The initiation, persistence, and termination of harmful algal blooms (HABs) can all be influenced by nutrient availability. Recent studies have highlighted the role of both organic and inorganic nitrogen sources in HAB dynamics. The pelagophyte Aureoumbra lagunensis causes ecosystem disruptive algal blooms and is responsible for the longest recorded harmful algal bloom (1989-1997). Because of Aureoumbra's small size and its inability to use nitrate, it has been hypothesized that its ability to use ammonium and organic nitrogen, especially at low concentrations, contributed to the unusual persistence of this bloom. This project aimed to assess the response of Aureoumbra to inorganic and organic nitrogen sources by examining the expression of genes responsible for nitrogen assimilation, with an eventual intent of developing expression assays that are indicative of nitrogen source use and/or sufficiency in Aureoumbra. Large volume batch cultures of Aureoumbra were grown with either ammonium or urea as a nitrogen source. Physiological characteristics (C:N, chlorophyll [alpha] cell⁻¹, and Fv/Fm) were monitored throughout the growth period, and the expression of the AMT-1, AMT-2 and UREC genes was assayed at early-, mid- and late-exponential phases. The results show that Aureoumbra can use both ammonium and urea, and that it is well adapted to low-nutrient environments. Only one gene, AMT-1, appeared to be transcriptionally regulated in response to changing nitrogen concentration, and only to ammonium. The results of this study contribute to our understanding of how algae in general cope with low nutrient availability and should ultimately help to define the dynamics of these HAB events. / text

The purpose of this study was to identify materials and products in preschools that may contain harmful chemicals and to suggest possible areas of improvement. Another purpose was to examine if a supervisory project focused on chemicals leads to reduced incidence of harmful chemicals and improved routines in preschools. Inspection reports from 46 preschools in Lidingö were examined to see what routines, materials and products that currently existed. The results were compared with inventories of preschools in two other municipalities and a national inventory project. Follow-up questionnaires were sent to 41 of the preschools in Lidingö to examine if the preschools continued to work for a non-toxic environment after the supervision period ended. Preschools at Lidingö showed similar results as the rest of the country, except that the prevalence of old electronics was much lower. Vinyl gloves, soft plastic toys and other plastic objects appeared in more than half of the preschools, and the presence of inappropriate material showed that there is a need for initiatives that promote a non-toxic preschool. The follow-up survey showed that inspections focused on chemicals generally leads to improvements in many areas and can therefore be a good method. The respondents in this study consider the inspectors to be an important support in the process of eliminating harmful substances. Proper cleaning and good purchasing procedures are important to avoid exposure to harmful substances and the removal of phthalates and plastic kitchenware should be a priority for future inspections.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Algal blooms are directly related to human-caused nutrient enrichment of water bodies. The cyanobacteria Microcystis aeruginosa produces microcystin (MC), a toxin that has been linked with mortalities and illness of many organisms. We show that MC is not constrained by the aquatic-terrestrial ecotone. MC was detected in a primary consumer and emerging aquatic invertebrate (Hexagenia Mayfly), a terrestrial insect and predator of emerging aquatic invertebrates (Tetragnathidae Spider), and a vertebrate consumer (Prothonotary Warbler). Mayfly and spider MC levels varied across the blooming period. MC levels in prothonotary warbler livers varied by age class; nestlings having the highest levels. MC levels decreased in fledglings over time. A more aquatic diet was related to higher MC levels in nestlings at one site and nestling fecal-sacs varied spatially, also indicating that aquatic diet is related to MC consumption. Warbler body condition and growth rate was not related to liver microcystin levels.

Master of Public Health / Department of Diagnostic Medicine/Pathobiology / Deon Van der Merwe / Cyanobacteria are Gram-negative photosynthetic bacteria capable of producing toxins responsible for morbidity and mortality in humans and domestic animals. Many are capable of forming concentrated blooms that impact the environment by limiting the growth of sub-surface plants and phytoplankton. Harmful algal blooms (HABs) are also capable of producing multiple types of toxins, creating a potential hazard to recreational water users and animals drinking water from or near a bloom. Characterization of HABs is necessary to prevent these human and animal exposures and includes classifying of the type of cyanobacteria present and whether or not they are capable of toxin production, and the exact type of cyanotoxin that is actually present in bloom. Current methods used to classify cyanobacteria and cyanotoxins include microscopy, bioassays, ELISA, PCR, HPLC, and LC/MS. All of these methods, however, have limitations that include time, labor intensity, or cost. Fourier-Transform Infrared Spectroscopy (FTIR) is another potential tool for cyanobacterial classification that is not limited by these factors. To examine the practicality of this method, library screening with default software algorithms was performed on diagnostic samples received at the Kansas State University Veterinary Diagnostic Lab, followed by PCA of samples meeting minimum quality requirements to produce cluster analyses and dendrograms. Both spectrometers and software packages used were successful at distinguishing cyanobacteria from green algae in clean samples with 89.13% agreement. PCA resulted in clear classification of cyanobacteria or green algae demonstrated by a large order of magnitude difference produced by average Euclidian distance dendrograms. While this method is only capable of differentiating cyanobacteria from green algae or other aquatic environmental constituents, its simple, rapid use and low cost make it a beneficial screening tool when coupled with toxin-detection methods to characterize HABs.

A presente pesquisa foi conduzida com o objetivo verificar a interferência das plantas daninhas no desenvolvimento inicial de Tangerineira 'poncã' (Citrus reticulata Blanco) enxertada sobre Limão "cravo" [Citrus limonia (L.) Osbeck], através de áreas de controle das plantas daninhas em coroamento ou em faixas de controle próximas as mudas no campo. Para tal finalidade foi conduzido um experimento em área do Departamento de Produção Vegetal, da Escola Superior de Agricultura "Luiz de Queiroz", localizada no município de Piracicaba, Estado de São Paulo.As mudas de tangerina poncã foram plantadas em 10/03/1999, obedecendo o espaçamento de 6,0 m entrelinhas e 4,0 m entre plantas. As entrelinhas foram mantidas roçadas com roçadora tratorizada convencional. Os tratamentos experimentais foram dispostos em blocos casualizados com parcelas subdivididas, com quatro repetições. Os dados obtidos foram submetidos ao teste F aplicado à análise de variância, e as médias confrontadas pelo teste de comparação múltipla de Tukey ao nível de 1 % e 5 % de probabilidade. Cada parcela experimental foi constituída por quatro plantas. As sub-parcelas foram constituídas por duas plantas. As plantas foram mantidas capinadas, com enxada, no sentido da linha para entrelinhas, a 25 cm, 50 cm, 75 cm e 100 cm de distância do tronco, além da parcela sem capina, e da parcela capinada. Nas sub-parcelas as capinas foram balizadas com arame em forma de circunferência, suspenso por seis estacas de madeira, para a capina em coroamento, e balizadas com quatro estacas as sub-parcelas destinadas a capina em faixas, conforme cada tratamento.O desenvolvimento das plantas de tangerina foi avaliadotrimestralmente, de 04/05/1999 até 19/07/2001, sendo medido o diâmetro do tronco, diâmetro da copa e altura. Os dados obtidos permitiramm as seguintes conclusões: No primeiro ano de implantação do pomar, são necessárias capinas na linha da cultura, para controle das plantas daninhas, de 75 cm em coroamento, ou de 25 cm em faixas de cada lado do tronco. No segundo ano de implantação do pomar, são necessárias capinas na linha da cultura, para controle das plantas daninhas, de 100 cm em coroamento, ou em faixas de 25 cm de cada lado do tronco. Os tratamentos com capinas em faixas permitiram um melhor desenvolvimento das plantas. No terceiro ano de implantação do pomar, são necessárias capinas na linha da cultura de 100 cm em coroamento ou 25 cm em faixas de cada lado do tronco. / The objective of this research was to evaluate the weed interference on the initial development of "Ponkan" Mandarin trees grafted on "Cravo" [Citrus limonia (L.) Osbeck], through areas of weed control in rows (crown or strips) near to the young plants in the field. For that it was conducted an experiment in the experimental area of the Departamento de Produção Vegetal, Escola Superior de Agricultura "Luiz de Queiroz", in Piracicaba county, São Paulo state, Brazil.The young plants of mandarin were transplanted in 03/10/1999, in a 6,0 m by 4,0 m spacing. The inter rows were mowed using conventional mower powered by a tractor.The experimental treatments were set in a randomized block design with subplots, four replications. The data obtained were submitted to F test and analysis of variance, and the averages were compared using Tukey test at 1% and 5% level of probability. Each experimental plot had four plots. The sub-plots were constituted of two plants. The weeds surrounding the plants were manually hoed from the row center to the inter row direction, at 25 cm, 50 cm, 75 cm and 100 cm distance from the tree trunk, besides a plot weeded, and a plot entirely hoed. In the sub plots the weeds were hoed in a circle forming a crown unweeded around the tree trunk according to the treatments. The mandarin plant development was evaluated every three months from 05/04/99 to 07/19/01, being measured the trunk diameter, shot diameter and height. The obtained data allowed the following conclusions:In the first year after the orchard establishment, it was necessary weed control in the citrus row extending to a 75 cm of the crown, or 25 cm strips wide each side of the tree trunk. During the second year of mandarin orchard establishment manual weed control using hoe is necessary in a 100 cm crown diameter surrounding the tree trunk, or in the strips of 25 cm each side of the tree trunk. The treatments with manual hoe the strips allowed a better plants development. During the third year of mandarin orchard establishment manual weed control using hoe is necessary in the 100 cm diameter of the crown surrounding the tree trunk or in strips of 25 cm each side of the tree trunk.

Em 2014, foi criado pela ABNT (Associação Brasileira de Normas Técnicas), um grupo de trabalho, autointitulado GT- Segurança Química em Têxteis, vinculado ao CB-17 ABNT Comitê Brasileiro de Têxteis ao qual,sua premissa, é criar normalizações nacionais por meio do estudo das legislações e normas internacionais vigentes que versam sobre as questões de toxicidade de produtos têxteis e confeccionados. Onde, sua adaptação, atua diretamente às condições tecnológicas das indústrias nacionais e das necessidades de proteção da saúde dos consumidores. Onze grupos de substâncias, consideradas perigosas, foram inicialmente foco das discussões, que deram origem às sistemáticas de definição qualitativa e quantitativa da presença de classes de produtos químicos em produtos têxteis e confeccionados. No entanto, em razão do volume e da complexidade total do estudo, o objetivo deste projeto foi identificar e quantificar a presença de formaldeído utilizada nos processos de obtenção de fibras, fios, ou tecido, bem como nos processos de beneficiamentos têxteis, com ênfase no residual presente em artigos têxteis e confeccionados, produto este que pode ser encontrado em muitos artigos têxteis e couros, devido a sua presença na composição de uma variedade de auxiliares químicos utilizados no beneficiamento. A Metodologia utilizada foi a pesquisa bibliográfica constituída em procedimento básico para os estudos monográficos, a pesquisa tecnológica que visa à materialização de um produto, protótipo, processo, instalação piloto ou um estudo de viabilização desses e, para análise de dados, utilizou-se a pesquisa quantitativa e os resultados experimentais mostraram que o método adotado foi adequado para a proposta do estudo / In 2014, was established by ABNT (Associação Brasileira de Normas Técnicas), a working group, self-titled GT-chemical safety in textile, linked to the CB-17-ABNT-Brazilian Committee of textiles which, your premise is to create national normalizations through the study of existing laws and international standards relating to the issues of toxicity of textile and made-up. Where your adaptation, acts directly to the technological conditions of national industries and the needs of protection of consumer health. Eleven groups of substances considered dangerous, were initially focus the discussions, giving rise to systematic qualitative and quantitative definition of classes of chemicals in textiles and made-up. However, due to the volume and the total complexity of the study, the objective of this project was to identify and quantify the presence of formaldehyde used in the process of getting fiber, yarn, or fabric, as well as in cases of processed textiles, with emphasis on the present in residual textile and made-up, this product can be found in many textile and leather due to your presence in a variety of auxiliary chemicals used in processing. The methodology used was bibliographical research consists in basic procedure for the monographic studies, technological research aimed at the materialization of a product prototype, pilot installation process or a feasibility study of these and, for data analysis, quantitative research and experimental results showed that the method adopted was suited to the proposal of the study

No ensino da medicina veterinária esta implícito o uso de animais para o aprendizado das mais diversas habilidades profissionais, sendo que na maioria das vezes os animais utilizados nas práticas pedagógicas sofrem algum tipo de prejuízo ou morrem para este fim. Com o aumento da preocupação ética em relação aos animais, nas últimas duas décadas, surgiu a necessidade de se substituir estes métodos de ensino onde havia prejuízo aos animais e ao aprendizado do aluno, por métodos humanitários. Este estudo teve como objetivo avaliar o conhecimento e opinião dos alunos das Faculdades de Medicina Veterinária brasileiras acerca da implementação dos chamados “métodos substitutivos“ ao uso prejudicial de animais e os métodos que estão sendo utilizados atualmente. Foram obtidas 1383 respostas de estudantes de medicina veterinária de 26 estados brasileiros e do Distrito Federal, que responderam questionário semiaberto divulgado de forma online e as respostas foram submetidas à uma analise estatística que nos permitiu concluir que 47,9% dos entrevistados desconhecem a principal legislação acerca do uso de animais, 66,4% afirmaram conhecer o que é um método substitutivo ao uso de animais, 87,7% entendem como "uso prejudicial de animais” a eutanásia de um animal saudável para fins didáticos”; 55,6% acreditam que métodos substitutivos podem sim substituir o uso de animais, desde que seja o método apropriado e que a principal vantagem desta substituição seria o fato de que são métodos eticamente aceitáveis onde não há crueldade contra animais” (57,3%) e a principal desvantagem seria o custo para aquisição (51,8%). Cerca de 93% indicaram que há utilização de animais no seu curso, sendo que a principal espécie o cão (76,5%) e a anatomia apontada como a disciplina que mais utiliza animais. Quanto as aulas de técnica cirúrgica, o método mais citado foi o uso de cadáveres preservados (27,2%).Quanto a utilização de métodos substitutivos, 47,3% responderam que seus cursos utilizam estes métodos e que a disciplina que mais utilizava métodos como manequins, simuladores, vídeos, e softwares era a de anatomia, seguidas das disciplinas de clinica e cirurgia de pequenos animais, que utilizavam atendimento clinico de animais da comunidade ou de ONGs. De acordo com os dados analisados, podemos afirmar que os alunos de Instituições de ensino públicas tiveram mais contato com o conceito dos 3Rs que os alunos de Instituições de ensino privadas e que não há diferenças significativas entre as Instituições públicas e privadas quanto ao uso de métodos substitutivos. Diante destes resultados, faz-se necessário um esforço de toda comunidade acadêmica, dos docentes, dos coordenadores e do comitê de ética da escola no sentido de se desenvolver e implantar métodos didáticos humanitários e eficazes, que possam ir ao encontro das necessidades e posicionamentos éticos dos estudantes de medicina veterinária / In veterinary medicine teaching is implicit the use of animals for learning different professional skills, and most of the time these animals used in pedagogical practices suffer some kind of injury or die for this purpose. With the increasing of the ethical concern for animals in the last two decades, emerged the necessity to replace these teaching methods to humane methods. This study aimed to evaluate the implementation of the "substitutive methods" to the harmful use of animals in veterinary teaching and training in Brazilian Schools, through information obtained from undergraduate students. They were obtained 1383 answers of veterinary medical students from 26 Brazilian states and the Federal District, who responded an online semi-open questionnaire, the responses were submitted to a statistical analysis and we concluded that 47.9% of respondents are unaware of the main legislation about the use of animals, 66.4% said they knew what is a substitute method to animal use, 87.7% perceive as "harmful use of animals' - euthanasia of healthy animals for teaching purposes"; 55.6% believe that substitutive methods can replace the use of animals, but depends of the method, the main advantage of these humane methods is the fact that they are ethically acceptable and avoid animal cruelty"(57.3%) and the main problem would be the cost of acquisition (51.8%). About 93% indicated that use animals in its course, and the main specie is the dog (76.5%) and the anatomy was considered the discipline that use most animals. In the surgical classes, the most cited method was the use of preserved cadavers (27.2%). Regarding the use of substitutive methods, 47.3% answered that their courses using these methods and the discipline that most used methods such as mannequins, simulators, videos, and software was the anatomy, followed by clinical disciplines and surgery of small animals who used clinical care of animals from the community or NGOs. According to the data analysed, we can say that most students of public education institutions had contact with the concept of the 3Rs than students in private educational institutions and there are no significant differences between public and private institutions on the use of substitutive methods. According to this result, is necessary an effort of the academic community (teachers, coordinators and school ethics committee) in order to develop and implement humane and effective teaching methods, which can meet the ethical requirements and positions of students of veterinary medicine

O Filo Microsporidia é composto por parasitas intracelulares obrigatórios que infectam de invertebrados a mamíferos. Alguns gêneros de microsporídeos entomopatogênicos são de extrema importância, visto que diversos estudos epizootiológicos indicam tais agentes como detentores de um papel fundamental na regulação da densidade populacional de seus hospedeiros. Além disso, esses patógenos são considerados como um dos principais obstáculos na manutenção da sanidade nas criações de insetos em laboratório. No Brasil, a partir de 1977, foram relatadas as primeiras ocorrências de nosemoses em criações de laboratório da broca-da-cana, Diatraea saccharalis (Fabr.) (Lepidoptera: Crambidae). Este problema agravou-se no decorrer dos anos em função de alterações nas técnicas de criação da broca visando aumentar a escala produtiva deste inseto e do parasitoide Cotesia flavipes (Cam.) (Hymenoptera: Braconidae). Os objetivos deste trabalho consistiram na: (i) caracterização morfológica e molecular do patógeno, abordando ciclo de vida, patogenicidade a outros lepidópteros de importância agrícola e prevalência em populações de laboratório e campo de D. saccharalis e C. flavipes; (ii) determinação da virulência de Nosema sp. a D. saccharalis em laboratório; (iii) caraterização da propagação do patógeno nas lagartas e sua disseminação pelas fezes; (iv) efeitos da infecção na biologia de D. saccharalis e de C. flavipes e no desempenho do parasitoide quanto à seleção de hospedeiros infectados e não infectados; (v) transmissão do patógeno por C. flavipes a sua progênie e seus hospedeiros e (vi) controle de Nosema sp. em D. saccharalis por produtos antimicrobianos. Foi confirmado que o microsporídeo isolado de D. saccharalis pertence ao gênero Nosema, sendo patogênico à todas as espécies-praga avaliadas. A prevalência do patógeno em C. flavipes foi maior que a prevalência nas criações de D. saccharalis. Os esporos de Nosema sp. foram liberados nas fezes de D. saccharalis, variando o tempo até a liberação e a quantidade de esporos de acordo com o inóculo inicial de infecção. Embora Nosema seja considerado por muitos cientistas como enzoótico e com baixo potencial como agente de controle microbiano para ser usado de forma inundativa, a DL50 para D. saccharalis de 1º ínstar foi estimada em 5,6 esporos, demonstrando como as lagartas recém-eclodidas são muito suscetíveis ao microsporídeo. Infecções por Nosema sp. afetaram negativamente a biologia de D. saccharalis, exceto a duração da fase de pupa, sendo transmitido horizontal e verticalmente. Não foram observadas diferenças significativas na mortalidade de D. saccharalis infectadas por Nosema sp. tratadas com os antimicrobianos utilizados neste estudo em comparação à mortalidade do tratamento controle. Os parâmetros biológicos e o comportamento de C. flavipes sofreram alterações causadas pelo patógeno Nosema sp., que foi transmitido pelo parasitoide para o hospedeiro e por pelo menos quatro geraçõe de C. flavipes. Estes resultados ressaltam a relevância dos estudos sobre o impacto de Nosema sp. em D. saccharalis e C. flavipes, justificando esforços futuros no manejo da doença, dada a importância dessas espécies no agroecossistema da cana-de-açúcar. / The phylum Microsporidia consists of obligatory intracellular parasites that infect from invertebrates to mammalians. Some genera of entomopathogenic microsporidia are extremely important, considering that several epizootiological studies indicate that these agents as having a key role in density population regulating of their hosts. In addition, these pathogens are considered a major obstacle in maintaining healthiness in laboratory insect rearing. In Brazil occurrences of nosemoses were first reported in laboratory rearing of sugarcane borer, Diatraea saccharalis (Fabr.) (Lepidoptera: Crambidae), in the 1977. This problem has worsened over the years due to changes in the rearing methods aiming to increase the production scale of this insect and the parasitoid Cotesia flavipes (Cam.) (Hymenoptera: Braconidae). The objectives of this project consisted of (i) morphological and molecular characterization of the pathogen, addressing life cycle, pathogenicity to other lepidopterans of agricultural importance and prevalence in D. saccharalis and C. flavipes in laboratory rearing and in sugarcane plantations in the State of São Paulo, (ii) virulence of Nosema sp. to D. saccharalis in laboratory, (iii) transmission of the pathogen in D. saccharalis larvae and their dissemination in feces, (iv) the effects of infection on D. saccharalis and C. flavipes biology and performance of the parasitoid on the selection of infected and uninfected hosts, (v) the transmission of the pathogen by C. flavipes to their progeny and their hosts and (vi) the control of Nosema sp. in D. saccharalis by antimicrobial products. It was confirmed that the microsporidium isolated from D. saccharalis belongs to the genus Nosema, being pathogenic to all pest species evaluated in the host specificity study. The prevalence of the pathogen in C. flavipes was higher than the one in the D. saccharalis rearing facilities. Nosema sp spores were disseminated in the feces of D. saccharalis, varying the time until their release and the quantity of spores according to the initial inoculum of infection. Although Nosema is considered by many scientists as enzootic and low potential as a microbial control agent to be used inundatively, the LD50 for 1st instar D. saccharalis was estimated as 5.6 spores, demonstrating how that the newly-hatched larvae are very susceptible to this pathogen. Nosema sp. infections negatively affected the biology of D. saccharalis, except in the duration of the pupal stage, being transmitted horizontally and vertically. There were no significant differences in mortality of D. saccharalis infected by Nosema sp. treated with the antibiotics used in this study compared with the mortality of the control treatment. The biological parameters and behavior of C. flavipes suffered adverse effects caused by the pathogen Nosema sp., which was transmitted to the host by the parasitoid and its progeny to four C. flavipes generation. These results underscore the relevance of studies on the impact of Nosema sp. in D. saccharalis and C. flavipes, justifying future efforts in managing the disease, given the importance of these species in the sugarcane ecosystem.

A presente pesquisa foi conduzida com o objetivo verificar a interferência das plantas daninhas no desenvolvimento inicial de Tangerineira 'poncã' (Citrus reticulata Blanco) enxertada sobre Limão "cravo" [Citrus limonia (L.) Osbeck], através de áreas de controle das plantas daninhas em coroamento ou em faixas de controle próximas as mudas no campo. Para tal finalidade foi conduzido um experimento em área do Departamento de Produção Vegetal, da Escola Superior de Agricultura "Luiz de Queiroz", localizada no município de Piracicaba, Estado de São Paulo.As mudas de tangerina poncã foram plantadas em 10/03/1999, obedecendo o espaçamento de 6,0 m entrelinhas e 4,0 m entre plantas. As entrelinhas foram mantidas roçadas com roçadora tratorizada convencional. Os tratamentos experimentais foram dispostos em blocos casualizados com parcelas subdivididas, com quatro repetições. Os dados obtidos foram submetidos ao teste F aplicado à análise de variância, e as médias confrontadas pelo teste de comparação múltipla de Tukey ao nível de 1 % e 5 % de probabilidade. Cada parcela experimental foi constituída por quatro plantas. As sub-parcelas foram constituídas por duas plantas. As plantas foram mantidas capinadas, com enxada, no sentido da linha para entrelinhas, a 25 cm, 50 cm, 75 cm e 100 cm de distância do tronco, além da parcela sem capina, e da parcela capinada. Nas sub-parcelas as capinas foram balizadas com arame em forma de circunferência, suspenso por seis estacas de madeira, para a capina em coroamento, e balizadas com quatro estacas as sub-parcelas destinadas a capina em faixas, conforme cada tratamento.O desenvolvimento das plantas de tangerina foi avaliadotrimestralmente, de 04/05/1999 até 19/07/2001, sendo medido o diâmetro do tronco, diâmetro da copa e altura. Os dados obtidos permitiramm as seguintes conclusões: No primeiro ano de implantação do pomar, são necessárias capinas na linha da cultura, para controle das plantas daninhas, de 75 cm em coroamento, ou de 25 cm em faixas de cada lado do tronco. No segundo ano de implantação do pomar, são necessárias capinas na linha da cultura, para controle das plantas daninhas, de 100 cm em coroamento, ou em faixas de 25 cm de cada lado do tronco. Os tratamentos com capinas em faixas permitiram um melhor desenvolvimento das plantas. No terceiro ano de implantação do pomar, são necessárias capinas na linha da cultura de 100 cm em coroamento ou 25 cm em faixas de cada lado do tronco. / The objective of this research was to evaluate the weed interference on the initial development of "Ponkan" Mandarin trees grafted on "Cravo" [Citrus limonia (L.) Osbeck], through areas of weed control in rows (crown or strips) near to the young plants in the field. For that it was conducted an experiment in the experimental area of the Departamento de Produção Vegetal, Escola Superior de Agricultura "Luiz de Queiroz", in Piracicaba county, São Paulo state, Brazil.The young plants of mandarin were transplanted in 03/10/1999, in a 6,0 m by 4,0 m spacing. The inter rows were mowed using conventional mower powered by a tractor.The experimental treatments were set in a randomized block design with subplots, four replications. The data obtained were submitted to F test and analysis of variance, and the averages were compared using Tukey test at 1% and 5% level of probability. Each experimental plot had four plots. The sub-plots were constituted of two plants. The weeds surrounding the plants were manually hoed from the row center to the inter row direction, at 25 cm, 50 cm, 75 cm and 100 cm distance from the tree trunk, besides a plot weeded, and a plot entirely hoed. In the sub plots the weeds were hoed in a circle forming a crown unweeded around the tree trunk according to the treatments. The mandarin plant development was evaluated every three months from 05/04/99 to 07/19/01, being measured the trunk diameter, shot diameter and height. The obtained data allowed the following conclusions:In the first year after the orchard establishment, it was necessary weed control in the citrus row extending to a 75 cm of the crown, or 25 cm strips wide each side of the tree trunk. During the second year of mandarin orchard establishment manual weed control using hoe is necessary in a 100 cm crown diameter surrounding the tree trunk, or in the strips of 25 cm each side of the tree trunk. The treatments with manual hoe the strips allowed a better plants development. During the third year of mandarin orchard establishment manual weed control using hoe is necessary in the 100 cm diameter of the crown surrounding the tree trunk or in strips of 25 cm each side of the tree trunk.