Genetically modified (GM) maize was developed mainly to control lepidopteran pests such as the maize stem borer (Busseola fusca) (Lepidoptera: Noctuidae). Since the first commercialization of GM crops with insecticidal properties, possible non-target effects such as the effect at the third trophic level on important predators for example lacewing species (Chrysoperla spp.) have been of concern. Contradicting results were reported in previous studies with regard to the effect of Cry 1Ab protein produced by Bt maize on the performance of lacewings. Some studies found that Bt proteins had no effect while others reported that C. carnea performed poorly if they consumed prey that consumed Cry 1Ab protein. In South Africa one of the most common chrysopid species in maize ecosystems is Chrysoperla pudica (Navás) (Neuroptera: Chrysopidae). Evolution of Bt resistant pests, such as B. fusca in South Africa facilitates a new pathway for exposure of predators to healthy prey that consumes Cry 1Ab proteins. The aims of this study was to determine the effect of the Cry 1Ab protein expressed in Bt maize on a non-target organism‟s (C. pudica) biology via indirect exposure, and to determine the concentration of Cry 1Ab protein in the plant, prey and predator. Chrysoperla pudica larvae were indirectly exposed to the Bt-toxin through healthy Bt-maize feeding prey (B. fusca larvae) in two feeding experiments and lacewing survival and life history parameters recorded. Bt had a limited effect on some parameters that were evaluated. The larval and pupal periods of C. pudica larvae that were exposed to the Bt-toxin had a significant difference from that of the control treatment. The Bt-toxin had a significant effect on fecundity, fertility and malformation after emergence of C. pudica adults of which larvae fed only on Bt resistant B. fusca larvae, but not on the mortality rate. Cry 1Ab concentration was the highest in the plant, followed by the prey and lacewing larvae. This study showed that the Cry 1Ab protein had a slight adverse effect only on certain life parameters of C. pudica, and that Cry 1Ab protein was hardly detectable in C. pudica larvae. However, since this study represented a worst-case scenario where diverse prey was not available, insignificant effects is expected under field conditions where prey is diverse. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Genetically modified (GM) maize was developed mainly to control lepidopteran pests such as the maize stem borer (Busseola fusca) (Lepidoptera: Noctuidae). Since the first commercialization of GM crops with insecticidal properties, possible non-target effects such as the effect at the third trophic level on important predators for example lacewing species (Chrysoperla spp.) have been of concern. Contradicting results were reported in previous studies with regard to the effect of Cry 1Ab protein produced by Bt maize on the performance of lacewings. Some studies found that Bt proteins had no effect while others reported that C. carnea performed poorly if they consumed prey that consumed Cry 1Ab protein. In South Africa one of the most common chrysopid species in maize ecosystems is Chrysoperla pudica (Navás) (Neuroptera: Chrysopidae). Evolution of Bt resistant pests, such as B. fusca in South Africa facilitates a new pathway for exposure of predators to healthy prey that consumes Cry 1Ab proteins. The aims of this study was to determine the effect of the Cry 1Ab protein expressed in Bt maize on a non-target organism‟s (C. pudica) biology via indirect exposure, and to determine the concentration of Cry 1Ab protein in the plant, prey and predator. Chrysoperla pudica larvae were indirectly exposed to the Bt-toxin through healthy Bt-maize feeding prey (B. fusca larvae) in two feeding experiments and lacewing survival and life history parameters recorded. Bt had a limited effect on some parameters that were evaluated. The larval and pupal periods of C. pudica larvae that were exposed to the Bt-toxin had a significant difference from that of the control treatment. The Bt-toxin had a significant effect on fecundity, fertility and malformation after emergence of C. pudica adults of which larvae fed only on Bt resistant B. fusca larvae, but not on the mortality rate. Cry 1Ab concentration was the highest in the plant, followed by the prey and lacewing larvae. This study showed that the Cry 1Ab protein had a slight adverse effect only on certain life parameters of C. pudica, and that Cry 1Ab protein was hardly detectable in C. pudica larvae. However, since this study represented a worst-case scenario where diverse prey was not available, insignificant effects is expected under field conditions where prey is diverse. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Made available in DSpace on 2015-03-26T13:30:46Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1034963 bytes, checksum: 2f8ddfdc0ab599a1ee63766057899a95 (MD5) Previous issue date: 2013-07-22 / Worldwide sugar cane plantations suffer the pest attack A major pest is the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). A striking feature of D. saccharalis is the penetration on the stalk, feeding on the tissues; affecting the developmet point, resulting in a condition known as "dead heart" due to the presence of the fungus Colletotrichum falcatum The plants can protect itself from herbivores attack by a combination of constitutive and/or inducible defenses that reduces the performance of herbivores, interrupting the spread of the damage. Accordingly, plants respond to feeding herbivorous arthropods producing a series of secondary metabolites, including volatile organic compounds (VOCs), which are known to attract natural enemies. Natural enemies such as parasitoids, are able to exploit these volatiles to locate their prey, for exemple, using feeding chemical signals. Thus, behavioral studies are important for understanding the interactions that occur between organisms in a food Web. As the knowledge of the chemical compounds that mediate the location of plants infested with herbivores by natural enemies, to have a better understanding of insect-plant interaction influencing the third trophic level. Given this, in this study was investigated the responses of cotesia flavipes (Cameron) (Hymenoptera: Braconidae) to volatile plant sugar cane rustic and current (Archi, White pararia and RB867515) unscathed and infested by D. saccharalis. In the chapter 1 was investigated the preferences of C. flavipes to the set of plants induced to herbivory and plants unharmed in laboratory and semi-field conditions. The results show that the parasitic wasp provides different responses, in the laboratory showed choice for infested specie and semi-infested field conditions show no preference, but present parasitism in the host. In the second chapter we identify the volatile compounds emitted by plants infested with D. Saccharalis and undamaged plants of sugarcane. To access this result was used for GC-MS for the identiñcation of compounds, showing that when compared uninjured plants with infested plants were found and identified a larger quantity of volatile components in the infested plants, especially on the species Archi and White pararia, the profile of volatile of the specie RB867515 is very similar between infested and unharmed sugar cane plants. The results obtained through the identification of these volatile compounds may explain the outputs obtained in the chapter 1, which may mediate the foraging behavior of C. flavipes. In general it can be concluded that this wasp showed parasitism, independently of the complex plant-herbivore, reducing infestation and damage by D. saccharalis in sugarcane plants. / Em todo o mundo plantações de cana de açúcar sofrem o ataque de pragas. Uma das principais pragas é a broca da cana Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), uma caraterística marcante de D. saccharalis é a penetração no colmo, onde se alimenta do tecido afetando o ponto de desenvolvimento, produzindo o chamado "coração morto" devido à presença do fungo Colletotrichum falcatum. As plantas se protegem contra o ataque dos herbívoros através da combinação de defensas constitutivas e/ou induzidas que reduzem o desempenho dos herbívoros, interrompendo a propagação do dano. Consequentemente, as plantas respondem à alimentação de herbívoros artrópodes produzindo uma série de compostos secundários, incluindo os compostos voláteis orgânicos (VOCs), os quais são conhecidos por atrair os inimigos naturais. Os inimigos naturais como parasitoides, são capazes de explorar esses voláteis para localizar seus hospedeiros, como por exemplo, usando os sinais químicos da alimentação. Dessa forma, estudos de comportamento para fontes de odores são importantes para o entendimento das interações que ocorrem entre os organismos em uma teia alimentar. Assim como o conhecimento dos compostos químicos que meiam a localização de plantas infestadas com herbívoros pelos inimigos naturais, para ter uma melhor compreensão da interação inseto-planta influenciando o terceiro nível trófico. Diante isto, este trabalho investigou as respostas de Cotesia flavipes (Cameron) (Hymenóptera: Braconidae) aos voláteis de plantas de cana de açúcar rústicas e atual (Archi, White pararia e RB867515), ilesas e infestadas por D. saccharalis. No capítulo 1 foram investigadas as preferências de C. flavipes ao conjunto de plantas induzidas a herbivoria e plantas ilesas tanto em laboratório quanto em condições de semi-campo. Os resultados mostram que a vespa parasítica apresenta diferentes respostas, sendo que em laboratório mostra escolha por espécies infestadas quanto em semi-campo não mostra preferência, no entanto apresentando parasitismo no hospedeiro. No segundo capítulo identificamos os compostos voláteis emitidos por plantas infestadas com D. saccharalis e plantas ilesas de cana de açúcar. Para acessar a esse resultado foi utilizado o GC-MS para a identificação dos compostos, mostrando que quando comparamos plantas ilesas com plantas infestadas foram encontrados e identificados uma quantidade superior de compostos voláteis nas plantas infestadas, principalmente das espécies Archi e White pararia, já que o perfil de voláteis da espécie RB867515 é bastante similar quando ilesa e infestada. Os resultados obtidos através da identificação destes compostos voláteis podem explicar as respostas obtidas no capítulo 1, os quais podem mediar no comportamento de forrageamento de C. flavipes. Em linhas gerais, pode-se concluir que esta vespa apresenta parasitismo independente do complexo planta-herbívoro, reduzindo a infestação e o dano por parte de D. saccharalis em plantas de cana de açúcar.

Plusieurs recherches sont effectuées sur la laitue commercialisée (Lactuca sativa L.), afin d’améliorer sa résistance aux ravageurs. L’objectif de cette étude est d’examiner les impacts de la résistance de la laitue sur le puceron de la laitue, Nasonovia ribisnigri (Mosley) (Hemiptera : Aphididae) et son parasitoïde, Aphidius ervi Haliday (Hymenoptera: Braconidae). La résistance de la laitue affecte négativement la valeur adaptative du puceron en augmentant sa mortalité et son temps de développement et en diminuant sa fécondité, sa taille et son poids. Cet impact sur la valeur adaptative du puceron affecte aussi négativement le parasitoïde qui s'y développe en diminuant le pourcentage d’émergence, la taille et le poids des adultes, et en diminuant la fécondité des femelles. La femelle parasitoïde estime de manière absolue la qualité de ses hôtes puisqu’elle peut discriminer entre des hôtes de bonne et de faible qualité, sans expérience préalable. L’acceptation des hôtes de bonne qualité est similaire lorsqu’ils sont présentés successivement à la femelle; l’estimation de la valeur des hôtes est donc adéquate dès la première rencontre. Cependant, cet estimé absolu est modifié par l'expérience, puisque la femelle peut changer son exploitation selon la qualité des agrégats rencontrés. Lorsque des hôtes de basse qualité sont présentés successivement, l’acceptation de la femelle augmente. Accepter des hôtes de mauvaise qualité pour l’oviposition peut être préférable que de risquer de ne pas pondre tous ses œufs. L’utilisation d’une estimation absolue et relative par A. ervi peut mener à une exploitation optimale des agrégats. / New cultivars of commercialized lettuce (Lactuca sativa L.) with an improved resistance to pests are now available. The objective of this study was to examine the impacts of lettuce resistance on the lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) and one of its parasitoids, Aphidius ervi Haliday (Hymenoptera: Braconidae). Lettuce resistance negatively affects aphid fitness by: increasing its mortality and developmental time and decreasing its fecundity, size and mass. This impact on aphid fitness also negatively impacts the parasitoid by decreasing its proportion of emergence, the size and mass of adults and decreasing fecundity of females. Female parasitoids estimate hosts quality in an absolute way as they can discriminate between high and low quality hosts, without previous experience. High quality host acceptation remains constant when hosts are successively offered to a female, indicating that the female can adequately estimate host value without experience. However, this absolute estimate of host quality is modified through experience as the female changes her patch exploitation according to the quality of the patches she encounters. When low quality hosts are successively offered, female acceptation increases. Accepting low quality hosts for oviposition can be preferable to the risk of not using all her eggs. The two strategies combined, using an absolute and a relative estimation, could lead to optimal patch exploitation by A. ervi.

Plusieurs recherches sont effectuées sur la laitue commercialisée (Lactuca sativa L.), afin d’améliorer sa résistance aux ravageurs. L’objectif de cette étude est d’examiner les impacts de la résistance de la laitue sur le puceron de la laitue, Nasonovia ribisnigri (Mosley) (Hemiptera : Aphididae) et son parasitoïde, Aphidius ervi Haliday (Hymenoptera: Braconidae). La résistance de la laitue affecte négativement la valeur adaptative du puceron en augmentant sa mortalité et son temps de développement et en diminuant sa fécondité, sa taille et son poids. Cet impact sur la valeur adaptative du puceron affecte aussi négativement le parasitoïde qui s'y développe en diminuant le pourcentage d’émergence, la taille et le poids des adultes, et en diminuant la fécondité des femelles. La femelle parasitoïde estime de manière absolue la qualité de ses hôtes puisqu’elle peut discriminer entre des hôtes de bonne et de faible qualité, sans expérience préalable. L’acceptation des hôtes de bonne qualité est similaire lorsqu’ils sont présentés successivement à la femelle; l’estimation de la valeur des hôtes est donc adéquate dès la première rencontre. Cependant, cet estimé absolu est modifié par l'expérience, puisque la femelle peut changer son exploitation selon la qualité des agrégats rencontrés. Lorsque des hôtes de basse qualité sont présentés successivement, l’acceptation de la femelle augmente. Accepter des hôtes de mauvaise qualité pour l’oviposition peut être préférable que de risquer de ne pas pondre tous ses œufs. L’utilisation d’une estimation absolue et relative par A. ervi peut mener à une exploitation optimale des agrégats. / New cultivars of commercialized lettuce (Lactuca sativa L.) with an improved resistance to pests are now available. The objective of this study was to examine the impacts of lettuce resistance on the lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) and one of its parasitoids, Aphidius ervi Haliday (Hymenoptera: Braconidae). Lettuce resistance negatively affects aphid fitness by: increasing its mortality and developmental time and decreasing its fecundity, size and mass. This impact on aphid fitness also negatively impacts the parasitoid by decreasing its proportion of emergence, the size and mass of adults and decreasing fecundity of females. Female parasitoids estimate hosts quality in an absolute way as they can discriminate between high and low quality hosts, without previous experience. High quality host acceptation remains constant when hosts are successively offered to a female, indicating that the female can adequately estimate host value without experience. However, this absolute estimate of host quality is modified through experience as the female changes her patch exploitation according to the quality of the patches she encounters. When low quality hosts are successively offered, female acceptation increases. Accepting low quality hosts for oviposition can be preferable to the risk of not using all her eggs. The two strategies combined, using an absolute and a relative estimation, could lead to optimal patch exploitation by A. ervi.