The chemical defences of insects against predators are either passive or aggressive. Passive defence is achieved through crypsis, and aggressive defence is maintained by a conspicuous or 'aposematic' (Poulton, 1890) appearance that advertises some noxious quality of the insect harmful to a predator. Aposematism is mutually beneficial to both the bearer and its predator, whereas crypsis only benefits the prey species. It is therefore not surprising that the fascinating array of chemical defences in insects is both diverse and widespread (Roth and Eisner, 1962). Intro. p. 1.

No description available.

De nombreux insectes s’avèrent être des ravageurs de culture, pouvant de surcroît transmettre des pathogènes aux plantes et ainsi causer des dégâts d’importance économique notables. Leur contrôle repose essentiellement sur l’utilisation d’insecticides, mais cela pose problème en termes de pollution de l’environnement, d’effets non désirés sur les espèces non-cibles, d’apparition de populations d’insectes résistants aux insecticides, sans parler de leur toxicité pour l’homme. L’olfaction joue un rôle clef dans le développement de nombreux comportements chez les insectes, comme la recherche de la plante nourricière ou du partenaire sexuel, le repérage de sites de ponte ou de prédateurs. Leurs organes olfactifs portent les sensilles sensorielles dans lesquelles se déroulent les étapes de la réception du signal : les molécules odorantes pénètrent par les pores et sont transportées à travers la lymphe sensillaire par des "odorant binding proteins" jusqu’aux récepteurs olfactifs (Ors) avec lesquels elles interagissent pour déclencher la cascade de transduction, puis le signal olfactif est inactivé. Si les interactions odeurs/ORs sont largement étudiées et élucidées, il n’en est pas de même pour le transport et l’inactivation du signal. En particulier, les "odorant-degrading enzymes" (ODEs) qui seraient impliquées dans cette dernière étape, en dégradant les molécules odorantes en métabolites inactifs, i.e. ne pouvant plus stimuler les récepteurs. Les ODEs appartiennent à diverses familles d’enzymes de biotransformation, comme les cytochromes P450s (CYPs), les carboxylestérases (CCEs), les glutathion-S-transférases (GSTs), ou les UDP-glucosyltransférases (UGTs). La plupart sont exprimées fortement dans les antennes. Peu d’entre-elles ont été caractérisées fonctionnellement, principalement par des approches in vitro, peu d’études ont été réalisées in vivo avec des approches électrophysiologiques ou comportementales. Au cours de ma thèse, nous avons caractérisé deux CCEs antennaires, l’Estérase6 (Est6) et la « Juvenile Hormone Esterase duplication » (JHEdup), chez Drosophila melanogaster, en combinant des approches transcriptomiques et fonctionnelles. Nous avons montré que ces deux estérases étaient exprimées très fortement dans les antennes et capables de métaboliser in vitro certaines odeurs alimentaires émises par les fruits mûrs. Nous avons aussi démontré que ces deux estérases étaient impliquées in vivo dans les réponses physiologiques et comportementales à ces odorants, et qu’elles s’avèrent donc être des ODEs.. Pour deux ODEs candidates, Ugt35b (UGT) et Cyp308a1 (CYPs), nous avons établi leur patron d’expression dans les antennes afin de préciser les types de sensilles impliquées, en préliminaire à des études fonctionnelles plus ciblées. Enfin, pour ugt35b, cyp308a1 et jhedup, nous avons mis en évidence une expression dans différentes structures gustatives, posant la question de leur rôle possible dans le métabolisme de molécules sapides. Les quatre enzymes antennaires présentées ici ne sont que le début d’une longue liste d’ODEs candidates identifiées lors de l’analyse du transcriptome antennaire de D. melanogaster. Ce travail participe à une meilleure compréhension des mécanismes moléculaires impliqués dans le fonctionnement du système olfactif. Du point de vue appliqué, les ODEs pourraient constituer des cibles d’intérêt (via des inhibiteurs spécifiques par exemple) pour modifier des comportements olfacto-induits, et ce dans un contexte de contrôle de populations d’insectes ravageurs plus respectueux de l’environnement. Par ailleurs, les connaissances acquises sur les ODEs chez cette espèce modèle pourraient contribuer à leur caractérisation chez d’autres espèces, en particulier des ravageurs de cultures. / Insects can be hazardous crop pests that do not only feed on crops but also transmit plant pathogens, causing yearly a great economical damage. Pest control relies mainly on insecticides but an extensive use bears problems such as the pollution of environment, unpredictable effects on non-target species, an increase of insecticide resistant populations and toxicity for humans. Olfaction is fundamental for the implementation of many insect behaviours like host plant and mating partner foraging, identification of suitable oviposition sites and predator avoidance. Insects smell with hairshaped olfactory sensilla, which are located on their antennae and palps. These sensilla are the showplace of early olfactory processing involving several steps: the odor uptake through the sensillar pores and their transport through the sensillar lymph mediated by odorant binding proteins, the detection of odors by olfactory receptors (ORs) and eventually the inactivation of the olfactory signal. Odor/OR interactions have been intensely studied, contrary to odor transport and inactivation that remain not well understood. Odorant-degrading enzymes (ODEs) have been suggested to be responsible for odor inactivation by degrading odorants into inactive metabolites which no longer activate ORs. The ODEs identified to date belong to various biotransformation enzyme families, including cytochrome P450s (CYPs), carboxylesterases (CCEs), glutathione-S-transferases (GSTs), UDP-glucosyltransferases (UGTs). Most of them are highly expressed in insect antennae. To date, only some ODEs have been functionally characterized, most of them in vitro using recombinant protein and showing their ability to efficiently metabolize various odorant molecules. Only a very few studies were investigating ODE function in vivo using electrophysiological and behavioural approaches. In this thesis we functionally characterize two antennal CCEs, Esterase6 (Est6) and Juvenile Hormone Esterase duplication (JHEdup), in the insect model Drosophila melanogaster combining transcriptomic, in vitro and in vivo approaches. We found that both CCEs are highly expressed in antennae and are able to efficiently metabolize certain odors emitted by rotting fruits in vitro. Furthermore, we showed that both are involved in physiological and behavioural responses to these odors. Therefore we propose Est6 and JHEdup as sensillar candidate ODEs. Moreover, we investigated the precise antennal gene expression pattern in toto for two antennal biotransformation enzymes belonging to other classes, Ugt35b (UGT) and Cyp308a1 (CYPs), which will be helpful for further investigations in order to clarify their potential role in olfaction. In case of three ODE candidate genes (ugt35b, cyp308a1 and jhedup) we discovered an interesting expression pattern in various gustatory organs posing new questions about additional functions of these antennal enzymes in taste processing. The antennal enzymes discussed in this thesis are only four of many candidate ODEs that we identified in the antennal transcriptome of the fruit fly. These candidates comprise also enzymes that belong to other classes such as GSTs, aldehyde oxidases, alcohol dehydrogenases or lipases. This work contributes to a deeper understanding of the insect olfactory system including its molecular actors. From an applied point of view ODEs are interesting targets to modify odorant-driven insect behaviours. The identification of specific ODE inhibitors that could interfere with insect ability to respond to environmental olfactory cues, emitted by mating partners or host plants, would contribute to a broader variety of “eco-friendly” olfactory-based insect pest control strategies. In the future the obtained knowledge in the insect model Drosophila will contribute to the characterization of ODEs in different hazardous insect pests which will be the next step to develop new inhibitor-based strategies.

Yes / The first archaeobotanical studies of the Middle Bronze Age lakeshore settlement demonstrate the enormous potential of this site for appropriate analyses. On the basis of the well-preserved layers a multitude of plant remains and wide diversity of species are present at this site. Evidence of emmer, spelt, tetraploid naked wheat, hulled barley, peas and broad beans conforms to the basic cultural crop spectrum of the Middle Bronze Age. The wild plants originate from various locations in the direct vicinity and allow an insight into the landscape at that time. Numerous wild plants were intentionally used by the settlers. Fruits gathered include cornelian cherries, hazelnuts, crab apples and a diversity of berries. Furthermore, archaeobotanical analyses support observations already made on site that within the settlement there are at least two functionally different areas. While in section 50/51 the layers contain the remains of daily food preparation, section 7 indicates a link to animal fodder. / National Geographic

Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.

Thesis (PhD )--Stellenbosch University, 1981. / EKSERP: Vanwee die voortdurende probleme wat die valskodlingmot, Cryptoph lebia leucotreta (Meyr.), by die verbouing van nawels in die Oos-Transvaalse Laeveld daarstel, is 'n indringende studie van hierdie insekprobleem onderneem. Die biologie van die insek is onder sowel laboratorium as natuurlike toestande nagevors. Daar is bevind dat temperatuur 'n belangrike rol in die ontwikkeling van die insek speel. By 20 tot 30°C het temperatuurstygings die ontwikkeling van die insek laat versnel. By 35°C het die lewensduur van die volwasse motte afgeneem en is geen eiers gelê nie . Die valskodlingmot is deur middle van 'n kunsmatige metode geteel om genoegsame proefmateriaal te verkry. Verskeie verbeteringe is in die bestaande tegniek aangebring.

The control of the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in sugarcane fields of KwaZulu-Natal, South Africa has proved problematical. Researchers at the South African Sugarcane Research Institute (SASRI) have since 1974 been intensively investigating various means of controlling the pest. Among the methods of control currently being investigated are biological control, chemical control, production of more resistant varieties and crop management. These investigations, however, require many years of experimentation before any conclusions can be made. In order to aid the research currently being carried out in the Entomology Department at SASRI (to investigate biological control strategies, insecticide application strategies and the carry-over decision), a simulation model of E. saccharina growth in sugarcane has been formulated. The model is cohort-based and includes the effect of temperature on the physiological development of individuals in each life-stage of the insect. It also takes into account the effect of the condition of sugarcane on the rate of E. saccharina infestation, by making use of output from the sugarcane growth model CANEGRO. Further, a crop damage index is defined that gives an indication of the history of E. saccharina infestation levels during the sugarcane’s growth period. It is linked to the physiological activity of the borer during the period spent feeding on the stalk tissue. The damage index can further be translated into length of stalks bored and hence the percentage of the stalk length bored can be calculated at each point in the simulation using the total length of stalks calculated in the CANEGRO model. Using an industry accepted relationship between percent stalks damaged and reduction in sucrose content of the crop, reductions in losses in the relative value of the crop when the various control measures are implemented can be compared. Relationships between the reduction in percent stalk length bored (and hence gains in the relative value of the crop) and the various control strategies are obtained. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermartzburg, 2008.

The entomopathogenic fungus Beauveria bassiana and the bacterium Bacillus thuringiensis var. israelensis (Bti) have been widely studied for their role in biocontrol against many arthropods and extensively exploited for insect pest control. The purpose of this study was to evaluate the effect of four B. bassiana and two Bti formulations and their respective combinations, for the biological control of the common house fly, Musca domestica L., a major pest in poultry facilities. In vitro screening was undertaken to select the best B. bassiana isolates from 34 B. bassiana isolates and two Paecilomyces isolates. All the isolates of B. bassiana were found to be effective against adult house flies, but were marginally effective in controlling fly larvae. The Paecilomyces isolates were non-pathogenic towards both adult house flies and larvae. The best four isolates R444, 7320, 7569 and 7771 caused >90% mortality within 2d and were subjected to dose-mortality bioassays. Microscopic studies using light and scanning electron microscopy indicated the different durations of the lifecycle of B. bassiana development on the house fly. High temperature was found to delay conidial germination. Spore germination and mycelial growth were also inhibited by high adjuvant concentrations. Laboratory baseline bioassay data established, a dose-time response relationship using a waterdispersible granules (WDG) Bti formulation that demonstrated that the susceptibility of M. domestica larvae to a given concentration of Bti increased as the duration of exposure increased. In the laboratory studies, the LC50 and LC90 values of Bti for the larvae ranged between 65 - 77.4 and 185.1 - 225.9?g ml-1, respectively. LT50 and LT90 values were 5.5 and 10.3d respectively. In the field, a concentration of 10g Bti kg-1 (bran formulation) of feed resulted in 90% reduction of larvae for 4wk post-treatment. A higher concentration (2g L-1) of Bti in spray (WDG) applications was not significantly more effective than the lower concentration of 1g L-1. Thus, adding Bti to chicken feed has potential for the management and control of house flies in cagedpoultry facilities. The impact of oral feed applications of a bran formulation of Bti and a commercial chemical larvicide, Larvadex®, were compared with respect to their efficacy on the control of house fly 3 larval populations in poultry manure. The sublethal effects were manifested in terms of decreasing emergence of adult house flies. Although Larvadex® reduced larval density and caused significant reductions in emergence of adult house flies, it generally exhibited weaker lethal effects than Bti. The reduction levels achieved as a result of feeding 250mg Bti kg-1 at 5wk were similar to those achieved as a result of feeding twice the amount of Larvadex® at 4wk to the layers. From both an efficiency and economic perspective, comparisons to assess the impact of combining different concentrations of the two Bti formulations were carried out to evaluate their success in controlling house fly larvae and adults in poultry houses. The percentage mortality of larvae accomplished as a result of using a combination of 250mg kg-1 Bti in feed and 2g L-1 spray applications was equivalent to that obtained as a result of combining 500mg kg-1 Bti in feed and 1g L-1 spray application. The cost-benefit analysis (expressed in terms of mortality of larvae) indicated that the most effective combination for control of house fly larvae and fly emergence was the 500mg kg-1 in feed and 2g L-1 spray application combination that resulted in 67% larval mortality and 74% inhibition of adult house fly emergence. This study presents commercial users with possible combinations of applications of the two Bti formulations. Comparisons of larval mortalities and house fly emergence resulting from the Bti - B. bassiana treatments with those from Larvadex® - B. bassiana treatments, showed better control levels compared to any of the individual agents alone. The Bti treatments were more effective at controlling larval populations and inhibiting the emergence of house flies than Larvadex®, even when Larvadex® was applied together with B. bassiana. The effects of the Bti - B. bassiana and the Larvadex® - B. bassiana interactions were additive. These trials suggest that the efficacy of Bti in the control of house fly larvae may be improved with frequent applications of B. bassiana. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Made available in DSpace on 2015-03-26T13:30:15Z (GMT). No. of bitstreams: 1 texto completo.pdf: 526506 bytes, checksum: 599838531677d80fdf541112b66fb2cd (MD5) Previous issue date: 2007-02-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objectives of the present study were to evaluate the ozone toxicity to populations of Tribolium castaneum, Rhyzopertha dominica and Oryzaephilus surimanensis, to determine if there is cross resistance between ozone and phosphine; to verify if there is relationship between the ozone toxicity and respiratory metabolism of the insects; to determine the reproductive standards of the populations in the absence of selective pressure and provide evidence of adaptive costs associated with phosphine resistance. Sixteen Brazilian populations of T. castaneum, 11 of R. dominica and nine of O. surinamensis were collected from the states of Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná and São Paulo. In the toxicity bioassays, the concentration of the ozone was fixed in 150 ppm (2 L min-1 flow). The lethal exposure time for 50 or 95% of mortality (TL50 and TL95) of each insect population was estimated through time-response bioassays and used to calculate respective resistance ratios (RRs). The respiratory and instantaneous growth rates (ri) of each population of three species were evaluated. In addition, the development and population growth rate of two phosphine resistant and two susceptible populations of each specie were evaluated. None of the tested populations showed ozone resistance. The resistance ratios at TL50 of the populations of T. castaneum, R. dominica and O. surinamensis ranged, respectively, from 1.00 to 1.76, 1.03 to 1.32, and 1.0 to 1.58- fold. In contrast, some of these populations showed high resistance to phosphine, indicating that there was no cross resistance between ozone and phosphine. Different respiratory standards were observed among the populations of each species, suggesting that ozone toxicity was not influenced by the respiratory metabolism of insects. Different reproductive standards were found in the development and populational growth rates, where some phosphine resistant populations showed adaptative costs in the absence of the insecticide. Since these populations did not show ozone resistance, independent of the resistance or susceptibility to phosphine, ozone can be one of the major eco-friendly alternative to phosphine for use in managing resistant pest populations. / Este trabalho teve por objetivos avaliar a toxicidade do ozônio a populações de Tribolium castaneum, Rhyzopertha dominica e Oryzaephilus surimanensis; determinar se existe resistência cruzada entre o ozônio e a fosfina; averiguar se há relação entre a toxicidade do ozônio e o metabolismo respiratório dos insetos; determinar os padrões reprodutivos das populações na ausência de pressão seletiva e prover evidências de custos adaptativos associados à resistência à fosfina. Foram utilizadas 16 populações brasileiras de T. castaneum, 11 de R. dominica e nove de O. surinamensis coletadas nos estados de Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná e São Paulo. Nos bioensaios de toxicidade, fixou-se a concentração do ozônio em 150 ppm, em fluxo contínuo de 2 L min-1. Os tempos letais para causar 50 e 95% de mortalidade (TL50 e TL95) de cada população foram estimados por meio de bioensaios de tempo-resposta e usados para calcular as respectivas razões de resistência (RRs). Os padrões da taxa respiratória e do crescimento instantâneo (ri) de cada população das três espécies foram avaliados. Adicionalmente, foram avaliadas as taxas de desenvolvimento e de crescimento populacional de duas populações resistentes à fosfina e duas susceptíveis de cada espécie. Nenhuma das populações estudadas mostrou resistência ao ozônio. A razão de resistência para os TL50 das populações de T. castaneum, R. dominica e O. surinamensis variou, respectivamente, de 1,00 a 1,76; 1,03 a 1,32; e 1,0 a 1,58 vezes da população de maior para a de menor susceptibilidade. Por outro lado, algumas destas populações apresentam elevada resistência à fosfina, indicando que não há resistência cruzada entre o ozônio e a fosfina. Foram observados diferentes padrões respiratórios entre as populações de cada espécie, indicando que a toxicidade do ozônio não teve relação com o metabolismo respiratório dos insetos. Diferentes padrões reprodutivos foram verificados nas taxas de desenvolvimento e de crescimento populacional, onde algumas populações resistentes à fosfina apresentaram custo adaptativo na ausência do inseticida. Como essas populações não mostraram resistência ao ozônio, independentemente de serem resistentes ou susceptíveis à fosfina, é possível que o ozônio venha a se tornar uma alternativa ao uso da fosfina nos programas de manejo de resistência a esse fumigante.

Made available in DSpace on 2015-03-26T13:30:23Z (GMT). No. of bitstreams: 1 texto completo.pdf: 162408 bytes, checksum: 5205f0f30ad35343551ffe6ad627d350 (MD5) Previous issue date: 2009-02-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Coccus viridis (Green) (Hemiptera: Sternorrhyncha: Coccidae) is insect pest of coffee, especially in stand density in plantations. Despite the importance of C. viridis as peste coffee at the moment do not know the critical stage of their life cycle and the key factor governing mortality of their populations. The aim of this study was to determine the factors of natural mortality of C. viridis in coffee as well as determine the critical stage and key factor of mortality of their life cycle. The mortality and its causes were monitored daily in the development stages of C. viridis until the scales become reproductive females. We constructed eight scales of ecological life to C. viridis during the years of 2004 to 2006 in coffee. The total mortality of C. viridis was 96.08% and 70.47 occurred, 54.16, 53.31 and 38.06% in the first, second and third instars and adulthood. The factors of mortality of C. viridis were rainfall, parasitism, predation, and drop-leaf fungus Lecanicillium lecanii. Predation is important in all stages of C. viridis, with marginal mortality 28.76, 23.31, 17.96 and 19.03% for nymphs of the first, second, third instar and adults. The younger stages of C. viridis were more affected by parasitism with mortality of 31.86 (first instar) and 25.16% (second instar). But the fungus L. lecanii caused higher mortality in more advanced stages of C. viridis, with 15.99 and 12.07% in the third instar nymphs and adults. The fall of leaves caused high mortality in all immature stages of C. viridis, with mortality of 34.64, 11.91 and 15.99% for nymphs of the first, second and third instars. The critical level of mortality of C. viridis was the second-instar nymphs. The key factor of mortality was the action of parasitoids on second-instar nymphs, followed by deaths caused by falling leaves and rain of this instar. / Coccus viridis (Green) (Hemiptera: Sternorrhyncha: Coccidae) é uma cochonilha praga do cafeeiro, sobretudo em locais sombreados e plantios adensados. Apesar da importância de C. viridis como praga do cafeeiro até o presente momento não se conhece a fase crítica do seu ciclo de vida nem o fator-chave de mortalidade que regula suas populações. Assim, o objetivo deste trabalho foi determinar os fatores de mortalidade natural de C. viridis no cafeeiro, bem como determinar a fase crítica e o fator-chave de mortalidade do seu ciclo de vida. As mortalidades e suas causas foram monitoradas diariamente nos estádios de desenvolvimento de C. viridis até que as cochonilhas se tornassem fêmeas reprodutivas. Foram construídas oito tabelas de vida ecológicas para C. viridis durante as estações dos anos de 2004 a 2006 em cafeeiro. A mortalidade total de C. viridis foi 96,08%, sendo que ocorreram 70,47; 54,16; 53,31 e 38,06% no primeiro, segundo e terceiro ínstares e na fase adulta. Os fatores de mortalidade de C. viridis foram chuva, parasitismo, predação, queda de folha e o fungo Lecanicillium lecanii. A predação foi importante em todos os estádios de C. viridis, com mortalidades marginais de 28,76; 23,31; 17,96 e 19,03%, para ninfas de primeiro, segundo, terceiro ínstar e adultos. Os estádios mais jovens de C. viridis foram mais afetados pelo parasitismo, com mortalidades de 31,86 (primeiro ínstar) e 25,16% (segundo ínstar). Já o fungo L. lecanii causou maiores mortalidades em estádios mais avançados de C. viridis, com 15,99 e 12,07%, nas ninfas de terceiro ínstar e adultos. A queda de folhas causou elevadas mortalidades durante todos os estádios imaturos de C. viridis, com mortalidades de 34,64; 11,91 e 15,99% para ninfas de primeiro, segundo e terceiro ínstares. O estádio crítico de mortalidade de C. viridis foi o de ninfas de segundo ínstar. O fatorchave de mortalidade foi a ação de parasitóides sobre ninfas de segundo ínstar, seguido pela mortalidade causada por queda das folhas e chuvas neste ínstar.