Augmenter la diversité végétale au sein même du champ permet de réguler les populations de ravageurs dans de nombreux agroécosystèmes. Les mélanges variétaux (diversité intraspécifique) ou les associations de cultures avec une plante compagne (diversité interspécifique) sont considérées comme des pratiques agroécologiques prometteuses pour les systèmes de culture à bas intrants ou l'agriculture biologique. En effet, ces pratiques favorisent de nombreux services écosystémiques tels que la régulation des ravageurs, des maladies ou des adventices, ainsi que la fertilisation azotée. Cependant, le potentiel de régulation des ravageurs du blé par la combinaison de ces deux pratiques de diversification n'a pas encore été étudié.Nous avons combiné ces deux pratiques dans le cadre d'expérimentations menées en plein champ et sur deux saisons de culture, afin d'examiner leurs impacts sur les populations de pucerons et d'ennemis naturels. Nous avons également évalué le potentiel de régulation des ravageurs en mesurant les taux de prédation de proies sentinelles.La combinaison des diversités intra- et interspécifique n'est pas plus performante pour réduire les populations de pucerons que les pratiques prises séparément. L'association de culture blé-trèfle tend à être moins infestée par les pucerons, tandis que le mélange variétal est plus infesté que la variété la moins sensible. Les variations annuelles des conditions climatiques impactent fortement le développement du blé et du trèfle, ainsi que la date d'apparition du pic de puceron. Le rendement du blé, ainsi que le taux d'azote du grain sont réduits par l'association de culture par 7 à 10%, mais pas par le mélange variétal. La présence d'un couvert de trèfle dans les champs de blé, semble avoir favorisé la biodiversité fonctionnelle, particulièrement les ennemis naturels tels que les carabes, mais pas le mélange variétal. Les résultats sont variables selon la famille d'arthropodes concernée et leur position au sein du couvert végétal (au sol ou dans le feuillage). Le couvert de trèfle et le champ ont influencé la composition de la communauté de carabes prédateurs. Les taux de prédation des proies sentinelles n'ont pas été impactés par les pratiques de diversifications.En laboratoire, nous avons évalué comment l'association du blé avec des légumineuses (trèfle ou pois) pouvait modifier le comportement du puceron du blé Sitobion avenae en terme de location de sa plante hôte et du développement de la population. Les pucerons ont résidé moins de temps sur le blé quand il était associé à du trèfle. Les populations de pucerons se sont moins développées dans les associations du blé avec une légumineuse par rapport à du blé seul, mais si l'on prend en compte la biomasse du blé, seulement l'association blé-trèfle a considérablement réduit les densités de pucerons sur le blé. Ainsi l'espèce associée et sa densité sont des paramètres importants qui devraient être pris en compte dans les études sur la diversité interspécifique, car ils pourraient expliquer la grande variation dans les résultats rapportés par les analyses bibliographiques.Nos résultats suggèrent qu'augmenter la diversité cultivée au sein du champ peut aider à réguler les pucerons dans une certaine mesure, mais la combinaison des deux pratiques de diversification ne résultent pas en un trade-off entre la régulation des ravageurs et les performances agronomiques particulièrement attractifs pour les agriculteurs. / Increasing intrafield plant diversity has been shown to regulate pest populations in various agroecosystems. Polyvarietal mixtures of a crop species (intraspecific diversity) or associations of a crop and a companion plant (interspecific diversity) are both considered as promising agroecological practices for low-input or organic agriculture systems by providing several ecosystem services such as pest, disease and weed control, and nitrogen fertilization. However, combining both diversification practices has not been studied yet in perspective of winter wheat pest control.In organic field experiments over two growing seasons, we combined both practices and examined the direct impact on aphid and natural enemy populations and on wheat production. We also investigated the potential pest regulation service through the assessment of the rate of predation by using sentinel preys.Results show that combining intra- and interspecific diversity did not outperform each practice individually in reducing aphid populations, thus not clearly showing synergetic effects. Taken separately, intercropping tended to have lower aphid infestation, while it the cultivar mixtures was more infested by aphids than the least susceptible cultivar. Yearly variation in climatic conditions strongly impacted wheat and clover development, as well as the appearance of aphid peaks. Wheat yields and grain nitrogen content were reduced in intercropping by 7 to 10%, but not in cultivar mixtures. Functional biodiversity, especially natural enemies such as ground beetles, tended to be positively correlated to the presence of a clover cover in the wheat fields (interspecific diversification), but did not respond to the wheat cultivar mixture (intraspecific diversification). Results varied according to the family of arthropods concerned and their position within the vegetation layer (ground dwelling or foliage dwelling arthropods). The cover of white clover and the field context influenced the community composition of predatory ground dwelling beetles. Rates of predation on sentinel preys were not influenced by any of the diversification practices.Under laboratory conditions, we evaluated how combining wheat and legumes (clover or pea) modifies the behaviour of the cereal aphid Sitobion avenae in terms of host-plant location, and population growth. We observed that aphids’ residence time on wheat was decreased when this host-plant was intercropped with clover. At the population level, wheat-legume intercrops reduced the number of aphids on wheat plants compared to wheat sole crops but if we take into account plant biomass, only intercropping clover with wheat significantly reduced aphid densities on wheat. The species used as non-host plants and their density are important parameters that should be taken into account in studies on intercropping systems and that may explain the large variability in the results observed in the literature.Our findings suggest that intrafield diversification may regulate wheat aphids to some extent, but combining the two diversification practices did not result in an interesting trade-off between pest regulation and wheat production in real farming conditions.

Made available in DSpace on 2016-04-28T14:57:34Z (GMT). No. of bitstreams: 1 2008 - Alice Teodorio Lixa.pdf: 2009465 bytes, checksum: a5ff9f635d75eab4106b026e084105fb (MD5) Previous issue date: 2008-06-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Among the natural enemies of agriculture pests, the Coccinellidae predators are detached. Some coccinellids only complete their development and produce viable eggs and progenies when they consume their preferred prey. However, when this prey is scarce or in presence of a prey of low quality, certain coccinellids feed on alternative food resources, such as extra floral nectar and pollen, to guarantee their survivorship. Thus, the absence of these floral resources limits the occurrence and abundance of ladybeetles in the agroecosystems. Due to these characteristics, the coccinellids have great potential for being managed by the three strategies of biological control: classic, augmentative and conservation. However, to use the coccinellids as biological control agent, more information about their biology and ecology are still necessary. In this context, the present work was conducted with the general objective of producing information about ecological and biological aspects of the Coccinellidae. These approaches are in the Chapters I and II, respectively. In the Chapter I, the studies aimed to determine if Anethum graveolens (dill), Coriandrum sativum (coriander) and Foeniculum vulgare (sweet fennel) favor the abundance of Coccinellidae; to evaluate the potential of these aromatic plants to provide vital resources for these predators; to determine the species diversity of these insects attracted by these plants; and to characterize their community structure. The experiment was carried out in an integrated crop-livestock organic production area (Seropedica/RJ, Brazil) in a completely randomized design with three treatments (aromatic plants) and three replicates. From September 14th, 2007 to January 21st, 2008, samplings of adults and immature stages of ladybeetles were realized. Besides an unidentified species of Chilocorini, Coleomegilla maculata, Coleomegilla quadrifasciata, Cycloneda sanguinea, Eriopis connexa, Harmonia axyridis, Olla v-nigrum and Hippodamia convergens were collected. The dill provided significant increase in the abundance of coccinellids in relation to the coriander and sweet fennel. These three aromatic vegetal species were used as ovipositon sites and shelter for immature forms and adults of ladybeetles. The dill and sweet fennel were also used as mating sites and proved food resources (pollen and/or alternative prey). The principal species visiting these aromatic plants were C. sanguinea, H. convergens, and E. connexa (more frequent, constant and dominant). In the Chapter II, the studies aimed to determine biology aspects of Coleomegilla maculata and Eriopis connexa feed on two diets: ultraviolet-unviable and frozen eggs of Anagasta kuehniella (Lepidoptera: Pyralidae) and the alive aphids of Lipaphis erysimi (Hemiptera: Aphididae) under laboratory condition (25 ? 1?C, relative humidity of 70 ? 10%, and photophase of 12 hours). The experimental design was complete randomized in a 2x2 split-plot arrangement (two ladybeetle species and two diets). In general, the biological characteristics of C. maculata and E. connexa were similar, when their larvae and adults fed on the two diets. Both diets were suitable for C. maculata and E. connexa, keeping their development and oviposition for a generation, and the eggs of A. kuehniella still maintained the rearing of these ladybeetles for one more generation. / Entre os inimigos naturais de pragas agr?colas, destacam-se os Coccinellidae predadores. Alguns coccinel?deos s? completam seu desenvolvimento e produzem ovos e prog?nie vi?vel quando consomem sua presa preferencial. Todavia, quando esta presa est? escassa ou na presen?a de uma presa de qualidade inferior, certos coccinel?deos alimentam-se de alimentos alternativos, tais como n?ctar extrafloral e p?len, para garantir sua sobreviv?ncia. Desse modo, a aus?ncia desses recursos florais limita a ocorr?ncia e abund?ncia de joaninhas nos agroecossistemas. Devido essas caracter?sticas, os coccinel?deos apresentam grande potencial para serem manejados por meio do controle biol?gico cl?ssico, aumentativo e conservativo. Todavia, para usar os coccinel?deos como agente de controle biol?gico, mais informa??es sobre sua biologia e ecologia s?o ainda necess?rias. Neste contexto, o presente trabalho foi realizado com o objetivo geral de gerar informa??es sobre aspectos ecol?gicos e biol?gicos dos Coccinellidae, sendo esses temas abordados nos Cap?tulos I e II, respectivamente. No cap?tulo I, os estudos foram conduzidos com os seguintes objetivos: determinar se Anethum graveolens (endro), Coriandrum sativum (coentro) e Foeniculum vulgare (erva-doce) favorecem a abund?ncia de Coccinellidae; avaliar o potencial dessas esp?cies arom?ticas como provedoras de recursos vitais para esses predadores; determinar a diversidade de esp?cies desses insetos atra?dos por essas plantas; e caracterizar a estrutura de sua comunidade. O experimento foi conduzido em ?rea de produ??o org?nica integrada animalvegetal (Serop?dica/RJ), em delineamento de blocos casualizados, com tr?s tratamentos (esp?cies arom?ticas) e tr?s repeti??es. De 14 de setembro de 2007 a 21 de janeiro de 2008, foram realizadas amostragens de adultos e formas imaturas de joaninhas. Al?m de uma esp?cie n?o identificada da tribo Chilocorini, coletou-se Coleomegilla maculata, Coleomegilla quadrifasciata, Cycloneda sanguinea, Eriopis connexa, Harmonia axyridis, Olla v-nigrum e Hippodamia convergens. O endro proporcionou aumento significativo na abund?ncia de coccinel?deos em compara??o ao coentro e ? erva-doce. Essas tr?s esp?cies arom?ticas foram usadas como s?tios de oviposi??o e abrigo para formas imaturas e adultas de joaninhas. O endro e a erva-doce tamb?m foram utilizados como s?tios de acasalamento e de alimenta??o pelas joaninhas. As principais esp?cies visitantes das arom?ticas foram C. sanguinea, H. convergens e E. connexa (mais freq?entes, constantes e dominantes). No cap?tulo II, os estudos foram conduzidos com os seguintes objetivos: 1) determinar aspectos biol?gicos de C. maculata e E. connexa alimentadas com duas dietas: ovos de Anagasta kuehniella (Lepidoptera: Pyralidae) inviabilizados com ultravioleta e congelados e pulg?es vivos de Lipaphis erysimi (Hemiptera: Aphididae), em condi??es de laborat?rio (25?1?C, 70?10% UR e fotofase de 12 horas). O delineamento foi inteiramente casualizado em arranjo fatorial 2 x 2 (duas esp?cies de joaninhas e duas dietas). No geral, as caracter?sticas biol?gicas de C. maculata e E. connexa foram bem semelhantes, quando suas larvas e adultos se alimentaram das duas dietas. Ambas as dietas foram adequadas para C. maculata e E. connexa, assegurando seu desenvolvimento e oviposi??o por uma gera??o e os ovos de A. kuehniella permitiram ainda manter a cria??o dessas joaninhas por mais uma gera??o.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-09-26T12:19:08Z No. of bitstreams: 1 2013 - Alice Teodorio Lixa.pdf: 7684993 bytes, checksum: f6675b748532a5b5835d14d6a4480870 (MD5) / Made available in DSpace on 2018-09-26T12:19:08Z (GMT). No. of bitstreams: 1 2013 - Alice Teodorio Lixa.pdf: 7684993 bytes, checksum: f6675b748532a5b5835d14d6a4480870 (MD5) Previous issue date: 2013-02-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Coccinellid predators are natural enemies of agricultural pests such as aphids and scale insects. They are known colloquially as ladybirds, ladybugs or lady beetles. Some species only complete their development and produce viable eggs and offspring when they consume their preferred prey. However, in the absence of this prey, or in presence with lower nutritional quality prey, the ladybugs tend to consume alternative foods, such as pollen and nectar, to ensure their survival. Thus, the choice and maintenance of useful floral resources to ladybugs in agroecosystems is a strategy favorable to the conservation of natural enemy populations in the production environment. Another line is the use of pesticides that cause fewer negative impacts on natural enemies of pests. This study worked on these two fronts, seeking to know floral species beneficial in situ conservation of biodiversity of ladybugs, and to evaluable the impact of pesticides used in organic agriculture on these insects. The thesis is organized in three chapters. Chapter I aimed to identify plant families and/or plant species are natural sources of pollen grains for predatory ladybug adults in diversified organic system. Adults were collected from 26 August 2010 to 22 August 2011, at area of Integrated Agroecological Production System (IAPS), in Serop?dica, RJ, Brazil. Baker's legs and wings have been removed to avoid contamination with pollen attached to the outside of the insects, the remainder of the body subjected to acetolysis analysis, aiming at the identification of pollen possibly ingested. We identified pollen from different plant species: star fruit (Averrhoa carambola, Oxalidaceae), coriander (Coriandrum sativum, Apiaceae), sunflower (Helianthus annuus, Asteraceae), maize (Zea mays, Poaceae), elderberry (Sambucus nigra, Adoxaceae), and different families: coming from Amaranthaceae, Asteraceae, Fabaceae, Malvaceae, Myrtaceae, and Passifloraceae. Pollens were found in seven species of ladybugs. Just Cycloneda sanguinea ingested pollen of all these families, and pollen unidentified families. Chapter II aimed to determine the diversity of adult ladybugs community in the area of IAPS, and characterize the population structure by faunistic indexes. Species richness was equal to seven [Cycloneda sanguinea, Hippodamia convergens, Coleomegilla maculate, Coleomegilla quadrifasciata, Eriopis connexa, Harmonia axyridis, and Olla v-nigrum]. C. sanguinea, H. convergens, and C. maculata were classified as dominant, being the first constant and others accessories. In Chapter III, the studies were conducted with C. maculata at laboratory conditions, with the objective of evaluating the effect of different concentrations of alternative pesticides used in organic agriculture (Natuneem?, Nim-I-Go?, Rotenat?, Lime sulfur, and Agrobio?) on biological aspects of this insect. The two neem based products (Natuneem and Nim-I-Go) to 2 % and the ?timb?? based product (Rotenat) 1% and 2 % decreased egg viability of C. maculata. Nim-I-Go at concentrations of 1% and 2% caused higher mortality than the control treatment (water) in all larval instars. Except Agrobio, all pesticides adversely affected the reproduction of C. maculata. The neem based products should be used sparingly to avoid negative effects on the development of C. maculata. / Dentre os inimigos naturais das pragas agr?colas, destacam-se os coccinel?deos predadores, tamb?m conhecidos como joaninhas. Algumas esp?cies s? completam seu desenvolvimento e produzem ovos e prog?nies vi?veis quando consomem sua presa preferencial. Todavia, na aus?ncia dessa presa ou na presen?a de uma presa com qualidade nutricional inferior, as joaninhas tendem a consumir alimentos alternativos, tais como p?len e n?ctar, para garantir sua sobreviv?ncia. Desse modo, a escolha e a manuten??o de recursos florais ?teis ?s joaninhas no agroecossistema ? uma estrat?gia favor?vel ? conserva??o de popula??es dos inimigos naturais no ambiente de produ??o. Outra linha ? o uso de defensivos que causem menos impactos negativos aos inimigos naturais das pragas. O presente trabalho atuou nessas duas frentes, buscando conhecer esp?cies florais ben?ficas a conserva??o in situ da biodiversidade das joaninhas e defensivos agr?colas, usados na agricultura org?nica, menos danosos a esses insetos. A tese foi organizada em tr?s cap?tulos. No Cap?tulo I objetivou-se identificar, em sistema org?nico diversificado, quais fam?lias e/ou esp?cies bot?nicas s?o fontes naturais de gr?os de p?len para adultos de joaninhas predadoras. Os adultos foram coletados de 26 de agosto de 2010 a 22 de agosto de 2011, em ?rea do Sistema Integrado de Produ??o Agroecol?gica (SIPA), em Serop?dica, RJ. Asas e pernas das joaninhas foram retiradas a fim de evitar contamina??es por polens presos ? parte externa dos insetos, sendo o restante do corpo submetido ? an?lise de acet?lise, objetivando a identifica??o dos polens possivelmente ingeridos. Foram identificados polens de diferentes esp?cies bot?nicas: carambola (Averrhoa carambola, Oxalidaceae), coentro (Coriandrum sativum, Apiaceae), girassol (Helianthus annuus, Asteraceae), milho (Zea mays, Poaceae), sabugueiro (Sambucus nigra, Adoxaceae); e de diferentes fam?lias: oriundos de Amaranthaceae, Asteraceae, Fabaceae, Malvaceae, Myrtaceae e Passifloraceae. Os polens foram encontrados em sete esp?cies de joaninhas afid?fagas. Apenas a Cycloneda sanguinea ingeriu p?len de todas essas fam?lias, al?m de polens de fam?lias n?o identificadas. No Cap?tulo II, objetivou-se determinar a diversidade comunidade de joaninhas adultas, em ?rea do SIPA, e caracterizar a estrutura das popula??es por meio da an?lise faun?stica. A riqueza de esp?cies foi igual a sete [Cycloneda sanguinea, Hippodamia convergens, Coleomegilla maculata, Coleomegilla quadrifasciata, Eriopis connexa, Harmonia axyridis e Olla v-nigrum]. C. sangu?nea, H. convergens e C. maculata foram classificadas como dominantes, sendo a primeira constante e as demais acess?rias. No Cap?tulo III, os estudos foram conduzidos com C. maculata, em condi??es de laborat?rio, com o objetivo de avaliar o efeito de diferentes concentra??es de produtos fitossanit?rios alternativos usados em agricultura org?nica (Natuneem?, Nim-I-Go?, Rotenat?, Calda sulfoc?lcica e Agrobio?), sobre aspectos biol?gicos desse inseto. Os dois produtos ? base de nim (Natuneem e Nim-I-Go) a 2% e o produto ? base de timb? (Rotenat) a 1% e 2% diminu?ram a viabilidade dos ovos de C. maculata. Nim-I-Go nas concentra??es de 1% e 2% causou maior mortalidade do que o tratamento controle (?gua) em todos os instares larvais. Com exce??o do Agrobio todos os produtos fitossanit?rios influenciaram negativamente a reprodu??o de C. maculata. Os produtos ? base de nim devem ser utilizados com parcim?nia para evitar efeitos negativos ao desenvolvimento de C. maculata.

Organic mulches and cover crops mulched in situ were assessed for their effects on B. cinerea primary inoculum and disease levels in inflorescences at flowering and/or bunches at harvest. Organic mulches were used to enhance biological degradation of vine debris to reduce levels of B. cinerea primary inoculum the following season. Four mulch types (anaerobically and aerobically fermented marc (grape pressings), inter-row grass clippings and shredded office paper) were applied under ten-year-old Riesling vines in a ten-replicate randomized block design in New Zealand over two consecutive years. Plastic mesh bags, each containing naturally infected vine debris, were placed under vines on bare ground (control) and at the soil-mulch interface, in winter (July) 2003 and 2004. In each year, half the bags were recovered at flowering (December) and the remainder at leaf plucking (February), for assessment of B. cinerea sporulation from the vine debris and debris degradation rate. Bait lamina probes, which measure soil biological activity, were placed in the soil-mulch interface three weeks before each of the two bag-recovery dates in both years and were then removed and assessed at the same times as were the bags. All mulches led to a reduction in B. cinerea sporulation. This reduction was significantly correlated with elevated rates of vine debris decomposition and increased soil biological activity. Over both years, compared with the controls, all treatments gave a 3-20-fold reduction in B. cinerea sporulation, a 1.6-2.6-fold increase in vine debris degradation and in the two marc and the paper treatments, a 1.8-4-fold increase in activity of soil organisms. The mulches also altered vine characteristics and elevated their resistance to B. cinerea through changes to the soil environment. Functional soil biological activity, as measured by Biolog Ecoplates and bait lamina probes, was increased 2-4 times in the two marc and paper treatments, compared with the control, an effect relating to the elevated soil moisture and reduced temperature fluctuations under these mulches. Soil nutrient levels and the C:N ratios were also affected in these treatments. The mulched paper lowered vine canopy density by up to 1.4 times that of the other treatments, an effect which probably led to elevated light penetration into the canopy and consequent increased canopy temperature, photosynthesis and lowered canopy humidity. These changes to soil and vine characteristics increased grape skin strength by up to 10% in the paper treatment and sugar concentrations by 1.2-1.4 °Brix in the two marc and paper treatments. The severity of B. cinerea infections in the anaerobic marc, aerobic marc and paper treatments were reduced to 12%, 3% and 2.2% of the control, respectively, in field assessments averaged over two consecutive harvests. Cover crops mulched in situ had similar effects to those of the organic mulches, increasing soil biological activity and reducing B. cinerea primary inoculum and the severity of B. cinerea infection in grapes at harvest (2006). Inter-row phacelia and ryegrass were mulched in winter 2005 and compared with a bare ground control, under 10-year-old Chardonnay vines in a ten-replicate randomized block design. Functional soil biological activity increased by 1.5-4.5 times in the two cover crop treatments compared with the control, an effect possibly related to elevated soil moisture in these treatments. This increase in soil moisture and soil biological activity increased vine debris degradation, reduced B. cinerea primary inoculum on the debris and decreased B. cinerea severity at flowering (December 2005) and harvest (April 2006). These results show the potential of organic mulches and cover crops mulched in situ to enhance soil ecosystem services and improve the sustainability of viticultural practices.

Experiments were conducted to assess whether a concept termed 'attract and reward' (A&R) could enhance conservation biological control (CBC). In A&R, a synthetically-produced herbivore induced plant volatile (HIPV) ('attract') is combined with a floral resource ('reward'). It is anticipated that the two will work synergistically attracting natural enemies into the crop ('attract') and maintaining them within the crop ('reward'). The study system consists of brassica, the most commonly occurring brassica herbivores, their natural enemies and higher order natural enemies. The HIPV deployed is methyl salicylate (MeSA) and the floral resource is buckwheat Fagopyrum esculentum. The aim of the first two field experiments, in 2007 and 2008, was to evaluate the effects of MeSA and MeSA combined with buckwheat (A&R) on the abundance of arthropods from three trophic levels. In 2007, a field experiment was conducted using MeSA alone. The mean abundance of the leafmining fly Scaptomyza flava (trophic level 2), the diamondback moth (trophic level 2)(DBM) parasitoid Diadegma semiclausum (trophic level 2) and the hoverfly Melangyna novaezealandiae (trophic level 3) was increased in MeSA-treatments by up to 300% and for the brown lacewing parasitoid Anacharis zealandica a maximum mean increase of 600% was recorded. Significantly more females of the D. semiclausum and M. novaezealandiae were attracted to MeSA than males. When A&R was deployed in 2008, were arthropods from the third and fourth trophic levels affected. For none of the species was there a synergistic effect between 'attract' and 'reward' on their abundance. The brown lacewing Micromus tasmaniae (trophic level 3), two parasitoids of DBM and one of cabbage white butterfly Pieris rapae (trophic level 2) increased significantly in treatments with buckwheat. The hoverfly Melanostoma fasciatum (trophic level 3) was significantly more abundant in treatments with MeSA, but significantly less abundant in treatments with buckwheat. The effect of MeSA on the fourth trophic level parasitoid Anacharis zealandica (trophic level 4) was inconsistent between years. Here it significantly decreased its abundance, while treatments with buckwheat increased it. Significantly fewer male than female D. semiclausum were attracted to MeSA only treatments. These experiments show that MeSA and buckwheat can have unwanted effects on arthropod abundance which may disrupt CBC. To assess the effect of A&R on CBC a further field experiment evaluating herbivore densities, predation, parasitism and hyper-parasitism rates was conducted. The only effect was significantly higher aphid parasitism in treatments with MeSA. Based on the results from the field experiments it remained unclear whether it was MeSA or a blend of volatiles produced by MeSA-induced host plants that were attractive to the arthropods. An olfactory experiment was conducted to evaluate if the aphid parasitoid Aphidius colemani can be attracted to two different concentrations of MeSA diluted in Synertrol oil. Significantly more parasitoids were attracted to 2.0% MeSA than to air while the parasitoid did not respond to the 0.5% concentration. These results indicate that A&R has potential as a CBC technique, as long as any unwanted side effects can be managed. Although there were no synergistic effects between 'attract' and 'reward' on the abundance of individual natural enemies, combining MeSA and buckwheat could still be beneficial because the two techniques increase the abundance of different natural enemies.

Experiments were conducted to assess whether a concept termed 'attract and reward' (A&R) could enhance conservation biological control (CBC). In A&R, a synthetically-produced herbivore induced plant volatile (HIPV) ('attract') is combined with a floral resource ('reward'). It is anticipated that the two will work synergistically attracting natural enemies into the crop ('attract') and maintaining them within the crop ('reward'). The study system consists of brassica, the most commonly occurring brassica herbivores, their natural enemies and higher order natural enemies. The HIPV deployed is methyl salicylate (MeSA) and the floral resource is buckwheat Fagopyrum esculentum. The aim of the first two field experiments, in 2007 and 2008, was to evaluate the effects of MeSA and MeSA combined with buckwheat (A&R) on the abundance of arthropods from three trophic levels. In 2007, a field experiment was conducted using MeSA alone. The mean abundance of the leafmining fly Scaptomyza flava (trophic level 2), the diamondback moth (trophic level 2)(DBM) parasitoid Diadegma semiclausum (trophic level 2) and the hoverfly Melangyna novaezealandiae (trophic level 3) was increased in MeSA-treatments by up to 300% and for the brown lacewing parasitoid Anacharis zealandica a maximum mean increase of 600% was recorded. Significantly more females of the D. semiclausum and M. novaezealandiae were attracted to MeSA than males. When A&R was deployed in 2008, were arthropods from the third and fourth trophic levels affected. For none of the species was there a synergistic effect between 'attract' and 'reward' on their abundance. The brown lacewing Micromus tasmaniae (trophic level 3), two parasitoids of DBM and one of cabbage white butterfly Pieris rapae (trophic level 2) increased significantly in treatments with buckwheat. The hoverfly Melanostoma fasciatum (trophic level 3) was significantly more abundant in treatments with MeSA, but significantly less abundant in treatments with buckwheat. The effect of MeSA on the fourth trophic level parasitoid Anacharis zealandica (trophic level 4) was inconsistent between years. Here it significantly decreased its abundance, while treatments with buckwheat increased it. Significantly fewer male than female D. semiclausum were attracted to MeSA only treatments. These experiments show that MeSA and buckwheat can have unwanted effects on arthropod abundance which may disrupt CBC. To assess the effect of A&R on CBC a further field experiment evaluating herbivore densities, predation, parasitism and hyper-parasitism rates was conducted. The only effect was significantly higher aphid parasitism in treatments with MeSA. Based on the results from the field experiments it remained unclear whether it was MeSA or a blend of volatiles produced by MeSA-induced host plants that were attractive to the arthropods. An olfactory experiment was conducted to evaluate if the aphid parasitoid Aphidius colemani can be attracted to two different concentrations of MeSA diluted in Synertrol oil. Significantly more parasitoids were attracted to 2.0% MeSA than to air while the parasitoid did not respond to the 0.5% concentration. These results indicate that A&R has potential as a CBC technique, as long as any unwanted side effects can be managed. Although there were no synergistic effects between 'attract' and 'reward' on the abundance of individual natural enemies, combining MeSA and buckwheat could still be beneficial because the two techniques increase the abundance of different natural enemies.

La lutte biologique par conservation des habitats est une voie pour réduire la dépendance et l’impact des traitements insecticides qui sont nombreux et toxiques. Elle est particulièrement appropriée pour les vergers d’agrumes qui comprennent, souvent, de grandes surfaces non cultivées. Les auxiliaires présents en plus grand nombre dans un enherbement sont alors plus facilement mobilisables lors d’attaques massives de ravageurs sur les arbres. Ce travail de thèse a pour objectif d’évaluer l’impact des modes de gestion de l’enherbement (fauche, broyage, travail du sol et herbicide) sur les communautés végétales et les populations d’auxiliaires au sein du verger, en s’intéressant à deux communautés évoluant à deux échelles spatiales distinctes : les Phytoseiidae et les Coccinellidae. Nos résultats ont montré une différenciation fonctionnelle des communautés végétales soumises à différents modes de gestion dans le temps. Les Phytoseiidae sont présents en abondances comparables dans toutes ces communautés végétales mais sont cependant influencés par l’abondance dans le couvert des espèces végétales portant des densités de trichomes modérés et des domaties. De même, les abondances de Coccinellidae sont positivement corrélées à l’abondance des Poaceae sur la parcelle alors que les modalités de gestion de l’enherbement testées n’ont pas montré d’effet significatif. Ces connaissances ont pu être mobilisées et articulées pour l’élaboration d’un prototype d’outil d’aide à la décision contribuant à la conception de vergers agroécologiques. Il permet l’évaluation ex ante de scénarios de pratiques de gestion de l’enherbement en vue d’optimiser la lutte biologique par conservation au sein des vergers d’agrumes. Nous avons choisi une approche fonctionnelle qui permettra de généraliser facilement l’outil à d’autres cultures moyennant un élargissement de la base de données comportant les traits fonctionnels aux espèces végétales non renseignées et une bonne connaissance des affinités des auxiliaires que l’on cherche à favoriser / Biological control through habitat conservation is a way to reduce the reliance on and the impact of insecticide treatments that are numerous and toxic. It is particularly suitable for citrus orchards which include large areas often uncultivated. The natural enemies present in greater number in a vegetal cover are then more easily mobilized during massive attacks of pests on trees. The aim of this thesis is to evaluate the impact of different weed management methods (mowing, milling, tillage and herbicide) on plant communities and natural enemies populations within the orchard, focusing on two communities that evolve at two distinct spatial scales: the Phytoseiidae and the Coccinellidae. Our results showed a functional differentiation of vegetal communities managed with different weed management methods over time. Phytoseiidae are present in comparable abundances in all these plant communities but are influenced by the abundance of plant species with densities of moderate trichomes and domaties in the vegetal cover. Similarly, the abundances of Coccinellidae are positively correlated with the abundance of Poaceae species on the plot whereas the weed management modalities have no significant impact. This knowledge has been mobilized and articulated for the development of a decision-making tool prototype contributing to the design of agro-ecological orchards. It allows ex ante evaluation of scenarios of weed management practices in order to optimize biological control by conservation in citrus orchards. We have chosen a functional approach which will easily allow to generalize the tool to other crops by expanding the database with functional traits to non-informed plant species and a good knowledge of the affinities of natural enemies to promote

Dans un contexte de réduction de la pression phytosanitaire sur les cultures il est importantde recourir à des méthodes permettant de réduire l’usage des pesticides pour lutter contreles ravageurs. Un des moyens consiste à réguler les ravageurs par leurs ennemis naturels(Lutte biologique par conservation). Le carpocapse du pommier, Cydia pomonella, est unravageur majeur des vergers de pommiers au Sud Est de la France. L’objectif de cette thèseétait de définir les déterminants du parasitisme larvaire de ce ravageur. Nous avonscaractérisé la composition de la communauté des parasitoïdes sur les larves diapausantes etde saison du carpocapse. Cette communauté est majoritairement représentée par troisespèces d’hyménoptères : Ascogaster quadridentata, Pristomerus vulnerator (parasitoïdesprimaires) et Perilampus trisits (parasitoïde secondaire d’A. quadridentata et de P.vulnerator) dans les zones étudiées. Nous avons déterminé les caractéristiques des pratiquesagricoles et des éléments semi-naturels au niveau du verger et du paysage qui affectent letaux de parasitisme et la composition de la communauté de parasitoïdes pour des larvesdiapausantes du carpocapse. Les haies brise-vent et les haies composites autour du vergersemblent jouer sur la composition de la communauté en favorisant par leur présence lesparasitoïdes primaires A. quadridentata et P. vulnerator par rapport au parasitoïdesecondaire P. tristis. La protection phytosanitaire au niveau du verger et du paysageenvironnant a un effet sur le taux de parasitisme. Le taux de parasitisme est plus élevé dansles vergers en agriculture biologique que dans les vergers conventionnels ainsi que dans lesvergers entourés d’une faible proportion de vergers conventionnels dans un voisinage de250 m. Nous avons étudié les dynamiques temporelles de la communauté des parasitoïdesdu carpocapse. Le taux de parasitisme a globalement augmenté au cours de la saison dedéveloppement du carpocapse et il est plus élevé lorsque l’on piège de jeunes larves dans lesfruits que des larves âgées dans les bandes cartonnées enroulées autour des troncs. Lacomposition de la communauté varie au cours du temps. La proportion relative duparasitoïde secondaire P. tristis augmente au cours de la saison en parallèle d’unediminution de la proportion relative d’A. quadridentata. Les émergences des adultes A.quadridentata sont de plus synchronisées avec celles des adultes carpocapses. Enfin, nousavons développé et testé une méthode de PCR-RFLP et des marqueurs ADN spécifiques pourdétecter et identifier les parasitoïdes du carpocapse. La PCR-RFLP permet d’identifier lesparasitoïdes adultes et leurs hôtes. Les marqueurs spécifiques permettent, en outre, ladétection de parasitoïdes dans les oeufs et les jeunes larves de carpocapse. Ces approchesmoléculaires ont également permis d’évaluer le parasitisme dans des populations naturellesde carpocapse et d’estimer les interactions trophiques au sein de la communauté desparasitoïdes / In the context of a more environment-friendly agriculture, it is important to design methodsthat enable us to reduce the use of pesticides to fight pests. One possible way consists inincreasing pest regulation by their natural enemies (Conservation biological control). Thecodling moth, Cydia pomonella, is a major insect pest of apple orchards in SoutheasternFrance. The aim of this thesis was to identify determinants of the larval parasitism of thispest. We characterized the composition of the parasitoid community on diapausing and nondiapausing codling moth larvae. This community is mainly represented by threeHymenoptera species: Ascogaster quadridentata, Pristomerus vulnerator (two primaryparasitoids) and Perilampus trisits (a secondary parasitoid of A. quadridentata and P.vulnerator) in the study sites. We determined the characteristics of agricultural practices andsemi- natural habitats at the orchard and landscape level that affect the parasitism rate andthe composition of the parasitoid community of diapausing codling moth larvae. Thewindbreak and spontaneous hedgerows around the orchard seemed to impact theparasitoid community composition by promoting, when present, the primary parasitoids A.quadridentata and P. vulnerator versus the secondary parasitoid P. tristis. Crop protectionpractices at the orchard and surrounding landscape levels affected the parasitism rate.Parasitism rate was higher in organic orchards than in conventional orchards as well as inorchards surrounded by a low proportion of conventional orchards in a 250 m vicinity. Wefurther studied the within-season temporal dynamics of the codling moth parasitoidcommunity. The parasitism rates globally increased along the season among cohorts ofmature codling moth larvae and were higher in young larvae trapped in fruits than in maturelarvae trapped in band traps around the tree trunks. The community composition variedalong the season. The relative proportion of the secondary parasitoid P. tristis increasedamong the codling moth cohorts whereas the proportion of A. quadridentata decreased.Furthermore, the emergences of adult A. quadridentata were synchronized with theemergences of the adult codling moths. Finally, we developed and tested a PCR -RFLPmethod and specific DNA markers to detect and identify parasitoids of the codling moth. ThePCR -RFLP method was powerful to identify adult parasitoids and their hosts. Specificprimers allowed detection of parasitoids in the eggs and young larvae of codling moth. TheseDNA-based techniques allowed molecular evaluation of parasitism in C. pomonella naturalpopulation and reconstructing quantitative food web of the parasitoid community.

Les carabes et les araignées sont des auxiliaires généralistes susceptibles d'exercer un contrôle efficace des ravageurs des cultures. La structure et composition de leurs communautés, ainsi que l'efficacité du contrôle biologique, dépendent de l'hétérogénéité des paysages, et en particulier de la présence d'habitats semi-naturels. Mais le rôle de la mosaïque agricole, susceptible de présenter une forte hétérogénéité dans l'espace et dans le temps, reste aujourd'hui peu connu. L'objectif de ce travail a été d'évaluer les effets de l'hétérogénéité spatiale et temporelle des paysages agricoles sur des auxiliaires généralistes et sur le potentiel de contrôle biologique. Nous avons échantillonné les communautés de carabes et d'araignées dans des parcelles de céréales, et estimé le potentiel de prédation par des pucerons sentinelles collés sur des cartes de prédation. Nous avons caractérisé l'hétérogénéité spatiale des paysages autour des parcelles de céréales par le pourcentage d'éléments boisés et la longueur du réseau de haies, la taille moyenne des parcelles agricoles, et la diversité des cultures. Nous avons également mis au point quatre nouvelles métriques qui synthétisent différents aspects de l'hétérogénéité temporelle interannuelle des surfaces cultivées. Nos résultats montrent qu'au printemps les araignées sont plus abondantes dans les parcelles de céréales situées dans des paysages composés de petites parcelles. Au début de l'été, ces paysages favorisent également les taux de prédation de pucerons mesurés par les cartes de prédation, et l'abondance des carabes qui se reproduisent au printemps et qui hivernent en tant qu'adultes dans des habitats semi-naturels. Les carabes qui hivernent dans le sol des parcelles au stade larvaire et se reproduisent à l'automne sont quant à eux favorisés par la diversité des cultures dans le paysage. Nos résultats montrent enfin que l'hétérogénéité temporelle de la mosaïque agricole - caractérisée par les changements de la diversité de cultures au cours des cinq dernières années - favorise elle aussi certaines espèces de carabes communément rencontrées dans les parcelles agricoles (Poecilus cupreus ou Pterostichus melanarius) et susceptibles de jouer un rôle important en tant qu'auxiliaires. Ces résultats mettent en avant le rôle complémentaire des bordures de champs non cultivées et de la mosaïque des cultures pour différents groupes d'auxiliaires, et soulignent l'importance de prendre en compte l'hétérogénéité spatiale et temporelle des surfaces cultivées dans l'étude de la biodiversité des paysages agricoles. Dans le contexte de réduction des produits phytosanitaires, nos résultats suggèrent que des paysages présentant une diversité de cultures importante variable dans le temps, et des petites parcelles qui favorisent l'intrication entre les habitats semi-naturels et les cultures, sont susceptibles de favoriser les auxiliaires généralistes ainsi que le potentiel de contrôle biologique des ravageurs. / In the context of reducing pesticide use, the potential role of some arthropod groups as pest natural enemies provides them an ecological and economic interest. In particular, ground beetles and spiders are generalist predators likely to be effective biocontrol agents. Previous studies have shown that the structure and composition of their communities, as well as the effectiveness of biological control, are influenced by landscape heterogeneity, and in particular by the presence of semi-natural habitats. However, the role of the crop mosaic, which can be highly heterogeneous in space and time, have been little considered. The main objective of our study was to determine the influences of spatial and temporal heterogeneity of agricultural landscapes on generalist natural enemies and the potential for biological pest control. We sampled carabid and spider communities in winter cereal fields, and estimated biological control potential using sentinel aphids glued on predation cards. We characterized the spatial heterogeneity of the landscapes around each cereal field by 1) the amount of wooded habitats and the length of the hedgerow network, 2) the average size of the agricultural fields, and 3) crop diversity. We also proposed four new metrics that synthesize different aspects of the multi-year temporal heterogeneity of cropped areas. Our results show that in spring, landscapes characterized by small fields, and therefore by a high density of non-cropped field margins, promote spiders abundance in cereal fields. In early summer, landscapes with small fields also promote aphid predation rates and the abundance of carabid spring breeders, which overwinter as adults in semi-natural habitats. Crop diversity promotes the abundance of carabids overwintering in soils of arable fields and breeding in autumn. Our results also show that the temporal heterogeneity of the crop mosaic - characterized among other things by the changes in crop diversity over a five year period - benefits some carabid species commonly found in agricultural landscapes (such as Poecilus cupreus and Pterostichus melanarius) which are likely to play an important role as pest natural enemies. These results highlight the complementary role of the crop mosaic and the non-cropped field borders for generalist natural enemies, and show the importance of taking into account the spatial and temporal heterogeneity of the cultivated area in further ecological studies on biodiversity in agricultural landscapes. In the context of reducing pesticide use, our results suggest that landscapes with 1) a high crop diversity that change over time, and 2) small fields that promote the interspersion between crops and semi-natural habitats, are likely to promote generalist natural enemies and biological pest control.

[EN] Aphis spiraecola Patch. (Hemiptera: Aphididae) is a key pest of clementines. Biological control of A. spiraecola is still poorly known and efforts were based on the use and conservation of parasitoids but it did not success. With all this said, the aims of this thesis were: i) to disentangle the reasons behind the low parasitism of A. spiraecola; ii) to determine when and how predators can control A. spiraecola populations; and, finally, iii) to evaluate whether a ground cover of Poaceae plants can enhance the biological control of this aphid in clementines by improving the establishment of its predators. In the first objective we sampled four orchards and determine the parasitoid complex and parasitism (and hyper-) rates weekly. Binodoxys angelicae Haliday (Hymenoptera: Braconidae) was the unique primary parasitoid emerged from mummies of A. spiraecola. At least six hymenopteran hyperparasitoid species were identified attacking this primary parasitoid: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) and Phaenoglyphis villosa (Hartig) (Figitidae). We developed a DNA-based approach to untangle the structure of the aphid-parasitoid food web in citrus. This methodology confirmed that all six species hyperparasitized B. angelicae And they dominated this food web and they were abundant from the beginning of the season. Thus, hyperparasitism probably explains the low impact of B. angelicae on A. spiraecola populations. For the second objective we sampled three clementine orchards to determine the effect of aphid predators on A. spiraecola colonies over a three-year period. Life parameters of A. spiraecola colonies varied among the orchards over the three years. The maximum number of aphids and the longevity of A. spiraecola colonies were negatively correlated with the time of first attack by predators. More importantly, the percentage of shoots occupied by A. spiraecola (damages) remained below or close to the intervention threshold when colonies were attacked prior to ~200 degree days (DD) since the beginning of the aphid colonization. These results suggest that: i) the presence of predators at the beginning of the season should be considered to develop new intervention thresholds and ii) biological control programs should promote the early presence of predators in clementine orchards. To promote the early presence of predators in clementine orchards, in the third objective we evaluated ground cover management. This ground cover management may provide alternative preys to natural enemies. The effect of a sown ground cover (based on Poaceae plants) on the biological control of A. spiraecola was evaluated in four orchards with ground cover management compared with four orchards with bare soil management. This sown Poaceae cover coexists with a complex of wild plants that might also affect biological control of A. spiraecola. Finally, we compared the presence of A. spiraecola and its natural enemies in these orchards. While Poaceae plants represented ~66% of the ground cover, the rest of the cover comprised mainly Malva sp. (13%), Oxalis sp. (5%) and Sonchus sp. (2%). Poaceae plants harbored aphids which appeared sooner in the system than citrus aphids. These aphids serve as alternative prey/hosts for natural enemies. By contrast, Malva sp. and Sonchus sp. harbored aphids with potential to become citrus pest. Although these wild plants may act as reservoirs for A. spiraecola as well as other aphid species that can disrupt the biocontrol services of natural enemies, overall, the sown cover was effective in terms of biological control of A. spiraecola in the citrus canopy. It promoted the early presence of predators in citrus canopies. These attacks resulted in satisfactory aphid control, because citrus orchards with ground cover never exceeded the aphid economic threshold. / [ES] Aphis spiraecola Patch. (Hemiptera: Aphididae) es una de las plagas claves en el cultivo de clementinos. Los esfuerzos realizados hasta la fecha se han centrado en el uso y conservación de parasitoides aunque se desconocen las causas de su baja eficacia. Por todo ello, los objetivos de esta tesis han sido i) desentrañar las razones por las que se dan bajos niveles de parasitismo de A. spiraecola ii) determinar cuándo y cómo los depredadores pueden controlar las poblaciones de A. spiraecola y finalmente iii) determinar si una cubierta de poáceas puede mejorar el control biológico de este pulgón en clementinos mediante la mejora en el establecimiento de sus depredadores. En el primer objetivo se muestrearon semanalmente cuatro parcelas y se identificó el complejo de parasitoides y las tasas de parasitismo (e hiperparasitismo). Los porcentajes de parasitismo fueron bajos (~menos del 5%) y Binodoxys angelicae Haliday (Hymenoptera: Braconidae) fue el único parasitoide primario emergido de las momias de A. spiraecola. Se identificaron al menos seis especies de hiperparasitoides atacando este parasitoide primario: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) y Phaenoglyphis villosa (Hartig) (Figitidae). Se desarrolló un método basado en la detección de ADN con el cual se confirmó que todas las especies de hiperparasitoides hiperparasitan B. angelicae. Los hiperparasitoides dominaron esta red trófica y fueron abundantes desde el inicio de la estación. De este modo, el hiperparasitismo probablemente explica el bajo impacto que B. angelicae tiene sobre las poblaciones de A. spiraecola. Para el segundo objetivo se muestrearon tres campos de clementinos donde se determinó el efecto de los depredadores en las colonias de A. spiraecola. Los parámetros de vida de las colonias de A. spiraecola variaron entre los diferentes cultivos los tres años. El máximo número de pulgones y la longevidad de las colonias de A. spiraecola se correlacionaron negativamente con el momento del primer ataque del depredador a la colonia. Cabe destacar que el porcentaje de brotes ocupados por A. spiraecola permaneció por debajo o cerca del umbral de tratamiento cuando las colonias fueron atacadas antes de los 200 grados días (GD) desde el inicio de formación de la colonia. Estos resultados sugieren: i) la presencia de depredadores al inicio de la temporada de pulgón debes ser considerado para el desarrollo de nuevos umbrales de tratamiento y ii) los programas de control biológico deben promover el adelanto de la presencia de depredadores en los campos de clementinos. Para promover la presencia anticipada de depredadores en los campos de clementinos, como tercer objetivo se evaluó el manejo de cubiertas vegetales a base de poáceas. Con este manejo se persigue aportar presas alternativas para los enemigos naturales de A. spiraecola. Para ello, se compararon cuatro campos de cítricos con cubierta vegetal frente a cuatro con suelo desnudo. En los campos con cubierta sembrada apareció además de las poáceas sembradas, un complejo de plantas salvajes que podrían afectar también el control biológico de A. spiraecola. Las poáceas representaron un 66% de la cubierta vegetal. Las poáceas y Oxalis sp. albergaron respectivamente pulgones estenófagos de plantas poáceas y Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae). Estas especies de pulgones aparecieron más pronto en el ecosistema que los pulgones de cítricos y sirvieron como presas/hospederos alternativos para los enemigos naturales. Al contrario, Malva sp. y Sonchus sp. albergaron especies de pulgón que podrían ser potenciales plagas de cítricos. El efecto total de la cubierta sembrada resultó positivo para el control de A. spiraecola. Por lo tanto, las parcelas de cítricos con cubierta vegetal tendieron a no / [CAT] Aphis spiraecola Patch. (Hemiptera: Aphididae) és una de les plagues clau en el cultiu de clementins. Els esforços realitzats fins ara s'han centrat en el us i conservació de parasitoids encara que es desconeix les causes de la seua baixa eficàcia. Tenint en compte estos antecedents, els objectius d'esta tesis foren: i) desentrampar les raons per les quals els parasitoids no són efectius; ii) determinar quan i com els depredadors poden controlar les poblacions d'A. spiraecola; i finalment iii) determinar si una coberta de poàcies pot millorar el control biològic d'este àfid en clementins mitjançant la millora en el establiment del seus depredadors. En el primer objectiu es van mostrejar setmanalment quatre parcel·les i s'identificà el complex de parasitoids i les taxes de parasitisme (i hiperparasitisme). Binodoxys angelicae Haliday (Hymenoptera: Braconidae) va ser l'únic parasitoid primari emergit de les mòmies d'A. spiraecola. Se van identificar al menys sis especies d' hiperparasitoids atacant este parasitoid primari: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) i Phaenoglyphis villosa (Hartig) (Figitidae). Se desenvolupà un mètode basat en la detecció de DNA amb el que es confirmà que totes les especies d'hiperparasitoids hiperparasiten B. angelicae. Els hiperparasitoids dominaren aquesta xarxa tròfica i foren abundants a l'inici de l'estació. Per tant, l'hiperparasitisme podria explicar el baix impacte que B. angelicae té sobre les poblacions d'A. spiraecola. Per al segon objectiu es mostrejaren tres camps de clementins on es determinà l'efecte dels depredadors en les colònies d'A. spiraecola. Els paràmetres de vida de les colònies d'A. spiraecola variaren entre les tres parcel·les els tres anys. El màxim número d'àfids i la longevitat de les colònies d'A. spiraecola es correlacionaren negativament amb el moment del primer atac del depredador a la colònia. Caldria destacar que el percentatge de brots ocupats per A. spiraecola es mantingué per baix o prop del llindar de tractament quan les colònies foren atacades abans dels ~200 graus dia (GD) des de l'inici de formació de la colònia. Estos resultats sugereixen que: i) la presència de depredadors a l'inici de la estació de l'àfid podria ser considerada per al desenvolupament de nous llindars de tractament i ii) els programes de control biològic deurien promoure l'avançament de la presència de depredadors en els camps de clementins. Per promoure la l'avançament de la presència de depredadors en els camps de clementins, com tercer objectiu s'avaluà el maneig de cobertes vegetals basades en poàcies. Amb aquest maneig es persegueix aportar preses alternatives per als enemics naturals d'A. spiraecola. Se compararen quatre camps de clementins amb coberta vegetal front a quatre amb sol nu. En els camps amb coberta sembrada creix, junt a les Poáceas sembrades, un conjunt de plantes salvatges que podrien afectar també el control biològic d'A. spiraecola. S'investigà quines especies de plantes componien la coberta vegetal així com les especies d'àfids que les habitaven. Les poàcies representaren un 66% de la coberta vegetal, sent les plantes salvatges més abundants Malva sp. (13%), Oxalis sp. (5%) i Sonchus sp. (2%). Les poàcies hostejaren àfids estenòfags de poàcies. Estes espècies d'àfid aparegueren més prompte en l'ecosistema que aquells àfids associats a cítrics. Al contrari, Malva sp. i Sonchus sp. hostejaren especies d'àfids que podrien ser potencials plagues de cítrics. Este últim grup pot atenuar l'atac dels enemics naturals a les poblacions d'A. spiraecola que habiten les copes. Encara així, l'efecte total de la coberta sembrada a base de poàcies va resultar positiu per al control d'A. spiraecola. En conseqüència les parcel·les de cítrics am / Gómez Marco, F. (2015). Integrated Pest Management of Aphis spiraecola (Hemiptera: Aphididae) in clementines: enhancing its biological control [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/53732 / TESIS