillata et la dernière au genre Alternaria. Le troisième volet visait à identifier le mode d’action d’une souche par une double approche, métabolomique et microscopique. La souche de B. exigua var exigua secrète des métabolites phytotoxiques mais également infeste et semble détruire les tissus végétaux sous-épidermique de la plante hôte.Ce projet exploratoire a fourni des pistes de taxons fongiques associés à des symptômes observés sur adventices en analysant la diversité par une approche moléculaire et a fourni des souches fongiques, mycoherbicides potentiels, par une approche microbiologique dont on voit bien qu’elle reste une méthode incontournable, malgré ses limites, pour obtenir des candidats fongiques à action herbicide
A project aiming at identifying mycoherbicides to control weeds has been initiated between the UMR Agroécologie (Dijon) and the company DE SANGOSSE® (Agen, France). Three axes structured this project after a sampling collection of 475 plants representative of 23 species of symptomatic and asymptomatic weeds was carried out in Burgundy and Beauce. The first part was based on a metabarcoding approach (Illumina technology), to evaluate end compare the diversity of endophytic fungi communities of symptomatic and asymptomatic weeds. 542 fungal genera have been identified. Taxa associated with symptomatic plants have been identified. Of these, some are known pathogens, others are not, and both constitute avenues to exploit for the research of mycoherbicide candidates. The second axe is based on a conventional approach to microbiology and pathology. A collection of 194 fungi associated with weed symptoms was established. The pathogenicity of these isolates was tested through a series of increasingly selective screenings that resulted in the selection of five strains that were identified by sequencing of ITS or other taxonomic markers. One strain belongs to the species Boeremia exigua var exigua, another species Alternaria alternata, two belong to the species A. penicillata and the last to the genus Alternaria. The third axe aimed at identifying the mode of action of a strain by a dual metabolomics and microscopic approach. The strain of B. exigua var exigua produced phytotoxic secondary metabolites but also infested and apparently destroyed the sub-epidermal plant tissues of the host plant.This exploratory project provided tracks to exploit fungal taxa associated with observed weeds symptoms, by analyzing the diversity, by a molecular approach and provided fungal strains, potential mycoherbicides by a conventional microbiological approach that we can see it remains an unavoidable method, despite its limitations, to obtain fungal candidates with herbicidal action

A identificação de plantas invasoras é de extrema importância em diversos procedimentos utilizados na agricultura. Apesar de ser uma tarefa computacionalmente difícil, esta identificação tem se tornado muito importante no contexto da agricultura de precisão. A agricultura de precisão substitui os tratos culturais de grandes áreas da cultura, feitos pela média do nível dos problemas encontrados nessas áreas, por tratamento específicos e pontuais. As pricipais vantagens são o aumento de produtividade, relacionado com a diminuição da variabilidade na produção, a economia de insumos e a preservação do meio ambiente. Este trabalho enfoca o reconhecimento de plantas invasoras em tempo real. Para manter o requisito de tempo real, são utilizadas redes neurais artificiais como meio para o reconhecimento de padrões. Entre as diversas plantas invasoras de ocorrência freqüente no cerrado brasileiro, foi selecionado o picão preto para a avaliação das técnicas adotadas. Uma arquitetura modular de reconhecimento é proposta, com o uso de processamento paralelo, facilitando a inclusão de módulos de reconhecimento de outras plantas invasoras sem a deterioração do desempenho do sistema. Os resultados obtidos são amplamente satisfatórios, demonstrando a possibilidade do desenvolvimento de um sistema embarcado completo de identificação de plantas invasoras em tempo real. Este sistema, apoiado pelo sistema de posicionamento global GPS, pode servir de base para uma série de máquinas agrícolas inteligentes, como pulverizadores de herbicidas e outros defensivos utilizados na agricultura.
Weed identification is an important task in many agricultural procedures. In spite of being a computation intensive task, this identification is very important in the role of precision agriculture. Conventional procedures in agriculture are based on the average level of the problems found in large areas. Precision agriculture introduces new punctual management procedures, dealing with very small areas. The main advantages are: productivity increase, related with the decrease in production unevenness, economy and environment preservation. This work focuses on the real time recognition of weeds. To maintain the real time requirement, neural networks are used to carry out the recognition of image patterns. Among the several weeds frequently found in the Brazilian savannah, the "picão preto" was selected for the evaluation of the adopted techniques. A modular architecture is proposed, using parallel processing, making easier the use of new recognition modules (for other weeds), still preserving the real time capabilities of the system. Results obtained are thoroughly adequate, demonstrating the possibility of the development of embedded systems for the identification of several weeds in real time. These systems, jointly with the global positioning system (GPS), can be used in a family of intelligent equipment, such as spraying machines for herbicides and other agricultural products.

Weld joint penetration determination is the key factor in welding process control area. Not only has it directly affected the weld joint mechanical properties, like fatigue for example. It also requires much of human intelligence, which either complex modeling or rich of welding experience. Therefore, weld penetration status identification has become the obstacle for intelligent welding system. In this dissertation, an innovative method has been proposed to detect the weld joint penetration status using machine-learning algorithms. A GTAW welding system is firstly built. Project a dot-structured laser pattern onto the weld pool surface during welding process, the reflected laser pattern is captured which contains all the information about the penetration status. An experienced welder is able to determine weld penetration status just based on the reflected laser pattern. However, it is difficult to characterize the images to extract key information that used to determine penetration status. To overcome the challenges in finding right features and accurately processing images to extract key features using conventional machine vision algorithms, we propose using convolutional neural network (CNN) to automatically extract key features and determine penetration status. Data-label pairs are needed to train a CNN. Therefore, an image acquiring system is designed to collect reflected laser pattern and the image of work-piece backside. Data augmentation is performed to enlarge the training data size, which resulting in 270,000 training data, 45,000 validation data and 45,000 test data. A six-layer convolutional neural network (CNN) has been designed and trained using a revised mini-batch gradient descent optimizer. Final test accuracy is 90.7% and using a voting mechanism based on three consequent images further improve the prediction accuracy.

In this study we found that tumour cells can be radiosensitised by targeting the DNA damage response kinases, ATM and ATR. Furthermore, we highlight that Wee1 inhibitors, which are already under the clinical trials need to be further investigated in combination with radiation in the context of tumour hypoxia. In addition, we observed that induction of autophagy using STF-62247 can lead to radiosensitisation of VHL deficient RCC cells. Our studies with the rapamycin analogue temsirolimus, already in the clinic for the treatment of various cancers, can be a potential candidate as a radiosensitiser for RCC cells. Overall, these finding led us to investigate further whether autophagy inducing compounds, which are either in clinic or in clinical trials, can effect the response to radiation. From a panel of candidate drugs which are known to induce autophagy we identified an aminopeptidase inhibitor, CHR-2797. CHR-2797 induces autophagy in the oesophageal cancer cell lines FLO-1 and OE21. Although, our results with CHR-2797 demonstrate it as a potential radiosensitiser, the mechanism of its radiosensitisation needs to be established. Our results from CHR-2797-induced radiosensitisation, further led us to investigate if other aminopeptidase inhibitors have a role in radiosensitisation. Therefore, we selectively screened candidate aminopeptidase inhibitors and identified some promising effects on radiosensitivity.

Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 8, 2009) Includes bibliographical references.

L’objectif principal de cette thèse est d’étudier les mécanismes liés au pouvoir pathogène de V. tapetis.Pour cela, nous avons développé 2 axes de recherche. Le premier axe vise à étudier la virulence de V. tapetis en répondant aux 2 problématiques suivantes : Quels sont les gènes impliqués dans la virulence de V. tapetis ? et Existe-t-il des marqueurs hôtes-spécifiques de la virulence de V. tapetis ? Le second axe de recherche concerne l’interaction hôte pathogène et répond aux 2 problématiques suivantes : Quels sont les gènes exprimés lors de l’infection chez l’hôte ? et Quelles sont les modulations au sein de l’animal associées au pH et à la température lors de l’infection ?Les principales découvertes de cette thèse sont : (i) La bactérie V. tapetis, dans le cadre de la MAB, induit une sous expression des gènes impliqués dans la réponseimmunitaire et une dérégulation des gènes impliqués dans la stabilisation et la synthèse des filaments d’actine (ii) Ce pathogène induit également une diminution de l’activité lysosomale sur les hémocytes exposés (iii) L’effet de V. tapetis sur le cytosquelette d’actine et sur la diminution de l’activité lysosomale est indépendante du système de sécrétion de type IV (T4SS) (iv) Le système de sécrétion de type IV (T4SS) est impliqué dans le développement de la MAB mais n’est pas essentiel pour induire cette affection(v) Dans le cadre de la MAB et de la perte des adhérences des hémocytes in vitro, V. tapetis est capable de moduler le pH des fluides extra-palléaux, respectivement dans les premiers jours et premières heures de l’infection (vi) Enfin, l’approche de « strains typing » basée sur la technique MALDI-TOF permet de discriminer les souches de V. tapetis en fonction de leur pouvoir pathogène vis à vis de la palourde japonaise
The main objective of this thesis is to study the mechanisms related to the pathogenicity of V. tapetis. For this purpose, we developed 2 research axes. The first one aimed at studying the virulence of V. tapetis by answering the following 2 issues: What are the genes involved in the virulence of V. tapetis? and Are there host-specific markers of the virulence of V. tapetis? The second research axis concerned pathogen-host interactions and addressed the following 2 issues: What are the genes expressed during infection in the host? and What are the modulations in the animal associated with pH and temperature during infection? The main findings of this thesis are: (i) V. tapetis, in the context of BRD, induces a down expression of genes involved in the immune response anda deregulation of genes involved in the stabilization and synthesis of actin filaments (ii) This pathogen also induces a decrease in lysosomal activity on exposed hemocytes (iii) The effect of V. tapetis on the actin cytoskeleton and on the decrease in lysosomal activity is independent of the type IV secretion system (T4SS) (iv) The type IV secretion system (T4SS) is involved in the development of BRD but is not essential to induce this disease (v) In the context of BRD and of the loss of hemocyte adhesions properties in vitro, V. tapetis is able to modulate the pH of extrapallial fluids, respectively in the first days and hours of infection (vi) Finally, the "strains typing" approach based on MALDITOF makes it possible to discriminate between V. tapetis strains according to their pathogenicity with regard to Manila clam

This thesis gives an overview of factors used in weed risk assessments and explores the disparity between the measured high accuracy rate of the weed risk assessment system (WRA) as implemented in Australia and the pessimistic assessments of some workers about the possibility of predicting the weed potential of plant species imported in the future. The accuracy of the WRA may not be as high as previously thought, and it varies with weed definition and taxonomic groups. Cluster analysis and comparative analysis by independent contrasts were employed to determine the value of individual biological and ecological questions on the WRA questionnaire. Results showed that some WRA questions could be deleted from the questionnaire and the scores for others weighted differently. The WRA is not a reliable predictor of weeds when it is considered in the context of the base-rate probability of an introduced plant becoming weedy in Australia. As a result a far greater number on non-weeds will be placed on the prohibited imported list than was initially expected.
Thesis (M.Appl.Sci.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 1999

碩士
國立中興大學
農藝學系所
107
Using herbicides is an important way to control weeds in traditional crop field, but repeating use of the same herbicide will enforce weeds to evolve herbicide resistance. Chemical herbicides have been registered and used in Taiwan since 1963, more than 50 years. However, there is little formal survey. In order to detect herbicide resistant weeds in time, this study focused on the establishment of a complete notification system to collect and identify resistant weeds more efficiently. After receiving notification from farmers, we will prepare to sample putative herbicide-resistant weeds. All weeds sampled were cultivated in greenhouse, and herbicide damage of these weeds were observed within 30 days after transplanting. If weed has a suspected herbicide resistance, its seeds will be collected and planting for subjecting to dose-response analysis. According to the results of five cases, weed samples from four of them may be resistant to herbicides. And record of applying the same herbicide for many years have been found in three cases. This study mainly focused on the herbicide resistance in goosegrass [Eleusine indica (L.) Gaertn] from DaCun vineyard, and to establish the standard of procedure for observation and identification of resistance to glufosinate, quizalofop-ethyl, and glyphosate. The results showed that the goosegrass from DaCun vineyard generally had low-level herbicide resistance to glufosinate, and some had high-level herbicide resistance to quizalofop-ethyl, whereas all goosegrass sampled was extremely sensitive to glyphosate. Three biotypes (DC4, DC7, DC8) also showed a multiple resistance to glufosinate and quizalofop-ethyl.

Tese de mestrado em Ecologia e Gestão Ambiental, Universidade de Lisboa, Faculdade de Ciências, 2020
Xylella fastidiosa Wells et al. é uma fitobactéria gram-negativa, estritamente aeróbia, restrita ao xilema, com cinco subespécies conhecidas, nomeadamente X. fastidiosa subsp. fastidiosa, X. fastidiosa subsp. multiplex, X. fastidiosa subsp. pauca, X. fastidiosa subsp. morus e X. fastidiosa subsp. sandyi. A sua transmissão ocorre através de insetos picadores-sugadores do xilema e, até a data, são conhecidas mais de 560 espécies hospedeiras da bactéria, distribuídas por mais de 260 géneros e 80 famílias. As dez famílias com maior número de espécies de plantas suscetíveis são, em ordem decrescente: Fabaceae, Asteraceae, Vitaceae, Poaceae, Rosaceae, Rutaceae, Fagaceae, Rubiaceae, Lamiaceae e Oleaceae. As principais doenças provocadas por X. fastidiosa, em termos de importância económica, são a Doença de Pierce, na vinha, a Clorose Variegada dos Citros, em citrinos, o “Almond Leaf Scorch”, em amendoeira, a “Peach Phony Disease” em pessegueiro e o Declínio Súbito do Olival, em oliveira, entre outras. A transmissão da bactéria é um processo progressivo que inclui três passos: (i) aquisição pelo vetor de uma planta infetada (ii) fixação e retenção na cutícula do estomódeo do vetor, onde a bactéria forma uma espécie de biofilme, e (iii) inoculação numa nova planta hospedeira. À medida que a população bacteriana cresce na planta saudável pode ocorrer o bloqueio de vasos xilémicos, devido à sua agregação através da formação de um biofilme, desencadeando respostas na planta, como por exemplo o aparecimento de tilos, reduzindo o fluxo de água e sais minerais. No entanto, uma transmissão bem-sucedida de X. fastidiosa depende de vários fatores, como por exemplo, a espécie e o comportamento de vetor – como as preferências de local de alimentação na planta, a planta hospedeira e a subespécie da bactéria. Também a ecologia, as alterações climáticas, a sazonalidade e as práticas de gestão da cultura são igualmente fatores relevantes. Todavia, é importante notar que não há especificidade entre o par vetor-fitopatógeno, visto que os insetos vetores podem transmitir todos os genótipos de X. fastidiosa. Tal como referido, X. fastidiosa é transmitida por insetos com armadura bucal picadora-sugadora, que se alimentam da seiva xilémica (Hemiptera: Auchenorrhyncha), o que parece ser o único requisito para a competência do vetor, tornando largo o espectro de potenciais vetores. No entanto, nem todos os potenciais vetores têm um papel significativo na transmissão da bactéria, pois outros fatores influenciam a sua propagação, nomeadamente o habitat, o hospedeiro e sua interação com os vetores, a mobilidade dos vetores e a sua distribuição. As espécies de vetores, atuais e potenciais, de X. fastidiosa presentes na Europa encontram-se distribuídas pelas seguintes famílias/subfamílias: Aphrophoridae (27 espécies), Cercopidae (7 espécies), Cicadidae (61 espécies), Cicadellinae (5 espécies) e Evacantinae (3 espécies). Atendendo à sua ampla distribuição e frequência, algumas das espécies mais relevantes são: Philaenus spumarius Linnaeus, Cicadella viridis Linnaeus, Aphrophora alni Fallén e Aphrophora salicina Goeze. Sendo uma bactéria endémica nas Américas, foi já reportada em Taiwan, Irão, Israel e em alguns países europeus. No ano de 2013, ocorreu a primeira confirmação de X. fastidiosa na Europa, na região da Apúlia (sul da Itália), onde a bactéria foi responsável pela destruição de milhares de hectares de oliveiras. Desde então, as prospeções anuais nacionais obrigatórias nos Estados-Membros da União Europeia levaram à descoberta de surtos de X. fastidiosa em vários países, como por exemplo em França, Alemanha, Espanha e, em 2018, Portugal. O fitopatógenio foi detetado no município de Vila Nova de Gaia, em plantas de lavanda (Lavandula dentata Linnaeus) no jardim do Zoo Santo Inácio. Desde essa primeira deteção verificaram-se pelo menos 84 focos, tanto em jardins públicos, como em jardins privados. Portugal é um dos quatro maiores produtores de azeite, a seguir a Espanha, Itália e Grécia, possuindo a cultura da oliveira grande significância cultural e económica, especialmente na região do Alentejo, que é responsável por 70% da produção nacional de azeitona. A importância da olivicultura em Portugal e as consequências devastadoras da propagação de X. fastidiosa nos olivais italianos, evidenciam o potencial risco de contaminação desta cultura pela bactéria. Dessa forma as medidas de gestão adequadas para limitar a ocorrência da bactéria dependem em grande parte do conhecimento local dos seus potenciais vetores e da sua dinâmica, sendo imperativo o estudo da sua ocorrência nos olivais desta região. Face ao exposto, o objetivo deste estudo consistiu na prospeção de potenciais insetos vetores de X. fastidiosa no Alentejo, em olivais livres de produtos fitofarmacêuticos, como contributo para a construção de um mapa de risco e subsequente plano de monitorização contínua dos vetores, elementos úteis para limitar a ocorrência do declínio súbito do olival em olivais da região. A amostragem ocorreu entre 3 de maio e 8 de junho de 2017 na região do Alentejo, a qual foi dividida em 18 unidades geográficas (UGs) de 30 × 30 km, onde sete olivais sem aplicação de inseticidas por UG foram selecionados para prospeção, resultando num total de 126 pontos de amostragem. Em cada ponto de amostragem, os artrópodes foram capturados em oliveiras e vegetação rasteira circundante com um aspirador de artrópodes. Os Auchenorrhyncha foram separados e identificados até ao nível taxonómico mais baixo possível. No caso dos adultos, quando não foi possível a determinação da espécie, foram consideradas morfoespécies. Posteriormente, foram efetuados testes moleculares para detetar a presença de X. fastidiosa em potenciais vetores. Procedeu-se, também, à avaliação do efeito de 22 variáveis independentes na abundância dos vetores de X. fastidiosa, por análise de variância não paramétrica (teste de Kruskal-Wallis) para identificar diferenças estatisticamente significativas associadas a essas variáveis. Na presença de diferenças significativas (p <0.05), os dados posteriormente ranqueados das variáveis foram discriminados pelo teste post hoc de diferenças mínimas significativas (LSD). Foram triadas 300 amostras recolhidas na Região do Alentejo, das quais 99 em oliveira, 21 na vegetação rasteira mista e 180 em espécies vegetais individuais. No total foram coletados 39 527 artrópodes (incluindo adultos e estágios imaturos), dos quais 11 022 eram Hemiptera e destes 1 145 eram Auchenorrhyncha. De todos os Auchenorrhyncha, 954 indivíduos eram da infra-ordem Cicadomorpha e 191 pertenciam à infra-ordem Fulgoromorpha. Os resultados demostraram que apesar de X. fastidiosa ainda não ter sido detetada na Região do Alentejo, cinco vetores / vetores potenciais estão presentes na área de estudo, nomeadamente, Philaenus spumarius, Philaenus tesselatus Melichar, Cercopis intermedia Kirschbaum, Lepyronia coleoptrata (Linnaeus) e Neophilaenus campestris (Fallén). De acordo com os resultados obtidos, P. tesselatus foi a espécie de cigarrinha-de-espuma mais comum, com uma ampla distribuição na Região do Alentejo. Apenas um indivíduo masculino de P. spumarius e um indivíduo feminino de C. intermedia foram encontrados neste estudo. Neophilaenus campestris embora presente em baixa abundância, representa uma ameaça potencial para a cultura da oliveira e para as culturas circundantes, uma vez que a sua capacidade de transmissão foi comprovada por outros autores. Tendo isso em consideração, deve-se realizar um plano de monitorização contínua destes vetores/ potenciais vetores na Região do Alentejo, em especial foco nas espécies de P. spumarius, P. tesselatus e N. campestris. A identificação dos vetores, possibilitou também observar uma clara diferença na morfologia do edeago do P. spumarius e P. tesselatus, especialmente nos apêndices superiores e inferiores, com P. tesselatus exibindo medidas sempre maiores do que P. spumarius. Nenhuma diferença foi observada na preferência da planta hospedeira pelos vetores, exceto para Philaenus sp., que apresentou maior abundância na vegetação herbácea do que na oliveira. Assim, os estratos herbáceos presentes na região devem ser submetidos a prospeção e, se a presença destes indivíduos se tornar crítica, os estratos devem ser removidos. Especial atenção deve ser dada às famílias de plantas onde os insetos vetores foram mais abundantes ou às famílias mais vulneráveis à bactéria, especialmente Asteraceae, Apiaceae (Daucus carota Linnaeus, Conium maculatum Linnaeus) e Convolvulaceae (Convolvulus arvensis Linnaeus). Foram capturadas várias outras espécies de Auchenorrhyncha que são vetores de outras doenças. Identificou-se também dois indivíduos de Arocephalus punctum (Flor) neste estudo, sendo que tanto quanto é do conhecimento da autora, este é o primeiro relato desta cigarrinha em Portugal. Além disso, foram encontrados onze indivíduos de Auchenorrhyncha parasitados, com a maioria parasitados por Dryinidae (Hymenoptera). Novos estudos devem ser realizados para verificar se Dryinidae pode, de facto, parasitar cigarrinhas bem como, estudos de identificação de inimigos naturais de vetores nos olivais alentejanos, as suas relações ecológicas e se a gestão dos inimigos naturais pode contribuir para o controlo biológico dos vetores de X. fastidiosa. Por fim, foi demonstrado que na área de estudo a temperatura e a precipitação desempenham um papel significativo na abundância de Philaenus spp. Philaenus tesselatus apresentou diferenças significativas na abundância face à precipitação total e Philaenus sp. em relação à temperatura média, com a sua maior abundância a registar-se a 24 °C. Isto significa que as alterações climáticas futuras são um elemento com impacto na epidemiologia do declínio súbito do olival na Região do Alentejo, visto que podem influenciar a distribuição e as dinâmicas populacionais de potenciais vetores, o crescimento das plantas hospedeiras, a eficiência da transmissão da bactéria e as relações vetor/planta hospedeira.
Xylella fastidiosa Wells et al. is a xylem-limited phytopathogen, originating in America and transmitted by sap-sucking insects. The current database on X. fastidiosa host plants includes more than 560 species distributed by more than 260 genera and 80 families. The emergence of the bacterium throughout Europe and its first report in Portugal in 2018, with at least 84 detections in Portugal to date, showed that the phytopathogen is spreading at an alarming rate. Considering the spreading rate, the economic and cultural significance of olive culture in Portugal, and the devastating consequences in Italian olive groves, it is pertinent to know the presence of capable vectors and host plants of the bacterium in Alentejo olive groves. This study aims to survey the presence of vector species of X. fastidiosa, during spring, in traditional Alentejo olive orchards and to contribute to a continuous monitoring plan of vectors, thus preventing or limiting the occurrence of olive quick decline syndrome. The results showed that, despite the phytopathogen has not been detected in the Alentejo Region, five vector species were present, Philaenus spumarius Linnaeus, Philaenus tesselatus Melichar, Cercopis intermedia Kirschbaum, Lepyronia coleoptrata (Linnaeus) e Neophilaenus campestris (Fallén). Philaenus tesselatus was the most abundant species, however only one individual of P. spumarius and C. intermedia were found. Also, although present in low abundance in this study, N. campestris represents a potential threat to olive culture and surrounding areas since its transmission ability has been demonstrated. Taking this into consideration, the continuous monitoring plant should focus on P. spumarius, P. tesselatus and N. campestris. No difference was observed in host plant preference by vectors, except for Philaenus sp., which showed significantly higher abundance on ground cover that on olive trees. Nevertheless, the herbaceous strata present in the region should also be subjected to prospection and, if the situation becomes critical, should be removed. Special attention must be payed to families were the insect vectors found were most abundant or to the families that are vulnerable to the bacterium, specially Asteraceae, Apiaceae (Daucus carota Linnaeus, Conium maculatum Linnaeus) and Convolvulaceae (Convolvulus arvensis Linnaeus). Multiple Auchenorrhyncha species that are vectors of other plant diseases were captured. Two individuals of Arocephalus punctum (Flor) were found in this study, which to the author’s knowledge, may be the first report of this leafhopper in Portugal. Also, eleven parasitized Auchenorrhyncha individuals were found, with most of parasitized specimens parasitized by Dryinidae (Hymenoptera). Finally, in the study area, climatic variables played a significant role in the abundance of Philaenus spp. Statistical analysis showed that total precipitation and mean temperature had a significant effect on P. tesselatus and Philaenus sp. abundance, respectively. The conditions in Alentejo Region are very suitable for the establishment and spread of X. fastidiosa and future climate change could impact the epidemiology of olive quick decline syndrome in the region, since climatic variables influence the distribution and dynamics of vector populations, the host plants growth, the efficiency of pathogen transmission and vector/host plant dynamics.

Thesis (Ph. D.)--University of Georgia, 2003.
Directed by Robert Ivarie. Includes an article published in Poultry science, and articles submitted to BioTechniques, Poultry science, and Proteomics. Includes bibliographical references.