Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Plantings with forest species have economical, social and environmental importance for Brazil, contributing to decrease the suppression of native forests. Implantation is a decisive step towards the success of a forestry enterprise and, among the precautions to be taken at this stage, stands out the control of weeds. However, the removal of these plants can eliminate food sources and shelter for natural predators of pest insects, favoring the prevalence of some species over others and causing environmental and economical damages. Considering that ants are potential bioindicators of these changes, this study aimed to evaluate the ant fauna in an initial planting of Eucalyptus grandis Hill ex Maiden, under different systems of weeds control. To this end, in March 2011, was installed a planting of E. grandis, spaced 3m x 2m, together the State Foundation of Agricultural Research in Santa Maria, RS. The Experimental design was the Entirely Randomized, with six treatments, being each having an area half a hectare, comprising: total chemical control of weeds in the line and interline planting, with glyphosate (T1); total chemical control of weeds, in the line planting, with glyphosate (T2); chemical control of monocots in the line and interline planting, with sethoxydim (T3); chemical control of dicots in the line and interline planting, with bentazone (T4); total chemical control of weeds in the range of one meter parallel to the line planting, with glyphosate, and one meter in the central part of the leading, without control (T5), e witness, without weed control (T6). The herbicides application was sequential, in total area, before planting and after transplant in the planting line. The survey was conducted from March 2011 to February 2012, using attractive baits, soil trap and Berlese funnel. Each method contained six repetitions per treatment, at each sampling date. Were collected 46,675 ants, belonging to seven subfamilies and 37 species. There was not statistical difference (ANOVA, p> = 0.05) between the total of ant specimens collected in the areas assessed. The T2 treatment presented the greatest observed richness of species (Sobs = 35), and sampling efficiency of 99.0%. The genera Camponotus and Pheidole were the richest in species number, with six each. Camponotus punctulatus, commonly found in antropized areas, it was demonstrated very frequent (mf) in the area of T3 treatment, and uncommon (mp) in T6. There was significant difference (ANOVA, p < 0.05) between mean values of observed richness per sample, with the lowest value found in T1 treatment (Sobs = 0.4), in Berlese funnel. In terms of vegetation, was verified similarity among the areas least altered, and between the areas most simplified. Ectatomma permagnum e Gnamptogenys sulcata, potential predators of pest insects, demonstrated higher occurrence frequency, respectively, in the areas of treatments T6 (51.4%) and T2 (41.7%). We conclude that the indirect effects of the herbicides affect more the composition of ant species than the ant species richness. / Plantios com espécies florestais possuem importância econômica e socioambiental para o Brasil, contribuindo para a diminuição da supressão das matas nativas. A implantação é uma etapa decisiva para o sucesso de um empreendimento florestal e, dentre os cuidados a serem tomados nessa fase, destaca-se o controle de plantas infestantes. Porém, a retirada dessas plantas pode eliminar fontes de alimento e abrigo para predadores naturais de insetos-praga, favorecendo a prevalência de algumas espécies em detrimento de outras e provocando prejuízos ambientais e econômicos. Haja vista que as formigas são potenciais bioindicadoras dessas alterações, este estudo objetivou avaliar a mirmecofauna em um plantio inicial de Eucalyptus grandis Hill ex Maiden, submetido a diferentes tipos de controle de plantas infestantes. Para tanto, em março de 2011, foi instalado um plantio de E. grandis, com espaçamento 3m x 2m, junto à Fundação Estadual de Pesquisa Agropecuária, em Santa Maria, RS. O Delineamento experimental arranjado foi Inteiramente Casualizado com seis tratamentos, sendo cada um com área de meio hectare, constituídos por: controle químico total de plantas infestantes, na linha e na entrelinha de plantio, com glifosato (T1); controle químico total de plantas infestantes, na linha de plantio, com glifosato (T2); controle químico de monocotiledôneas na linha e entrelinha de plantio, com setoxidim (T3); controle químico de dicotiledôneas na linha e entrelinha de plantio, com bentazona (T4); controle químico total de plantas infestantes em faixa de um metro paralela à linha de plantio, com glifosato, e de um metro na parte central da entrelinha, sem controle (T5); e testemunha, sem controle de plantas infestantes (T6). A aplicação dos herbicidas foi sequencial, em área total, antes do plantio e após o transplante na linha de plantio. O levantamento foi realizado de março de 2011 a fevereiro de 2012, utilizando-se isca atrativa, armadilha de solo e funil de Berlese. Cada método continha seis repetições por tratamento, em cada data de coleta. Foram coletadas 46.675 formigas, pertencentes a sete subfamílias e 37 espécies. Não houve diferença estatística (ANOVA, p>=0,05), entre o total de espécimes de formigas coletados nas áreas avaliadas. Na área do tratamento T2 verificou-se o maior número de espécies capturadas (Sobs = 35) e eficiência amostral de 99,0%. Os gêneros Pheidole e Camponotus foram os mais ricos em número de espécies, com seis cada um. Camponotus punctulatus, comum em áreas antropizadas, demonstrou-se muito frequente (mf) na área do tratamento T3, e pouco frequente (pf) em T6. Houve diferença significativa (ANOVA, p < 0,05) entre os valores médios de riqueza observada por amostra, sendo o menor valor foi encontrado na área do tratamento T1 (Sobs = 0,4), em funil de Berlese. Em termos de vegetação, verificou-se similaridade entre as áreas com estrutura florística menos alterada, e entre as áreas mais simplificadas. Ectatomma permagnum e Gnamptogenys sulcata, potenciais predadoras de insetospraga, demonstraram maior frequência de ocorrência, respectivamente, nas áreas dos tratamentos T6 (51,4%) e T2 (41,7%). Conclui-se que os efeitos indiretos da ação dos herbicidas afetam mais a composição local de espécies de formigas do que sua riqueza. Palavras-chave: Bioindicadores Ambientais. Entomologia Florestal. Formicidae. Matocompetição. Plantio Inicial

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this study was to investigate the effect of alternative chemical control of weeds in the arthropod fauna in Eucalyptus grandis (W. Hill). The study was conducted in an area belonging to Fepagro Forests in Santa Maria, RS, with planting of E. grandis, being composed of the following treatments: T1 - Chemical control of weeds with glyphosate in total area (planting rows and lines), T2 - Total Chemical control of weeds in the crop row (50 cm), T3 = Chemical control of plants grasses and weeds in the row spacing of planting, T4 - chemical control of broadleaved weeds in row spacing and planting, T5 - full control of weeds in strips with a width of 1.0 m beside the row, leaving 1. 0 m interrow unchecked, T6 - Treatment (control). Results showed that the herbicides glyphosate, bentazon and setoxidin and in doses not have a direct influence on the mega, macro and mesofauna of the soil, and environmental variables have influence on the temporal distribution of soil fauna, with significant interaction between treatment and the collection periods for most groups edaphic collected. Observed that the treatments with vegetation strips of weeds with fewer plants attacked by insects pests, and greater diversity of soil organisms collected, in addition to providing significant ground cover, and showing good initial development when compared to treatment with control of weeds. Accordingly, the adoption of tracks chemical control of weeds with herbicides for the control of weeds in Eucalyptus, constitutes a viable alternative to be used in programs for Integrated Pest Management, by increasing plant diversity and arthropod, ecosystems grown. / O objetivo deste trabalho foi investigar o efeito de alternativas de controle químico de plantas daninhas na fauna de artrópodos em plantios de Eucalyptus grandis (W. Hill). O estudo foi conduzido em área pertencente à Fepagro Florestas, em Santa Maria, RS, com plantio de E. grandis, sendo composto pelos tratamentos: T1 - Controle químico de plantas daninhas com glifosato (área total/ linhas de plantio e entrelinhas); T2 - Controle químico total de plantas daninhas na linha de plantio (50 cm); T3= Controle químico de plantas daninhas poáceas na linha e entrelinha de plantio; T4 - Controle químico de plantas daninhas dicotiledôneas na linha e entrelinha de plantio; T5 - Controle total de plantas daninhas em faixas com largura de 1,0m, ao lado da linha de plantio, deixando-se 1,0m na entrelinha sem controle; T6 - Tratamento sem controle (testemunha). Os resultados mostraram que os herbicidas glifosato, setoxidin e bentazon, nas doses aplicadas, não exercem influência direta na mega, macro e mesofauna do solo, sendo que as variáveis ambientais apresentam distribuição temporal da fauna de com interação significativa entre os tratamentos períodos coleta para a maioria dos grupos edáficos coletados. Observou-se faixas vegetação plantas daninhas apresentaram menor número atacadas por insetos-praga maior diversidade organismos coletados, além propiciar cobertura solo. Também bom desenvolvimento inicial, quando comparados ao tratamento controle total infestantes. Assim, adoção químico herbicidas específicos, visando o daninhas, em plantios Eucalyptus, constitui-alternativa viável ser usada programas Manejo Integrado Pragas, pelo aumento vegetal artropodofauna promovem, nos ecossistemas cultivados.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Brazil is the world's leader in productivity of Eucalyptus plantations, with approximately 6 million hectares of planted area and optimistic expansion projections in the coming years. Native to Oceania, the species was introduced to Brazil, and its production has been supported by the development of silvicultural and breeding techniques and a wide genetic base for clonal production. However, poor phytosanitary measures have led to the occurrence of exotic pests, which are potentiated by the absence of specific natural enemies and plantation homogeneity. This fact increases the cost with forest protection and directly interferes with the country's competitiveness in foreign markets. Thaumastocoris peregrinus is a key-pest in Eucalyptus plantations,that occurs worldwide, being detected in Brazil in 2008. The pest feeds on the sap of leaves, resulting in chlorosis, followed by tanning; in severe infestations, the damage can lead to leaf abscission and plant death. Chemical control (Bifenthrin) is used in emergency cases. However, environmental certification systems do not recommend this practice due to the high toxicity to humans and the environment. Therefore, alternative control strategies have been studied, such as biological control, which is potentially less toxic and is in compliance with the social and environmental aspects of forest plantations, according to environmental certification systems. Microbial control has been extensively and successfully studied in the country, such as entomopathogenic fungi, and thus, this procedure has been considered as a potential alternative to combat Thaumastocoris peregrinus. The first pathogens associated with insects control can be found naturally or isolated, or can be massively produced and stored for use in the field. Due to the possibility of being isolated and massively produced, a market for entomopathogenic fungi has been created, which enabled the development of mycoinseticide products. The fungi Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea and Beauveria brongniartii have been used in this industry. The present study aimed to evaluate the efficiency of microbial control applied to T. Peregrinus in field conditions as a viable alternative to be inserted in the integrated management of this pest. The most effective treatment is the chemical control (Bifenthrin), followed by the biological control with I. fumosorosea, B. bassiana, and Metarril®. The entomopathogenic fungi I. fumosorosea and B. bassiana proved to be potential alternatives for biological control in the Integrated Management of T. peregrinus. / Líder mundial de produtividade em plantações de eucalipto, o Brasil possui, aproximadamente, 6 milhões de hectares com a cultura e tem otimistas projeções de expansão do setor nos próximos anos. Com sua origem na Oceania, o eucalipto foi introduzido no Brasil e alicerçado em técnicas silviculturais e de melhoramento. Com isso, o país desenvolveu a eucaliptocultura e uma ampla base genética para a produção clonal. No entanto, falhas em fronteiras fitossanitárias possibilitam a introdução de pragas exóticas potencializadas pela ausência de inimigos naturais específicos e pela homogeneidade das plantações. Como consequência, os custos com a proteção florestal são elevados e interferem diretamente na competitividade do país no mercado externo. Presente em todo o mundo e detectado no Brasil em 2008, o Thaumastocoris peregrinus é praga-chave na eucaliptocultura. Esta praga dispersou-se para todo o país associado à cultura do eucalipto que ao utilizar a sua seiva na alimentação, provoca danos que levam a clorose, seguida de bronzeamento e, em infestações severas, pode levar a absição da folha e morte da planta. Emergencialmente, utiliza-se o controle químico com Bifentrina, no entanto, não é recomendado devido à alta toxidade ao homem e ao meio ambiente e não sugerido por sistemas de certificação ambiental. Assim, estratégias de controle alternativos vêm sendo estudadas, como o controle biológico, potencialmente menos tóxico, que atestam os aspectos sócio-ambientais das plantações florestais para tais sistemas de certificação. Com uma ampla gama de estudos e casos de sucesso no país, o controle microbiano, integrante do controle biológico, é visto como uma alternativa potencial; em destaque está o uso de fungos entomopatogênicos. Os primeiros patógenos associados ao controle de insetos podem ser encontrados naturalmente, reisolados, produzidos massalmente e armazenados para a utilização em campo. Concebendo a criação de um mercado para tal, os fungos entomopatogênicos possibilitaram a criação de produtos micoinseticidas Entre os fungos mais utilizados destacam-se o Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea e Beauveria brongniartii. O presente trabalho objetivou avaliar a eficiência do controle microbiano do T. peregrinus em condições de campo, a fim de obter uma alternativa viável a ser inserida do Manejo Integrado do T. peregrinus. O tratamento mais eficiente foi com o controle químico (Bifentrina), seguido dos controles biológicos com I. fumosorosea, B. bassiana e Metarril®. Sendo assim, os fungos entomopatogênicos I. fumosorosea e B. bassiana são alternativas potenciais para a inserção do controle biológico no Manejo Integrado do T. peregrinus. / São Cristóvão, SE

Dans l’hémisphère Nord, le climat des deux derniers millions d’années a été marqué par une alternance de périodes froides et de brefs intervalles chauds. Cette succession d’évènements a laissé des traces durables au niveau de l’arrangement spatial de la diversité et de la structure génétique au sein des espèces.<p>En décrivant la répartition spatiale des lignées d’une espèce au moyen d’informations génétiques, la phylogéographie vise à identifier les processus évolutifs responsables de cette répartition. La phylogéographie comparée permet de gagner en compréhension en confrontant les patrons de variation génétique présents chez plusieurs espèces codistribuées :en étudiant des espèces partageant une même histoire au moyen de plusieurs sources d’information indépendantes (par exemple, plusieurs fragments d’ADN ou des données bioclimatiques historiques externes), il est possible de mettre en évidence des éléments de cette histoire commune tels que des refuges glaciaires ou des routes de recolonnisation post-glaciaires. Par contre, il est aussi possible que les caractéristiques biologiques intrinsèques à chaque espèce, telles que des stratégies dispersives ou reproductives différentes, engendrent une différenciation dans la structure et la diversité de cette variation génétique. <p>Dans cette thèse de doctorat nous nous sommes intéressés à deux espèces inféodées à un même hôte (Picea abies) et appartenant à une même sous-famille taxonomique (Coleoptera :Curculionidae, Scolytinae). Il sagit du typographe, Ips typographus et du dendroctone, Dendroctonus micans. Au moyen de plusieurs fragments génétiques spécialement identifiés pour cette étude ainsi que par le recours à des modèles bioclimatiques et des tests statistiques basés sur la théorie de la coalescence, nous avons étudié la phylogéographie de ces espèces.<p>Les résultats obtenus au cours de ce travail ont permis de mettre en évidence l’influence contrastée de stratégies écologiques différentes sur l’arrangement de la variation génétique. Une espèce opportuniste aux capacités de dispersion élevées telle qu’I. typographus présente un patron génétique peu structuré (des variants génétiques appelés haplotypes sont présents dans des régions très disparates) et un degré de polymorphisme nucléaire relativement élevé. Au contraire, une espèce parasitique adaptée à un environnement stable et caractérisée par une stratégie de dispersion limitée telle que D. micans présente un patron génétique très structuré (un nombre restreints et spécifiques d’haplotypes sont observés dans des régions géographiquement proches) et un degré de polymorphisme nucléaire dramatiquement faible.<p>Par ailleurs la comparaison de nos résultats à ceux de leur hôte, l’épicéa, ainsi qu’à ceux d’autres espèces partageant une même niche écologique (ex. Rhizophagus grandis), nous a permis de mettre en évidence des éléments communs dans l’histoire de ces espèces boréo-montagnardes :les populations européennes et asiatiques présentent une même divergence ancienne (antérieure à la dernière glaciation) et les populations européennes affichent des traces de structure génétique. Ces éléments nous ont permis de reconsidérer l’histoire de ces deux espèces en proposant et testant de nouveaux scénarios historiques./In the North Hemisphere, the climate of the last two million years has been paced by<p>the alternation of ice ages and warm interglacial periods. This succession of events has markedly shaped the present-day spatial arrangement of genetic diversity and structure within species. <p>By analyzing the geographical distribution of genetic variation within species, Phylogeography aims to identify evolutionary processes responsible for the current spatial patterns in the distribution of populations. Comparative phylogeography is used to gain insights into the understanding of driving evolutionary processes by co-analyzing the current genetic variation patterns of several co-distributed species; the study of species sharing a same history by several independent sources of information (e.g. different DNA fragments or historical bioclimatic data) allows to identify similar historical events such as glacial refugia or post-glacial recolonization pathways. However differences in life-history traits related to specific ecological strategies may also influence contrasting patterns of genetic structure and diversity. <p>In this PhD thesis, we focused on two insect associated with a same host (Picea abies) and belonging to a same taxonomic sub-familly (Coleoptera :Curculionidae, Scolytinae). The two insects are the Eurasian spruce bark beetle, Ips typographus, and the great spruce bark beetle, Dendroctonus micans. By the use of several genetic markers specifically designed for the purpose of this study and by bioclimatic modeling approach combined with coalescent-based statistical method, we have studied the phylogeography of both species. <p>Our results enable us to highlight the influence of contrasting ecological strategies on the spatial arrangement of genetic variation. On the one hand, opportunistic species characterized by high dispersal capacities, such as I. typographus, exhibits poor genetic structure (same genetic variants named haplotypes are found in really distant geographic regions) and a relatively high polymorphism level. On the other hand, parasitic species well-adapted to stable environmental conditions and characterized by limited dispersal strategy, such as D. micans, exhibits high genetic structure (same specific haplotypes found in same or neighboring geographic countries) and an extremely low polymorphism level.<p>Moreover, the comparison of our results with those of their specific host plant Picea abies and of other sympatric species (e.g. Rhizophagus grandis), has enable us to identify common patterns typical of boreo-montane species :a same old divergence between european and asiatic populations (older than the last glaciation) and genetic structure in european populations. These findings have been used to infer past of both species by identifying and testing new historical scenarii.<p><p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

The Eurasian spruce bark beetle Dendroctonus micans is a major pest of spruce which is expanding its range in France, Turkey, England and Wales. Its monospecific predator Rhizophagus grandis has followed naturally the bark beetle into most areas and, since the 1960s, has also been mass-produced and successfully released within newly infested locations. In this scope, the development of an effective trapping method would be very useful to assess the bark-beetle presence at previously uninfested sites, or predator establishment after release or natural spread. We demonstrated the efficiency of oxygenated monoterpenes-baited kairomone traps to monitor R. grandis in various epidemiological conditions, including areas localized behind or at the limit of the pest’s distribution, or in areas where artificial releases were performed. Because the predator is strictly species-specific, another exciting possibility offered by the kairomone trapping is the indirect monitoring of the pest itself in areas of unknown status (e.g. areas under colonization, or considered as at risk at medium- term). R. grandis is also considered as one of the most valuable natural enemies to strike aggressive North-American Dendroctonus species. In this respect, R. grandis has been recently applied in a neo-classical biological program against the red turpentine beetle D. valens, which invaded China from North America in the late 1990’s. In laboratory tests conducted on pine logs in the laboratory, or on living pine trees in the field, we demonstrated that R. grandis adults can successfully enter and reproduce into D. valens galleries. In Europe, R. grandis is the only species regularly found in the brood systems of D. micans, where adults and larvae attack the gregarious larvae of their prey. In such enclosed systems, R. grandis’ functional response is therefore influenced by various interrelated components, such as the prey density, the predator density, or the prey distribution. Measuring the predator’s success in terms of larval survival and growth rates, we demonstrated the time spent by R. grandis larvae to wound and kill their prey to be the main factor limiting their development. This factor may be considerably influenced by the proportions of diseased, wounded or molting prey rise in the brood system, for instance as a result of an increase in prey density, or due to the presence of conspecific adults (which wound their prey but do not consume them entirely). Furthermore, our tests suggest that no cannibalism or noticeable intraspecific competition occurred between R. grandis larvae, whereas some lighter mode of competition probably took place. R. grandis also exhibits a reproductive numerical response to prey density, which mainly relies on the perception of chemical stimuli and inhibitors released in the bark beetle brood system. In the current study, we developed a non-destructive approach to follow the dynamics of volatile compound production, using sequential sample collection on SPME fibers. Our tests demonstrated that the larval activity of D. micans or D. valens strongly influences the release of some oxygenated monoterpenes. However, our attempts to correlate the relative quantities of some identified chemicals to offspring production were less successful as it concerns the identification of potential oviposition stimuli and inhibitors. The problematic rose by the progression of D. micans, as well as detailed results of each of the described above studies are discussed in the two published papers and the three manuscripts forming this thesis. Bringing all these studies together, several perspectives are also presented in the general discussion. / Ravageur des épicéas, Dendroctonus micans est toujours en voie d’extension en France, en Turquie, en Angleterre et au Pays de Galles. Dans la plupart de ces zones, le dendroctone est accompagné de manière naturelle par son prédateur monospécifique, Rhizophagus grandis. Depuis les années 1960, le prédateur a également fait l’objet d’une production de masse et de programmes de lâchers dans les zones d’arrivée récente du scolyte. Dans le cadre de la lutte biologique contre D. micans, les gestionnaires forestiers doivent donc estimer au plus tôt la présence du ravageur dans des zones jusque là indemnes, mais également vérifier l’établissement du prédateur par progression naturelle ou résultant d’introductions délibérées. Dans la présente étude, nous avons démontré l’efficacité de pièges d’interception appatés à l’aide de monoterpènes oxygénés pour la capture de R. grandis. Celle-ci s’est faite dans différentes conditions épidémiologiques, incluant notamment des zones situées en arrière du front de progression du scolyte et des zones où des lâchers artificiels ont été réalisés. Comme R. grandis est strictement inféodé au dendroctone, un autre avantage de la technique est la possibilité de réaliser un dépistage indirect du ravageur dans les zones où son statut est incertain (zones en cours de colonisation, ou considérées comme à risque à moyen terme). Par ailleurs, R. grandis est également considéré comme un des meilleurs ennemis naturels potentiels pour lutter contre d’autres espèces de Dendroctonus aggressifs. Dans cette optique, R. grandis a été récemment utilisé dans un programme de lute biologique contre D. valens, ravageur invasif arrivé en Chine dans la fin des années 1990 en provenance d’Amérique du Nord. Nous avons démontré la capacité de R. grandis à s’introduire et à se reproduire dans les galeries de D. valens lors de tests de laboratoire, mais aussi sur des arbres vivants en pinèdes. En Europe, R. grandis est strictement inféodé aux galeries de D. micans, où larves et adultes du prédateur s’attaquent aux larves grégaires du scolyte. Dans ce système clos, la réponse fonctionelle de R. grandis est influencée par plusieurs facteurs étroitement corrélés, la densité de proies, la densité de prédateurs, et la distribution des proies. En mesurant l’efficacité de prédation de R. grandis en termes de survie des larves et de taux de croissance, nous avons démontré l’influence sur leur développement du temps passé par les larves à blesser et à tuer leurs proies. Ce facteur est par ailleurs fortement dépendant de la proportion de larves malades, blessées ou en cours de mue au sein du système ; une proportion qui peut augmenter en réponse à une augmentation de la densité de proies, ou lorsque des adultes sont présents (ceux-ci blessent les proies mais ne les consomment pas entièrement). Enfin, nos tests suggèrent qu’il n’existe que peu de cannibalisme ou de compétition intraspécifique entre larves de R. grandis, tandis que des modes de compétition moins importants prennent vraisemblablement place. R. grandis présente également une réponse numérique reproductive à la densité de proies disponibles, principalement basée sur la perception de stimuli et d’inhibiteurs présents dans les galeries du scolyte. Par la collecte de composés volatils présents dans ces systèmes à l’aide de fibres SPME, nous avons développé une méthode non-destructive pour suivre la dynamique de production des médiateurs chimiques. Nos tests ont démontré que l’activité des larves de D. micans ou D. valens influence fortement la dynamique de production de certains monoterpènes oxygénés. En revanche, il n’a pas été été possible de corréler les différents composés identifiés au nombre de larves de R. grandis présentes dans le système. La problématique soulevée par la progression de D. micans, de même que les résultats détaillés de chacune des études décrites ci-dessus sont discutés dans les deux papiers publiés et les trois manuscrits formant cette thèse. Les différentes perspectives apportées par ce travail sont également présentées dans la discussion générale.

The Eurasian spruce bark beetle Dendroctonus micans is a major pest of spruce which is expanding its range in France, Turkey, England and Wales. Its monospecific predator Rhizophagus grandis has followed naturally the bark beetle into most areas and, since the 1960s, has also been mass-produced and successfully released within newly infested locations. <p>In this scope, the development of an effective trapping method would be very useful to assess the bark-beetle presence at previously uninfested sites, or predator establishment after release or natural spread. We demonstrated the efficiency of oxygenated monoterpenes-baited kairomone traps to monitor R. grandis in various epidemiological conditions, including areas localized behind or at the limit of the pest’s distribution, or in areas where artificial releases were performed. Because the predator is strictly species-specific, another exciting possibility offered by the kairomone trapping is the indirect monitoring of the pest itself in areas of unknown status (e.g. areas under colonization, or considered as at risk at medium- term).<p>R. grandis is also considered as one of the most valuable natural enemies to strike aggressive North-American Dendroctonus species. In this respect, R. grandis has been recently applied in a neo-classical biological program against the red turpentine beetle D. valens, which invaded China from North America in the late 1990’s. In laboratory tests conducted on pine logs in the laboratory, or on living pine trees in the field, we demonstrated that R. grandis adults can successfully enter and reproduce into D. valens galleries. <p>In Europe, R. grandis is the only species regularly found in the brood systems of D. micans, where adults and larvae attack the gregarious larvae of their prey. In such enclosed systems, R. grandis’ functional response is therefore influenced by various interrelated components, such as the prey density, the predator density, or the prey distribution. Measuring the predator’s success in terms of larval survival and growth rates, we demonstrated the time spent by R. grandis larvae to wound and kill their prey to be the main factor limiting their development. This factor may be considerably influenced by the proportions of diseased, wounded or molting prey rise in the brood system, for instance as a result of an increase in prey density, or due to the presence of conspecific adults (which wound their prey but do not consume them entirely). Furthermore, our tests suggest that no cannibalism or noticeable intraspecific competition occurred between R. grandis larvae, whereas some lighter mode of competition probably took place. <p>R. grandis also exhibits a reproductive numerical response to prey density, which mainly relies on the perception of chemical stimuli and inhibitors released in the bark beetle brood system. In the current study, we developed a non-destructive approach to follow the dynamics of volatile compound production, using sequential sample collection on SPME fibers. Our tests demonstrated that the larval activity of D. micans or D. valens strongly influences the release of some oxygenated monoterpenes. However, our attempts to correlate the relative quantities of some identified chemicals to offspring production were less successful as it concerns the identification of potential oviposition stimuli and inhibitors. <p>The problematic rose by the progression of D. micans, as well as detailed results of each of the described above studies are discussed in the two published papers and the three manuscripts forming this thesis. Bringing all these studies together, several perspectives are also presented in the general discussion. <p>/<p>Ravageur des épicéas, Dendroctonus micans est toujours en voie d’extension en France, en Turquie, en Angleterre et au Pays de Galles. Dans la plupart de ces zones, le dendroctone est accompagné de manière naturelle par son prédateur monospécifique, Rhizophagus grandis. Depuis les années 1960, le prédateur a également fait l’objet d’une production de masse et de programmes de lâchers dans les zones d’arrivée récente du scolyte.<p>Dans le cadre de la lutte biologique contre D. micans, les gestionnaires forestiers doivent donc estimer au plus tôt la présence du ravageur dans des zones jusque là indemnes, mais également vérifier l’établissement du prédateur par progression naturelle ou résultant d’introductions délibérées. Dans la présente étude, nous avons démontré l’efficacité de pièges d’interception appatés à l’aide de monoterpènes oxygénés pour la capture de R. grandis. Celle-ci s’est faite dans différentes conditions épidémiologiques, incluant notamment des zones situées en arrière du front de progression du scolyte et des zones où des lâchers artificiels ont été réalisés. Comme R. grandis est strictement inféodé au dendroctone, un autre avantage de la technique est la possibilité de réaliser un dépistage indirect du ravageur dans les zones où son statut est incertain (zones en cours de colonisation, ou considérées comme à risque à moyen terme).<p>Par ailleurs, R. grandis est également considéré comme un des meilleurs ennemis naturels potentiels pour lutter contre d’autres espèces de Dendroctonus aggressifs. Dans cette optique, R. grandis a été récemment utilisé dans un programme de lute biologique contre D. valens, ravageur invasif arrivé en Chine dans la fin des années 1990 en provenance d’Amérique du Nord. Nous avons démontré la capacité de R. grandis à s’introduire et à se reproduire dans les galeries de D. valens lors de tests de laboratoire, mais aussi sur des arbres vivants en pinèdes. <p>En Europe, R. grandis est strictement inféodé aux galeries de D. micans, où larves et adultes du prédateur s’attaquent aux larves grégaires du scolyte. Dans ce système clos, la réponse fonctionelle de R. grandis est influencée par plusieurs facteurs étroitement corrélés, la densité de proies, la densité de prédateurs, et la distribution des proies. En mesurant l’efficacité de prédation de R. grandis en termes de survie des larves et de taux de croissance, nous avons démontré l’influence sur leur développement du temps passé par les larves à blesser et à tuer leurs proies. Ce facteur est par ailleurs fortement dépendant de la proportion de larves malades, blessées ou en cours de mue au sein du système ;une proportion qui peut augmenter en réponse à une augmentation de la densité de proies, ou lorsque des adultes sont présents (ceux-ci blessent les proies mais ne les consomment pas entièrement). Enfin, nos tests suggèrent qu’il n’existe que peu de cannibalisme ou de compétition intraspécifique entre larves de R. grandis, tandis que des modes de compétition moins importants prennent vraisemblablement place.<p>R. grandis présente également une réponse numérique reproductive à la densité de proies disponibles, principalement basée sur la perception de stimuli et d’inhibiteurs présents dans les galeries du scolyte. Par la collecte de composés volatils présents dans ces systèmes à l’aide de fibres SPME, nous avons développé une méthode non-destructive pour suivre la dynamique de production des médiateurs chimiques. Nos tests ont démontré que l’activité des larves de D. micans ou D. valens influence fortement la dynamique de production de certains monoterpènes oxygénés. En revanche, il n’a pas été été possible de corréler les différents composés identifiés au nombre de larves de R. grandis présentes dans le système. <p>La problématique soulevée par la progression de D. micans, de même que les résultats détaillés de chacune des études décrites ci-dessus sont discutés dans les deux papiers publiés et les trois manuscrits formant cette thèse. Les différentes perspectives apportées par ce travail sont également présentées dans la discussion générale.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished