Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Two experiments were carried out aiming to evaluate pasture attributes and productive and reproductive performance of beef heifers from nine to 13 months of age (Experiment 1) and subsequently from 15 to 18 months of age (Experiment 2). Pasture and livestock assessment in Experiment 1 totaled 112 days, from July to November 2008. The beef heifers were kept grazing on Italian ryegrass (Lolium multiflorum Lam), with heifers either exclusively on pasture or receiving fat as a supplement (0.15 or 0.30% of body weight (BW)). Experiment 2 was carried out from January to April 2009 and pasture attributes, productive and reproductive performance and beef heifers ingestive behavior in Coastcross (Cynodon dactylon (L.) with forage on offer (FO) of 10% and Alexandergrass (Urochloa plantaginea) with FO of 8 and 12% were studied. On both experiments continuous grazing method was used with variable number of animals. The experimental design was completely randomized with repeated measures over time. The following variables were measured in Experiment 1: animal performance, pasture and supplement efficiency of conversion to kg of body weight, height , body weight:height ratio, pelvic area and reproductive tract score of heifers. Pasture variables were similar between supplement levels and the average values of forage mass and forage on offer were 1497.6 kg ha-1 DM and 11.45 kg DM 100 kg-1 BW, respectively. The productive and reproductive variables were not affected by fat levels tested. Heifers supplemented with fat had higher average daily gain, body weight, height, condition score and body weight: height ratio than heifers exclusively on pasture. The use of supplemental fat promoted no change in pelvic area and reproductive tract score of heifers, which presents inadequate development to allow breeding at 12/14 months old. In Experiment 2, the ingestive behavior was measured in four continuous 12 hour periods. Pasture variables, animal performance and ingestive behavior in Alexandergrass were similar in both forage on offer. There was both stocking rate and gain per hectare increase of 22 and 75%, respectively when heifers grazed on Alexandergrass in relation to Coastcross. The heifers present similar individual and reproductive performance when grazing on either Coastcross or Alexandergrass on both forage on offer and are considered capable of breeding at 18 months of age. / Foram conduzidos dois experimentos com o objetivo de avaliar os atributos das pastagens e o desempenho produtivo e reprodutivo de novilhas de corte dos nove aos 13 meses de idade (Experimento 1) e posteriormente dos 15 aos 18 meses de idade (Experimento 2). No Experimento 1 o período destinado a avaliação da pastagem e dos animais totalizou 112 dias, de18 julho a quatro de novembro de 2008. As bezerras foram mantidas em pastagem de azevém anual (Lolium multiflorum Lam.), com animais exclusivamente em pastagem ou recebendo suplemento lipídico (0,15% ou 0,30% do peso corporal (PC)). O Experimento 2 transcorreu de 29 de janeiro a 23 de abril de 2009 e foram estudados os atributos das pastagens, desempenho produtivo e reprodutivo e o comportamento ingestivo de novilhas de corte em Coastcross (Cynodon dactylon (L.)) com oferta de forragem (OF) de 10% e Papuã (Urochloa plantaginea) com OF de 8% e 12%. Nos dois experimentos foi utilizado o método de pastejo continuo com número variável de animais. O delineamento experimental foi o inteiramente casualizado com medidas repetidas no tempo. No experimento 1 foram avaliadas as seguintes variáveis resposta: desempenho animal, eficiência de transformação do pasto e do suplemento em kg de peso corporal, altura, relação peso corporal:altura, área pélvica e escore de trato reprodutivo das bezerras. As variáveis do pasto foram semelhantes entre os níveis de suplemento utilizados e os valores médios de massa de forragem e oferta de forragem foram de 1497,6 kgha-1 de MS e 11,45 kg de MS/100 kg de PC. As variáveis do desempenho produtivo e reprodutivo não foram afetadas pelos níveis de gordura utilizados. As bezerras suplementadas com gordura apresentaram maior ganho médio diário, peso corporal, escore de condição corporal, altura e relação peso corporal:altura do que bezerras exclusivamente em pastejo. O uso de suplementação com gordura não expressou alteração na área pélvica e escore de trato reprodutivo das bezerras, as quais não mostraram desenvolvimento adequado para serem acasaladas aos 12/14 meses de idade. No experimento 2, o comportamento ingestivo foi medido em quatro períodos contínuos de 12 horas. As variáveis do pasto, desempenho animal e comportamento ingestivo foram semelhantes em Papuã nas duas ofertas de forragem. Houve acréscimo na taxa de lotação e no ganho por área quando as novilhas pastejaram Papuã em relação à Coastcross de 22% e 75%, respectivamente. As novilhas apresentaram desempenho individual e reprodutivo semelhante quando pastejaram Coastcross ou Papuã em ambas as ofertas, sendo consideradas aptas a reprodução aos 18 meses de idade.

Dans le contexte politique (réduction 50% de l'utilisation des pesticides à échéance de 2018 -Plan Ecophyto) et social actuel (mise en place de modes de production plus respectueux pour l'environnement), la sévérité des dommages causés par le puceron cendré du pommier, Dysaphis plantaginea Passerini (Hemiptera : Aphididae), surtout en agriculture biologique, rend nécessaire la mise au point de solutions alternatives s'appuyant sur le rôle des ennemis naturels. Nous avons donc essayé d'apporter des éléments nouveaux sur la connaissance des relations entre le puceron cendré et ses ennemis naturels et sur les conditions à même de favoriser leur action. Des suivis hebdomadaires des arthropodes présents sur les rameaux infestés par D. plantaginea, ont mis en évidence l'effet négatif des auxiliaires sur les populations de D. plantaginea, sans pour autant atteindre une véritable régulation à même d'éviter les dégâts économiques. Nous avons également montré l'action favorisante des fourmis sur la dynamique du puceron cendré et négative sur celle des auxiliaires. Nous avons pu identifier trois groupes d'auxiliaires dominants avec une arrivée séquentielle marquée : les syrphes, dont l'installation coïncide avec le début de l'infestation de D. plantaginea, puis les coccinelles et les forficules qui arrivent plus tardivement. Pour que les auxiliaires jouent un rôle plus important contre D. plantaginea, il faut d'autres pratiques permettant d'abaisser significativement le nombre de traitements pesticides. Une innovation très récente permet la réduction drastique des traitements insecticides : les filets Alt'Carpo. Malgré son influence négative sur l'abondance et la richesse du cortège des auxiliaires présents dans les colonies de D. plantaginea, surtout les coccinelles, cette technique freine le développement des populations de D. plantaginea à l'échelle du rameau ou de l'arbre lorsque les filets sont fermés après la floraison (en conformité avec les préconisations contre le carpocapse). Cependant, la réduction des populations de D. plantaginea sous les filets requiert la présence d'au moins un stade actif d'auxiliaire par rameau, ce qui interroge sur la réalité de la régulation de ce ravageur par le simple usage des filets. Sur la base de leur précocité, pour Episyrphus balteatus De Geer (Diptera : Syrphidae) et de leur abondance dans les colonies de D. plantaginea, pour Forficula auricularia Linnaeus (Dermaptera : Forficulidae) et E. balteatus, ces deux espèces apparaissent comme de bons candidats pour la régulation de D. plantaginea. Nos études en conditions contrôlées ont démontré leur potentiel régulateur sur D. plantaginea, en particulier aux stades les plus âgés. L'efficacité optimale intervient à 20°C pour les deux prédateurs, pour lesquels nous n'observons par ailleurs pas d'interaction négative lorsqu'ils sont associés en présence de fortes densités de D. plantaginea. Sur la base de ces résultats de laboratoire nous avons analysé les possibilités de lâchers printaniers de ces deux prédateurs sur de jeunes colonies de D. plantaginea. Dans nos conditions expérimentales en vergers de pommiers, des lâchers précoces de larves du 3ème stade de F. auricularia n'ont pas permis de limiter les populations de D. plantaginea, confirmant la difficulté des lâchers de prédateurs en cultures de plein champ. De la même manière, des lâchers précoces d'E. balteatus pourtant réalisés sous filets Alt'Carpo restent sans effet sur l'infestation par D. plantaginea. Cette thèse, en s'appuyant sur des essais en conditions contrôlées, semi contrôlées et de plein champ, constitue une étape dans un processus d'élaboration d'un modèle dynamique du développement de D. plantaginea à l'échelle du rameau, prenant en compte le rôle des fourmis et des auxiliaires et l'influence des pratiques de protection (par exemple, les filets Alt'Carpo et les lâchers d'auxiliaires). Elle confirme, si besoin en était, la complexité des phénomènes de régulation, des pucerons en particulier, et la nécessité d'études complémentaires pour définir les conditions d'application de la lutte biologique contre D. plantaginea

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-27T13:30:34Z No. of bitstreams: 5 37.pdf: 3780972 bytes, checksum: 25735fd7c2f94a2a52a7a996adefcb6b (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-27T18:41:07Z (GMT) No. of bitstreams: 5 37.pdf: 3780972 bytes, checksum: 25735fd7c2f94a2a52a7a996adefcb6b (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) / Made available in DSpace on 2015-02-27T18:41:07Z (GMT). No. of bitstreams: 5 37.pdf: 3780972 bytes, checksum: 25735fd7c2f94a2a52a7a996adefcb6b (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) Previous issue date: 2011 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) / Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG) / Avaliaram-se neste trabalho os efeitos da competi??o entre cultivares de milho, feij?o e mandioca e seis esp?cies de plantas daninhas no ac?mulo e na aloca??o de mat?ria seca e nutrientes pelas plantas; o potencial de algumas dessas esp?cies em reciclar nutrientes e a efici?ncia nutricional do feijoeiro. Para isso foi realizado um experimento para cada cultura com tr?s gen?tipos de milho, tr?s de feij?o e dois de mandioca, cultivados em competi??o com seis esp?cies de plantas daninhas, al?m dos tratamentos adicionais, correspondentes ?s cultivares de milho, feij?o e mandioca e ?s esp?cies daninhas ausentes de competi??o. O per?odo de conviv?ncia entre as cultivares de milho, feij?o e mandioca e as plantas daninhas foi de 60, 45 e 75 dias ap?s emerg?ncia das culturas, respectivamente. Para a cultura do milho e do feij?o foi avaliada a aloca??o de mat?ria seca e de nutrientes, inclusive entre os diferentes ?rg?os. Ainda para o feij?o foram estimados os coeficientes para efici?ncia de absor??o, transporte e utiliza??o dos nutrientes. Para a cultura da mandioca, foram determinadas, al?m da aloca??o de mat?ria seca, caracter?sticas morfofisiol?gicas ligadas ? ?rea foliar. A folha e o caule do milho foram os principais ?rg?os afetados negativamente pela competi??o, enquanto as ra?zes das esp?cies competidoras foram os ?rg?os mais prejudicados. Em competi??o com o feijoeiro, as folhas e o caule das esp?cies daninhas foram os ?rg?os mais prejudicados. Com mandioca, os componentes vegetativos das plantas daninhas sofreram reduzidas modifica??es, sem preju?zos quanto ? produ??o de mat?ria seca. As ra?zes do feijoeiro e de mandioca foram os principais ?rg?os afetados negativamente pela competi??o. Os gen?tipos AL 25 (milho) e IPR Colibri (feij?o) foram os que menos toleraram a competi??o. De forma contr?ria, as cultivares P?rola (feij?o) e Periquita (mandioca) demonstraram possuir as maiores habilidades competitivas. O milho mostrou-se sens?vel ? competi??o com B. brizantha e C. benghalensis e competitivo com B. plantaginea. Esta esp?cie, entretanto, mostrou-se altamente competitiva com feij?o e mandioca. Al?m disso, A. spinosus, em competi??o com o feijoeiro, demonstrou possuir a maior habilidade competitiva. A capacidade competitiva entre esp?cies vegetais, quando se trata do ac?mulo de mat?ria seca e relativo de nutrientes, n?o representou vantagem para as esp?cies de plantas daninhas, quando elas foram mantidas em conviv?ncia com o milho. O feijoeiro apresentou baixa capacidade de competi??o por nutrientes, particularmente N e P. A ?rea foliar espec?fica e a raz?o de ?rea foliar da mandioca n?o foram afetadas pela competi??o. B. brizantha e C. echinatus, livre da conviv?ncia com o milho, apresentaram elevado potencial em reciclar nutrientes. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2011. / ABSTRACT There were evaluated in this study the effects of competition between maize, beans and cassava, and six weed species in the accumulation and allocation of dry matter and nutrients by plants, the potential of some of these species in recycling nutrients and nutritional efficiency of bean. For this end an experiment was performed to each culture with three genotypes of maize, beans and two of three cassava grown in competition with six weeds species, apart from additional treatment corresponding to the maize, beans and cassava cultivars and weed species absent from the competition. The period of coexistence among maize, beans and cassava cultivars and the weeds was 60, 45 and 75 days after crop emergence, respectively. For the corn and beans there were evaluated allocation of dry matter and nutrients, including between different organs. Even for the beans there were estimated coefficients for uptake, transport and utilization of nutrients. For cassava plants there were determined, besides the allocation of dry matter, morphological and physiological characteristics related to leaf area. The leaf and stalk of corn were the main adversely affected organs by competition, while the roots of competing species were the most affected organs. In competition with the beans, leaves and stems of weeds were the most affected organs. With cassava, the weeds vegetative components suffered reduced modifications without losses in the production of dry matter. The roots of bean and cassava were the main adversely affected organs by competition. Genotypes AL 25 (maize) and IPR Colibri (beans) were the less tolerant in the competition. Conversely, the P?rola (beans) and Periquita (cassava) have showed the greatest competitive abilities. The corn was sensitive to competition with B. brizantha and C. benghalensis and competitive with B. plantaginea. This species, however, proved to be highly competitive with beans and cassava. Furthermore, A. spinosus, in competition with the bean, has demonstrated the greatest competitive ability. The competitive ability of plant species when it comes to the accumulation of dry matter and related nutrients did not represent the advantage to the weeds, where they were kept in close contact with the corn. The bean had low capacity to compete for nutrients, particularly N and P. The specific leaf area and leaf area ratio of cassava were not affected by competition. B. brizantha and C. echinatus, free of coexistence with the corn, had high potential to recycle nutrients.

Submitted by (edna.saturno@ufrpe.br) on 2017-05-17T15:31:54Z No. of bitstreams: 1 Marta Gerusa Soares da Silva.pdf: 1019521 bytes, checksum: dafe6a7ce15446dca593cbcc3e9179b2 (MD5) / Made available in DSpace on 2017-05-17T15:31:54Z (GMT). No. of bitstreams: 1 Marta Gerusa Soares da Silva.pdf: 1019521 bytes, checksum: dafe6a7ce15446dca593cbcc3e9179b2 (MD5) Previous issue date: 2010-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this study was to evaluate the dynamics of the association of „capim-de-raiz‟ (Chloris orthonoton Doell.) and „capim-milhã‟ [Brachiaria plantaginea (Link.) Hitchc.], concerning growth, persistence and production, as well to morphanatomically characterize the legume „orelha de onça‟ (Macroptilium martii Benth.). In order to evaluate the dynamics of the association „capim-de-raiz‟ and „capim-milhã‟, two experiments were carried out: I. Evaluation of deferred native pasture concerning botanical composition and forage mass; II. Growth dynamics of „capim-milhã‟ and „capim-de-raiz‟. Experiment I was conducted at the Experimental Station of IPA, in São Bento do Una - PE from 2007 to 2008 with different evaluation periods for forage mass and botanical composition. Experiment II was conducted at a greenhouse in the Animal Science Department - UFRPE, from 09.26.06 to 07.26.07. Soil blocks with the plant community were taken from native pasture area of the Experimental Station of Instituto Agronômico de Pernambuco - IPA, in São Bento do Una - PE, and placed in plastic pots remaining at a greenhouse in UFRPE. Pots were submitted to four irrigation schedules: Irrigation I - irrigation at the beginning of the experiment; Irrigation II - started two months after Irrigation I; Irrigation III - started four months after irrigation I and Irrigation IV - started six months after irrigation I. After the initial irrigation of each period, all pots were irrigated every seven days until drainage and regrowth number, seedling number, plant number and inflorescence number were evaluated. Morphanatomical characterization of „orelha de onça‟ leaf was analyzed with optical microscopy in cross-sections confectioned laminae. 10 families, 15 genera and 18 species were identified in the deferred pasture. In botanical composition from May to August 2007, „capim-milhã‟ was the main component from 60 to 90 days with 46.75 and 52.09%, respectively. In August 2007, other species participated with 57.75% of the botanical composition; at the end of evaluation in year 2008 other species occupied 100% of the composition. The highest forage mass (kg DM/ha) for „capim-milhã‟ (2.736) occurred at 90 days, for other species (3.141) and „capim-de-raiz‟ (2.701) at 120 days. In soil blocks it was observed that regrowth occurred only after 30 days of assessment for initial irrigation and the highest number of seedlings to the pots occurred at 30 days. It was observed at 60 days the largest number of grasses for irrigation III and at 90 days for irrigation IV, and that most of inflorescence appeared at 90 days. In deferred area the use of stockpiled forage should preferably take place from 60 to 90 days. The main form of establishment of „capim-de-raiz‟ was by germination and at 150 days it was observed population growth of other species. It was observed paracytic and amphistomatic stomata, simple and uniseriate hairs, palisade and spongy chlorophyll parenchyma in „orelha de onça‟ leaf blade. In stem vascular system it was observed a range of libero-ligneous beams in the internodes area, separating cortex of medulla. Foliar and stem anatomical characteristics are common to legumes. / O objetivo deste trabalho foi avaliar a dinâmica da associação capim-de-raiz (Chloris orthonoton Doell.) e capim-milhã [Brachiaria plantaginea (Link.) Hitchc.], quanto ao crescimento, persistência e produção, bem como caracterizar morfoanatomicamente a leguminosa orelha de onça (Macroptilium martii Benth.). Para avaliar a dinâmica da associação capim-de-raiz e capim-milhã, foram realizados dois experimentos: I. Avaliação de um pasto nativo diferido quanto à composição botânica e massa de forragem; II. Dinâmica do crescimento do capim-milhã e capim-de-raiz. O experimento I foi conduzido na Estação Experimental do IPA, no município de São Bento do Una - PE, de 2007 a 2008, sendo utilizados diferentes períodos para avaliação da massa de forragem e composição botânica. O experimento II foi realizado em telado no Departamento de Zootecnia - UFRPE, durante o período de 26.09.06 a 26.07.07. Cubos de solos com a comunidade vegetal foram retirados de área de pastagem nativa, da Estação Experimental do Instituto Agronômico de Pernambuco - IPA, no município de São Bento do Una - PE, e colocados em vasos plásticos permanecendo em telado da UFRPE. Os vasos foram submetidos a quatro épocas de início de irrigação: Irrigação I ¿ irrigação por ocasião da implantação do experimento; Irrigação II ¿ iniciada dois meses após a irrigação I; Irrigação III ¿ iniciada quatro meses após a irrigação I e Irrigação IV ¿ iniciada seis meses após a irrigação I. Após a irrigação inicial de cada período, todos os vasos foram irrigados a cada sete dias até drenagem e foram avaliados o número de rebrotes, número de plântulas, número de plantas e número de inflorescências. A caracterização morfoanatômica foliar da orelha de onça foi analisada em microscopia óptica em lâminas confeccionadas em secções transversais. Foram identificadas 10 famílias, 15 gêneros e 18 espécies no pasto diferido. Na composição botânica de maio a agosto de 2007, o capim-milhã foi o componente principal dos 60 aos 90 dias com 46,75 e 52,09%, respectivamente. Em agosto de 2007, outras espécies participaram com 57,75% da composição botânica; no ano de 2008 ao final da avaliação, outras espécies ocuparam 100% da composição. As maiores massas de forragem (kg de MS/ha) para o capim-milhã (2.736) foram aos 90 dias, e para outras espécies (3.141) e capim-de-raiz (2.701) aos 120 dias. Nos cubos de solo, observou-se que o rebrote ocorreu apenas aos 30 dias de avaliação para irrigação inicial e o maior número de plântulas para os vasos ocorreu aos 30 dias. Foi observado aos 60 dias o maior número de gramíneas para irrigação III e aos 90 dias para irrigação IV, e que a maioria das inflorescências surgiu aos 90 dias. Em área diferida, o aproveitamento da forragem acumulada deve ocorrer preferencialmente dos 60 aos 90 dias. A principal forma de estabelecimento foi por germinação de sementes e aos 150 dias observou-se crescimento populacional de outras espécies. Foram observados na lâmina foliar da orelha de onça estômatos paracíticos e anfiestomáticos, pelos simples e unisseriados, parênquima clorofiliano em paliçada e esponjoso. Nos sistemas vasculares do caule observou-se, nas áreas dos entrenós, uma faixa de feixes líbero-lenhosos separando o córtex da medula. As características anatômicas foliares e caulinares são comuns às leguminosas.

Les pucerons sont des ravageurs importants des principales espèces fruitières en France, pêcher et pommier notamment. Dans le but de réduire l’usage des produits phytosanitaires, différentes alternatives sont envisagées pour contrôler les pucerons en verger. Nous avons commencé ce travail de thèse par une synthèse des différentes méthodes alternatives de contrôle envisageables et leur positionnement au cours des différentes étapes du cycle biologique du puceron. Puis nous avons étudié les effets de la modulation des caractéristiques de la plante hôte, via les pratiques culturales, sur l’abondance des pucerons. Notre étude se base sur l’hypothèse « Plant Vigor » qui énonce que les insectes phytophages sont plus performants sur les plantes ou les organes de forte vigueur. Par conséquent, sur nos deux dispositifs expérimentaux factoriels nous avons combiné des suivis dynamiques de croissance végétative et d’abondance de pucerons : Prunus persica - Myzus persicae (2 niveaux d’irrigation × 2 niveaux d’apport azoté) et Malus domestica - Dysaphis plantaginea (2 niveaux d’irrigation × 2 génotypes d’arbre). Les facteurs ont été choisis pour leur impact potentiel sur la croissance végétative et la qualité nutritionnelle de la plante hôte. Les expérimentations ont été menées sur de jeunes arbres en pot, ne portant pas de fruit. Au niveau du rameau, l’abondance des pucerons est positivement corrélée à la croissance végétative sur les deux systèmes étudiés. Sur pêcher, la relation disponibilité en azote et abondance de pucerons semble être médiée par le fort impact de l’azote sur la croissance végétative. L’effet négatif de la restriction hydrique sur l’abondance de pucerons ne semble pas lié à un impact sur la croissance végétative. Aussi sur le second système étudié : pommier-puceron cendré, nous avons choisi de faire varier les apports en eau et de travailler sur deux génotypes, pour tester la généricité de la réponse observée. A l’échelle du rameau, l’effet de la restriction hydrique sur l’abondance de pucerons est négatif pour un génotype et positif pour l’autre. Par contre à l’échelle de l’arbre, sur les deux génotypes l’abondance de pucerons est corrélée positivement à la croissance végétative et la restriction hydrique impacte négativement l’abondance de pucerons, ce qui suggère que la performance des pucerons est limitée sur les arbres en restriction hydrique par une autre composante que la vigueur de l’arbre. Ce travail de thèse montre que la restriction hydrique et le contrôle de la vigueur via les apports azotés peuvent s’avérer être des leviers pour le contrôle des pucerons en verger fruitier. Cependant les relations mises en évidence sont dépendantes du génotype, ainsi que de l’échelle d’analyse. Il reste à évaluer l’applicabilité de telles mesures sur des arbres en conditions de production, en prenant en compte notamment l’effet des restrictions hydrique et azotée sur la production fruitière. / Aphids are major pests of important fruit trees in France, especially peach and appletrees. In order to reduce chemical use, various alternatives can be implemented for themanagement of aphids in orchards. This thesis starts by a review of the different alternativemanagement methods and their positioning at different aphid life cycle stages. Then our workfocuses on the study of the effects of modulation of host plant characteristics, through culturalpractices, on aphid abundance. Our study is based on the Plant Vigor Hypothesis which statesthat phytophagous insects are more performant on vigorous plant or organ. Thus, in theexperimental part we combined dynamic assessment of vegetative growth and aphid abundanceduring two factorial experiments: Prunus persica – Myzus persicae (2 levels of water supply ×2 levels of nitrogen supply) and Malus domestica – Dysaphis plantaginea (2 levels of watersupply × 2 tree genotypes). We chose those factors for their possible impact on vegetativegrowth and nutritional quality of the host plant. We conducted the experiments on young nonbearingpotted trees. At shoot scale, aphid abundance is positively correlated to vegetativegrowth for both studied systems. On peach tree, the positive impact of nitrogen availability onaphid abundance seems to be mediated by the strong positive impact of nitrogen on vegetativegrowth. The negative effect of water restriction on aphid abundance seems to be unrelated toan impact of water availability on vegetative growth. Thus on the second studied system: appletree – rosy apple aphid, we chose to vary water supply and to work on two genotypes to test thegenericity of the observed pattern. At shoot scale, water restriction has a positive effect on aphidabundance on one tree genotype and a negative effect on the other one, whereas at tree scalefor both tree genotypes aphid abundance is positively correlated to vegetative growth and waterrestriction negatively impacts aphid abundance. These results suggest that aphid performanceon water restricted trees is limited by another host plant characteristics than vegetative growth.This thesis shows that water restriction and vigour management through nitrogen fertilizationcan be implemented to manage aphids in fruit orchards. However, the patterns evidenced aredependent on tree genotype and on the scale of analysis. The applicability of these alternativemethods remains to be assessed in producing orchards, taking into account the effects of waterand nitrogen restrictions on fruit production.