PFAS are anthropogenic substances used in many different industrial operations and products because of their unique properties. Due to their negative impact on human health and environmental bioaccumulative characteristics different authorities have addressed the issue. In Sweden the limit is4 ng/L for four different PFAS in drinking water. Another risk to human health is elevated concentrations of toxic elements, causing Sweden to include them in the drinking water regulations withlimits such as 5 µg/L for arsenic, 25 µg/L for chromium and 5 µg/L for lead.This study is a continuation of an investigation for PFAS remediation in contaminated water by sorption to pine and spruce bark. The earlier study was a laboratory scale and implied that pine and spruce have some sorption capacity for long-chain PFAS. In this study pine and spruce bark were used as sorbent at an industrial site. The analysis was performed by weak-anion exchange extraction followed bysupercritical fluid chromatography coupled with a tandem mass spectrometer (SFC-MS/MS) and liquid chromatography coupled with tandem mass spectrometer (LC-MS/MS) for instrumental analyses of target ultra-short-chain PFAS, short- and long chain PFAS and branched PFOS isomers. An elemental analysis was executed with inductively coupled plasma mass spectrometry. The obtained results indicated removal for certain long-chain PFAS, potential for sorption of a specific ultra-short-chain PFAS and the elemental analysis implied some reduction of the chromium concentrations.

Forests have as a of late become increasingly plagued with bark beetle infestations as a result of climate change. The damage caused by tree killing bark beetles has within recent years seen a substantial increase. Detecting and removing infested trees at an early stage is an essential part of mitigating the spread of and the damage caused by the beetle. Today, the most common way of early detection is visual detection by forestry personnel. However, this is time consuming with highly variable results. In this thesis a novel approach to tracing the European spruce bark beetle through pheromone detection is investigated. With this approach, the antennae of the beetle were paired with an epitaxial graphene chip in order to create a bioinspired smell sensor. Tests were conducted on the sensor in order to investigate how the resistance changed over the chip as a result of the sensor being exposed to the pheromone 2-methyl-3-buten-2-ol. As a result of the tests, a corelation between exposing the sensor to pheromone and an increase of the resistance over the graphene chip was noted. However, more tests need to be conducted in order to draw any definite conclusions about the efficacy of the sensor in its current form. Additionally there are opportunities to investigate further optimization alternatives regarding the design of the sensor.

Granbarkborre är en av Sveriges mest destruktiva skadeinsekter som angriper granskog. Insekten har medfört förödande konsekvenser för granskog, framför allt sedan2018 där stora arealer granskog nästan har eliminerats. Insekten trivs i varmt ochtorrt klimat. Växthuseffekten i form av värmeböljor och perioder av minskad nederbörd tros gynna denna skadliga insekt då de kan fortplanta sig flera gånger och erövra nya områden under en enda sommarsäsong. En vital och nödvändig åtgärd vid bekämpning av skadeinsekter är att föra bort angripna träd innan granbarkborren lämnar barken. Dock är det nästan omöjligt attundersöka all granskog på det traditionella sättet, det vill säga till fots eftersom detär mycket tids- och resurskrävande. I det tidiga skedet visar det angripna trädet ingabetydande färgförändringar i det synliga spektrumet inom fjärranalys, vilket försvårar tidig upptäckt. Men för att försöka göra detta möjligt ämnar det här arbetet undersöka skillnaderna hos friska och angripna träd i tid, där det användes band i detosynliga spektrumet som ShortWave Infrared. Detta användes bland annat i form avbandkombinationer, som Atmospheric Penetration och Agriculture. Dessutom utfördes empiriska experiment på olika vegetationsindex (VI) som var NormalizedSimple Ratio, Enhanced Vegetation Index, Green Chlorophyll Vegetation Index,Normalized Difference Vegetation Index, Normalized Difference Moisture Indexoch Normalized Distance RED and SWIR. I denna studie användes satellitbilder från Sentinel-2 över studieområdet i Mellansverige under månaderna maj-september från 2020 till juli 2022. Inrapporterade dataför angrepp av granbarkborren i studieområdet hämtades från databasarkiven GlobalBiodiversity Information Facility och Holmen AB. Skogsstyrelsens öppna karttjänstanvändes för att erhålla data över Sveriges skogsarter, för att säkerställa att studieområdet bestod av granskog. Genom att utföra empiriska experiment av de olika VI och bandkombinationer sompresenteras i denna studie kunde några indikationer utmärkas. På grund av problematiken med de olika påverkande faktorerna, som bland annat lokalt klimat i kombination med tröskelvärden, var det svårt att fastställa en fullständig bedömning. Vårslutsats visar att de använda vegetationsindex och de två bandkombinationer tillsammans med den spatiala upplösningen, som Sentinel-2 erbjuder, inte uppnår det someftersträvas i denna studie. Anledningen till detta var att möjligheten att identifieraenstaka sjuka träd i studieområdet saknades. / The spruce bark beetle is one of Sweden's most destructive pests that attack spruceforests. The insect has had devastating consequences for spruce forests, especiallysince 2018 where large areas of spruce forest have been almost eliminated. The insect thrives in warm and dry climates. The greenhouse effect in the form of heatwaves and periods of reduced rainfall is believed to favor this harmful insect as theycan reproduce several times and conquer new areas in a single summer season. A vital and necessary measure in combating pests is to remove infested trees beforethe spruce bark beetle leaves the bark. However, it is almost impossible to examineall the spruce forest in the traditional way, which is on foot, because it is time- andresource-consuming. In the early stage, the infested tree shows no significant colorchanges in the visible spectrum in remote sensing, which makes early detection difficult. To try to make this possible, this work intends to investigate the differences inhealthy and infested trees in time, where bands in the invisible spectrum such asShortWave Infrared were used. This was used, among other things, in the form ofband combinations, such as Atmospheric Penetration and Agriculture. In addition,empirical experiments were performed on different vegetation indices (VI) whichwere Normalized Simple Ratio, Enhanced Vegetation Index, Green ChlorophyllVegetation Index, Normalized Difference Vegetation Index, Normalized DifferenceMoisture Index and Normalized Distance RED and SWIR. In this study, satellite images from Sentinel-2 were used over the study area in central Sweden during the months of May-September from 2020 to July 2022. Reported data for attacks by the spruce bark beetle in the study area were retrievedfrom the Global Biodiversity Information Facility and Holmen AB database archives.The Forestry Agency's open map service was used to obtain data on Sweden's forestspecies, to ensure that the study area consisted of spruce forest. By performing empirical experiments of the different VI and band combinationspresented in this study, some indications could be distinguished. Due to the problems with the various influencing factors, such as local climate in combination withthreshold values, it was difficult to establish a complete assessment. Our conclusionshows that the used vegetation indices and the two band combinations together withthe spatial resolution offered by Sentinel-2 do not achieve what is sought in thisstudy. The reason for this was that the possibility of identifying individual diseasedtrees in the study area was missing.

Spruce Bark contains several fundamental main substances; lignin, non-cellulose polysaccharides, cellulose and extractives. This undergraduate study focuses on developing a process to extract each of these components from spruce bark using a biorefinery concept, with a main focus on extracting lignin without degradation. The purpose of the Bark biorefinery concept is to contribute to a circular bioeconomy, by making use of natural resources. With extended research on the area, it will be possible to produce polymers, green chemicals and biofuel from the components in bark.  This report covers the extraction of the bark components with soxhlet extraction, Hot-water extraction, organosolv extraction and peracetic acid delignification. The extraction was made on two samples, matchstick-sized bark (MS) and 20 mesh-sized bark with a diameter of 0.8 mm (20M). The purpose was to be able to compare the efficiency of the extraction between the two samples. Afterwards, the characterisation of extracts and residue was executed with carbohydrate analysis, 2D HSQC-NMR and FTIR-analysis.  The results showed that a smaller particle size led to more efficient extractions of all components as well as more pure extract solutions. Lignin concentration determinations of samples at each step showed that a significant amount of lignin was lost prior to the organosolv extraction. Future research should look into ways to reduce this loss in order to increase the lignin yield. The findings in the FTIR and NMR analyses correlates with what could be seen in other reports, discussing similar subjects. For upscaling of this process, future research should go toward optimization of all extraction methods in order to make an upscaling of the process economically viable.

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.

This thesis discusses the responsibility of and risk for infestations of spruce bark beetle. The spruce bark beetle, Ips typographus, is a natural part of the Swedish forest ecosystem but causes severe financial damage in forestry. Since 2018, the spruce bark beetle infestations have been substantial in Sweden. The first task of the thesis is to evaluate the balance between the forest production interests and the environmental interests, based on the legal regulation of spruce bark beetle control. Production and environment are the equal aims of the Swedish Forestry Act. The regulation of spruce bark beetle control differs depending on whether the forest is in a conservation area or not. For example, owners of forests outside conservation areas are obliged to take care of damaged, fresh wood of spruce and pine, while such an obligation in general does not exist in conservation areas. In this evaluation, I conclude that the balance between the two interests in the spruce bark beetle regulation is good as a whole.  The second question of the thesis is the legal allocation of risk for spruce bark beetle infestations. In this investigation, it is examined whether established law presents a possibility to claim damages for spruce bark beetle infestations that may derive from an adjacent forest. The conclusion drawn is that the regulation of compensation for certain kinds of environmental damage in the Swedish Environmental Code probably would not be applicable as a legal basis for such a claim. By contrast, neighbour law and the Swedish Torts Act could be used as the basis of an action for damages. However, to prove causality regarding the origins of a specific infestation might bring problems, which altogether means that an action for damages faces considerable difficulties. Therefore lastly, some alternative ways of allocating the risk for spruce bark beetle infestations are presented. / I denna uppsats diskuteras ansvar och risk för granbarkborreangrepp. Granbarkborren, Ips typographus, är en naturlig del av skogens ekosystem men orsakar stora ekonomiska skador i skogsbruket. Sedan 2018 har granbarkborreangreppen i Sverige varit omfattande.  Uppsatsens första uppgift är att utifrån regleringen av granbarkborrebekämpning i skogen utvärdera avvägningen mellan produktions- och miljöintresset, som är skogsvårdslagens jämställda mål. Den rättsliga regleringen av bekämpning av granbarkborrar skiljer sig åt beroende på om skogen är skyddad eller oskyddad. Bland annat är ägare av oskyddad skog ålagda att ta hand om skadat, färskt barrvirke, medan en sådan skyldighet ofta saknas i skyddade områden. I utvärderingen kommer jag fram till att avvägningen mellan de två intressena över lag är god i granbarkborreregleringen.  Den andra frågan i uppsatsen är fördelningen av risk för granbarkborreangrepp. För att undersöka det utreds om det enligt gällande rätt är möjligt att få skadestånd för granbarkborreangrepp som kan härstamma från närliggande skyddad eller oskyddad skog. Slutsatsen är att 32 kap. miljöbalken förmodligen inte skulle vara tillämplig, medan däremot grannelagsrätten och skadeståndslagen kan läggas till grund för en sådan talan. Att bevisa orsakssambanden kan dock innebära problem, vilket sammantaget gör att en skadeståndstalan för granbarkborreangrepp från närliggande skog möter ansenliga hinder. Sist presenteras därför några alternativa sätt att fördela risken för barkborreangrepp.

Norway spruce (Picea abies) is a vital tree species in Sweden's extensive forested landscape. However, the planting of spruce beyond its natural range has made it vulnerable to pests like the spruce bark beetle (Ips typographus), which has caused substantial damage to Swedish forests. With the effects of global warming and climate change becoming increasingly apparent, understanding the factors influencing spruce mortality is crucial for effective forest management. This study aimed to investigate the impact of soil moisture and tree size on the susceptibility of Norway spruce to spruce bark beetle attacks. Using a combination of an Artificial Intelligence (AI) program detecting dead spruce trees and soil moisture data from the Swedish University of Agricultural Sciences (SLU), areas in Stockholm County with dead spruce trees were identified. Spatial analysis using Geographic Information System (GIS) tools and a field survey were conducted to evaluate the hypotheses: H1: Spruce mortality will be higher in areas occurring within mesic soil moisture class (1) than within mesic-moist soil moisture class (2) and moist-wet soil moisture class (3). H2: Large diameter spruce trees will have a higher mortality rate from spruce bark beetle than smaller diameter trees. H3: Spruce mortality will be higher in areas located inside nature reserves. The results confirmed that spruce mortality was higher in areas with dryer soil, Additionally, larger diameter spruce trees exhibited higher mortality rates from spruce bark beetle attacks than smaller trees. Contrary to the initial hypothesis, the study did not find a higher spruce mortality rate in areas located outside nature reserves. The conclusion of this study is that both tree size and soil moisture affect the Norway spruce’s ability to defend itself from spruce bark beetle attacks, but it does not confirm that spruce trees inside nature reserves have a greater mortality rate due to bark beetle attacks than the surrounding areas. The study has contributed to a better understanding of how spruce bark beetles choose trees. It has also provided more knowledge and validation of the Swedish Forest Agency AI program, which is trained to find dead spruce trees. The fact that this is a working tool opens a lot of possibilities for further use. The knowledge of soil moisture’s effect on spruce survival will also help forest managers make better choices when selecting areas for planting spruce. This will also benefit both the forest owners economically and help suppress the spread of spruce bark beetle. / Gran (Picea abies) är en viktig trädart i Sveriges omfattande skogslandskap. Dock har plantering av gran utanför dess naturliga utbredningsområde gjort den sårbar för skadedjur så som Granbarkborre (Ips typographus), vilket har orsakat betydande skador på svenska skogar. Med effekterna av klimatförändringar är det alltmer viktigt att förstå vilka faktorer som påverkar granens sårbarhet mot granbarkborren för en effektiv skogsförvaltning. Denna studie syftade till att undersöka påverkan av markfuktighet och trädstorlek. Genom att använda en kombination av ett artificiellt intelligensprogram (AI) som identifierar döda granar och markfuktighetsdata från Sveriges lantbruksuniversitet (SLU), identifierades områden i Stockholms län där det fanns döda granar. En spatial analys med hjälp av geografiska informationssystem (GIS) och en fältundersökning genomfördes för att utvärdera hypoteserna: H1: Granens dödlighet kommer att vara högre i områden med torr-frisk mark (1) jämfört med områden med frisk-fuktig markfuktighet (2) och fuktig-våt markfuktighet (3). H2: Granar med större diameter kommer att ha en högre dödlighetsgrad från granbarkborrsangrepp än granar med mindre diameter. H3: Granens dödlighet kommer att vara högre i områden i naturreservat än utanför. Resultaten bekräftade att granens dödlighet var högre i torrare områden. Dessutom uppvisade granar med större diameter högre dödlighetsgrad från garnbarkborreangrepp än mindre träd. Resultatet kunde inte bekräfta hypotes H3, man fann inte en högre dödlighetsgrad hos gran i områden inom naturreservat. Slutsatsen av denna studie är att både trädstorlek och markfuktighet påverkar granens förmåga att försvara sig mot granbarkborreangrepp, men den bekräftar inte att naturreservat har en påverkan på granens dödlighet till följd av granbarkborreangrepp än omgivande områden. Studien har bidragit till en bättre förståelse för hur granbarkborren väljer granar. Den har också tillfört mer kunskap och bekräftat att Skogsstyrelsens AI-program hittar döda granar. Att AI-programmet är ett fungerande verktyg öppnar upp många möjligheter för framtida användningsområden. Kunskapen om markfuktighetens effekt på granens överlevnad kommer också att kunna hjälpa skogsförvaltare att fatta bättre beslut vid val av områden för plantering av gran. Detta kommer att gynna både skogsägarna ekonomiskt och bidra till att minska antalet granbarkborreangrepp.

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