Academic literature on the topic 'Defoliators'

Made available in DSpace on 2015-03-26T13:30:36Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2505271 bytes, checksum: ba47cbd5b7b70a7df9f833e0c3a80f65 (MD5) Previous issue date: 2011-07-25<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The work was performed to expand the knowledge about the biology of Oncideres ocularis Thomson, 1868 (Col.: Cerambycidae), during the period of September/2009 to March/2011. Girdled twigs and adult insects of this species were collected from three commercial plantations of Acacia mangium Willd. located in the Coimbra county, Minas Gerais State, and from one silvipastoral system of Eucalyptus urophylla S.T. Blake x E. grandis W. Hill ex Maiden, A. mangium and Brachiaria spp. located at Viçosa county, Minas Gerais State, Brazil. The egg, when recently laid, was white, show an elongated ellipsoid shape, 2,44 ± 0,02 mm average length and 0,58 ± 0,12 mm width. The eggs incubation period was 12,1 ± 0,2 days and the eggs viability was 60,78%. The first instar larvae were yellowish-white, had no legs, body covered with tiny hairs, mainly, on the last abdomen segments. Larvae were 1,90 ± 0,03 mm long, 0,61 ± 0,01 mm wide, with head capsule measuring 0,35 ± 0,01 mm wide. The occurrence period adults was from December to March. Females made 17,27 ± 1,0 incisions per girdled branch, laying just one egg per incision. Incisions were more concentrated at the lower-medium and medium section of the girdled branches, and less concentrated at the upper section. Males and females adults can be distinguished by the last antennal segment length; it was seven times longer than it pedicel on males and around two times and a half longer on females. They also can be distinguished by the shape of the last abdominal segment; it had a inverted &#8220;v&#8221; shape on males, and a rounded shape on females. Girdles twigs were 9,88 ± 0,18 mm in diameter and 99,21 ± 2,23 cm in length. A girdle made by one O. ocularis can cause an average loss of 4.233,05 ± 726,75 cm² of foliar area, per tree. Females were upside down while girdling the branches, and spent from one to two days to girdle one twig, and adults fed upon twig bark. Other cerambycids also emerged from twigs girdled by O. ocularis: Engyum quadrinotatum (Thomson, 1864), Orthostema abdominale (Gyllenhal, 1817), Nesozineus bucki (Breuning, 1954) and Lepturges sp., and beetles in the Buprestidae, Scolytidae and Bostrichidae families. Such insects co-inhabiting the branches were token in account as very important competitors for space and food against O. ocularis. Variables as twig diameter, girdled area, twig length, foliar mass, twig mass, number of secondary branches, twig volume, twig superficial area, number of incisions and number of larvae hatched, evaluated on 100 girdled branches were used to search for patterns on the twig morphology that affect the reproduction of this insect . The best models had included the twig superficial area and twig volume. So biological stages of the twig girdler O. ocularis were characterized, and become clear that only the twig morphology is insufficient to explain variations on the reproduction of this insect.<br>Este estudo teve o objetivo de caracterizar das fases biológicas de Oncideres ocularis Thomson, 1868, bem como verificar se existem padrões na morfologia do galho roletado por esse serrador, ou em sua atividade de oviposição que venham a interferir na reprodução da espécie. Os estudos foram realizados com galhos e insetos coletados em três plantios comerciais de Acacia mangium Willd. localizados em Coimbra-MG e um plantio consorciado entre Eucalyptus urophylla S.T. Blake x E. grandis W. Hill ex Maiden, Acacia mangium e Brachiaria spp., localizado em Viçosa-MG, entre novembro de 2009 e março de 2011. No estudo das fases biológicas desse inseto, conduzido em Viçosa-MG, constatou-se que os ovos de O. ocularis quando recém-depositados, são de coloração branca, possuem forma elipsóide de revolução alongada, têm comprimento médio de 2,44 ± 0,02 mm e largura média de 0,58 ± 0,12 mm; o período de incubação foi de 12,1 ± 0,2 dias e a viabilidade foi de 60,78%. As larvas recém-eclodidas são de coloração amarela-pálidas, ápodas, corpos providos de pelos curtos, apresentando grande quantidade nos últimos segmentos do abdômen, e possuem uma placa calcária na parte dorsal do protórax. Essas larvas tinham comprimento médio de 1,90 ± 0,03 mm, largura média de 0,61 ± 0,01 mm e largura de cápsula cefálica média de 0,35 ± 0,01 mm. A época de atividade dos adultos foi de dezembro a março. As fêmeas realizaram, em média, 17,27 ± 1,0 incisões de postura por galho roletado, colocando apenas um ovo em cada incisão. As incisões se concentraram nas seções médio-basal e mediana dos galhos roletados e tiveram menor concentração na porção apical dos galhos. Machos e fêmeas dessa espécie foram diferenciados baseando-se no comprimento do último segmento antenal; nos machos ele era sete vez mais comprido do que o próprio pedicelo, enquanto nas fêmeas essa diferença era de apenas duas vezes e meia. Os adultos puderam ser sexualmente diferenciados pela forma do último segmento abdominal, tendo a forma de &#8220;v&#8221; invertido nos machos e arredondado nas fêmeas. Esse serrador roletou galhos com diâmetro e comprimento médios de 9,88 ± 0,18 mm e 99,21 ± 2,23 cm, respectivamente. O roletamento feito por O. ocularis pode resultar na perda média de área foliar de 4.233,05 ± 726,75 cm² por árvore. As fêmeas roletaram os galhos posicionando-se de cabeça para baixo, e demorando-se de um a dois dias para consumar o roletamento. Os insetos adultos se alimentaram da casca de galhos, tanto das partes mais tenras quanto das mais lenhosas. Dos galhos roletados por essa espécie também emergiram os cerambicídeos: Engyum quadrinotatum (Thomson, 1864), Orthostema abdominale (Gyllenhal, 1817), Nesozineus bucki (Breuning, 1954) e Lepturges sp., além de besouros das famílias Buprestidae, Scolytidae e Bostrichidae. Esses insetos associados foram considerados importantes competidores por espaço e por alimento, em relação a O. ocularis. Na outra parte do trabalho, procurou-se verificar se existiam padrões na morfologia do galho que influenciasse na reprodução de O. ocularis. Para isso avaliaram-se o diâmetro do galho, a área do roletamento, o comprimento do galho,a massa foliar, massa do galho, a quantidade de ramos secundários, o volume útil do galho, a área superficial do galho, a quantidade de incisões de postura e a quantidade de larvas eclodidas em 100 galhos roletados em A. mangium. Nenhuma destas variáveis foi satisfatória para se obter um modelo capaz de prever a quantidade de ovos depositados por galho e a quantidade de larvas eclodidas, entretanto, a área superficial e o volume do galho roletado foram as que apresentaram maior coeficiente de determinação. Ficam assim, caracterizadas algumas fases biológicas dessa espécie de besouro serrador e evidente que apenas caracteres morfológicos dos galhos roletados são insuficientes para afetar a reprodução de O. ocularis em A. mangium.

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia<br>Thaumetopoea pityocampa is a major pine defoliatior over the Mediterranean Basin. An atypical population with a shifted phenology, ongoing an allochronic differentiation process, was recently discovered in Mata Nacional Leiria, Portugal. The shifted population reproduces in spring achieving its larval development during summer (SP), whereas the sympatric typical population reproduces in summer and has winter larval development (WP). They are reproductively isolated through time, although sharing the same space and host species. General objectives of this work were to characterize the current and potential distribution range of this population, its spatial/temporal genetic and demographic patterns, and ecological adaptations. Field monitoring of presence/absence of SP nests throughout Leiria showed that it is expanding to North and South. Current distribution is restricted to coastal areas, along ca. 120 x 20 km area. Distribution models predict that its distribution will be restricted to coastal areas, due to unsuitable climate inland, being the maximal temperatures of the summer months the main constraint. A phylogeographic study confirmed high SP differentiation from other Portuguese populations. A spatio-temporal sampling along two geographic transects in Leiria zone revealed high stability in time of the genetic composition and structure. A striking demographic result showed that SP tends to apparently displace the WP from the coastal zones suggesting a possible competition phenomenon. Gene flow between the two populations was shown to remain low, even if some SP males actually emerge late. Ecological differentiation was assessed at egg and larval stages. The effect of a wide range of high temperatures on egg survival and development showed higher performances of the SP. Furthermore, SP larvae showed a better ability to cope with host plant water stress, evidencing adaptation to summer feeding activity. This study highlights intra-specific variations on the response of this insect to environmental constraints evidencing ecological adaptation following allochronic differentiation<br>N/A

Fall cankerworm (FCW) outbreaks have recently increased in frequency and intensity in the mid-Atlantic region of the United States, especially around cities of Charlotte, NC and Richmond, VA. This study evaluated the effects of two landscape features associated with urbanization, impervious surface and forest cover, on population patterns of FCW and its parasitoids across eastern Virginia. Forest cover was positively related to parasitism rates while impervious surface was positively related to FCW abundance, suggesting that FCW outbreaks may be amplified in urban areas. FCW abundance declined over the two-year period of this study, but parasitism rate increased at most sites. Parasitism was highest at sites that experienced FCW outbreaks first, indicating that parasitoid populations are responding to moth abundances. It remains to be seen whether this outbreak was an aberrant occurrence, or represents a regime shift to more frequent defoliation in Virginia, similar to that in North Carolina urban areas.

Made available in DSpace on 2015-03-26T13:39:30Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1252229 bytes, checksum: 0b4593a2852a3887d9a7973222e702d8 (MD5) Previous issue date: 2009-02-11<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>The soybean [Glycine max (L.) Merr.] is an important crop in the world with high economic and social value. The carterpillar Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae) is the most important defoliator of soybean in North and South Americas and the search for useful insecticides to control this pest has been studied. The neem, Azadirachta indica A. Juss (Meliaceae) is the plant with high insecticide potential of the world. The azadirachtin, synthesized mainly in the fruits of this plant is the main component responsible for the lethal and sub-lethal action of the extracts obtained from neem. The objective of this study was evaluate the potential of products derived from A. indica on A. gemmatalis in the laboratory and greenhouse conditions. Third stage larvae of A. gemmatalis were fed for four days with artificial diet containing neem seed ethanol extract and oil trade, AzamaxTM. Mortality, food consumption, feces production, weight gain, weight and deformation of pupae at 24 hours old and the number of eggs per female emerged from larvae fed on sub-lethal doses of azadirachtin were evaluated in laboratory. The effects of neem seed extract and the oil trade on mortality and food consumption of larvae of A. gemmatalis in soybean plants in the greenhouse were also evaluated. The neem seed extract and trades Azamax, caused deleterious effects on the A. gemmatalis larvae, as larval and pupal mortality, reduction of food intake and weight gain, disruption of midgut cells and changes in the fat body. Lower dosages of neem seed extract reduced the egg productions of the A. gemmatalis moths. Soybean plants sprayed with both products from A. indica caused high mortality and reduced the damages by A. gemmatalis in greenhouse conditions. The neem products can be used in integrated program management of A. gemmatalis in the soybean crop.<br>A soja [Glicine max (L.) Merr.] é uma das mais importantes plantas cultivadas no mundo com grande valor econômico e social. Insetos pragas podem reduzir a produção dessa cultura, destacando-se Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae), como o desfolhador mais importante da soja nas Américas do Sul e Norte. O nim indiano, Azadirachta indica A. Juss (Meliaceae), é a planta com maior potencial inseticida do mundo. A azadiractina, sintetizada principalmente nos frutos dessa planta, é o principal composto responsável pela ação letal e subletal dessa substância. Os efeitos da azadiractina sobre A. gemmatalis não foram, ainda, estudados, mas, essa praga demonstrada elevada suscetibilidade à inseticidas sintetizados por plantas. Os objetivos desse trabalho foram avaliar o potencial de produtos derivados de A. indica sobre A. gemmatalis em condições de laboratório e casa de vegetação. Lagartas de terceiro estádio de A. gemmatalis foram alimentadas por quatro dias com dieta artificial contendo extrato etanólico de sementes de A. indica e óleo comercial, Azamax®. A mortalidade, consumo alimentar, produção de fezes, ganho de peso vivo, peso e deformação de pupas com 24 horas após o inicio desse estágio e sobrevivência e a quantidade de ovos produzidos por fêmea emergida a após a exposição ao estrato de nim na fase jovem foram avaliados em laboratório. Os efeitos da aplicação de extrato de sementes de nim e do óleo comercial, Azamax® sobre a mortalidade e consumo alimentar de lagartas de A. gemmatalis em plantas de soja, em casa de vegetação foram, também, avaliados. O extrato de sementes de nim e óleo comercial, Azamax, causaram efeitos deletérios nas lagartas de A. gemmatalis, como mortalidade larval e pupal, redução do consumo alimentar e do ganho de peso, desorganização nas células do intestino médio, modificações no corpo gorduroso e redução da síntese de proteínas no corpo gorduroso. Mariposas A. gemmatalis expostas ao extrato de nim apresentarm redução na quantidade de ovos produzidos. A pulverização de plantas de soja com produtos derivado de A. indica causou elevada mortalidade e reduziu os danos por A. gemmatalis nessa cultura. Isto torna possível a utilização desses produtos em programas de manejo integrado de A. gemmatalis na cultura da soja.

This work identified semiochemicals that might mediate host selection by the eucalyptus weevil Gonipterus platensis (Coleoptera, Curculionidae) and by its egg parasitoid Anaphes nitens (Hymenoptera, Mymaridae), as well as pheromones emitted by the weevil. Characterization of Eucalyptus globulus and G. platensis volatile organic compounds was conducted using one and two-dimensional gas chromatographic techniques, coupled to different detectors. Antennal active compounds for the weevil and for the parasitoid, were detected by gas chromatography-mass spectrometry/electroantenography. Bioassays were performed in an olfactometer and Petri dish arenas, respectively. For G. platensis, 51 compounds emitted by E. globulus elicited antennal responses, eight of which showed kairomonal activity and two allomonal property. Behavioural responses depended both on sex and physiological condition (mated or virgin) of the insects.<br>Neste trabalho identificaram-se semioquímicos potencialmente utilizados pelo gorgulho do eucalipto, Gonipterus platensis (Coleoptera, Curculionidae) e pelo seu parasitóide oófago, Anaphes nitens (Hymenoptera, Mymaridae), no processo de selecção de hospedeiro, bem como feromonas emitidas pelo gorgulho. As fracções voláteis de Eucalyptus globulus e G. platensis foram caracterizadas utilizando técnicas de cromatografia gasosa uni- e bidimensional abrangente, acopladas a diferentes detectores. Os compostos percepcionados pelas antenas do gorgulho e do seu parasitoide foram detectados por cromatografia gasosa acoplada a espectrometria de massa e electroantenografia. Realizaram-se bioensaios comportamentais num olfactómetro e em arenas. Foi registada resposta das antenas de G. platensis a 51 compostos voláteis emitidos pelo eucalipto, oito dos quais se revelaram atractivos e dois repelentes, dependendo as respostas comportamentais tanto do sexo como do estado fisiológico (virgem ou acasalado) dos gorgulhos.

The tachinid fly Compsilura concinnata (Meigen) was introduced to North America in 1906 for the biocontrol of the forest defoliators Lymantria dispar (L.) and Euproctis chrysorrhea (L.) when these caterpillars were defoliating large areas of eastern Massachusetts. Most of the flies released, however, were the progeny of adults emerging from E. chrysorrhea caterpiliars collected in Eastern Europe. Although this tachinid is a generalist parasitoid, in Europe it is considered an important specialist of pestiferous species based on the level of its recovery there. Also, as one of the first insects established against forest defoliators in the Northeast, C. concinnata is in a premier position of providing information about colonization that increases the understanding in population genetics of how founder effects and dispersal influence the establishment of exotic insect populations. Initially in this study, a historical analysis was conducted to prepare a chronology of release of C. concinnata into North America and delimit its distribution. The introduction and release of C. concinnata was relatively restricted as they were primarily reared from one host E. chrysorrhea collected in Eastern Europe. More importantly, the extent to which this fly moved ahead of successive releases suggested there may be a historical basis to expect little differentiation among their nearctic populations. The literature on population genetics and use of electrophoretic analyses were surveyed to establish their use with C. concinnata in North America. Enzyme electrophoresis has been widely used for delimiting populations of non-native parasitoids and tracking their movement into new hosts and localities. To determine the suitability of enzyme electrophoresis for a population genetic analysis of C. concinnata, selected isozymes were identified and cataloged in an established laboratory strain. The analysis of isoenzyme patterns for measuring the relatedness among and between individuals, is useful in molecular studies of population genetics provided these patterns are heritable. To determine the heritablility of isozymes in C. concinnata, an electrophoretic analysis was conducted using both the parents and adult progeny of observed matings. The genetics of some C. concinnata isoenzymes followed simple patterns of Mendlian inheritance and were allozymic. The population genetic structure of C. concinnata in North America was examined with trap-hosts placed throughout the Northeast. The flies reared out were sampled with protein electrophoresis. There were slight differences in the allozymes and allele frequencies of C. concinnata and in comparison with other Diptera, the variation among Northeastern populations was relatively low. The variability among Northeastern populations of this parasitoid reflect limited genotypes in the founding populations. Over time new differences in protein loci between geographically separated populations probably arise through selection or drift than through non-lethal mutations. The time needed for protein coding loci between distantly spaced populations of introduced insects to diverge sufficiently for them to be detectable has not been determined. Estimating the time needed for allozymes of introduced insects to reject such differentiation is useful in understanding the evolution of biotypes, but is not a trivial process. Historical research in combination with analyses of the variability in allele frequencies among populations can be useful in determining the extent of divergence in non-native species that may lead toward new biologically adapted forms.

Acacicola orphana (Erichson) is a winter developing insect that severely defoliates its host trees, Acacia dealbata (Link.) and A. mearnsii (De Wild.). Both adults and larvae feed on green bark and foliage, resulting in damage which may lead to tree death. This study investigates the biology and ecology of A. orphana, focussing on its developmental biology, distribution and host-plant relationships. At the commencement of this project a basic guide to the different stages of A. orphana was established. Developmental biology was examined in the laboratory, where development from eggs to adults was found to require 1266 DD > 4.4 °C. Field development studies suggested a lower threshold. Consequently, inaccuracies were observed when laboratory information was used to predict the timing of stages in the field. Management strategies therefore need to be based on field estimates. Natural enemies of A. orphana identified were; a tachinid, Lixophaga sp., a braconid hyperparasitoid, Meteorus sp. and a fungal pathogen, Beauveria bassiana. Fourth instar mortality attributable to the tachinid was up to 17%. Beauvaria bassiana was recovered from adults only and caused up to 12% mortality. Geographical distribution of A. orphana was mapped throughout southeastem Australia. This information was then used to predict the distribution throughout Australia and globally using CLIMEX, a climate modelling package. Global mapping predicted populations could survive in African and Asian countries where some Acacia species (in particular A. mearnsii) are economically important. On the Australian mainland, A. orphana was observed predominantly on A. mearnsii, rather than on A. dealbata, which was its main host in Tasmania. Thus, experiments examining oviposition, larval development and survival between A. dealbata and A. mearnsii were undertaken. Whilst both species experienced similar levels of defoliation in the field, larval development was 25% faster on A. mearnsii. Acacia orphana and its interactions with Acacia dealbata were the main focus of this study. Consumption studies showed final instar A. orphana consumed `0.93 g^-1g^-1day^-1` and the efficiency of conversion was 40%. Initial hypotheses relating to bark feeding behaviour were disproved, with findings that green bark feeding does not occur due to a lack of foliage, nor does it enhance the foliage quality for the next generation of larvae. Further investigations of host-plant interactions involved assessing first instar larval survival and defoliation on four different A. dealbata provenances. General differences in nutrition, colour and fluctuating asymmetry of the trees were also assessed. One provenance experienced significantly less defoliation. Phenotypic differences showed that low foliar nitrogen, low moisture and redder-coloured foliage were related to increased defoliation and larval survival. It was hypothesised that climate and environmental conditions primarily regulate the host-plant interactions of A. orphana.

Tese de doutoramento em Biociências, na especialidade de Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra<br>As aves insectívoras foram o objecto desta investigação sistemática realizada no montado com o propósito de determinar a sua importância no controlo de pragas de sobreiro (Quercus suber) e azinheira (Q. rotundifolia), nomeadamente desfolhadores. Numa revisão bibliográfica focada na dieta e ecologia alimentar das aves reprodutoras, invernantes e residentes no sudoeste da Península Ibérica foram identificadas vinte e seis espécies como potenciais predadores regulares das principais pragas de sobreiro e azinheira. Os nichos alimentares destas aves mostraram uma relação com a biologia das pragas consumidas: aves que se alimentam no solo ingerem pupas e larvas de insectos carpófagos, aves que se alimentam nas árvores consomem ovos, larvas e pupas de desfolhadores e de insectos xilófagos, e aves que se alimentam em voo capturam insectos voadores na fase adulta. No que respeita aos desfolhadores, o impacto das aves nas suas populações supõe-se maior durante a Primavera-Verão, coincidindo com a fase de desenvolvimento larvar nas folhas na qual estes estão particularmente expostos à predação por várias espécies de passeriformes arborícolas que ocorrem em densidades elevadas e apresentam uma larga distribuição no montado. Este princípio foi verificado no terreno, ao mesmo tempo que a selecção entre sobreiro e azinheira pelas aves insectívoras foi investigada tendo em conta a espécie arbórea dominante no montado. Quase 95% da predação de artrópodes pelas aves nas árvores foi efectuada por apenas sete espécies de passeriformes, que, por sua vez, representaram mais de 60% da abundância total de aves: chapim-azul (Cyanistes caeruleus), chapim-real (Parus major), chapim-de-crista (Lophophanes cristatus), tentilhão (Fringilla coelebs), toutinegra-de-cabeça-preta (Sylvia melanocephala), trepadeira-azul (Sitta europaea) e trepadeira-comum (Certhia brachydactyla). As variações na dominância de sobreiro e azinheira tiveram pouca influência nas comunidades de aves nidificantes do montado, contudo as aves que se alimentam na casca preferiram moderadamente o sobreiro. Também foi sugerido, via modelação estatística do tempo dispendido pelas aves em alimentação em cada árvore, que algumas características morfológicas, fenológicas e fisiológicas relacionadas com a abundância de artrópodes nos sobreiros e azinheiras podem ser utilizadas para avaliar a qualidade do habitat para as aves insectívoras florestais. As respostas numéricas e funcionais das aves insectívoras a surtos localizados de larvas de duas importantes pragas de desfolhadores, a lagarta-do-sobreiro (Lymantria dispar) e a lagarta-verde (Periclista andrei), em montados de sobro foram comparadas com uma área-controlo não-infestada. Quatro espécies responderam positivamente aos surtos de desfolhadores: as densidades de trepadeira-azul e de tentilhão foram superiores nas áreas atacadas por lagarta-do-sobreiro e lagarta-verde, respectivamente (respostas numéricas), e o chapim-azul e o chapim-de-crista passaram mais tempo em alimentação nas árvores infestadas por lagarta-do-sobreiro (respostas funcionais). Estes resultados estão de acordo com as teorias de predação generalista e salientam a importância do controlo biológico natural pelas aves, nomeadamente através de mecanismos de regulação dependentes da densidade das pragas. A função das aves como predadores de larvas de desfolhadores foi avaliada em diferentes nichos das árvores na ausência de surtos, comparando a densidade, o tamanho e a composição das lagartas capturadas e a frequência de alimentação de crias em caixas-ninho de três espécies-chave: chapim-azul, chapim-real e trepadeira-azul. As lagartas foram a principal ou a segunda principal presa consumida pelas crias das três espécies. Em particular, o chapim-azul consumiu uma percentagem de lagartas significativamente mais elevada do que as outras espécies, e apresentou igualmente uma taxa de remoção de lagartas significativamente maior à escala do habitat. Por outro lado, não se verificaram diferenças entre as três espécies na provisão de biomassa de lagartas à escala do habitat devido a uma predação complementar dos instars iniciais e finais das lagartas pelo chapim-azul e pelas outras duas espécies, respectivamente. Por fim, numa experiência onde se testou o aumento da densidade reprodutora de passeriformes por intermédio da colocação de caixas-ninho, foi registado um aumento significativo na densidade de chapim-azul nas parcelas onde foram colocadas caixas-ninho em comparação com as parcelas-controlo (+ 38.2%), tendo as caixas-ninho contribuído também para um aumento considerável das populações nidificantes de chapim-real e trepadeira-azul (+ 26.8% e + 14.3%, respectivamente). No geral, esta tese afirma a importância do controlo biológico natural proporcionado por espécies comuns de passeriformes residentes no montado e apela aos proprietários para considerarem o efeito das práticas de gestão nas populações destas aves de modo a prevenir surtos de pragas.<br>A systematic investigation on insect predation by birds was conducted in Mediterranean oak woodlands of southwestern Iberian Peninsula with the purpose of assessing the services provided by insectivorous birds in the control of cork oak (Quercus suber) and holm oak (Q. rotundifolia) pests, particularly defoliators. Through a literature review concerning foraging ecology and diet of breeding, wintering and resident birds in southwestern Iberian Peninsula, twenty-six species were listed as potential regular predators of the main cork and holm oak pests. A strong interaction was found between bird foraging guilds and the biology of consumed pests: ground-foragers prey on overwintering pupae and larvae of seed-borers, tree-foragers prey on eggs, larvae and pupae of defoliator and wood-boring pests, and aerial-sweepers prey on airborne imagines. Regarding defoliators, spring-summer was recognized as the period when bird predation is supposed to have the greatest impact on their populations because caterpillars, throughout their development on foliage, are highly vulnerable to predation by various tree-foraging passerine species which occur in high densities and are widespread in Mediterranean oak woodlands. Such prediction was validated in the field at the same time that tree selection between cork oak and holm oak by insectivorous birds was studied with respect to dominant tree species of Mediterranean oak woodlands. Approximately 95% of arthropod predation by birds on trees was carried out by only seven passerine species, which, by themselves, represented more than 60% of total bird abundance: blue tit (Cyanistes caeruleus), great tit (Parus major), crested tit (Lophophanes cristatus), chaffinch (Fringilla coelebs), Sardinian warbler (Sylvia melanocephala), nuthatch (Sitta europaea) and short-toed treecreeper (Certhia brachydactyla). Local scale variation in cork oak- and holm oak-dominance had little effect on breeding bird communities, although bark-gleaners moderately preferred cork oak. It was also suggested, via statistical modeling of the time spent by foraging birds on each tree, that some characteristics regarding morphology, phenology and physiological condition of cork and holm oak trees can be used to predict habitat quality for insectivorous forest birds. Numerical and functional responses of the tree-foraging guild to localized larval outbreaks of two major defoliator pests – gypsy moth (Lymantria dispar) and the sawfly Periclista andrei – in cork oak woodlands were compared with a non-infested control. Four species evidenced positive responses to defoliator outbreaks: densities of nuthatch and chaffinch were higher in the outbreak areas of gypsy moth and P. andrei, respectively (numerical responses), and blue tits and crested tits spent a significantly larger amount of time foraging on trees infested with gypsy moth (functional responses). These results are consistent with predictions of the generalist predator hypothesis and drawed attention to the importance of natural biological control by birds, namely through density-dependent mechanisms of pest regulation. Bird predation on defoliator caterpillars was estimated in non-outbreak conditions, through identification of food given to nestlings by three hole-nesting passerine species which forage on different niches of trees: blue tit (Cyanistes caeruleus; foliage-gleaner), great tit (Parus major; bark-foliage-gleaner) and nuthatch (Sitta europaea; bark-gleaner). Their specific roles were compared using breeding densities, size and composition of preyed caterpillars and provisioning rates to nestlings reared in nest-boxes. Caterpillars were the most, or second-most, common prey consumed by nestlings of the three species. Blue tits, in particular, consumed a significantly higher percentage of caterpillars than the other two passerine species, and showed a significantly higher removal rate of caterpillars at the habitat scale. On the other hand, the supply of caterpillar biomass to each species showed little differences at the habitat scale due to caterpillar size segregation between blue tit and the other two species, which preyed on early and late instars of caterpillars, respectively. Finally, a before-after control-impact (BACI) experience used to test the increase of the breeding density of hole-nesting passerines by setting nest-boxes, achieved a significant increase in the density of blue tit in manipulated nest-box plots compared with control plots (+ 38.2%) while it also contributed for a considerable increase in breeding populations of great tit and nuthatch (+ 26.8% and + 14.3%, respectively). On the whole, this thesis shows the importance of natural biological control by common resident passerine species in Mediterranean oak woodlands and calls on landowners to consider the effect of management interventions on their populations in order to prevent pest outbreaks.<br>FCT - SFRH/BD/78813/2011