Made available in DSpace on 2017-05-12T14:47:57Z (GMT). No. of bitstreams: 1 Patricia Stadler Rosa Lucca.pdf: 1596078 bytes, checksum: 26545cacc279bf8104c7bd2edea4d008 (MD5) Previous issue date: 2010-06-10 / The use of natural substances for pest management in agriculture is, economically, a viable option and has benefits for both human-beings and environment, due to its low persistence and toxicity. Thus, this trial aimed at determining the insecticidal potential of extracts and essential oils of fennel (Foeniculum vulgare), sweet herb (Pimpinella anisum), clove (Caryophillus aromaticus) and of homeopathic preparations from CH 05 and CH 06 aphid on the control of Brevicoryne brassicae in cabbage (Brassica oleracea var. acephala). The treatments were: fennel extracts, sweet herb and cloves at 10%; fennel oils, sweet herb and cloves at 1%; homeopathic preparations with CH 05 and CH 06 aphid; control with distilled water. The mortality tests were done concerning nymphs and adults of aphids in laboratory, with three replications, each one consisting of a cabbage leaf kept inside a Petri dish containing moistened cotton. On each plate, ten nymphs were released added with a 1 mL spray of the respective solutions. The plates were covered with a perforated plastic film and incubated with a 12 hour photoperiod at 25 ° C. Evaluations were performed after 1, 12, 24, 48 and 72 hours. After analysis in the laboratory, some tests were done with the culture, in pots, only with the Indian cloves extracts at 10% and fennel oil at 1% treatments, since they were significant. There was, moreover, the sensorial analysis of cabbage, treated with clove extract at 10% and fennel oil at 1%. Data analysis was performed by analysis of variance and averages comparison by Tukey, at 5% of significance. In lab tests, it was found out that fennel oil at 1% showed the best rate of mortality on aphid nymphs, which means 70%, at 72 h, followed by clove extract at 10% with 37% of mortality. It was registered for survival of adults aphids that the fennel oil at 1%, fennel extract at 10% and clove extract at 10% had the lowest survival rates, as: 46%, 53% and 53 %, respectively. A mortality test was carried out in the culture and it was registered the effectiveness of clove extract at 10% and fennel oil at 1%, and they had 6% and 8% of survival in adults aphids, respectively. The sensorial analysis of cabbage did not indicate any significant difference among them, at 5% significance. / O uso de substâncias naturais para manejo de pragas da agricultura é uma opção economicamente viável e traz benefícios tanto ao homem como ao ambiente, devido a sua baixa persistência e toxicidade. Dessa forma, o objetivo do trabalho em questão foi verificar o potencial inseticida de extratos e óleos essenciais de funcho (Foeniculum vulgare), erva doce (Pimpinella anisum), cravo-da-Índia (Caryophillus aromaticus) e dos preparados homeopáticos para o controle de Brevicoryne brassicae em couve (Brassica oleracea var. acephala). Os tratamentos utilizados foram os extratos de funcho, erva-doce e cravo-da-Índia a 10%; óleos de funcho, erva-doce e cravo-daÍndia a 1%; preparados homeopáticos de pulgão CH 05 e CH 06 e controle com água destilada. Realizaram-se testes de mortalidade sobre ninfas e adultos de pulgão em condições de laboratório, com três repetições, cada uma constituída por uma folha de couve mantida no interior de uma placa de Petri contendo algodão umedecido. Em cada placa, foram liberadas dez ninfas e pulverizado 1 mL das respectivas caldas. As placas foram cobertas com filme plástico perfurado e incubadas com fotoperíodo de 12 horas a 25 °C. Avaliações foram realizadas após 1, 12, 24, 48 e 72 h. Após análise em condições de laboratório, realizaram-se testes na cultura, em vasos, somente com os tratamentos extrato de cravo-da-Índia a 10% e óleo de funcho a 1%, pois os mesmos apresentaram-se significativos. Realizou-se, ainda, análise sensorial das couves tratadas com o extrato de cravo a 10% e óleo de funcho a 1%. A análise dos dados ocorreu por análise de variância e comparação de médias por Tukey, a 5% de significância. Nos testes realizados em laboratório, verificou-se que, o óleo de funcho a 1% apresentou a melhor mortalidade sobre as ninfas de pulgão, ou seja, 70%, às 72 h, seguido do extrato de cravo a 10%, com 37% de mortalidade. Quanto à sobrevivência de adultos de pulgão, verificou-se que o óleo de funcho a 1%, extrato de funcho a 10% e o extrato de cravo a 10% apresentaram os menores índices de sobrevivência, ou seja, 46%, 53% e 53%, respectivamente. No teste de mortalidade realizado na cultura, observou-se a efetividade do extrato de cravo a 10% e do óleo de funcho a 1%, em que os mesmos obtiveram 6% e 8% de sobrevivência de adultos de pulgões, respectivamente. A análise sensorial das couves não indicou diferença significativa entre as mesmas, a 5% de significância.

O objetivo do trabalho foi avaliar, por meio de variáveis fisiológicas vegetais como fotossíntese, condutância estomática, transpiração foliar, concentração interna de CO2 e temperatura foliar, o efeito de insetos pragas de diferentes hábitos alimentares em suas plantas hospedeiras. Foram estimados os níveis de dano de um sugador, Orthezia praelonga Douglas, 1891, em limão cravo (Citrus limonia L.), e de Leucoptera coffeella (Guérin-Mènevile, 1842), um mastigador, em mudas de café 'Obatã'. Os ensaios foram realizados em condições ótimas de temperatura, com luz e CO2 saturantes, e diferentes porcentagens de área foliar lesionada, obtidas pela variação do número de insetos por folha, no caso de O. praelonga em limão cravo (de 0 a 35 cochonilhas/folha (0-6%), de 40 a 70 cochonilhas/folha (7-13%), de 80 a 220 cochonilhas/folha (14-40%) e >220 cochonilhas/folha (>40%)) ou por tecido vegetal consumido (intervalos de 0-25%, 26-36% e >37%), no caso de L. coffeella em mudas de cafeeiro. As leituras das variáveis fisiológicas vegetais foram feitas com um medidor portátil de fotossíntese (IRGA). Os dados foram analisados por meio de uma regressão não linear, e, nos dois casos, existe uma correlação negativa entre fotossíntese e área foliar lesionada, ou seja, quanto maior a área foliar lesionada, menor a fotossíntese; e o ponto de inflexão negativo da curva, no qual um pequeno aumento na área foliar lesionada resultou em uma grande perda fotossintética, é tomado como referência de nível de dano, sendo que o nível de controle destas pragas, esta abaixo destes valores. A condutância estomática, a transpiração foliar, a concentração interna de CO2 e a temperatura foliar, em ambos os casos, não demonstram uma correlação definida com a intensidade de danos. A transpiração foliar em limão cravo atacado por O. praelonga é maior nos pontos onde também é maior a condutância estomática, e nas folhas de café com ataque de L. coffeella a transpiração foliar mantem-se constante durante toda a curva, semelhante à variável condutância estomática. As relações matemáticas de fotossíntese/concentração interna de CO2, e fotossíntese/condutância estomática são, em ambos os casos, decrescentes, o que demonstra respectivamente queda na eficiência instantânea de carboxilação da rubisco e redução da eficiência intrínseca do uso da água em função do aumento da área foliar lesionada. A análise conjunta dos dados demonstrou que O. praelonga afeta o fotossistema I (PS I) de folhas de limão cravo; enquanto L. coffeella afeta, em primeiro plano, o fotossistema II (PS II). No caso de O. praelonga em limão cravo, determina-se a faixa de 7 a 13% de área foliar lesionada (de 40 a 70 cochonilhas/folha) como sendo o valor de nível de dano, e para L. coffeella em cafeeiro este valor ficou na faixa de 25 a 36% de área foliar lesionada (tecido consumido pelo inseto). Os valores obtidos em laboratório, necessitam ajustes efetivos na determinação do nível de controle destas pragas no campo. A técnica de leitura de fotossíntese mostrou-se adequada a este propósito, e a análise dessa variável demonstrou ser a melhor opção para tal correlação. / The goal of this work was to evaluate the effect of insect pests of different feeding habits in their host plants through readings of plant physiological variables as photosynthesis, stomatal conductance, leaf transpiration, internal carbon dioxide concentration and leaf temperature. Thus, one estimated the injury level of a sucking insect, Orthezia praelonga Douglas, 1891, in 'Rangpur' lime (Citrus limonia L.), and Leucoptera coffeella (Guérin-Mènevile, 1842), a chewing insect, in 'Obatã' coffee seedlings. The trials were carried out under optimum temperature conditions, with saturating light and CO2 , with different injured leaf area percentages, obtained by the variation of the number of insects per leaf, in the case of O. praelonga in 'Rangpur' lime (0-35 mealybugs/leaf (0-6%), 40-70 mealybugs/leaf (7-13%), 80-220 mealybugs/leaf (14-40%), and >220 mealybugs/leaf (>40%)), or through plant tissue consumed (0-25%, 26-36% and > 37% intervals), in the case of L. coffeella in coffee seedlings. Plant physiological variables readings were performed through a portable photosynthesis meter(IRGA). The data were analyzed by means of nonlinear regression, and, in both cases, a negative correlation was observed between photosynthesis and the injured leaf area, that is, the larger the injured leaf area, the lesser the photosynthesis; the negative inflection point of the curve, upon which a slight increase in the injured leaf area resulted in great photosynt hesis loss is taken as a damage level reference, and the control level of these pests is below these values. The stomatal conductance, leaf transpiration, internal CO2 concentration and the leaf temperature, in both cases, showed no defined correlation with the damage intensity. The leaf transpiration in 'Rangpur' lime attacked by O. praelonga is higher in points where the stomatal conductance is higher as well, and in coffee leaves attacked by L. coffeella the leaf transpiration remains constant throughout the curve, similarly to the stomatal conductance variable. The mathematical relationships of photosynthesis/internal CO2 concentration, and photosynthesis/stomatal conductance are, in both cases, decreasing, which respectively shows drop in instant Rubisco carboxylation efficiency and reduction of the intrinsic efficiency of water use according to the increase of the injured leaf area. The joint data analysis showed that O. praelonga affects photosystem I (PS I) of 'Rangpur' lime, while L. coffeella affects, at first, photosystem II (PS II). In the case of O. praelonga in 'Rangpur' lime the 7-13% range of the injured leaf area (40-70 mealybugs/leaf) is determined as the damage level value, and for L. coffeella in coffee the value ranges 25-36% of the injured leaf area (tissue consumed by the insect). The values found in laboratory require field validation for effective adjustments to determine the level to control these insect pests. Overall, the photosynthesis reading technique was shown adequate to this purpose, and the analysis of this variable was the best choice for such correlation.

The New Zealand pipfruit industry has changed dramatically over the past fifteen years due to major industry restructuring and deregulation, and also due to the adoption of more environmentally sustainable growing strategies. This thesis traces the socio-political context of pesticide use in the pipfruit industry over the past ten years (couched within a hundred year trajectory), through a content and discourse analysis of appropriate print and electronic material. The content analysis addresses the ways in which pesticide use has been framed in New Zealand's fruit journal entitled The Orchardist, and tracks its promotion of the ENZA Integrated Fruit Production program that was introduced to New Zealand pipfruit growers during the summer of 1997/98. The Foucauldian discourse analysis explores how print media reflects and produces knowledge, and how such knowledge causes transformation within the pipfruit industry. Identified in the print media are several central ideologies and themes that frequently serve as conceptual frameworks for interpreting issues that arise in the pipfruit industry, the most prominent of which, is risk. Therefore, risk is the key discourse explored in this thesis. The combined content and discourse analysis signal ways in which power operates through discourse to influence ideologies, world-making and modes of production.

Cashew, Anacardium occidentale Linnaeus, is an economically important cash crop for more than 300,000 rural households in Tanzania. Its production is, however, severely constrained by infestation by sap-sucking insects such as Helopeltis anacardii Miller, H. Schoutedeni Reuter and Pseudotheraptus wayi Brown. The African weaver ant (AWA), Oecophylla longinoda Latreille, is an effective biocontrol agent of hemipteran pests in coconuts in Tanzania; but its efficacy for the control of sap-sucking insects, especially Helopeltis spp. and P. wayi, has not been investigated so far in cashew crops in Tanzania. Field trials were carried out at the Coast region of Tanzania to evaluate the effect of seasonality and abundance of AWA on Helopeltis spp. and P. wayi. Results showed that AWA abundance expressed, as number of leaf nests per tree, and colonization of trails on main branches varied significantly between cashew-seasons and off-seasons. There was a negative correlation between numbers of nests and pest damage. AWA-colonized cashew trees had the lowest shoot damaged by Helopeltis spp., 4.8 and 7.5% in 2010 and 2011, respectively, compared to 36 and 30% in 2010 and 2011, respectively, in uncolonized cashew trees. Similarly, nut damage by P.wayi was lowest in AWA-colonized trees with 2.4 and 6.2% in 2010 and 2011, respectively, as compared to 26 and 21% in 2010 and 2011, respectively, in uncolonized trees. Interaction between AWA and dominant ant species, namely big-headed ant (BHA), Pheidole megacephala Fabricius, and common pugnacious ant (CPA), Anoplolepis custodiens Smith, was examined because of the implication that the dominant ant species may have on the efficacy of AWA in its control of sap-sucking pests of cashew. Abundance of AWA was significantly negatively correlated to BHA (r(39) = -0.30; P < 0.0001) and CPA (r(39) = -0.18; P = 0.01) at Bagamoyo in 2010. A similar trend was also observed at Mkuranga. The presence of these ant species may therefore hinder effectiveness of AWA to control sap-sucking pests in cashew in Tanzania. Therefore, suppression of these two inimical ant species should be emphasized for effective control of the sap-sucking pests in cashew fields. It was therefore also important to establish the abundance and diversity of ant species occurring in cashew agro-ecosystems. Results from pitfall traps revealed the diversity and abundance of ants in cashew agro-ecosystems: a total of 14001 ants were trapped belonging to six subfamilies, 18 genera and 32 species. The ant species diversity was high in the cashew fields at two of the four sites, namely Mkuranga A and Kibaha during both seasons. CPA was the most abundant ants in the pitfall traps. It is an important aspect that should be addressed for effective control of sap-sucking pests in cashew fields with AWA, since the correlation between AWA and CPA abundance was found to be negative. The effect of alternative fungicides to sulphur dust used for powdery mildew disease (PMD) on AWA was also investigated. No significant difference could be found in the effect ofthe different fungicides on the number of leaf nests and colonization of trails. In order to develop AWA as a component of cashew integrated sap-sucking insect management, strategies for their conservation during cashew off-seasonswas evaluated. The use of fish and hydramethylon (Amdro®) as baits increased the number of leaf nests and colonization trails of AWA over the control during off-season; however, the increase was significantly high when both fish and hydramethylon were used together. Fish and hydramethylon can therefore be used for conservation of AWA during off-season. It can therefore be concluded that AWA effectively controls sap-sucking pests on cashew and can be conserved during off-season using disposal waste such as fish intestines. Fungicides used for the control of PMD did not have detrimental effects on AWA abundance and can therefore be integrated as a component of cashew IPM. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2013

Cashew, Anacardium occidentale Linnaeus, is an economically important cash crop for more than 300,000 rural households in Tanzania. Its production is, however, severely constrained by infestation by sap-sucking insects such as Helopeltis anacardii Miller, H. Schoutedeni Reuter and Pseudotheraptus wayi Brown. The African weaver ant (AWA), Oecophylla longinoda Latreille, is an effective biocontrol agent of hemipteran pests in coconuts in Tanzania; but its efficacy for the control of sap-sucking insects, especially Helopeltis spp. and P. wayi, has not been investigated so far in cashew crops in Tanzania. Field trials were carried out at the Coast region of Tanzania to evaluate the effect of seasonality and abundance of AWA on Helopeltis spp. and P. wayi. Results showed that AWA abundance expressed, as number of leaf nests per tree, and colonization of trails on main branches varied significantly between cashew-seasons and off-seasons. There was a negative correlation between numbers of nests and pest damage. AWA-colonized cashew trees had the lowest shoot damaged by Helopeltis spp., 4.8 and 7.5% in 2010 and 2011, respectively, compared to 36 and 30% in 2010 and 2011, respectively, in uncolonized cashew trees. Similarly, nut damage by P.wayi was lowest in AWA-colonized trees with 2.4 and 6.2% in 2010 and 2011, respectively, as compared to 26 and 21% in 2010 and 2011, respectively, in uncolonized trees. Interaction between AWA and dominant ant species, namely big-headed ant (BHA), Pheidole megacephala Fabricius, and common pugnacious ant (CPA), Anoplolepis custodiens Smith, was examined because of the implication that the dominant ant species may have on the efficacy of AWA in its control of sap-sucking pests of cashew. Abundance of AWA was significantly negatively correlated to BHA (r(39) = -0.30; P < 0.0001) and CPA (r(39) = -0.18; P = 0.01) at Bagamoyo in 2010. A similar trend was also observed at Mkuranga. The presence of these ant species may therefore hinder effectiveness of AWA to control sap-sucking pests in cashew in Tanzania. Therefore, suppression of these two inimical ant species should be emphasized for effective control of the sap-sucking pests in cashew fields. It was therefore also important to establish the abundance and diversity of ant species occurring in cashew agro-ecosystems. Results from pitfall traps revealed the diversity and abundance of ants in cashew agro-ecosystems: a total of 14001 ants were trapped belonging to six subfamilies, 18 genera and 32 species. The ant species diversity was high in the cashew fields at two of the four sites, namely Mkuranga A and Kibaha during both seasons. CPA was the most abundant ants in the pitfall traps. It is an important aspect that should be addressed for effective control of sap-sucking pests in cashew fields with AWA, since the correlation between AWA and CPA abundance was found to be negative. The effect of alternative fungicides to sulphur dust used for powdery mildew disease (PMD) on AWA was also investigated. No significant difference could be found in the effect ofthe different fungicides on the number of leaf nests and colonization of trails. In order to develop AWA as a component of cashew integrated sap-sucking insect management, strategies for their conservation during cashew off-seasonswas evaluated. The use of fish and hydramethylon (Amdro®) as baits increased the number of leaf nests and colonization trails of AWA over the control during off-season; however, the increase was significantly high when both fish and hydramethylon were used together. Fish and hydramethylon can therefore be used for conservation of AWA during off-season. It can therefore be concluded that AWA effectively controls sap-sucking pests on cashew and can be conserved during off-season using disposal waste such as fish intestines. Fungicides used for the control of PMD did not have detrimental effects on AWA abundance and can therefore be integrated as a component of cashew IPM. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2013

Soybean [Glycine max (L.) Merrill] is the most important crop grown in Brazil and worldwide. Nevertheless, the yield is still limited by several issues in which the damages by caterpillars and stink bugs are main ones if not controlled efficiently. The pest control is usually achieved by insecticide application, which results in an increased production cost, disturb biological control, and causes contamination in harvest and environment, so it is necessary to develop news techniques aiming to reduce the amount of sprayed insecticides. The preset study was carried out in five soybean grown areas during 2010/11 and 2011/12. This experiment aimed to analyze the spatial and temporal distribution in order to perform site-specific control of caterpillars and stink bugs by using agriculture-precision tools for mapping and control of insects. In addition, the technical and economic effects of this approach were surveyed. The first chapter shows the site-specific control for caterpillars while the chapter two for stink bugs. The population of soybean caterpillars can be suppressed by site-specific approach where the population exceeds the economic threshold and therefore saving insecticide. The site-specific control for stink bugs in soybean allows save insecticide and decreases the bugs population, but causes outbreaks far beyond the economic threshold. Economically speaking, the site-specific control of caterpillars and stink bugs is possible, but requires further studies to optimize the sampling procedure. / A soja [Glycine max (L.) Merrill] é uma cultura de grande expressão no Brasil e no mundo, no entanto a sua produtividade ainda é limitada por diversos fatores, onde destacam-se os danos significativos causados pelas lagartas e percevejos quando não manejadas eficientemente. O controle destes insetos é geralmente feito com aplicações de inseticidas, o que ocasiona o aumento dos custos da lavoura, prejudica o controle biológico pela morte de inimigos naturais, e deixa resíduos tóxicos no produto colhido e no ambiente, por isso, se faz necessário desenvolver técnicas visando a sua utilização mais eficiente, que resulte em menores quantidades aplicadas. Este estudo foi realizado em cinco áreas de cultivo com soja nas safras 2010/11 e 2011/12 objetivando analisar a distribuição espacial e temporal e realizar o controle localizado de lagartas e percevejos em soja, utilizando técnicas de agricultura de precisão para o mapeamento e controle dos insetos. Também foi realizada a análise técnica e econômica deste sistema de manejo. O primeiro capítulo apresenta o estudo do controle localizado de lagartas e o segundo capítulo o estudo do controle localizado de percevejos em soja. A população de lagartas da soja pode ser controlada de forma localizada nos pontos onde a população ultrapassa o nível de controle, proporcionando economia de inseticida. O controle localizado de percevejos em soja permite economia de inseticida e reduz a população, mas não impede a reinfestação da área acima do nível de controle. Em termos econômicos, o controle localizado de lagartas e percevejos é viável, porém são necessários estudos para aperfeiçoar o sistema de amostragem.

Made available in DSpace on 2015-03-26T13:30:22Z (GMT). No. of bitstreams: 1 texto completo.pdf: 265772 bytes, checksum: 3a271bab657c2bb822d08578c132b35e (MD5) Previous issue date: 2008-09-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Termites are considered a key pest of sugarcane in Brazil and preventive control measures are usually recommended. It is not known, however, if termites really cause yield losses in sugarcane at any level of infestation and if the loss economically justfies the preventive control currently in use in the country. The objective of this work was to evaluate the effect of natural termite infestations on sugarcane productivity, as a base to establish when termite control would be economically viable. Random block experimental design was used, with productivity parameters - cane yield (tonnes of stalk per hectare), sucrose content of the juice (pol) and expected sugar yield (tonnes of pol/ha) - as response variables; termite infestation, variety and cropping season as explanatory variables, and fields as blocks. This study demonstrates a signficant relationship between natural termite infestation in sugarcane and reduction in sugar yield. Termites cause mensurable damage to ratoon sugarcane by reducing the expected sugar yield as termite infestations increase, being the reduction of 0.04558 tonnes of pol/ha per year for increases of 1% of termite infestation. They do so by reducing the cane yield but they do not affect the sucrose content of the juice. The reduction in cane yield is of 0.2755 tonnes of stalk/ha per year related to increases of 1 % in termite infestation. Our study shows that given the dilution of the control price of termites over the period of the crop and the high level of damage related to termite presence in the field, higher investments in termite control are economically suitable and could increase sugarcane productivity. Methods of termite control that are environmentally safe and economically viable must be pursued in order to reduce losses associated to increase sugarcane productivity. / Cupins são considerados uma praga chave em cana-de- açúcar no Brasil e medidas preventivas são usualmente adotadas para o seu controle. Entretanto, não se sabe se cupins causam perdas à cultura em qualquer intensidade de infestação e tampouco se sabe quando a perda justiça economicamente o seu controle. O objetivo deste trabalho foi avaliar o efeito de infestações naturais de cupins sobre a produção da cana-de-açúcar como uma base para se estabelecer em que casos o controle seria economicamente justificável. O delineamento em blocos casualisados foi utilizado para a coleta dos dados. Avaliou-se a resposta dos parâmetros de produtividade - toneladas de colmo por hectare, conteúdo de sacarose do caldo e produção esperada de açúcar - às variáveis explicativas - intensidade da infestação por cupins, variedade da cana-de-açúcar e época da colheita. Foi encontrada uma relação significativa entre a intensidade de infestações naturais de cupins em cana-de- açúcar e redução na produtividade esperada de açúcar. Os cupins causam perdas na produtividade esperada de açúcar da ordem de 0.04558 toneladas de açúcar/ha/ano para cada 1% de infestação de cupins. Esta redução é devida a uma redução na biomassa da planta de 0.2755 toneladas de colmo/ha/ano para cada aumento de 1% na infestação. Por outro lado, os cupins não causaram redução no teor de sacarose do caldo. Nosso trabalho mostra que devido à diluição do custo do controle dos cupins ao longo do período de cultivo da cana e ao alto nível de dano associado à presença dos cupins, maiores investimentos são economicamente viáveis para o controle de cupins em cana e poderiam levar a um aumento na produtividade. Métodos de controle que sejam ambientalmente seguros e economicamente viáveis devem ser buscados para aumentar a produtividade da cana-de-açúcar.

Le système « plante-ravageur-ennemi naturel » fournit un modèle de base idéal pour comprendre comment les communautés d'arthropodes sont structurées et comment les interactions (directes et indirectes) entre les différents acteurs contribuent à façonner la structure des communautés. Dans les agroécosystèmes, les forces "top-down" correspondent aux effets de contrôle que les organismes arthropodes des niveaux trophiques supérieurs (par exemple, les prédateurs) ont sur les espèces des niveaux inférieurs (par exemple, leurs proies). Les communautés d'arthropodes peuvent également être influencées par des forces "bottom-up" induites par des variations dans les régimes de fertilisation ou d'irrigation ou par des variations de certains traits des plantes (résistance aux herbivores ou adaptations aux stress environnementaux). De plus, les forces "bottom-up" peuvent affecter l'impact "top-down" des ennemis naturels sur les herbivores soit directement (par exemple, les effets sur prédateur omnivore) ou médiées par les insectes herbivores intermédiaires. Dans ce contexte, les objectifs de cette thèse ont été de comprendre comment les variations de l'apport des ressources dans les agroecoécosytsèmes (disponibilité en azote et en eau) peuvent influencer les interactions entre les plantes, les herbivores et les ennemis naturels. Cette question a été étudiée aussi bien à l'échelle individuelle (traits d'histoire de vie des insectes) que populationnelle (dynamique des populations). Les études ont été réalisées sur deux agroécosystèmes basés sur les cultures de la tomate et du coton. / The “Plant-herbivorous insect-natural enemy” system provides an ideal basic model to understand how the plant-inhabiting arthropod communities are structured and how various mechanisms (i.e. direct and indirect interactions) contribute to shape the community structure. In agro-ecosystems, top-down forces encompass the controlling effects that arthropod organisms of the higher trophic level (e.g., predators) have on species at the next lower level (e.g., prey). Arthropod communities may also be influenced by bottom-up forces induced by environmental variations (e.g. fertilization or irrigation regimes) or plant traits (plant insect-resistance or plant-adaptive traits). Furthermore, bottom-up forces may affect top-down forces on herbivores either directly (e.g., effects on omnivorous predator) or mediated by the intermediate herbivorous insects. In this context, the aims of the PhD study were to disentangle how variations in resource inputs (i.e. nitrogen and water availability) affect interactions among plant, herbivores and their natural enemies at both the individual (life-history traits) and population (population dynamic) levels. The studies were carried out on two agrosystems based on tomato and cotton. On tomato, the system 'Solanum lycopersicum L - leafminer Tuta absoluta - omnivorous predator Macrolphis pygmaeus' was used under laboratory and greenhouse conditions in France. We found strong evidence of bottom-up effects of nitrogen and/or water inputs on the herbivore and the omnivorous predator. Feeding ecology of the predator was also strongly influenced by water availability.

Integrated Pest Management (IPM) has long been promoted as a means of reducing reliance on pesticide inputs as compared to conventional farming systems. Reduced pesticide application could be beneficial due to the links between intensive pesticide use and negative impacts upon biodiversity and human health as well as the development of pesticide resistance. Work assessing the potential of IPM in cereal production is currently limited, however, and previous findings have generally covered the subject from the perspective of either field trial data or social science studies of farmer behaviour. This thesis attempts to help to address this knowledge gap by providing a more holistic assessment of IPM in Scottish spring barley production (selected because of its dominance in Scotland’s arable production systems), in relation to three of its most damaging fungal pathogens: Rhynchosporium commune, Blumeria graminis f.sp. hordei, and Ramularia collo-cygni. Several IPM techniques of potential relevance to the sector were identified, and the prospects of three in particular – crop rotation, varietal disease resistance, and forecasting disease pressure – were assessed in several ways. Preliminary analysis of experimental field trial data collected from 2011 – 2014 across Scotland found that the majority of spring barley trials in this period (65%) did not show a statistically significant impact of fungicide treatment on yield, with the average yield increase due to fungicide application being 0.62 t/ha. This initial analysis was expanded upon using stepwise regressions of long-term (1996 – 2014) field trial data from the same dataset. Here, the difference between treated and untreated yields could be explained by disease resistance, average seasonal rainfall (whereby wetter seasons saw an increased impact of fungicide use on yield), and high combined disease severity. Stakeholder surveying provided information about current practice and attitudes towards the selected IPM techniques amongst a group of 43 Scottish spring barley farmers and 36 agronomists. Stakeholders were broadly open to taking up IPM measures on farm; sowing of disease resistant varieties was most frequently selected as the best technique in terms of both practicality and cost, though individual preference varied. However, a disparity was seen between farmer perception of their uptake of IPM and actual, self-reported uptake for both varietal disease resistance and rotation. Farmers and agronomists also overestimated the impact of fungicide use as compared with the field trials results – the majority of stakeholders believed fungicide treatment to increase yields by 1 - 2 t/ha, while the majority of 2011 – 2014 field trials had a yield difference of under 1 t/ha. The reasons behind these differences between perception and practice are not currently known. Finally, an annual survey of commercial crops, gathered from 552 farms across Scotland (from 2009 – 2015), highlighted two gaps where IPM practice could be improved upon. Firstly, relatively few of the varieties listed in the commercial crops database were highly resistant to the three diseases – 26.1% were highly resistant to Ramularia, 14.2% to Rhynchosporium, and 58.1% to mildew. Secondly, 71% of the farms included in the database had planted barley in at least two consecutive seasons, indicating that crop rotation practices could be improved. The overarching finding of this project is that there is scope for IPM uptake to be improved upon and fungicide use to be reduced while maintaining high levels of yield in Scottish spring barley production. Incorporating experimental field data, stakeholder surveying, and commercial practice data offered a unique view into the potential for IPM in this sector, and provided insights which could not have been gained through the lens of a single discipline.

Made available in DSpace on 2016-08-12T19:15:22Z (GMT). No. of bitstreams: 1 EwertonMC_DISSERT.pdf: 557868 bytes, checksum: d1b58bdf6490bc4896185f9bc99310f3 (MD5) Previous issue date: 2012-02-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Watermelon (Citrullus lanatus (Thumb) Matsum. & Nakai) is one of the main cucurbits cultivated in Brazil, and the Northeast region the country's the largest producer. In the state of Rio Grande do Norte, the third largest producer of watermelon from the northeast, the cultivation of this vegetable is an activity expanding, especially in the farming area Assu-Mossoró. Despite the expansion and technification the cultivation this cucurbit cultivation on RN, the lack of information about the insect community associated with the culture still represents a major barrier in pest management. Thus, the aim of this study was to survey the insect fauna associated with the watermelon crop in the municipality of Baraúna, RN. The insect fauna survey was conducted in an area of commercial production of watermelon. The catch of insects was carried out weekly during the crop cycle using three types of traps, Pitfall, Moericke (adapted) and McPhail, in density 20, 20:01 traps per hectare, respectively. Were collected a total of 14,460 insects, belonging to eight orders: Coleoptera, Hymenoptera, Hemiptera, Orthoptera, Dermaptera, Diptera, Thysanoptera and Lepidoptera, and distributed in 64 families. Orders Diptera, Coleoptera and Hymenoptera contributed the largest number of specimens, presenting the relative frequencies of total 37.88%, 26.83% and 21.60% respectively. We collected 24 families of Hymenoptera, 12 of Coleoptera, 16 of Diptera , 7 of Hemiptera and 2 of of orthopteros. The orders Dermaptera, Thysanoptera and Lepidoptera were represented by one family each. Was observed in the presence in field leafminer (Diptera: Agromyzidae) and whitefly (Hemiptera: Aleyrodidae). The natural enemies insect fauna (predators and parasitoids) associated with the watermelon crop was diversified and abundant. It was found in the region the occurrence of pests of watermelon and the presence of insects with the potential to become pests in this crop / A melancia (Citrullus lanatus (Thumb) Matsum. & Nakai) é uma das mais importantes cucurbitáceas cultivadas no Brasil, sendo a região Nordeste do país a principal produtora. No estado do Rio Grande do Norte, terceiro maior produtor de melancia do nordeste, o cultivo dessa olerícola é uma atividade agrícola em expansão, especialmente no pólo agrícola Assu-Mossoró. Apesar da expansão e tecnificação do cultivo da referida cucurbitácea no RN, a escassez de informações acerca da comunidade de insetos associados à cultura ainda representa um dos principais entraves no manejo de pragas. Desta maneira, o objetivo do presente trabalho foi realizar um levantamento da entomofauna associada à cultura da melancia no município de Baraúna, semiárido do RN. O levantamento da entomofauna foi realizado em uma área de produção comercial de melancia. As coletas dos insetos foram realizadas semanalmente durante o ciclo da cultura utilizando-se três tipos de armadilhas, Pitfall, Moericke e McPhail, na densidade de 20, 20 e uma armadilha por hectare, respectivamente. Foi coletado um total de 14.460 insetos, pertencentes a oito ordens: Coleoptera, Hymenoptera, Hemiptera, Orthoptera, Dermaptera, Diptera, Thysanoptera e Lepidoptera, e distribuídos em 64 famílias. As ordens Diptera, Coleoptera e Hymenoptera contribuíram com o maior número de espécimes, apresentando frequências relativas totais de 37,88%, 26,83% e 21,60%, respectivamente. Vinte e quatro famílias de himenópteros foram coletadas, 12 de coleópteros, 16 de díptera, 7 de hemíptera e 2 de orthopteros. As ordens Dermaptera, Thysanoptera e Lepidoptera foram representadas por uma família cada. Foi observada em campo a presença da mosca minadora (Diptera: Agromyzidae) e mosca branca (Hemiptera: Aleyrodidae). A entomofauna de inimigos naturais (predadores e parasitóides) associada à cultura da melancia foi diversificada e abundante. Constatou-se na região a ocorrência de insetos-praga da melancia e a presença de insetos com potencial para se tornar praga da cultura