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Delottococcus aberiae (Hemiptera: Pseudococcidae) es un pseudocóccido invasor originario del África subsahariana que fue detectado causando graves daños en cítricos del este de España en el año 2009. Debido al desconocimiento existente sobre esta especie, la gestión de D. aberiae se ha llevado a cabo mediante el uso de tratamientos químicos autorizados contra este tipo de insectos. Sin embargo, la última Directiva Europea (2009/128/EC) sobre el uso sostenible de productos fitosanitarios estipula que la aplicación de plaguicidas en el ámbito agrícola debe reducirse, promoviendo estrategias de manejo más sostenibles como es la aplicación del control biológico de plagas. Además, cuando una especie invasora llega por primera vez a un territorio es necesario estudiar su biología, comportamiento, daños causados y posibilidades de control. En esta tesis se presentan por primera vez estos estudios de biología y comportamiento de la plaga así como un análisis de los daños producidos por D. aberiae. También se han realizado estudios con el objetivo de implementar la aplicación de un programa de control biológico clásico sobre esta especie en cítricos en España. Para analizar la biología y comportamiento de D. aberiae se han muestreado durante tres años varias parcelas de cítricos con poblaciones de D. aberiae en la Comunidad Valenciana. En estas parcelas se han recogido muestras y contabilizado todos los pseudocóccidos presentes, su estadío de desarrollo y el estrato y órgano del árbol donde se encontraban. El periodo de daños al fruto fue estudiado en semicampo y campo mediante la infestación artificial con D. aberiae de frutos de distintos tamaños de diámetro. Por último se estudió el comportamiento y las posibilidades de control biológico de D. aberiae muestreando diversas parcelas de cítricos en su zona de origen (Sudáfrica). Los resultados mostraron que la abundancia de las poblaciones de D. aberiae en cítricos es elevada en primavera y verano, reduciéndose a niveles mucho más bajos en otoño e invierno. Además el insecto completa varias generaciones a lo largo del año, estando dos de ellas muy claramente definidas y siendo las que dan lugar a elevadas poblaciones de la plaga. En cuanto a su distribución, D. aberiae se instaló principalmente en la copa del árbol y se observaron migraciones entre los distintos órganos, mostrando una clara preferencia por el fruto en desarrollo. Entre febrero y septiembre parte de las poblaciones de D. aberiae se encontraron en tronco y suelo, existiendo movimientos de subida y de bajada a la copa en función de la fenología de la planta y las condiciones climáticas. La comparativa entre técnicas de muestreo reveló que las trampas de cartón corrugado proporcionan una medida cuantitativa de la abundancia de D. aberiae en las parcelas. Por su parte, las trampas pegajosas, provistas de hembras de D. aberiae, fueron capaces de detectar los principales vuelos de machos. Por otro lado, D. aberiae causó daños directos al fruto (deformación y/o reducción de tamaño) al alimentarse del ovario de la flor o de los primeros estados de desarrollo de éste. Estos daños son posiblemente debidos a su interferencia con el proceso de división celular. Por último, en Sudáfrica, lugar de origen de la plaga, los mayores niveles poblaciones de D. aberiae se encontraron en verano y la tasa de parasitismo fue máxima en otoño. Entre el complejo de enemigos naturales de D. aberiae encontrados destacaron dos especies, Anagyrus sp. nov. 1 (Hymenoptera: Encyrtidae) y Allotropa sp. nov. (Hymenoptera: Platygastridae). Ambos parasitoides podrían tener un papel importante en un programa de control biológico contra D. aberiae en España. Por ahora, Anagyrus sp. nov. 1 parece el mejor candidato por sus mayores tasas de parasitismo en Sudáfrica. / Delottococcus aberiae (Hemiptera: Pseudococcidae) is an invasive mealybug native to sub-Saharan Africa that was detected causing significant damage to citrus fruits in eastern Spain in 2009. Due to the lack of knowledge about this species, the management of D. aberiae has been carried out by the application of authorized insecticides against mealybugs. However, the latest European Directive (2009/128 / EC) on the sustainable use of pesticides stipulates that chemical treatments in agroecosystems must be reduced, promoting more sustainable management strategies such as the application of biological control methodologies. In addition, when an invasive species arrives for the first time in a territory it is necessary to study its biology, behavior, damage caused and control possibilities. This thesis presents for the first time these studies of biology and behavior of the pest as well as a characterization of the damage produced by D. aberiae. The possibilities of implementing a classical biological control program against this species in citrus in Spain have also been studied. To analyze the biology and behavior of D. aberiae, several citrus orchards infested with the mealybug have been sampled for three years in the Valencian Community (eastern Spain). Samples have been collected periodically and the number of mealybugs, their developmental stage as well as the infested stratum and organ where they were present have being recorded. The period of damage to the fruit was studied in semi-field and field conditions by the artificial infestation with D. aberiae of fruits of different diameter. Finally, the behavior and possibilities of biological control of D. aberiae were studied by sampling several citrus orchards in the native area of the mealybug (South Africa). Results showed that the density of D. aberiae populations in citrus orchards is high in spring and summer, decreasing to lower levels in autumn and winter. In addition, the insect completes several generations throughout the year and two of them are clearly defined and result in high population levels. Regarding its distribution, D. aberiae was mostly installed in the canopy of the tree and migrations were observed between different organs, showing a clear preference for the developing fruit. From February to September some mealybugs were found in the trunk and soil, moving upwards or downwards depending on the phenology of the plant and the climatic conditions. The comparison between sampling techniques revealed that corrugated cardboard band traps provide a quantitative measurement of D. aberiae density in the orchards. On the other hand, sticky traps, baited with D. aberiae females were able to detect the main male flight periods. D. aberiae caused direct damage to the fruit (deformation and/or reduction in size) by feeding on the ovary of the flower or on small fruits in development. These damages are probably due to their interference with the process of cell division. Finally, in South Africa, native area of the pest, the highest density levels of D. aberiae were found in summer and the highest parasitism rates occurred in autumn. Among the complex of D. aberiae natural enemies, the two most abundant species were Anagyrus sp. nov. 1 (Hymenoptera: Encyrtidae) and Allotropa sp. nov. (Hymenoptera: Platygastridae). Both parasitoids could play an important role in a biological control program against D. aberiae in Spain. For now, Anagyrus sp. nov. 1 seems the best candidate because of its higher rates of parasitism in South Africa. / Delottococcus aberiae (Hemiptera: Pseudococcidae) és un pseudocòccid invasor originari de l'Àfrica subsahariana que va ser detectat causant greus danys en cítrics de l'est d'Espanya l'any 2009. A causa del desconeixement existent sobre aquesta espècie, la gestió de D. aberiae s'ha dut a terme mitjançant l'ús de tractaments químics autoritzats contra aquest tipus d'insectes. No obstant això, l'última Directiva Europea (2009/128/EC) sobre l'ús sostenible de productes fitosanitaris estipula que l'aplicació de plaguicides en l'àmbit agrícola ha de reduir-se, promovent estratègies de maneig més sostenibles com és l'aplicació del control biològic de plagues. A més, quan una espècie invasora arriba per primera vegada a un territori és necessari estudiar la seua biologia, comportament, danys causats i possibilitats de control. En aquesta tesi es presenten per primera vegada els estudis de biologia i comportament de la plaga així com una anàlisi dels danys produïts per D. aberiae. També s'han realitzat estudis amb l'objectiu d'implementar l'aplicació d'un programa de control biològic clàssic sobre aquesta espècie en cítrics a Espanya. Per a analitzar la biologia i comportament de D. aberiae s'han mostrejat durant tres anys diverses parcel·les de cítrics amb poblacions de D. aberiae a la Comunitat Valenciana. En aquestes parcel·les s'han recollit mostres i comptabilitzat tots els pseudocòccids presents, el seu estadi de desenvolupament i l'estrat i òrgan de l'arbre on es trobaven. El període de danys al fruit va ser estudiat en semicamp i camp mitjançant la infestació artificial amb D. aberiae de fruits de diferents mides de diàmetre. Finalment es va estudiar el comportament i les possibilitats de control biològic de D. aberiae mostrejant diverses parcel·les de cítrics en la seua zona d'origen (Sud-àfrica). Els resultats van mostrar que l'abundància de les poblacions de D. aberiae en cítrics és elevada a la primavera i estiu, reduint-se a nivells molt més baixos a la tardor i hivern. A més l'insecte completa diverses generacions al llarg de l'any, estant dos d'elles molt clarament definides i sent les que donen lloc a elevades poblacions de la plaga. Quant a la seua distribució, D. aberiae es va instal·lar principalment en la copa de l'arbre i es van observar migracions entre els diferents òrgans, mostrant una clara preferència pel fruit en desenvolupament. Entre febrer i setembre part de les poblacions de D. aberiae es van trobar en tronc i sòl, existint moviments de pujada i de baixada a la copa en funció de la fenología de la planta i les condicions climàtiques. La comparativa entre tècniques de mostreig va revelar que les trampes de cartró corrugat proporcionen una mesura quantitativa de l'abundància de D. aberiae en les parcel·les. Per la seua banda, les trampes apegaloses proveïdes de femelles de D. aberiae van aconseguir detectar els principals vols de mascles. D'altra banda, D. aberiae va causar danys directes al fruit (deformació i/o reducció de mida) en l'alimentar-se de l'ovari de la flor o dels primers estats de desenvolupament d'aquest. Aquest danys són possiblement deguts a la seua interferència amb el procés de divisió cel·lular. Finalment, a Sud-àfrica, lloc d'origen de la plaga, els majors nivells poblacionals de D. aberiae es van trobar a l'estiu i la taxa de parasitisme va ser màxima a la tardor. Entre el complex d'enemics naturals de D. aberiae trobats van destacar dues espècies, Anagyrus sp. nov. 1 (Hymenoptera: Encyrtidae) i Allotropa sp. nov. (Hymenoptera: Platygastridae). Tots dos parasitoides podrien tindre un paper important en un programa de control biològic contra D. aberiae a Espanya. Per ara, Anagyrus sp. nov. 1 sembla el millor candidat per les seues majors taxes de parasitisme a Sud-àfrica. / Martínez Blay, V. (2018). Biology and management, by application of classical biological control, of the invasive mealybug Delotoccoccus aberiae (Hemiptera:Pseudococcidae) in citrus orchards in Spain [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/106363 / TESIS

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No description available.

<p>  </p> <p>Environmental conditions, like light quality and herbivory, can induce changes in plant physiology. Light quality can be manipulated using LEDs (light emitting diodes) to improve crop quality and yield in horticultural production. The manipulation of light quality has also been utilized in the management of agricultural insect pests. Previous research has provided evidence that changes in light quality can have effects on the growth and chemistry of cannabis crops (<em>Cannabis spp.</em>). Varieties of cannabis are grown for the production of the valued cannabinoids CBD and THC. Pest of cannabis include herbivorous arthropods that reduce hemp yield and quality. Arthropod herbivory can induce chemical and physical changes in plants. This thesis further investigates the role of light quality on both cannabis biology and the crop-pest interaction between cannabis and the cannabis aphid (<em>Phorodon cannabis</em>). In the experiments described herein, the effects of light quality and <em>P. cannabis </em>herbivory on cannabis were assessed by measuring impact on biomass accumulation, yield, and the production of CBD and THC. The effects of light quality on the life history traits of <em>P. cannabis </em>were also measured. Cannabis grown under red-blue light quality saw a reduction in vegetative growth but no reduction in yield. Light treatments had no measured effect on the concentrations of CBD and THC in the cannabis buds. Aphid herbivory decreased bud yield but increased vegetative growth. Aphid herbivory reduced the concentration of both CBD and THC in cannabis bud tissue. Under blue-rich light quality, <em>P. cannabis </em>experienced higher reproductive rates when compared to red-blue and full-spectrum lighting. </p>

Since many years, the agro-technical programs such as '3 reduction 3 increase', '1 must 5 reduction' and System of Rice Intensification (SRI) have been carried out with definite results. Recently, IPM program (integrated pest management) – a more comprehensive measure (using all possible techniques and methods to keep the pest populations below a level causing economic injury) – has been firstly piloted on a large scale in the Mekong Delta. This paper presents the main results of piloting IPM program in 2,610 hectares during 2014-2017 in Hau Giang province. As results, farmers have better economic benefit in production; the quality of rice has been gradually improved and can overcome the technical barriers of advanced countries in rice trade such as US, EU and Japan. In addition, the environmental and ecological consequences can be avoided due to overuse of fertilizer and pesticide. Field ecosystems will be gradually restored. / Từ nhiều năm nay những chương trình kỹ thuật nông nghiệp như '3 giảm 3 tăng', '1 phải 5 giảm' và hệ thống canh tác lúa cải tiến (SRI) đã được áp dụng và đã có những kết quả nhất định. Còn chương trình quản lý dịch hại tổng hợp IPM - một biện pháp tổng hợp và tích cực hơn (sử dụng tất cả các kỹ thuật và biện pháp thích hợp có thể được, nhằm duy trì mật độ của các loài gây hại dưới mức gây ra những thiệt hại kinh tế) – được thực nghiệm đầu tiên trên diện rộng ở Đồng bằng sông Cửu Long. Bài báo này trình bày những kết quả chính trong thử nghiệm ở 2.610 ha lúa trong thời gian 2014-2017 ở ở tỉnh Hậu giang. Kết quả là quản lý dịch hại ở ngưỡng cho phép, người nông dân có lợi hơn về kinh tế trong sản xuất, chất lượng gạo từng bước được cải thiện và có khả năng vượt qua các hàng rào kỹ thuật trong thương mại lúa gạo của các nước tiên tiến như USA, châu Âu, Nhật Bản. Ngoài ra tránh được hệ quả về môi trường sinh thái do sử dụng quá mức phân bón hóa học và ô nhiễm do thuốc bảo vệ thực vật và hệ sinh thái đồng ruộng dần được phục hồi.

<p dir="ltr">The striped cucumber beetle (<i>Acalymma vittatum</i>) is a leading pest across a variety of cucurbit crops in eastern North America. These beetles can rapidly infest and damage a field, leading to frequent insecticide applications to manage them. Chemical control is effective at reducing beetle populations, but it also causes detrimental non-target effects on pollinators, which are essential for cucurbit yield. Developing a holistic IPM (integrated pest management) approach is necessary to manage pests while avoiding non-target effects in cucurbit production systems. </p><p dir="ltr">A unique and well-characterized behavior of striped cucumber beetles is their olfactory attraction to both plant volatiles and their species-specific aggregation pheromone, vittatalactone. The interacting effects of combining these olfactory stimuli for cucumber beetle attraction have not previously been tested. I expected when presented with plant volatiles and pheromone together, the striped cucumber beetles will show synergistic attraction, resulting in enhanced attraction stronger than the sums of the separate effects. Along with targeting striped cucumber beetles, I expected to elicit cross-attraction of related cucurbit pests (e.g., spotted cucumber beetle) to these same signals based on previous findings indicating cross-attraction. The expected cross attraction may be due to the reliance on olfactory cues to inform the related insects on preferrable host plants and nutrition. </p><p dir="ltr">Cucurbit systems are also highly reliant on pollination services for high-quality fruit; thus, the feasibility of these semiochemical tools depends on their influence on pollinator behavior. I expect pollinators to be attracted to floral volatiles but not vittatalactone or individual plant volatiles without the full complement of floral scent (e.g., indole, leaf volatiles). Altogether, this research aims to develop a targeted management tool for striped cucumber beetles and other cucurbit pests, while avoiding pollinator distraction or other detrimental effects.</p><p dir="ltr">To measure the efficacy of using olfactory signals as attractants, clear sticky cards were deployed in the field with combinations of pheromone paired with volatiles (floral and/or leaf), as well as the individual components, to quantify pest responses. Simultaneously, a pan trap sampling method was implemented to measure pollinator responses to the same semiochemical combinations. The results of the study demonstrate that striped cucumber beetles are strongly attracted to volatile lures containing pheromones, floral volatiles, and combinations of the two, although the combined pheromone and floral volatile treatments did not synergize beetle attraction. </p><p dir="ltr">Though combined lures did not synergize attraction, this data demonstrates additive effects on beetle behavior. The findings also highlight the importance of understanding seasonal disparities between the behavior of early and late generations of striped cucumber beetles. Temporal variation in attraction demonstrated by the pests is crucial to understand when to implement lure-based management strategies. Two years of testing floral volatile and herbivory-induced plant volatile (HIPV) lure treatments on key cucurbit pollinators showed varying levels of attraction. There was no attraction of focal cucurbit bees to the striped cucumber beetle pheromone, but there were differences in the response of pollinators to plant volatile components. </p><p dir="ltr">Cucurbits require high pollination activity for successful fruit, though the most important bees in pollinating this system are bees belonging to the genera, <i>Apis</i> and <i>Eucera</i>. Along with these bee groups, other bees such as those belonging to <i>Melissodes</i>, <i>Lasioglossum</i>, and <i>Bombus</i> are also known important pollinators. <i>Lasioglossum</i> bees showed a strong attraction to the full-floral blend, TIC (1,2,4-trimethoxybenzene, indole, (E)-cinnamaldehyde), but no preference for indole or HIPVs. <i>Melissodes</i> bees were most attracted to methyl salicylate and TIC, whereas <i>Eucera</i> bees exhibited strong attraction to ocimene and TIC. These findings suggest that different pollinator taxa have unique preferences for plant volatiles, highlighting the importance of optimizing lure combinations to avoid disrupting pollination activities in cucurbit production.</p><p dir="ltr">Additionally, this study revealed that other key cucurbit pests, such as spotted cucumber beetles and western corn rootworms, also showed strong attraction to the tested volatile components. These findings suggest that the selected volatiles may have broader implications for pest management beyond striped cucumber beetles. Further research is needed to fully understand the efficacy and refine formulations of these volatile lures to implement in IPM.</p>

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae) (obscure mealybug), is a common and serious pest of apples and pears in South Africa. Consumer and regulatory pressure to produce commodities under sustainable and ecologically compatible conditions has rendered chemical control options increasingly limited. Information on the seasonal occurrence of pests is but one of the vital components of an effective and sustainable integrated pest management system needed for planning the initiation of monitoring and determining when damage can be expected. It is also important to identify which orchards are at risk of developing mealybug infestations while development of effective and early monitoring tools for mealybug populations will help growers in making decisions with regards to pest management and crop suitability for various markets. It is also essential to determine the presence and efficacy of naturally occurring biological control agents in orchards so as to ascertain the potential of biological control as a viable alternative in orchards. However, under the current integrated pest management protocol, it has been difficult to determine this, due to the sporadic and relatively low incidence of mealybug infestations in some orchards, or by simply relying on naturally occurring field populations of biocontrol agents. Knowledge of the environmental conditions under which P. viburni population levels may become destructive is also essential for timing the release of insectary reared natural enemies as well as understanding the population ecology of this pest and its natural enemies. Information was gathered regarding the seasonal phenology of P. viburni and its natural enemies in pome fruit orchards in the Western Cape Province during the 2007/08 and 2008/09 growing seasons. Seasonal population studies showed that P. viburni has multiple overlapping generations with all life stages present throughout the year. The highest orchard infestations occurred during the summer period until early winter (January to early June). This was followed by a decrease in population from late June to November, before another increase in December. Presence-absence sampling of mealybugs on the host plant revealed that woody parts of the tree, such as the trunk and old stems were the most preferred sites for mealybug habitation, due to the availability of protected refuge sites. Migration of mealybug populations to newer growth and the upper sections of the tree crown, such as the new stems, leaves and eventually the fruit, was observed from December throughout the summer period until the early winter in June. Fruit colonization in both apples and pears commenced in January, when the fruit had developed a size sufficient for P. viburni to penetrate and occupy spaces such as the fruit core, calyx and stem end. There was no evidence of P. viburni occurring beneath the soil surface or on the roots of host trees. Two natural enemies of mealybugs, namely Pseudaphycus maculipennis (Mercet) and Coccidoxenoides perminutus (Girault), were found to be active in apple and pear orchards in the Western Cape. However, the status of C. perminutus as a parasite of P. viburni still needs to be verified despite evidence of emergence from P. viburni mummies, which was not sufficient enough to suggest that it is a useful biological control agent. Seasonal abundance trends of the two natural enemies revealed that their lifecycle is synchronized with that of the host. However, there was no evidence of P. maculipennis activity in Ceres. No predators were found during the course of this study. The rate of P. viburni parasitism at harvest was 46.52%, with P. maculipennis and C. perminutus constituting 98.966% and 1.034% of the parasitoids recovered from mealybug mummies, respectively. Studies on the use of pheromone traps as early monitoring tools for P. viburni showed that there was a positive and significant relationship between the fruit infestation and number of P. viburni adult males caught in pheromone-baited traps (r2 = 0.454). The action threshold level was estimated to be 2.5 male P. viburni caught per trap per fortnight at an economic threshold of 2% fruit infestation. / AFRIKAANSE OPSOMMING: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae) (ligrooswitluis), is ‘n algemene en ernstige plaag van appels en pere in Suid-Afrika. Druk deur verbruikers en regulasies om kommoditeite onder volhoubare en ekologies verenigbare toestande te produseer het chemiese beheeropsies toenemend beperk. Inligting oor die seisoenale voorkoms van plae is een van die essensiële komponente van ‘n effektiewe en volhoubare geïntegreerde plaagbestuurprogram. Dit is in die aanvanklike beplanning van monitering en om te bepaal wanneer skade verwag kan word. Dit is ook belangrik om boorde vroegtydig te identifiseer wat die risiko het om witluisbesmettings te ontwikkel. Die ontwikkeling van effektiewe en vroeë moniteringstegnieke vir witluisbevolkings sal produsente help met besluitneming rakende plaagbestuur en die geskiktheid van gewasse vir verskeie markte. Dit is ook noodsaaklik om die teenwoordigheid en effektiwiteit van biologiese beheer agente wat natuurlik in boorde voorkom te bepaal ten einde die potensiaal van biologiese beheer as ‘n lewensvatbare alternatief vas te stel. Onder die huidige geïntegreerde plaagbestuurprotokol was dit egter moeilik om laasgenoemde te bepaal weens die sporadiese en relatiewe lae voorkoms van witluisbesmettings in sommige boorde of deur bloot staat te maak op die veldpopulasies van biologiese beheer agente wat natuurlik voorkom. Kennis van die omgewingstoestande waaronder P. viburni bevolkingsvlakke skadelik raak is ook noodsaaklik vir die beplanning van vrylating van biologiese beheer agente, asook om die bevolkingsekologie van hierdie plaag en sy natuurlike vyande te verstaan. Inligting oor die seisoenale fenologie van P. viburni en sy natuurlike vyande in sagtevrugte boorde in die Westelike Kaapprovinsie is gedurende die 2007/08 en 2008/09 groeiseisoene versamel. Seisoenale bevolkingstudies het getoon dat P. viburni verskeie oorvleuelende generasies het met alle stadia teenwoordig regdeur die jaar.

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 Tasmanian lacewing (Micromus tasmaniae Walker) is one of the most common aphid predators occurring in lucerne crops in New Zealand. A comparison of sampling techniques, and the output from a simulation model, suggest that the abundance of this lacewing may have been significantly underestimated in the past. Although the occurrence of aphid predators was erratic M. tasmaniae occurred more often and in far greater numbers (up to 100 m⁻²) than any other predator species. A simulation model for lacewing development in the field indicated that the large adult populations which occurred could be accounted for on the basis of reproductive recruitment. Independent evidence that immigration was not involved in the occurrence of these large populations was gathered using directional flight traps around the field perimeter. The major factors influencing lacewing population dynamics were the availability of aphid prey and, in the autumn, parasitism. Otherwise, survival of all life-histoty stages was high with no evidence of egg or larval cannibalism. Several instances of high lacewing mortality were identified by the model and the lack of any obvious cause for these highlights inadequacies in the understanding of lacewing bionomics. The model, which used a linear relationship (day-degrees) between development and temperature, was incapable of accurately predicting lacewing emergence under field temperatures which fluctuated outside the linear region of the development rate curve. Temperature thresholds and thermal requirements estimated under fluctuating temperatures similar to those in the field produced almost identical model output to those estimated under constant temperatures in the laboratory. Prey species was capable of influencing the rate of lacewing development. M. tasmaniae has the attributes necessary to produce large populations in the short time available between lucerne harvests. The asymptote of the functional response curve is low but the efficiency at converting aphids to eggs is high. Therefore, the lacewing is able to attain maximun reproductive output at low prey densities. A low temperature threshold for development (4-5° C), rapid development and short preoviposition period results in a short generation time (49 days at 15° C). Long adult life, high fecundity and the absence of any form of estivation or diapause, results in complete overlap of generations and multiple generations per year. M. tasmaniae's role as an aphid predator is restricted by its low appetite for prey and by the lucerne management regime currently practiced in New Zealand. Because it consumes relatively few aphids per day the lacewing's ability to destroy large aphid populations is limited. However, this may be offset by its ability to attack aphids early in the aphid population growth phase, and by the large numbers of lacewings which may occur. Under the present lucerne management schemes the large lacewing populations which do occur are forced out of the fields, or die, following harvest. A number of management options for increasing the lacewings impact as an aphid predator are briefly discussed.