Dissertations / Theses on the topic 'Conservation biological control'

Thesis (M.S.) -- University of Maryland, College Park, 2003.
Thesis research directed by: Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

In agroecosystems, conservation biological control is often constrained by low availability of pollen and nectar. Although floral resources can be integrated into agricultural systems, this usually requires sacrifice of productive land. This thesis describes experiments which test the influence of floral resources provided by species which have marketable value in their own right as food or medicinal crops. Floralresource strips comprising such species were intercropped with Brassica crops at plot, field and commercial scales in replicated field experiments. The abundance and distribution of key Brassica crop pests a,nd their natural enemies in the presence of floral resources was examined. Parasitoids displayed distinct flower species preferences; Fagopyrum esculentum significantly increased parasitoid abundance. Parasitoids also responded to distance; their abundance significantly declined with increasing distance from floral strips, especially in F. esculentum, and parasitism levels declined significantly after 8 m. Borago offtcinalis also proved attractive to parasitoids and Tanacetum parthenium to Syrphidae. In addition, F. esculentum and B. offtcinalis were found to suppress the second generation of Pierid larvae at field scale. This evidence suggests that several flower species could be intercropped within a Brassica crop to promote biological pest control.

Agriculture has done more damage to nature than any other human activity, and yet food production could need to be doubled by the middle of this century. As agricultural land is expanded and intensified, critical thresholds in the loss of natural habitats are crossed. This loss of non-crop habitats can have negative feedback on crop production, because it can cause a loss of “ecosystem services” that support and regulate crop production, such as the pollination of crops by bees and the biological control of crop pests by their natural enemies. Because of this connection between non-crop habitats and crop yields, there could be potential for habitat conservation to benefit both agriculture and nature. The research in this thesis focuses on pollinators and natural enemies, because these species constitute a vital connection between food production and biodiversity conservation. Could habitat management be used to conserve both pollinators and natural enemies in agricultural landscapes? Will the relationships between pollinators, natural enemies, and natural habitats change with climate change? Where should we prioritize the resolution of conflict between agriculture and nature, and how? This thesis addresses these questions through literature review and meta-analysis, geographic information systems (GIS) and hotspot analysis, field research on the distributions of trap-nesting bees and wasps on environmental gradients, and laboratory research on the development of bees and wasps at high temperatures. This thesis suggests that it might be possible to conserve communities of both pollinators and natural enemies, in general, by means of habitat management, but it might not be possible to conserve specific combinations of pollinators and natural enemies, which might have opposite responses to some forms of environmental change, such as global warming. This thesis also suggests that the resolution of conflict between agriculture and nature should be prioritized in sub-Saharan Africa, and it outlines a conceptual framework for systematic conservation planning in agricultural landscapes.

Peach and nectarine tree belongs to the species Prunus persica and is the third most produced fruit species in the world. Within Europe, Spain is a leading producer. Most of the crops are located in Catalonia (northeastern Spain). Peach tree is the primary host of Myzus persicae, which is one of the most damaging pests of the crop. To date, its management has mainly based on insecticides, but the risk they pose to the human health and the environment, requires a reduction in their usage. Biological control could be a good tool to improve its control because of the wide array of natural enemies. Among the different strategies, conservation of already natural enemies present in the agroecosystem seems the more promising. Therefore, the present thesis was undertaken to determine the possibility of implementing conservation biological control against M. persicae in peach orchards in the Mediterranean area. The identification of the key natural enemies has to be the first step to start a conservation biological control program. The inclusion of floral resources close to the orchards might help to enhance the control by providing natural enemies with food sources, therefore improving aphid biological control. The first two chapters of this thesis, are dedicated to identify the key natural enemies of M. persicae in the Segrià area (Catalonia) and to evaluate in field conditions, the potential contribution of insectary plants to enhance aphid natural enemy populations. Sentinel plants, were used to recruit the natural enemies, and molecular and morphological methods were used to identify them. Then, their attraction to Achillea millefolium, Lobularia maritima, Moricandia arvensis, and Sinapis alba was evaluated. Results showed that, the most abundant natural enemies were parasitoids with the species Aphidius matricariae the most prevalent. Regarding predators, Aphidoletes aphidimyza and Episyrphus balteatus were the most prevalent, followed by Orius majusculus. Insectary plants were highly attractive to hoverflies and parasitoids, and none of the plants was a reservoir of damaging aphids for peach crops. Lobularia maritima was one of the more suitable plants. However, the proximity of these plants did not increase the abundance of natural enemies, probably due to the size of the orchards. To effectively contribute to natural enemy fitness, flowering insectary plants have to provide profitable food. The third chapter focused on assess whether the insectary plant L. maritima is a potential food source for Aphidius ervi and A. aphidimyza. Results showed that L. maritima, with and without flowers, attracted both natural enemies. However, this attractiveness was disrupted when compared with peach shoots infested with aphids. L. maritima flowers did not improved the fitness of A. aphidimyza, since the floral morphology prevented females to feed on the nectar. Nevertheless, flowers increased the longevity of A. ervi. The high diversity of natural enemies increases the probability of intraguild predation, additionally the presence of natural enemies in an aphid colony can also produce behavioral changes in aphids. The last chapter had the aim to evaluate the interactions among predators and parasitoids, and how these interactions may influence the biological control of the aphid. The contribution of E. balteatus, A. aphidimyza and O. majusculus was determined. The changes in the aphid’s behavior mediated by the aphid cornicle exudate and the interaction of these predators with the parasitoid A. matricariae were also evaluated. The most voracious predator was E. balteatus. O. majusculus did not reduce pest population. The cornicle exudate triggers fecundity compensation A. aphidimyza and O. majusculus preferred to kill nonparasitized aphids, and avoid to feed on mummies. The results of this thesis, suggest that the conservation biological control can be a useful tool to improve M. persicae control in peach and nectarine crops.
El melocotero y la nectarina pertenecen a la especie Prunus persica (L.) Batsch y es el tercer cultivo frutal con mayor producción a nivel mundial. En Europa, España es uno de los mayores países productores representando más del 30% del total de la producción. La mayoría de las plantaciones de melocotoneros y nectarinas están localizados en Cataluña, al noreste de España. Prunus persica es el huésped primario de Myzus persicae (Sulzer) (Hemiptera: Aphididae), comúnmente conocido como el pulgón verde del melocotonero, que es una de las plagas más dañinas para el cultivo. Hasta la fecha el control de este pulgón se ha basado en la utilización de insecticidas pero, debido al riesgo que representan tanto para la salud humana como para el medio ambiente, se requiere reducir el uso de estos productos. El control biológico puede ser una buena herramienta para mejorar el control de la plaga en este cultivo debido a que los pulgones tienen un amplio rango de enemigos naturales que podrían contribuir a su control. Dentro de las diferentes estrategias de control biológico que se han utilizado contra los pulgones, la conservación de los enemigos naturales ya existentes en el agroecosistema parece ser la más prometedora para los cultivos frutales. Con estos antecedentes, la presente tesis se llevó a cabo para determinar la posibilidad de implementar el control biológico por conservación contra M. persicae en cultivos de melocotón y nectarina en el área del Mediterráneo. El control biológico por conservación, se basa en preservar a los enemigos naturales presentes en la zona e implementar estrategias para mejorar sus poblaciones. Por lo tanto, la identificación de los enemigos naturales clave involucrados en el control de M. persicae, debe ser el primer paso para comenzar un programa de control biológico por conservación. La inclusión de recursos florales cerca del cultivo, podría ayudar a mejorar el control al ofrecer a los enemigos naturales recursos alimenticios como néctar y polen, contribuyendo así a aumentar sus poblaciones en el momento adecuado para controlar eficazmente la plaga. Los dos primeros capítulos de esta tesis, están dedicados a identificar los depredadores y parasitoides clave de M. persicae en la comarca del Segrià (Cataluña), y a evaluar, en condiciones de campo, el potencial de ciertas plantas insectarias para mejorar sus poblaciones. Para recolectar a los enemigos naturales de M. persicae, se utilizaron plantas centinela, es decir plantones de melocotonero expresamente infestados con M. persicae, y para identificar a las especies más abundantes se utilizaron métodos moleculares y morfológicos. Posteriormente se evaluó la atracción de los enemigos naturales hacia manchas florales que incluían las siguientes especies: Achillea millefolium L. (Compositae), Lobularia maritima L. (Brassicaceae), Moricandia arvensis L. (Brassicaceae) y Sinapis alba L. (Brassicaceae). Los resultados mostraron que los enemigos naturales más abundantes de M. persicae fueron parasitoides. A pesar de que existió un amplio rango de especies, Aphidius matricariae Haliday (Hymenoptera: Braconidae: Aphidiinae) fue con mucho la más abundante. De los pulgones parasitados se identificaron, así mismo, diez especies de hiperparasitoides. Sin embargo, la ausencia de hiperparasitoides a principio de la temporada, cuando las poblaciones de M. persicae son elevadas, sugiere que el control biológico de este pulgón no se vería afectado negativamente. En cuanto a los depredadores, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae) y Episyrphus balteatus DeGeer (Diptera: Syrphidae) fueron los más abundantes, seguidos de Orius majusculus Reuter (Hemiptera: Anthocoridae). Los experimentos de campo realizados en esta tesis, mostraron que la presencia de manchas florales fue atractiva para los sírfidos y para los parasitoides y ninguna de las plantas evaluadas fue reservorio de pulgones dañinos para los cultivos de melocotón y nectarina. Entre las cuatro plantas insectarias evaluadas, L. marítima fue uno de los mejores para los enemigos naturales. Sin embargo, la proximidad de las plantas insectarias al cultivo no incrementó la abundancia de las poblaciones de enemigos naturales en las plantas centinela, probablemente a causa del tamaño de las parcelas. Para poder contribuir de manera positiva al estado físico (fitness en inglés) de los enemigos naturales, y por lo tanto al control biológico de M. persicae, las flores de las plantas insectarias deben proporcionar a los parasitoides y depredadores un alimento que puedan aprovechar, tanto en términos de calidad como de accesibilidad. En base a ello, el tercer capítulo de esta tesis se centró en evaluar si la planta insectaria L. marítima es una fuente de alimento adecuada para el parasitoide Aphidius ervi (Haliday) (Hymenoptera: Braconidae: Aphidiinae) y el depredador A. aphidimyza. Con este objetivo, se realizaron experimentos de laboratorio para investigar si ambos enemigos naturales eran atraídos hacia L. marítima en presencia y ausencia de flores. También se evaluaron los efectos de las flores en cuanto a la longevidad y el potencial reproductivo de estos insectos. Los resultados de los experimentos llevados a cabo en el olfactómetro mostraron que los compuestos volátiles producidos por L. maritima, con y sin flores, atraían a ambos enemigos naturales. Sin embargo, esta atracción se vio afectada cuando se comparó la L. marítima con brotes de melocotón infestados con M. persicae. Aunque A. aphidimyza se benefició de una alimentación rica en azúcar, la disponibilidad de L. marítima no mejoró ni la longevidad ni la reproducción del depredador, ya que la morfología floral de esta especie impidió que las hembras se alimentaran del néctar. En cambio, las flores de L. maritima incrementaron la longevidad de las hembras de A. ervi en ausencia de pulgones. Por lo tanto, la provisión de otros recursos azucarados, como nectarios extraflorales o flores con nectarios expuestos, pueden ser un recurso alimenticio viable para los enemigos naturales y por lo tanto ayudarían a mejorar el control biológico de M. persicae. Debido a la gran diversidad de enemigos naturales que atacan a M. persicae en el área de estudio, existe una alta probabilidad de que ocurra depredación intragremial porque estos enemigos naturales no solo compiten por el mismo recurso alimenticio, sino que también pueden depredarse entre sí. Además, dado que el desarrollo de las larvas de los parasitoides ocurre dentro del pulgón, los depredadores pueden comérselos al alimentarse del pulgón. Por otro lado, la presencia de enemigos naturales en una colonia de pulgones también puede producirles cambios en su comportamiento. El último capítulo de esta tesis tuvo como objetivo evaluar las interacciones entre depredadores y parasitoides, y estudiar cómo estas interacciones pueden influir en el control biológico de M. persicae. En ensayos de laboratorio, se determinó la contribución de E. balteatus, A. aphidimyza y O. majusculus al control de M. persicae. También se evaluaron los cambios en el comportamiento del pulgón asociados por las secreciones de los cornículos o sifones, y la interacción de estos depredadores con el parasitoide A. matricariae. Los resultados mostraron que el depredador más voraz fue E. balteatus, seguido de A. aphidimyza. Orius majusculus no redujo la población de M. persicae. La secreción de los cornículos de M. persicae desencadenó una compensación de la fecundidad, es decir, un aumento de la descendencia. Aunque, A. aphidimyza y O. majusculus prefirieron matar los pulgones no parasitados, ambos depredadores fueron capaces de matar a los individuos de M. persicae parasitados pero aún no momificados. Su preferencia por matar pulgones no parasitados indica que la coexistencia de parasitoides y depredadores no sería negativa para el control biológico de M. persicae. Los resultados de esta tesis, sugieren que el control biológico por conservación puede ser una herramienta útil para mejorar el control de M. persicae en cultivos de melocotón y nectarina.
Els préssecs i les nectarines Prunus persicae (L.) Batsch és el tercer conreu fruiter amb més producció a escala mundial. Dins d'Europa, Espanya és un dels majors productors amb el 30% del total de la producció europea. La majoria de camps de presseguer i nectarina estan localitzats a Catalunya, al nord-est d'Espanya. Prunus persicae és l'hoste primari del pugó verd del préssec, Myzus persicae (Sulzer) (Hemiptera: Aphididae) que és una de les plagues més nocives per al cultiu. Fins a la data actual, el control d'aquest pugó s'ha basat en l'ús d'insecticides, però el risc que representen tant per a la salut humana com per al medi ambient, fa necessari reduir-ne l’ús. El control biològic pot ser una bona eina per millorar el control d’aquesta plaga en els camps de cultiu, ja que els pugons tenen un ampli rang d'enemics naturals que podrien contribuir al seu control. Dins de les diferents estratègies de control biològic que s'han utilitzat contra els pugons, la conservació dels enemics naturals ja existents en l'agroecosistema sembla ser la més prometedora pels cultius de fruiters. Amb aquests antecedents, la present tesi es va dur a terme amb l'objectiu de determinar la possibilitat d'implementar el control biològic per conservació contra M. persicae en cultius de préssec i nectarina en l'àrea del Mediterrani. El control biològic per conservació es basa en preservar als enemics naturals presents a la zona i en la implementació d'estratègies per millorar les seves poblacions en l'agroecosistema. Per tant, la identificació dels enemics naturals clau involucrats en el control de M. persicae ha de ser el primer pas per a començar un programa de control biològic per conservació. La implementació de recursos florals prop dels camps, podria ajudar a millorar el control, ja que ofereixen als enemics naturals recursos alimentaris com nèctar i pol·len, contribuint així a augmentar les seves poblacions en el moment adient per a controlar eficaçment la plaga. Els dos primers capítols d'aquesta tesi, estan dedicats a identificar els depredadors i parasitoides clau de M. persicae en la comarca del Segrià (Catalunya), així com a avaluar, en condicions de camp, el potencial de certes plantes insectàries per incrementar les poblacions d’enemics naturals. Per a determinar els enemics naturals de M. persicae es van utilitzar plantes sentinella, plançons de presseguer expressament infestats amb M. persicae. Per identificar les espècies més abundants es van utilitzar mètodes moleculars i morfològics. Posteriorment es va avaluar l'atracció dels enemics naturals clau cap a marges florals que incloïen les següents espècies: Achillea millefolium L. (Compositae), Lobularia maritima L. (Brassicaceae), Moricandia arvensis L. (Brassicaceae) i Sinapis alba L. (Brassicaceae). Els resultats van mostrar que els enemics naturals predominants de M. persicae eren els parasitoides. Tot i l’ampli rang d'espècies, Aphidius matricariae Haliday (Hymenoptera: Braconidae: Aphidiinae) va ser amb diferència la més abundant. Dels pugons parasitats es van identificar també deu espècies d'hiperparasitoides. Amb tot, l'absència d'hiperparasitoides a principi de la temporada, quan les poblacions de M. persicae són elevades, suggereix que el control biològic d'aquest pugó no es veuria afectat negativament. Pel que fa als depredadors, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae) i Episyrphus balteatus DeGeer (Diptera: Syrphidae) van ser els més abundants, seguits de Orius majusculus Reuter (Hemiptera: Anthocoridae). Els experiments de camp realitzats en aquesta tesi, mostren que la presència de taques florals va ser atractiva per als sírfids i per als parasitoides, i cap de les plantes avaluades va ser reservori de pugons nocius per al cultiu. Entre les quatre plantes insectari avaluades, L. marítima va ser un bon recurs per als enemics naturals. No obstant això, la proximitat de les plantes insectàries no va incrementar l'abundància de les poblacions d'enemics naturals en les plantes sentinella, probablement degut a la mida de les parcel·les. Per a poder contribuir de manera positiva al estat físic (fitness en anglès) dels enemics naturals, i per tant al control biològic de M. persicae, les flors de les plantes insectàries han de proporcionar als parasitoides i depredadors aliment que puguin aprofitar tant pel que fa a la qualitat com a l’accessibilitat. Basat en l'anterior, el tercer capítol d'aquesta tesi es va centrar en avaluar si la planta insectària L. marítima és una font d'aliment adequada per al parasitoide Aphidius ervi (Haliday) (Hymenoptera: Braconidae: Aphidiinae) i el depredador A. aphidimyza. Amb aquest objectiu, es van realitzar experiments de laboratori per investigar si tots dos enemics naturals eren atrets cap a L. marítima en presència i absència de flors. També es van avaluar els efectes de les flors pel que fa a la longevitat i el potencial reproductiu. Els resultats dels experiments duts a terme en l'olfactòmetre van mostrar que els compostos volàtils produïts per L. maritima, amb i sense flors, atreien tots dos enemics naturals. Amb tot aquesta atracció es veia afectada quan L. marítima es van comparar amb brots de presseguer infestats amb M. persicae. Tot i que A. aphidimyza es va beneficiar d'una alimentació rica en sucre, la disponibilitat de L. maritima no va millorar ni la longevitat ni la reproducció d’aquest depredador, ja que la morfologia floral d'aquesta espècie va impedir que les femelles s'alimentessin del nèctar. D'altra banda, la disponibilitat de flors de L. maritima va incrementar la longevitat de les femelles d’ A. ervi en absència de pugons. Per tant, la provisió d'altres recursos rics en sucre, com nectaris extraflorals i flors amb nectaris exposats poden ser una opció per millorar el control biològic de M. persicae. A causa de la gran diversitat d'enemics naturals que ataquen a M. persicae en l'àrea d'estudi, existeix una alta probabilitat que hi hagi depredació intragremial, ja que aquests enemics naturals no només competeixen pel mateix recurs alimentari, sinó que també poden depredar-se entre ells. A més, degut al desenvolupament de les larves dels parasitoides dins del pugó, els depredadors se’ls poden menjar en alimentar-se de pugó. D’altra banda, la presència d'enemics naturals en una colònia de pugons també pot produir-los-hi canvis de comportament. L'últim capítol d'aquesta tesi va tenir com a objectiu avaluar les interaccions entre depredadors i parasitoides, i com aquestes interaccions poden influir en el control biològic de M. persicae. Es va determinar la contribució d’E. balteatus, A. aphidimyza i O. majusculus al control de M. persicae. També es van avaluar els canvis en el comportament del pugó derivats de el líquid secretat per les cornícules o sifons i la interacció d'aquests depredadors amb el parasitoide A. matricariae. Els resultats van mostrar que el depredador més voraç va ser E. balteatus, seguit d’ A. aphidimyza. Orius majusculus no va reduir la població de M. persicae. El líquid secretat per les cornícules de M. persicae va desencadenar una compensació de fecunditat, és a dir, un augment en la descendència. Tot i que, A. aphidimyza i O. majusculus van preferir matar pugons no parasitats, els dos depredadors van ser capaços de matar als individus de M. persicae parasitats que encara no estaven momificats. La seva preferència per matar pugons no parasitats suggereix que la coexistència de parasitoides i depredadors no seria negativa pel control biològic de M. persicae. Els resultats d'aquesta tesi, suggereixen que el control biològic per conservació, pot ser una eina útil per millorar el control de M. persicae en cultius de préssec i nectarina.

The goal of this study was to evaluate several sustainable turf maintenance techniques for their potential to increase beneficial insect populations, which could then provide ecosystem services including pest suppression and pollination. The three techniques in question were 1) raising mowing height in commercial and residential lawns, 2) establishing naturalized roughs on golf courses, and 3) creating pollinator refuges on golf courses through the program Operation Pollinator. We found that raising mowing heights did increase populations of some predators such as spiders and staphylinids, but did not increase predation, which was ubiquitously high because ant populations were unaffected by mowing height. In addition, we found that pests reared in high-mowed grass were less likely to survive and gained weight more slowly than when raised in low-mowed grass. On golf courses, we found that naturalized roughs and traditional roughs supported different populations of predators, but contrary to our original hypothesis, naturalized roughs had little impact on biological control on the rest of the golf course. Operation Pollinator was successful in supporting 49 species of pollinators, including rare and declining bumble bees, demonstrating that turf systems can provide valuable pollinator conservation services, especially in urban systems where pollinator habitats are already rare.

Natural enemies provide critical population regulation of many pest species, though their effects are not commonly incorporated into agricultural management decisions. Conservation biological control is an important tool that can be implemented to minimize pest damage, but applying it requires appropriate understanding of pest and natural enemy relationships. Through experimental cotton field trials, I identified predator: prey ratios based on key arthropod predators as action thresholds of the whitefly pest Bemisia tabaci MEAM1 (Dinsdale et al. 2010; equivalent to Bemisia argentifolii Bellows et al. 1994 [Hemiptera: Aleyrodidae]), validated their efficacy, and promoted them to cotton pest managers. This dissertation begins with a multi-year field trial where whitefly and natural enemy populations were manipulated with a series of insecticidal treatments to identify key arthropod predators. The critical abundance of four key predators necessary to suppress whiteflies was estimated through predator: prey ratios. These ratios were refined for commercial pest management and developed to conform to the current whitefly IPM framework as a simple to use management-decision tool that would be readily adopted and used by pest managers. Predator: prey ratios were then validated in 1) a second field trial, 2) commercial fields in Arizona and northern Mexico and 3) historical field trials conducted from 1997-2010, where whitefly management decisions made with the standard threshold and ratios, were compared with the standard threshold alone. I found no difference in management outcomes when decisions were made with the standard threshold alone, or with predator: prey ratios in the field trial, but analysis of potential decisions on commercial farms and with historical trial data indicated that the majority of sprays could be delayed if control decisions incorporated ratio-based thresholds. Finally, an outreach program was developed and deployed to present ratios as decision-making tools for cotton pest managers that reduce uncertainty in control decisions and optimize spray outcomes. Pest managers indicated positive changes in knowledge and a gradual adoption of ratios for decision-making. The implementation of whitefly control decisions that incorporate predator: prey ratios may reduce pest managers' uncertainty in decision-making, as well as insecticide use and management costs.

Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Insects have become increasingly resistant to chemical control methods, while at the same time public awareness of the harmful effects of synthetic pesticides has increased. The search for more environmentally 'friendly' means of pest suppression is gaining momentum and biological control (the use of natural enemies to reduce populations of noxious organisms) has become an increasingly sought-after option. Despite an increase in the establishment rate of insect natural enemies, classical biological control of arthropods is currently no more successful than it was one hundred years ago. Ecological theory relevant to population biology, food webs and diversity provides insight into how biological control agents can be made more effective, yet this theory has often been absent from the biological control literature. Examples of the use of ecological concepts (including intraguild predation, life-history omnivory and resource subsidies) in practical biological control are reviewed, and aspects of theory not yet considered in this context are discussed. Cereals are important as primary food crops, globally and within New Zealand. Possibly the greatest amount of damage sustained by cereal crops in New Zealand is caused by aphids and chemical control of these pests is very expensive relative to biological control. This thesis examines how biological control of the rose-grain aphid Metopolophium dirhodum (Walker) (Hemiptera: Aphidiidae) by the koinobiont, synovigenic endoparasitoid Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiidae) can be enhanced by floral resource subsidies. The mechanisms underlying this enhancement were determined in a series of laboratory experiments and then tested in laboratory microcosms and in the field. Sugar resources significantly increased longevity and egg load in A. rhopalosiphi and another species of aphidiid, Diaeretiella rapae McIntosh. Pollen had no significant effect on longevity or egg load in these species. These results are discussed in terms of the effects of resource subsidies on egg- versus time-limitation. Laboratory microcosm experiments tested whether the mechanisms of increased potential fecundity via enhanced egg load and longevity translate into increased rates of parasitism (i.e., realised fecundity). Only treatments receiving sugar showed increased reproductive success. The presence of flowering buckwheat Fagopyrum esculentum Moench (c.v. Kitawase) (Polygonaceae) plants caused a slight, non-significant increase in rates of parasitism. Field surveys of natural aphid populations in a wheat Triticum aestivum (L.) (c.v. Otane) (Gramineae) field showed that proximity to floral buckwheat patches, distance to the nearest edge or the leeward end of the field were not significantly correlated with rates of parasitism. These variables were significantly correlated with aphid density in some surveys. Rates of parasitism were not correlated with aphid density. When aphid population density was controlled by experimental placement of aphids, proximity to floral resource patches significantly affected rates of parasitism. Parasitism rates were highest at the edges of buckwheat patches and declined exponentially with distance, eventually reaching zero beyond 14 m. Lower levels of parasitism were observed within the floral patches than at their edges. This phenomenon is compatible with the concept of spatio-temporal partitioning between parasitoid feeding and host-searching behaviours. Potential costs (increased predation risk, opportunity costs) and benefits (increased fecundity and longevity) associated with floral feeding by parasitoids, and temporal variation in these factors, are discussed. It is concluded that resource subsidies are not only effective in the practical enhancement of the efficacy of a specific biological control agent, but their use is based on a sound foundation in ecological theory that allows extension of these principles across taxa.

Acacia cyclops A. Cunn. ex G. Don is an invasive alien plant that invades fynbos and coastal dunes. Several acacia species are grown commercially in South Africa and this has limited biocontrol agents to those that reduce only reproductive capacity. Dasineura dielsii was released in 2002 as a biocontrol agent for A. cyclops. This gall-forming midge destroys inflorescences and prevents seedpods from forming, but allows continued harvesting. Insects overwinter as larvae within their galls. This study examined the levels of parasitism experienced by dormant D. dielsii larvae, as well as the trigger that causes them to break dormancy. Gall clusters were sampled over autumn and early winter, and were dissected to determine occupancy. The effects of temperature and light on dormant larvae were also examined. Observations showed that as the season progressed, more D. dielsii larvae entered dormancy. At the same time, a greater proportion of dormant larvae were parasitized. Parasitism was highest, at 18.5%, at the end of the study period, but this level of parasitism is not enough to reduce the biocontrol power of D. dielsii. A positive relationship between mass of gall clusters and the number of galls they contain was established. Larval dormancy could not be artificially broken by either light or temperature, and it appears that neither factor alone can trigger a break in dormancy.

Orientadores: Mohamed Ezz El-Din Mostafa Habib, João Vasconcellos Neto
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Embora os agroecossistemas resultem da ação humana sobre os ecossistemas naturais, sua estrutura e funcionamento se matem a partir de princípios e processos ecológicos. Dadas as externalidades negativas causadas pela agricultura convencional, alguns setores acadêmicos e movimentos em prol da agricultura de base ecológica buscam por um novo paradigma de agricultura, pautado na sustentabilidade. Dentre as práticas utilizadas pela agricultura de base ecológica para o controle de pragas está o controle biológico, incluindo o uso dos himenópteros parasitoides. Estes são responsáveis por grande parte da regulação populacional de insetos fitófagos. O objetivo deste trabalho foi estudar a fauna de himenópteros parasitoides associada a um agroecossistema de manejo orgânico, e comparar três áreas com estruturas distintas ¿ bananal, horta e mata ¿ em relação à diversidade de famílias de himenópteros parasitoides presentes em cada área. Foram realizadas coletas mensais de janeiro a março de 2013, com o uso de armadilhas Malaise. Foram coletados 1990 indivíduos, distribuídos em 8 superfamílias e 25 famílias. As famílias mais abundantes foram Braconidae, Ichneumonidae e Figitidae. O maior número de indivíduos e a maior riqueza de famílias foram obtidos na área da horta. O maior número de famílias raras foi obtido na área de mata. As três áreas apresentaram valores muito próximos para os índices de diversidade, o que indica que as duas áreas manejadas, do bananal e da horta, apresentam diversidade razoável de famílias de himenópteros parasitoides, tomando como referência a área da mata. Bananal e horta apresentaram maior similaridade segundo o índice de Morisita, possivelmente por ambas as áreas servirem como área de forrageamento para os parasitoides. Segundo o índice de Bray-Curtis, bananal e mata apresentaram maior similaridade, talvez devido ao bananal apresentar estrutura mais complexa e mais semelhante à área de vegetação nativa, o que possibilita melhores condições para as famílias mais dominantes de himenópteros parasitoides. Os dados a respeito das famílias de himenópteros parasitoides obtidos neste estudo indicam que sistemas agrícolas mais diversificados e com manejo de base ecológica são importantes ferramentas na conservação da biodiversidade
Abstract: Although agroecosystems are a result of human action on natural ecosystems, their structure and function are maintained by means of ecological principles and processes. Due to the negative externalities caused by conventional agriculture, some ecologically-based agriculture researches and movements seek for a new paradigm of agriculture, based on sustainability. The biological control is one of the practices used by ecologically-based agriculture for pest control, including the use of parasitoid Hymenoptera. Such parasitic insects are responsible for a significant regulation of herbivorous insect populations. In this work we studied the parasitic Hymenoptera fauna associated with an organic managed agroecosystem, comparing the abundance and diversity of the hymenopterous families in three different ecosystems (banana plantation, horticulture area and forest). From January to March 2013, insect samples were collected monthly, using Malaise traps. We collected 1990 individuals, distributed in 8 superfamilies and 25 families of parasitic Hymenoptera. The most abundant families were Braconidae, Ichneumonidae and Figitidae. The largest number of individuals and richer families were obtained in the horticulture area. The largest number of rare families was obtained in the forest. The areas presented very close values for diversity indices, indicating that the two managed areas, banana and horticulture, have considerable parasitic Hymenoptera families diversity, in comparison to the forest. Banana plantation and horticulture area showed higher similarity according to Morisita index, possibly because both areas serve as foraging area for the parasitoids. According to the Bray- Curtis index, banana plantation and forest showed greater similarity, perhaps due to the more complex structure of both situations, and thus can provide better shelter conditions for the most dominant families of parasitic Hymenoptera. The data about families of parasitic Hymenoptera obtained in this study indicate that more diversified and ecologically-based agricultural management systems are important tools for insect biodiversity conservation
Mestrado
Ecologia
Mestra em Ecologia

Trichogramma carverae Oatman and Pinto is mass-released for biological control of the leafroller pest, light brown apple moth, Epiphyas postvittana (Walker) in Australian vineyards. Parasitoid performance can, however, be constrained by a lack of suitable adult food and no information is available on the effect of nectar on the parasitism and longevity of T. carverae. To address this, the effect of alyssum, Lobularia maritima (L.) flowers on E. postvittana parasitism was studied in a vineyard experiment with and without releases of T. carverae. Egg parasitoid activity was assessed with E. postvittana egg 'sentinel cards' and no parasitism was recorded in plots without T. carverae releases. Where T. carverae were released, there was no significant enhancement of parasitism by the presence of L. maritima flowers. Three hypotheses were subsequently tested to account for the lack of an effect: (i) T. carverae does not benefit from L. maritima nectar, (ii) T. carverae was feeding on nectar from other flowering plants (weeds) present in the vineyard, (iii) T. carverae was feeding on sugars from ripe grapes. A growth-cabinet experiment using potted L. maritima plants with and without flowers did not support hypothesis one. No parasitism was recorded after day two for T. carverae caged without flowers whilst parasitism occured until day eight in the presence of flowers. A laboratory experiment with common vineyard weeds (Trifolium repens, Hypochoeris radicata, Echium plantagineum) as well as L. maritima did not support hypothesis one but gave partial support to hypothesis two. Survival of T. carverae was enhanced to a small but statistically significant extent in vials with intact flowers of L. maritima, white clover (T. repens) and catsear (H. radicata) but not in vials with flowering shoots of these species from which flowers and flowering buds had been removed. Paterson's curse (E. plantagineum) flowers had no effect on T. carverae survival. In a laboratory study, punctured grapes significantly enhanced T. carverae survival compared with a treatment without grapes, supporting hypothesis three. Trichogramma carverae performance in the field experiment was probably also constrained by relatively cool and wet weather. Further work on the enhancement of T. carverae efficacy by L. maritima and other carbohydrate sources is warranted. Greenhouse and field experiments were conducted to investigate whether T. carverae benefit from different groundcover plant species. Ten T. carverae adults (<24h after eclosion) were caged with different groundcover species and a control with no plant materials. Epiphyas postvittana egg sentinel cards were used to measure parasitism and longevity was recorded visually. Survival and realised parasitism of T. carverae was significantly higher in L. maritima than in Brassica juncea, Coriandrum sativum, shoots of these species from which flowers had been removed and nil control treatments. A similar experiment with Fagopyrum esculentum (with- and without-flowers) and a control treatment showed that survival was significantly higher in intact F. esculentum than in without-flower and control treatments. There was no significant treatment effect on parasitism in the early stages of that experiment, though parasitism was recorded in the presence of F. esculentum flowers for 12 days, compared with 6 days in other treatments. Higher parasitism was observed in intact Borago officinalis than in the flowerless shoot, water only and no plant material control treatments in a third experiment. There was no significant treatment effect on parasitism. Fitted exponential curves for survival data differed significantly in curvature in the first, second and third experiments but the slope was a non-significant parameter in the second and third experiments. In a second series of laboratory experiments, one male and one female T. carverae were caged with groundcover species to investigate male and female longevity and daily fecundity. Both male and female longevity in F. esculentum and L. maritima treatments were significantly higher than on shoots of these species from which flowers had been removed, and than in the control treatments. Daily fecundity was significantly greater in the intact L. maritima treatment than in all other treatments. Fitted exponential curves for daily fecundity differed significantly in position and slope but not in curvature. There was no significant treatment effect on longevity or parasitism when a male and female were caged with intact B. juncea, B. officinalis or without-flower of these species, nor in the treatment with no plant materials. No parasitism was observed in a survey of naturally occurring egg parasitoids on two sites close to Orange and Canowindra in New South Wales, illustrating the importance of mass releases of T. carverae in biological control of E. postvittana. In an experiment on the Canowindra site, parasitism was significantly higher on day one and day two after T. carverae release when with-flower treatments were compared with without-flower treatments. Parasitism was significantly higher in the F. esculentum treatment than in C. sativum, L. maritima, vegetation without-flowers and control treatments on these dates. On day five, parasitism was higher in C. sativum than in all other treatments. There was no significant increase in parasitism in a second experiment conducted on the Orange site. Coriandrum sativum, F. esculentum and L. maritima appear to be suitable adult food sources for T. carverae and offer some scope for habitat manipulation in vineyards The adults of many parasitoid species require nectar for optimal fitness but very little is known about flower recognition. Flight cage experiments showed that the adults of T. carverae benefited from L. maritima bearing white flowers to a greater extent than was the case for light pink, dark pink or purple flowered cultivars, despite all cultivars producing nectar. Survival and realised parasitism on non-white flowers were no greater than when the parasitoids were caged on L. maritima shoots from which flowers had been removed. The possibility that differences between L. maritima cultivars were due to factors other than flower colour, such as nectar quality, was excluded by dyeing white L. maritima flowers by placing the roots of the plants in 5% food dye (blue or pink) solution. Survival of T. carverae was lower on dyed L. maritima flowers than on undyed white flowers. Mixing the same dyes with honey in a third experiment conducted in the dark showed that the low level of feeding on dyed flowers was unlikely to be the result of olfactory or gustatory cues. Flower colour appears, therefore, to be a critical factor in the choice of plants used to enhance biological control, and is likely to also be a factor in the role parasitoids play in structuring invertebrate communities. Provision of nectar producing plants to increase the effectiveness of biological control is one aspect of habitat manipulation, but care needs to be taken to avoid the use of plant species that may benefit pest species. Greenhouse experiments were conducted to investigate whether the adult E. postvittana and larvae benefit from nectar producing groundcover species. Newly emerged E. postvittana adults were caged with different groundcover species and a honey-based artificial adult diet. The longevity of male and female E. postvittana when caged with shoots of borage (B. officinalis) and buckwheat (F. esculentum) bearing flowers was as long as when fed a honey-based artificial diet. This effect was not evident when caged with shoots of these plants from which flowers had been removed. Longevity was significantly lower than in the artificial diet treatment when caged with coriander (C. sativum) or alyssum (L. maritima) irrespective of whether flowers were present or not. There was no significant treatment effect on the lifetime fecundity of E. postvittana. A second experiment with mustard (B. juncea) (with- and without-flowers), water only and honey-based artificial adult diet showed no significant treatment effects on the longevity of male and female E. postvittana or on the lifetime fecundity of E. postvittana. The anomalous lack of a difference between the water and honey-based diet treatments precludes making conclusions on the value of B. juncea for E. postvittana. Two greenhouse experiments were conducted to evaluate the effects of groundcover species on the larval development of E. postvittana. In the first experiment, larval mortality was significantly higher in C. sativum, and L. maritima than in B. juncea, B. officinalis and white clover (T. repens) a known host of E. postvittana. Coriandrum sativum and L. maritima extended the larval period. In B. juncea and B. officinalis, mortality did not differ from that in T. repens. In F. esculentum, larval mortality was significantly higher than in T. repens. A short larval period was observed on B. juncea, B. officinalis and F. esculentum. Fitted exponential curves for larval mortality differed significantly in curvature between plant treatments. Similarly, successful pupation was significantly lower in C. sativum, F. esculentum and L. maritima than in T. repens. The percentage of successful pupation in B. juncea and B. officinalis did not differ from F. esculentum and T. repens. Fitted exponential curves for pupation differed significantly in curvature. A similar trend was observed in a second experiment with potted plants. The overall results suggest that C. sativum and L. maritima denied benefit to E. postvittana adults and larvae, so could be planted as vineyard groundcover with minimal risk of exacerbating this pest. Overall results suggest that T. carverae require nutrients to reach their full reproductive potential and flowers provide such nutrients. Lobularia maritima and C. sativum may be considered 'selective food plants' for T. carverae whereas F. esculentum appears to be a 'non-selective food plant'; both T. carverae and E. postvittana benefited from it. Fruits such as grapes can be used as food resources in habitat manipulation and this merits further research. This result also suggests that within species flower colour is an important factor for flower selection in habitat manipulation.

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xvi, 166 p.; also includes graphics (some col.). Includes bibliographical references. Available online via OhioLINK's ETD Center.

Experiments were conducted to assess whether a concept termed 'attract and reward' (A&R) could enhance conservation biological control (CBC). In A&R, a synthetically-produced herbivore induced plant volatile (HIPV) ('attract') is combined with a floral resource ('reward'). It is anticipated that the two will work synergistically attracting natural enemies into the crop ('attract') and maintaining them within the crop ('reward'). The study system consists of brassica, the most commonly occurring brassica herbivores, their natural enemies and higher order natural enemies. The HIPV deployed is methyl salicylate (MeSA) and the floral resource is buckwheat Fagopyrum esculentum. The aim of the first two field experiments, in 2007 and 2008, was to evaluate the effects of MeSA and MeSA combined with buckwheat (A&R) on the abundance of arthropods from three trophic levels. In 2007, a field experiment was conducted using MeSA alone. The mean abundance of the leafmining fly Scaptomyza flava (trophic level 2), the diamondback moth (trophic level 2)(DBM) parasitoid Diadegma semiclausum (trophic level 2) and the hoverfly Melangyna novaezealandiae (trophic level 3) was increased in MeSA-treatments by up to 300% and for the brown lacewing parasitoid Anacharis zealandica a maximum mean increase of 600% was recorded. Significantly more females of the D. semiclausum and M. novaezealandiae were attracted to MeSA than males. When A&R was deployed in 2008, were arthropods from the third and fourth trophic levels affected. For none of the species was there a synergistic effect between 'attract' and 'reward' on their abundance. The brown lacewing Micromus tasmaniae (trophic level 3), two parasitoids of DBM and one of cabbage white butterfly Pieris rapae (trophic level 2) increased significantly in treatments with buckwheat. The hoverfly Melanostoma fasciatum (trophic level 3) was significantly more abundant in treatments with MeSA, but significantly less abundant in treatments with buckwheat. The effect of MeSA on the fourth trophic level parasitoid Anacharis zealandica (trophic level 4) was inconsistent between years. Here it significantly decreased its abundance, while treatments with buckwheat increased it. Significantly fewer male than female D. semiclausum were attracted to MeSA only treatments. These experiments show that MeSA and buckwheat can have unwanted effects on arthropod abundance which may disrupt CBC. To assess the effect of A&R on CBC a further field experiment evaluating herbivore densities, predation, parasitism and hyper-parasitism rates was conducted. The only effect was significantly higher aphid parasitism in treatments with MeSA. Based on the results from the field experiments it remained unclear whether it was MeSA or a blend of volatiles produced by MeSA-induced host plants that were attractive to the arthropods. An olfactory experiment was conducted to evaluate if the aphid parasitoid Aphidius colemani can be attracted to two different concentrations of MeSA diluted in Synertrol oil. Significantly more parasitoids were attracted to 2.0% MeSA than to air while the parasitoid did not respond to the 0.5% concentration. These results indicate that A&R has potential as a CBC technique, as long as any unwanted side effects can be managed. Although there were no synergistic effects between 'attract' and 'reward' on the abundance of individual natural enemies, combining MeSA and buckwheat could still be beneficial because the two techniques increase the abundance of different natural enemies.

Thesis (MScAgric)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Planococcus citri (Risso) (Hemiptera: Pseudococcidae), the citrus mealybug, is a highly destructive pest of citrus in South Africa. The ability of mealybugs to develop resistance to chemicals, as well as their cryptic nature and protective wax coverings, all individually and combined, impair the ability of insecticides to control them. Furthermore, chemicals deplete natural enemy populations that usually establish control over mealybug populations well before harvest in March to May. The inability of chemicals to control P. citri successfully and the growing public awareness of the detrimental environmental effects and health risks that are associated with pesticides are pressuring citrus growers to find alternative methods to chemical control. Entomopathogenic nematodes of the Rhabditida order, belonging either to the families Heterorhabditidae or Steinernematidae, have proven to be valuable biocontrol agents of a variety of insect pest species. These nematodes are, however, not yet commercially available in South Africa. Various laboratory bioassays were conducted to determine the potential of entomopathogenic nematodes to control P. citri. Adult female P. citri were screened for susceptibility to six indigenous nematode species. Planococcus citri was found to be most susceptible to Steinernema yirgalemense and Heterorhabditis zealandica, causing 97% and 91% mortality, respectively. Both H. zealandica and S. yirgalemense completed their life cycles inside adult female P. citri. Under optimal conditions, H. zealandica and S. yirgalemense, at an application rate of 170 infective juveniles (IJs) / insect (LD90), were able to control P. citri efficiently with a discriminating dosage of 11(LD50). The water activity (aw) bioassay indicated that S. yirgalemense was two times more tolerant to lower levels of free water than H. zealandica, with aw50 = 0.96 and aw90 = 0.99, compared to H. zealandica with aw50 = 0.98 and aw90 = 1.01. Furthermore, S. yirgalemense proved able to locate and infect P. citri at a faster rate than H. zealandica. Nematode activity was not significantly affected when exposed to 15°C, 20°C and 25°C. Results of the exposure trial also showed that the first 2−4 h post-application was the most decisive time for establishing successful infection of mealybugs. Further experiments were conducted to determine the ability of two polymer products, Zeba® and Xanthan gum, and a surfactant, Nu-Film-P®, to improve nematode application suspensions. Despite not being as effective as Xanthan gum, Zeba® still retarded sedimentation significantly. The addition of 0.02% Xanthan gum did not improve the ability of nematodes to control P. citri at 60% and 80% relative humidity containing H. zealandica and 0.03% Zeba® increased mortality by 14% at 60% RH and by 22% at 80% RH. The same polymer formulation was tested with S. yirgalemense, with mortality being found to have increased by 21% at 60% RH and by 27% at 80% RH. The combined addition of Nu-Film-P® and Zeba® was able to retard sedimentation significantly, increasing the average number of nematodes deposited on 2-cm2 leaf discs. To illustrate those factors that should be taken into consideration before applying nematodes in an integrated pest management (IPM) programme for citrus, the compatibility of H. zealandica and S. yirgalemense with biological control agents and agrochemicals to which they are most likely to be exposed was determined. Bioassays showed the coccinellid beetle, Cryptolaemus montrouzieri, to be susceptible to both nematode species. Beetle larvae proved to be highly susceptible, with H. zealandica obtaining 80%, and S. yirgalemense obtaining 92% control. Adult beetles were found to be twice as susceptible to S. yirgalemense, with 64% mortality recorded, as to H. zealandica, with 30% mortality recorded. Tolerance of H. zealandica and S. yirgalemense infective juveniles to the affect of aqueous solutions of an insecticide (Cyperphos 500 E.C.®), two biopesticides (CryptogranTM and HelicovirTM), and two adjuvants (Nu-Film-P® and Zeba®) on the infectivity and survival of H. zealandica and S. yirgalemense was evaluated. Heterorhabditis zealandica proved to be highly compatible with all products tested. Significant increase in mortality of S. yirgalemense was recorded after 12 h exposure to CryptogranTM, HelicovirTM and Cyperphos 500 E.C.®, and after 6 h exposure to Nu-Film-P®. However, there was no decrease in the ability of S. yirgalemense to infect the insect hosts. Towards selecting the appropriate nematode species for field studies, the ability of S. yirgalemense and H. zealandica to control P. citri was first evaluated under less harsh simulated glasshouse conditions. The ability of both the above-mentioned nematode species to control P. citri, with and without the addition of 0.03% Zeba® and 0.06% Nu-Film-P®, was evaluated in a growth chamber at 75 ± 8% relative humidity and 22°C. All treatments resulted in significantly higher mortality of adult female P. citri than did the control. The addition of 0.03% Zeba® and 0.06% Nu-Film-P® to an H. zealandica and an S. yirgalemense suspension increased resultant mortality from 26% to 30%, and from 34% to 45%, respectively. This increase in mortality was, however, not significant. The ability of this formulation to prolong the ability of S. yirgalemense to infect P. citri and to prolong nematode survival was also evaluated under the same conditions and showed the formulation to improve both infectivity and survival for up to 2–3 h post-application. In the semi-field trial, S. yirgalemense was unable to obtain significant control of P. citri without the addition of 0.03% Zeba® to nematode application suspensions. However, with the addition of 0.03% Zeba® S. yirgalemnse was able to obtain up to 53% control. The study established that the polymer product Zeba® improves the ability of S. yirgalemense to infect P. citri by retarding desiccation and by buffering nematodes from suboptimal environmental conditions.
AFRIKAANSE OPSOMMING: Planococcus citri (Risso) (Hemiptera: Pseudococcidae), die sitrus witluis, is ʼn baie skadelike pes van sitrus in Suid Afrika. Die vermoë van witluise om weerstand teen chemiese middels te ontwikkel, hul kriptiese lewenswyse en die beskermende waslaag wat hul liggame omhul inhibeer gesamentlik en individueel die vermoë van insektisiede om witluis bevolkings te beheer. Chemiese middels verminder ook die natuurlike vyande wat gewoonlik witluis bevolkings beheer voor die sitrus oestydperk in Maart tot Mei. Die onvermoë van chemiese middels om P. citri suksesvol te beheer en verhoogde bewustheid van die publiek rond om die vernietigende omgewings impak en gesondheidsrisiko’s verbonde aan chemiese insek beheer, noodsaak sitrus produsente om alternatiewe beheermetodes te ontwikkel. Entomopatogeniese nematodes, van die orde Rhabditida wat aan die families Heterorhabditidae of Steinernematidae behoort, is bekend as effektiewe biologiese beheeragente van ʼn verskeidenheid insek pes spesies. Hierdie nematodes is egter tans nie kommersieel beskikbaar in Suid- Afrika nie. Om ten einde die vermoë van plaaslike nematode spesies te bepaal om P. citri te beheer, is verskeie biotoetse in die laboratorium uitgevoer. ʼn Vinnige siftings proses is uitgevoer om vas te stel watter plaaslike nematode spesies die hoogste persentasie mortaliteit van P. citri wyfies veroorsaak. Daar is bevind dat P. citri die mees vatbaarste is vir Steinernema yirgalemense en Heterorhabditis zealandica wat 97% en 91% mortaliteit respektiewelik veroorsaak het. Die ontwikkeling van beide H. zealandica en S. yirgalemense na die infektering van volwasse P. citri wyfies is gevolg en daar is bevind dat beide nematode spesies hul lewensiklusse kon voltooi in insek kadawers. Onder optimale toestande was H. zealandica en S. yirgalemense in staat om P. citri effektief te beheer, as hul teen ʼn konsentrasie van 170 infektiewe larwes (JIs) per insek (LD90) toegedien word, met ʼn diskriminerende toedienings dosis van 11 (LD50). ʼn Water aktiwiteit biotoets het gewys dat S. yirgalemense twee keer so verdraagsaam is teenoor laer vlakke van vrye water as wat H. zealandica is met aw50 = 0.96 en aw90 = 0.99, in vergelyking met H. zealandica met aw50 = 0.98 en aw90 = 1.01. Resultate van ʼn blootstellings toets het ook gewys dat S. yirgalemense die vermoë het om P. citri vinniger op te spoor en te infekteer as H. zealandica. Die blootstellings toets was uitgevoer teen 15°C, 20°C en 25°C en daar is bevind dat die aktiwiteit van H. zealandica nie beduidend verhoog het met ʼn verhoging in temperatuur nie. Resultate vir die blootstellings toets het ook gewys dat die eerste 2 tot 4 uur na toediening van nematodes die mees kritieke tyd is om suksesvolle infektering van witluise te bevestig. Verdere eksperimente is uitgevoer om te bepaal of die byvoeging van twee polimeer produkte nl. Zeba® en Xanthan gum en ʼn benatter Nu-Film-P®, nematode toedienings suspensies kan verbeter. Deur 0.02% Xanthan gum by nematode toedienings suspensies te voeg is die vermoë van nematodes om P. citri by 60% en 80% relatiewe humiditeit (RH) te beheer nie beduidend verhoog nie, terwyl die byvoeging van 0.03% Zeba® wel ʼn beduidende verhoging in mortaliteit veroorsaak het. ʼn Suspensie van H. zealandica en 0.03% Zeba® het beheer met 14% by 60% RH en met 22% by 80% RH verhoog. Die invloed van dieselfde polimeer formulasie was ook getoets op S. yirgalemense en mortaliteit het verhoog met 21% by 60% RH en met 27% by 80% RH. Ten spyte daarvan dat “Xanthan gum” nie so effektief was om afsakking van nematodes te verhoed nie, het die byvoeginging van 0.03% Zeba® by toedienings suspensies steeds ʼn beduidende invloed gehad. Die gekombineerde byvoeging Nu-Film-P® en Zeba® was in staat om die gemiddelde aantal nematodes gedeponeer op 2-cm2 blaar skyfies te verhoog. Om te wys watter faktore in ag geneem moet word voor EPNs as deel van ʼn geïntegreerde pes beheer program toegedien word, is die verenigbaarheid van H. zealandica en S. yirgalemense vir biologiese beheer agente en landbouchemikalieë, waaraan hulle heel waarskynlik blootgestel gaan word, bepaal. Biotoetse het gewys dat die liewenheersbesie, Cryptolaemus montrouzieri, vatbaar is vir beide nematode spesies. Die larwale fase was hoogs vatbaar met mortaliteit van 80% en 92% verkry deur die toedeining van H. zealandica en S. yirgalemense respektiewelik. Daar is ook bepaal dat volwasse besies twee maal so vatbaar is vir S. yirgalemense wat 64% mortaliteit veroorsaak het, as vir H. zealandica met 30% mortaliteit aangeteken. Verdraagsaamheid van IJs van H. zealandica en S. yirgalemense met oplossings van ʼn insektisied (Cyperphos 500 E.C.®), twee bio-plaagdoders (CryptogranTM en HelicovirTM), en twee byvoegmiddels (Nu-Film-P® en Zeba®), vir infektiwiteit en oorlewing is bepaal. Resultate het gewys dat H. zealandica hoogs verenigbaar is met alle produkte wat getoets is. ʼn Beduidende verhoging in mortaliteit van S. yirgalemense is aangeteken na 12 ure se blootstelling aan CryptogranTM, HelicovirTM en Cyperphos 500 E.C.®, en na 6 ure se blootstelling aan Nu-Film-P®. Resultate het egter ook gewys dat die vermoë van S. yirgalemense om om gashere te infekteer nie deur beinvloed word nie. Om ten einde te bepaal watter een van H. zealandica of S. yirgalemense die beter isolaat sou wees om te gebruik in veldproewe, is hul vermoë om P. citri te beheer eers evalueer onder minder ongunstige gesimuleerde glashuis toestande. Die vermoë van beide nematode spesies om P. citri te beheer is bepaal in ʼn groeikamer by 75 ± 8% (RH) met en sonder die byvoeging van 0.03% Zeba® en 0.06% Nu-Film-P®. Mortaliteit verkry deur alle behandelings was beduidend hoër as die kontrole. Deur 0.03% Zeba® en 0.06% Nu-Film-P® by toedienings suspensies van H. zealandica en S. yirgalemense te voeg is die gevolglike mortaliteit van P. citri verhoog van 26% na 30% en van 34% na 45%, respektiewelik. Hierdie verhoging in mortaliteit was egter nie beduidend nie. Die vermoë van die bo-genoemde formulasie om oorlewing van S. yirgalemense en infeksie tydperk van P. citri te verleng was bepaal onder dieselfde toestande en daar is gevind dat die formulasie beide die infektiwiteit en oorlewing van nematodes met 2 tot 3 uur na toediening verleng het. Tydens die semi-veldproef was S. yirgalemense nie in staat om beduidend hoër mortaliteit van P. citri te verkry, in vergelyking met die kontrole, sonder die byvoeging van 0.03% Zeba® by toedienings suspensies nie. Met die byvoeging van Zeba® is daar tot 53% beheer verkry. Die studie het onweerlegbaar gewys dat die polimeer produk Zeba® die vermoë van S. yirgalemense om P. citri te infekteer verbeter deur die uitdroging van nematodes te vertraag en deur hul te beskerm teen ongunstige omgewings toestande.

Le verger-maraîcher est un type de parcelle diversifiée, agroforestière, associant des arbres fruitiers et des légumes. Dans ces parcelles, tout l’espace 3D disponible est utilisé pour la production de nourriture avec au sol des légumes et à différentes hauteurs des fruits. Les vergers-maraîchers sont en cela une réponse à la limitation de l’extension des surfaces agricoles. De plus, les parcelles diversifiées favorisent dans la plupart des cas la régulation des ravageurs par leurs prédateurs naturels mais les résultats semblent dépendre du contexte. L’objectif de cette thèse est de comprendre les mécanismes régissant la régulation des ravageurs des légumes dans les vergers-maraîchers. Les vergers-maraîchers étant complexes et multiples, nous avons choisi de baser notre étude sur la comparaison de ces mécanismes dans des parcelles expérimentales mimant un verger-maraîcher simplifié (associant pommiers et choux) et des parcelles maraîchères en monoculture, sans utilisation de pesticide, sur une saison de culture. Nous avons tout d’abord comparé les abondances des ravageurs du chou et de leurs prédateurs, entre parcelles témoins et parcelles en verger-maraîcher. En associant expérimentation de cages à exclusion et modèle de dynamique de populations, nous avons comparé entre les deux types de parcelles, le taux de prédation, de survie et d’immigration des ravageurs. Nous nous sommes ensuite focalisés sur la fonction de prédation et sur la communauté de prédateurs du sol. Nous avons déterminé si le verger-maraîcher favorisait l’émergence d’une communauté de prédateurs efficace dans la fonction de prédation c’est-à-dire avec : 1) des abondances plus élevées, 2) une forte complémentarité, 3) une prédation intraguilde limitée, et 4) présentant des espèces et des groupes fonctionnels clés de voûte dont les individus sont fortement consommateurs de ravageurs.D’après nos résultats, le verger-maraîcher favoriserait la plupart des ravageurs des légumes (Myzus persicae, les chenilles et les aleurodes) sauf le puceron du chou Brevicoryne brassicae, qui présentait une abondance plus faible. La survie de certains ravageurs est plus élevée en verger-maraîcher et l’immigration plus faible pour un ravageur. Les différences de prédation entre verger-maraîcher et témoin dépendent quant à elles du ravageur considéré. Pour Myzus persicae et les chenilles, la prédation était plus élevée en témoin et pour Brevicoryne brassicae, elle était plus élevée en verger-maraîcher. En parallèle, 20% des espèces prédatrices étaient moins abondantes en verger-maraîchers qu’en parcelles témoins et la richesse spécifique, la diversité de Shannon et l’équitabilité y étaient également plus faibles. L’araignée-loup Pardosa proxima s’est révélée être la seule espèce ayant un impact positif sur le taux de prédation et uniquement en verger-maraîcher. Les plus faibles taux de prédation de Myzus persicae et des chenilles en verger-maraîcher seraient expliqués par le fait que la communauté de prédateurs y serait moins riche et donc moins efficace. Le verger-maraîcher favoriserait une prédation due à quelques espèces fortement consommatrices de ravageurs dont l’impact serait plus fort sur les ravageurs plus regroupés comme Brevicoryne brassicae. Les résultats de cette thèse donnent une image des relations entre les mécanismes régissant la régulation des ravageurs dans un verger-maraîcher simplifié et pour une saison de culture, qui peut servir de base pour développer des aménagements optimisant le service de régulation des ravageurs
Mixed fruit-tree-vegetable plots are diversified, agroforestery plot associating fruit trees and vegetables. In this type of cropping systems, the whole available 3D space is used to produce food based on vegetables at the ground level and on fruits at several heights. Mixed fruit-tree-vegetable plots are thus a possible response to the limited available space for agricultural areas.Moreover, conservation biological control, i.e. control of pests by their naturally occurring predators, is frequently increased in diversified plots although results seem to be context-dependent. The objective of this PhD thesis is to understand the mechanisms governing conservation biological control of vegetable pests in mixed fruit-tree-vegetable plots. As mixed fruit-tree-vegetable plots are diverse and their structure can be complex, we chose to base our study on the comparison of these mechanisms in experimental plots. Two plots mimic a simplified mixed fruit-tree-vegetable orchard associating apple trees and cabbages, and two control plots are vegetable monocultures. All plots were pesticide-free and the experiment was carried out during one growing season. First of all, we compared abundances of the cabbage pests and their predators, between fruit-tree-vegetable plots and vegetable monocultures. Combining pest and predator monitoring, an exclusion experiment and a model of pest population dynamics, we compared the predation rate, the survival rate and the immigration rate of the pests between the two plot types. Then, we focused on the predation function and on the ground predator community. We investigated if the fruit-tree-vegetable plots fostered the emergence of an efficient predator community, i.e. a community with 1) high abundances, 2) high complementarity, 3) low intraguild predation and 4) including key-stone species or functional groups that were high consumers of pests. According to our results, most of the vegetable pests, i.e. Myzus persicae, caterpillars, and white flies, but not the cabbage grey aphid Brevicoryne brassicae, were more abundant in mixed fruit-tree-vegetable plots . The pest survival rate was higher in mixed fruit-tree-vegetable plots and immigration was lower for one pest. Differences in predation rates between mixed fruit-tree-vegetable plots were pest dependant. For Myzus persicae and the caterpillars, predation rate was higher in monocultures whereas for Brevicoryne brassicae, it was higher in mixed fruit-tree-vegetable plots. Concerning the predator community, we found that, 20% of predator species were less abundant in mixed fruit-tree-vegetable plots. The species richness, the Shannon diversity, the equitability were also lower. The wolf spider Pardosa proxima was the only species with a positive impact on predation rate and only in mixed fruit-tree-vegetable plots. Lower predation rate of Myzus persicae and caterpillars in mixed plots were thus possibly explained by the fact that the predator community was less rich and thus less efficient. Predation in mixed fruit-tree-vegetable plots may thus be mainly due to just few species that are high pest consumers, which would have a greater impact on aggregated pests such as Brevicoryne brassicae. This PhD thesis results provides a first hint of mechanisms ruling pest control in a simplified mixed fruit-tree-vegetable plot and for one culture season, which can serve as a basis to plot design optimising pest control

Trichogramma carverae Oatman and Pinto is mass-released for biological control of the leafroller pest, light brown apple moth, Epiphyas postvittana (Walker) in Australian vineyards. Parasitoid performance can, however, be constrained by a lack of suitable adult food and no information is available on the effect of nectar on the parasitism and longevity of T. carverae. To address this, the effect of alyssum, Lobularia maritima (L.) flowers on E. postvittana parasitism was studied in a vineyard experiment with and without releases of T. carverae. Egg parasitoid activity was assessed with E. postvittana egg �sentinel cards� and no parasitism was recorded in plots without T. carverae releases. Where T. carverae were released, there was no significant enhancement of parasitism by the presence of L. maritima flowers. Three hypotheses were subsequently tested to account for the lack of an effect: (i) T. carverae does not benefit from L. maritima nectar, (ii) T. carverae was feeding on nectar from other flowering plants (weeds) present in the vineyard, (iii) T. carverae was feeding on sugars from ripe grapes. A growth-cabinet experiment using potted L. maritima plants with and without flowers did not support hypothesis one. No parasitism was recorded after day two for T. carverae caged without flowers whilst parasitism occured until day eight in the presence of flowers. A laboratory experiment with common vineyard weeds (Trifolium repens, Hypochoeris radicata, Echium plantagineum) as well as L. maritima did not support hypothesis one but gave partial support to hypothesis two. Survival of T. carverae was enhanced to a small but statistically significant extent in vials with intact flowers of L. maritima, white clover (T. repens) and catsear (H. radicata) but not in vials with flowering shoots of these species from which flowers and flowering buds had been removed. Paterson�s curse (E. plantagineum) flowers had no effect on T. carverae survival. In a laboratory study, punctured grapes significantly enhanced T. carverae survival compared with a treatment without grapes, supporting hypothesis three. Trichogramma carverae performance in the field experiment was probably also constrained by relatively cool and wet weather. Further work on the enhancement of T. carverae efficacy by L. maritima and other carbohydrate sources is warranted. Greenhouse and field experiments were conducted to investigate whether T. carverae benefit from different groundcover plant species. Ten T. carverae adults (<24h after eclosion) were caged with different groundcover species and a control with no plant materials. Epiphyas postvittana egg sentinel cards were used to measure parasitism and longevity was recorded visually. Survival and realised parasitism of T. carverae was significantly higher in L. maritima than in Brassica juncea, Coriandrum sativum, shoots of these species from which flowers had been removed and nil control treatments. A similar experiment with Fagopyrum esculentum (with- and without-flowers) and a control treatment showed that survival was significantly higher in intact F. esculentum than in without-flower and control treatments. There was no significant treatment effect on parasitism in the early stages of that experiment, though parasitism was recorded in the presence of F. esculentum flowers for 12 days, compared with 6 days in other treatments. Higher parasitism was observed in intact Borago officinalis than in the flowerless shoot, water only and no plant material control treatments in a third experiment. There was no significant treatment effect on parasitism. Fitted exponential curves for survival data differed significantly in curvature in the first, second and third experiments but the slope was a non-significant parameter in the second and third experiments. In a second series of laboratory experiments, one male and one female T. carverae were caged with groundcover species to investigate male and female longevity and daily fecundity. Both male and female longevity in F. esculentum and L. maritima treatments were significantly higher than on shoots of these species from which flowers had been removed, and than in the control treatments. Daily fecundity was significantly greater in the intact L. maritima treatment than in all other treatments. Fitted exponential curves for daily fecundity differed significantly in position and slope but not in curvature. There was no significant treatment effect on longevity or parasitism when a male and female were caged with intact B. juncea, B. officinalis or without-flower of these species, nor in the treatment with no plant materials. No parasitism was observed in a survey of naturally occurring egg parasitoids on two sites close to Orange and Canowindra in New South Wales, illustrating the importance of mass releases of T. carverae in biological control of E. postvittana. In an experiment on the Canowindra site, parasitism was significantly higher on day one and day two after T. carverae release when with-flower treatments were compared with without-flower treatments. Parasitism was significantly higher in the F. esculentum treatment than in C. sativum, L. maritima, vegetation without-flowers and control treatments on these dates. On day five, parasitism was higher in C. sativum than in all other treatments. There was no significant increase in parasitism in a second experiment conducted on the Orange site. Coriandrum sativum, F. esculentum and L. maritima appear to be suitable adult food sources for T. carverae and offer some scope for habitat manipulation in vineyards The adults of many parasitoid species require nectar for optimal fitness but very little is known about flower recognition. Flight cage experiments showed that the adults of T. carverae benefited from L. maritima bearing white flowers to a greater extent than was the case for light pink, dark pink or purple flowered cultivars, despite all cultivars producing nectar. Survival and realised parasitism on non-white flowers were no greater than when the parasitoids were caged on L. maritima shoots from which flowers had been removed. The possibility that differences between L. maritima cultivars were due to factors other than flower colour, such as nectar quality, was excluded by dyeing white L. maritima flowers by placing the roots of the plants in 5% food dye (blue or pink) solution. Survival of T. carverae was lower on dyed L. maritima flowers than on undyed white flowers. Mixing the same dyes with honey in a third experiment conducted in the dark showed that the low level of feeding on dyed flowers was unlikely to be the result of olfactory or gustatory cues. Flower colour appears, therefore, to be a critical factor in the choice of plants used to enhance biological control, and is likely to also be a factor in the role parasitoids play in structuring invertebrate communities. Provision of nectar producing plants to increase the effectiveness of biological control is one aspect of habitat manipulation, but care needs to be taken to avoid the use of plant species that may benefit pest species. Greenhouse experiments were conducted to investigate whether the adult E. postvittana and larvae benefit from nectar producing groundcover species. Newly emerged E. postvittana adults were caged with different groundcover species and a honey-based artificial adult diet. The longevity of male and female E. postvittana when caged with shoots of borage (B. officinalis) and buckwheat (F. esculentum) bearing flowers was as long as when fed a honey-based artificial diet. This effect was not evident when caged with shoots of these plants from which flowers had been removed. Longevity was significantly lower than in the artificial diet treatment when caged with coriander (C. sativum) or alyssum (L. maritima) irrespective of whether flowers were present or not. There was no significant treatment effect on the lifetime fecundity of E. postvittana. A second experiment with mustard (B. juncea) (with- and without-flowers), water only and honey-based artificial adult diet showed no significant treatment effects on the longevity of male and female E. postvittana or on the lifetime fecundity of E. postvittana. The anomalous lack of a difference between the water and honey-based diet treatments precludes making conclusions on the value of B. juncea for E. postvittana. Two greenhouse experiments were conducted to evaluate the effects of groundcover species on the larval development of E. postvittana. In the first experiment, larval mortality was significantly higher in C. sativum, and L. maritima than in B. juncea, B. officinalis and white clover (T. repens) a known host of E. postvittana. Coriandrum sativum and L. maritima extended the larval period. In B. juncea and B. officinalis, mortality did not differ from that in T. repens. In F. esculentum, larval mortality was significantly higher than in T. repens. A short larval period was observed on B. juncea, B. officinalis and F. esculentum. Fitted exponential curves for larval mortality differed significantly in curvature between plant treatments. Similarly, successful pupation was significantly lower in C. sativum, F. esculentum and L. maritima than in T. repens. The percentage of successful pupation in B. juncea and B. officinalis did not differ from F. esculentum and T. repens. Fitted exponential curves for pupation differed significantly in curvature. A similar trend was observed in a second experiment with potted plants. The overall results suggest that C. sativum and L. maritima denied benefit to E. postvittana adults and larvae, so could be planted as vineyard groundcover with minimal risk of exacerbating this pest. Overall results suggest that T. carverae require nutrients to reach their full reproductive potential and flowers provide such nutrients. Lobularia maritima and C. sativum may be considered �selective food plants� for T. carverae whereas F. esculentum appears to be a �non-selective food plant�; both T. carverae and E. postvittana benefited from it. Fruits such as grapes can be used as food resources in habitat manipulation and this merits further research. This result also suggests that within species flower colour is an important factor for flower selection in habitat manipulation.

Doutoramento em Engenharia Agronómica - Instituto Superior de Agronomia - UL
The olive tree (Olea europaea L.) has been shaping and characterizing landscape and culture in the Mediterranean basin. This tree is attacked by pest that can cause significant losses. This thesis was focused on the conservation biological control of one of its most damaging pests: the olive moth, Prays oleae (Bernard). Naturally, a large number of parasitoid and predator species are associated to this pest, and in order to satisfy their needs they make use of ecological infrastructures occurring in the olive grove agroecosystem. However, how these ecological infrastructures can be used to enhance the olive moth conservation biological control needs to be disentangled. For that, two approaches were followed. First, the influence of ecological infrastructures on P. oleae and its natural enemies was analyzed through field surveys. Then, different food resources were evaluated as potential foods for P. oleae and its natural enemies, i.e., the parasitoid Elasmus flabellatus (Fonscolombe) and the predator Chrysoperla carnea s. l. (Stephens). In the first approach, P. oleae was found to disperse throughout non-crop patches, although the implications for the pest population are unknown. The heterogeneous landscapes composed by herbaceous and woody vegetation around the olive groves were exploited by syrphids as food sources. Finally, ground covers within the olive groves favored the parasitoid Ageniaspis fuscicollis (Dalman) while the herbicide application diminished it. In the second approach, insects’ honeydews [Saissetia oleae (Olivier) and Euphyllura olivina (Costa)] and the flowers of Malva sylvestris L. favored the survival and/ or reproduction of P. oleae, C. carnea and E. flabellatus. Several plant species such as Daucus carota L., Veronica persica Poir, and Lamium purpureum L. showed to be potential food resources for the studied natural enemies. From the results obtained in this research various applications for managing the olive grove agroecosystem are proposed

Thesis (MScAgric (Conservation Ecology and Entomology))--Stellenbosch University, 2008.
The codling moth, Cydia pomonella (L.), is a key pest in pome fruit orchards in South Africa. In the past, broad spectrum insecticides were predominantly used for the local control of this moth in orchards. Concerns over human safety, environmental impact, widespread dispersal of resistant populations of codling moth and sustainability of synthetic pesticide use have necessitated the development and use of alternative pest management technologies, products and programmes, such as the use of entomopathogenic nematodes (EPNs) for the control of codling moth. Entomopathogenic nematodes belonging to either Steinernematidae or Heterorhabditidae are ideal candidates for incorporation into the integrated pest management programme currently being developed for pome fruit orchards throughout South Africa with the ultimate aim of producing residuefree fruit. However, these lethal pathogens of insects are not exempted from governmental registration requirements and have therefore not yet been commercialized in South Africa. A nontarget survey was conducted to find suitable isolates of EPNs from local soils and to test their effectiveness as control agents against the codling moth. Soil samples were collected from several habitats and regions throughout South Africa and nematodes were recovered using the insect baiting technique. All EPN isolates obtained were identified to species level using a molecular taxonomic approach. Entomopathogenic nematodes were recovered from 20 of the 200 soil samples (10 %). Of these, eight (40 %) yielded Steinernema spp., identified as three isolates of S. khoisanae and five undescribed Steinernema spp. The other 12 (60 %) of the samples were positive for Heterorhabditis spp. and included six isolates of H. bacteriophora, five H. zealandica and one H. safricana. These isolates were then evaluated in laboratory bioassays for their potential as microbial agents of codling moth under varying conditions. A morphometric study indicated that all natural openings (mouth, anus and spiracles) of final instar codling moth were large enough for the infective juveniles (IJs) of all tested EPN species to gain entry into the larvae.

[EN] Aphis spiraecola Patch. (Hemiptera: Aphididae) is a key pest of clementines. Biological control of A. spiraecola is still poorly known and efforts were based on the use and conservation of parasitoids but it did not success. With all this said, the aims of this thesis were: i) to disentangle the reasons behind the low parasitism of A. spiraecola; ii) to determine when and how predators can control A. spiraecola populations; and, finally, iii) to evaluate whether a ground cover of Poaceae plants can enhance the biological control of this aphid in clementines by improving the establishment of its predators. In the first objective we sampled four orchards and determine the parasitoid complex and parasitism (and hyper-) rates weekly. Binodoxys angelicae Haliday (Hymenoptera: Braconidae) was the unique primary parasitoid emerged from mummies of A. spiraecola. At least six hymenopteran hyperparasitoid species were identified attacking this primary parasitoid: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) and Phaenoglyphis villosa (Hartig) (Figitidae). We developed a DNA-based approach to untangle the structure of the aphid-parasitoid food web in citrus. This methodology confirmed that all six species hyperparasitized B. angelicae And they dominated this food web and they were abundant from the beginning of the season. Thus, hyperparasitism probably explains the low impact of B. angelicae on A. spiraecola populations. For the second objective we sampled three clementine orchards to determine the effect of aphid predators on A. spiraecola colonies over a three-year period. Life parameters of A. spiraecola colonies varied among the orchards over the three years. The maximum number of aphids and the longevity of A. spiraecola colonies were negatively correlated with the time of first attack by predators. More importantly, the percentage of shoots occupied by A. spiraecola (damages) remained below or close to the intervention threshold when colonies were attacked prior to ~200 degree days (DD) since the beginning of the aphid colonization. These results suggest that: i) the presence of predators at the beginning of the season should be considered to develop new intervention thresholds and ii) biological control programs should promote the early presence of predators in clementine orchards. To promote the early presence of predators in clementine orchards, in the third objective we evaluated ground cover management. This ground cover management may provide alternative preys to natural enemies. The effect of a sown ground cover (based on Poaceae plants) on the biological control of A. spiraecola was evaluated in four orchards with ground cover management compared with four orchards with bare soil management. This sown Poaceae cover coexists with a complex of wild plants that might also affect biological control of A. spiraecola. Finally, we compared the presence of A. spiraecola and its natural enemies in these orchards. While Poaceae plants represented ~66% of the ground cover, the rest of the cover comprised mainly Malva sp. (13%), Oxalis sp. (5%) and Sonchus sp. (2%). Poaceae plants harbored aphids which appeared sooner in the system than citrus aphids. These aphids serve as alternative prey/hosts for natural enemies. By contrast, Malva sp. and Sonchus sp. harbored aphids with potential to become citrus pest. Although these wild plants may act as reservoirs for A. spiraecola as well as other aphid species that can disrupt the biocontrol services of natural enemies, overall, the sown cover was effective in terms of biological control of A. spiraecola in the citrus canopy. It promoted the early presence of predators in citrus canopies. These attacks resulted in satisfactory aphid control, because citrus orchards with ground cover never exceeded the aphid economic threshold.
[ES] Aphis spiraecola Patch. (Hemiptera: Aphididae) es una de las plagas claves en el cultivo de clementinos. Los esfuerzos realizados hasta la fecha se han centrado en el uso y conservación de parasitoides aunque se desconocen las causas de su baja eficacia. Por todo ello, los objetivos de esta tesis han sido i) desentrañar las razones por las que se dan bajos niveles de parasitismo de A. spiraecola ii) determinar cuándo y cómo los depredadores pueden controlar las poblaciones de A. spiraecola y finalmente iii) determinar si una cubierta de poáceas puede mejorar el control biológico de este pulgón en clementinos mediante la mejora en el establecimiento de sus depredadores. En el primer objetivo se muestrearon semanalmente cuatro parcelas y se identificó el complejo de parasitoides y las tasas de parasitismo (e hiperparasitismo). Los porcentajes de parasitismo fueron bajos (~menos del 5%) y Binodoxys angelicae Haliday (Hymenoptera: Braconidae) fue el único parasitoide primario emergido de las momias de A. spiraecola. Se identificaron al menos seis especies de hiperparasitoides atacando este parasitoide primario: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) y Phaenoglyphis villosa (Hartig) (Figitidae). Se desarrolló un método basado en la detección de ADN con el cual se confirmó que todas las especies de hiperparasitoides hiperparasitan B. angelicae. Los hiperparasitoides dominaron esta red trófica y fueron abundantes desde el inicio de la estación. De este modo, el hiperparasitismo probablemente explica el bajo impacto que B. angelicae tiene sobre las poblaciones de A. spiraecola. Para el segundo objetivo se muestrearon tres campos de clementinos donde se determinó el efecto de los depredadores en las colonias de A. spiraecola. Los parámetros de vida de las colonias de A. spiraecola variaron entre los diferentes cultivos los tres años. El máximo número de pulgones y la longevidad de las colonias de A. spiraecola se correlacionaron negativamente con el momento del primer ataque del depredador a la colonia. Cabe destacar que el porcentaje de brotes ocupados por A. spiraecola permaneció por debajo o cerca del umbral de tratamiento cuando las colonias fueron atacadas antes de los 200 grados días (GD) desde el inicio de formación de la colonia. Estos resultados sugieren: i) la presencia de depredadores al inicio de la temporada de pulgón debes ser considerado para el desarrollo de nuevos umbrales de tratamiento y ii) los programas de control biológico deben promover el adelanto de la presencia de depredadores en los campos de clementinos. Para promover la presencia anticipada de depredadores en los campos de clementinos, como tercer objetivo se evaluó el manejo de cubiertas vegetales a base de poáceas. Con este manejo se persigue aportar presas alternativas para los enemigos naturales de A. spiraecola. Para ello, se compararon cuatro campos de cítricos con cubierta vegetal frente a cuatro con suelo desnudo. En los campos con cubierta sembrada apareció además de las poáceas sembradas, un complejo de plantas salvajes que podrían afectar también el control biológico de A. spiraecola. Las poáceas representaron un 66% de la cubierta vegetal. Las poáceas y Oxalis sp. albergaron respectivamente pulgones estenófagos de plantas poáceas y Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae). Estas especies de pulgones aparecieron más pronto en el ecosistema que los pulgones de cítricos y sirvieron como presas/hospederos alternativos para los enemigos naturales. Al contrario, Malva sp. y Sonchus sp. albergaron especies de pulgón que podrían ser potenciales plagas de cítricos. El efecto total de la cubierta sembrada resultó positivo para el control de A. spiraecola. Por lo tanto, las parcelas de cítricos con cubierta vegetal tendieron a no
[CAT] Aphis spiraecola Patch. (Hemiptera: Aphididae) és una de les plagues clau en el cultiu de clementins. Els esforços realitzats fins ara s'han centrat en el us i conservació de parasitoids encara que es desconeix les causes de la seua baixa eficàcia. Tenint en compte estos antecedents, els objectius d'esta tesis foren: i) desentrampar les raons per les quals els parasitoids no són efectius; ii) determinar quan i com els depredadors poden controlar les poblacions d'A. spiraecola; i finalment iii) determinar si una coberta de poàcies pot millorar el control biològic d'este àfid en clementins mitjançant la millora en el establiment del seus depredadors. En el primer objectiu es van mostrejar setmanalment quatre parcel·les i s'identificà el complex de parasitoids i les taxes de parasitisme (i hiperparasitisme). Binodoxys angelicae Haliday (Hymenoptera: Braconidae) va ser l'únic parasitoid primari emergit de les mòmies d'A. spiraecola. Se van identificar al menys sis especies d' hiperparasitoids atacant este parasitoid primari: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouché) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) i Phaenoglyphis villosa (Hartig) (Figitidae). Se desenvolupà un mètode basat en la detecció de DNA amb el que es confirmà que totes les especies d'hiperparasitoids hiperparasiten B. angelicae. Els hiperparasitoids dominaren aquesta xarxa tròfica i foren abundants a l'inici de l'estació. Per tant, l'hiperparasitisme podria explicar el baix impacte que B. angelicae té sobre les poblacions d'A. spiraecola. Per al segon objectiu es mostrejaren tres camps de clementins on es determinà l'efecte dels depredadors en les colònies d'A. spiraecola. Els paràmetres de vida de les colònies d'A. spiraecola variaren entre les tres parcel·les els tres anys. El màxim número d'àfids i la longevitat de les colònies d'A. spiraecola es correlacionaren negativament amb el moment del primer atac del depredador a la colònia. Caldria destacar que el percentatge de brots ocupats per A. spiraecola es mantingué per baix o prop del llindar de tractament quan les colònies foren atacades abans dels ~200 graus dia (GD) des de l'inici de formació de la colònia. Estos resultats sugereixen que: i) la presència de depredadors a l'inici de la estació de l'àfid podria ser considerada per al desenvolupament de nous llindars de tractament i ii) els programes de control biològic deurien promoure l'avançament de la presència de depredadors en els camps de clementins. Per promoure la l'avançament de la presència de depredadors en els camps de clementins, com tercer objectiu s'avaluà el maneig de cobertes vegetals basades en poàcies. Amb aquest maneig es persegueix aportar preses alternatives per als enemics naturals d'A. spiraecola. Se compararen quatre camps de clementins amb coberta vegetal front a quatre amb sol nu. En els camps amb coberta sembrada creix, junt a les Poáceas sembrades, un conjunt de plantes salvatges que podrien afectar també el control biològic d'A. spiraecola. S'investigà quines especies de plantes componien la coberta vegetal així com les especies d'àfids que les habitaven. Les poàcies representaren un 66% de la coberta vegetal, sent les plantes salvatges més abundants Malva sp. (13%), Oxalis sp. (5%) i Sonchus sp. (2%). Les poàcies hostejaren àfids estenòfags de poàcies. Estes espècies d'àfid aparegueren més prompte en l'ecosistema que aquells àfids associats a cítrics. Al contrari, Malva sp. i Sonchus sp. hostejaren especies d'àfids que podrien ser potencials plagues de cítrics. Este últim grup pot atenuar l'atac dels enemics naturals a les poblacions d'A. spiraecola que habiten les copes. Encara així, l'efecte total de la coberta sembrada a base de poàcies va resultar positiu per al control d'A. spiraecola. En conseqüència les parcel·les de cítrics am
Gómez Marco, F. (2015). Integrated Pest Management of Aphis spiraecola (Hemiptera: Aphididae) in clementines: enhancing its biological control [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/53732
TESIS

Modern agriculture has been focused on very intensive agricultural systems that depend on external inputs such as fertilizers or pesticides. These practices have lead to a simplification of the landscape and a decline of abundance of natural enemies. Nevertheless in the last years there has been an increasing interest in the application of more environmentally friendly techniques in agriculture, such as biological control (BC). Specifically, conservation biological control (CBC) involves the manipulation of the environment to enhance natural enemy’s effectiveness, which can be achieved by means of reducing harmful conditions or improving favourable ones. Habitat management, a part of the CBC approach, consists of selecting plants that provide natural enemies with resources such as non-host foods including pollen or nectar, alternative preys or hosts or shelter from adverse conditions. There are several forms of habitat manipulation approaches that may enhance natural enemy’s numbers in crops; of all those different strategies, the use of insectary plants to conserve beneficial insects has been greatly used. The main objective of this work is to investigate the extent to which the use of vegetal resources may improve the CBC by means of habitat manipulation. This main objective has been developed in six specific objectives that have been carried out in sex chapters. In chapter 1, the potential of the Mediterranean plant Lobularia maritima to be used as an insectary plant for the conservation of the omnivorous predator Orius majusculus has been evaluated. This predator effectively preys on thrips in crops such as lettuce as its conservation in the Mediterranean area is very important. The results have shown that L. maritima provides the predator enough resources to survive in the absence of prey, which would allow the survival of the predator during periods of prey scarcity. In chapter 2, both O. majusculus and O. laevigatus have demonstrated that they prey on thrips in L. maritima plants and they are able to control these pest populations on this insectary plant. At the same time, O. majusculus effectively reproduces on L. maritime with thrips as prey. Therefore, L. maritima can be considered a good insectary plant for the conservation of O. majusculus that does not enhance thrips populations. Results in chapter 3 have demonstrated that different plant species affect very differently the survival, reproduction and nutrient status of the predatory bug O. insidiosus. These observed differences are in part due to the levels of access to the floral and extrafloral resources. Moreover, the predator reproduction is enhanced by an increase in biodiversity. These results show that it is very important to choose the most appropriate plant species for each specific situation and each specific CBC program. In chapter 4 the interactions of two important predators have been evaluated. It has been observed that O. insidiosus and N. americoferus are able to detect one another when they share the same habitat and in fact, they change their reproductive decisions depending on if they are exposed to the other species or they are only exposed to conspecifics. In chapter 5 tomato specific DNA markers have been designed. They allow the tomato DNA identification within the guts of three different species with different feeding habits in the laboratory. Moreover, these markers allow the tomato DNA identification within field collected insects. In chapter 6 is has been demonstrated that the use of mulches in vineyards not only enhance the arthropods abundance on the vineyard soil but also they improve several ecosystem services such as soil temperature and moisture and earthworm populations. On the other hand they improved some harvest parameters and they reduce pest and diseases on the vineyard canopy. Overall it can be concluded that the results of this work have demonstrated that the use of several vegetal resources can noticeably improve CBC programs despite the fact the vegetal species must be selected carefully and depending on every specific CBC program.
La agricultura moderna se ha centrado en sistemas de producción muy intensivos, lo cual ha mermado considerablemente el estado de salud tanto del medio natural como de los enemigos naturales que en el habitan. Sin embargo en los últimos años ha habido una cada vez más marcada tendencia hacia sistemas agrarios más respetuosos con el medio ambiente. En éste contexto el control biológico (CB) ha tomado una mayor relevancia y el número de trabajos de investigación centrados en esta disciplina ha ido creciendo en las últimas décadas. Dentro del CB, el control biológico por conservación (CBC) se basa en la conservación de enemigos naturales en campo bien mediante la mejora de aquellas condiciones que les favorecen bien mediante el detrimento de las condiciones que les perjudican. Dentro del CBC, la gestión del hábitat mediante el uso de plantas insectario favorece la conservación de dichos enemigos naturales en el campo, facilitando de esta manera el control de plagas en los cultivos. El objetivo general de esta tesis ha sido el de investigar hasta qué punto el uso de recursos vegetales puede contribuir al CBC mediante la gestión del hábitat. En el capítulo 1 se ha evaluado el potencial de una planta insectario mediterránea, Lobularia maritima, para conservar un importante depredador de trips, Orius majusculus, en cultivos como la lechuga. Esta planta ha demostrado que cuenta con los recursos suficientes para conservar a dicho depredador en el campo en periodos de escasez de presa. En el capítulo 2 se ha obtenido que tanto O. majusculus como O. laevigatus son capaces de controlar a su presa principal, trips, en plantas de L. maritima, en condiciones de laboratorio; así mismo, O. majusculus se reproduce eficazmente cuando se alimenta en trips en dicha planta insectario. Por tanto, L. marítima permite tanto el establecimiento del depredador como el control de trips por parte del anterior, lo cual la presenta como una buena candidata para la conservación de O. majusculus. En el capítulo 3 se ha observado que distintas especies vegetales afectan de manera muy diversa al desarrollo de otro depredador. O. insidiosus, y que dichas variaciones se deben en parte al acceso a los recursos florales y extra florales de las plantas. Este depredador además es capaz de optimizar su reproducción ante un aumento de la diversidad vegetal. Estos resultados revelan la importancia de elegir la especie vegetal más apropiada, evaluando cada contexto concreto. En el capítulo 4 se ha obtenido que dos importantes depredadores, O. insidiosus y N. americoferus, son capaces de detectar la presencia el uno del otro cuando comparten el mismo hábitat y que, de hecho, alteran sus decisiones reproductivas dependiendo de si se ven expuestos a individuos conspecíficos o de otra especie. En el capítulo 5 se han diseñado marcadores moleculares específicos de tomate que permiten la detección del mismo inmediatamente después de ser ingerido en 3 especies de insectos. Además estos marcadores permiten la detección de material vegetal de insectos de campo. En el capítulo 6 se ha obtenido que el uso de mantillos vegetales en viña permiten una mayor población de artrópodos beneficiosos y de lombrices de suelo, comparado con el suelo desnudo. Por otra parte, mejora las condiciones del suelo, así como puede mejorar la calidad de la uva y la cosecha. En general puede concluirse que los resultados de esta tesis han demostrado que el uso de varios recursos vegetales puede mejorar de manera notable la aplicación de programas de CBC, aunque las especies vegetales deben seleccionarse de manera cuidadosa y según se adapten mejor a cada situación concreta.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: Codling moth, Cydia pomonella, is a worldwide pest and of major economic importance to the South African pome fruit industry. Sterile insect release is applied as a component of area-wide integrated pest management and includes the mass-rearing, sterilization and the release of the sterile insects. For sterile insect release, the improvements of rearing methods in terms of the quality of the diet ingredients and the economical aspect of the rearing method are examined. The effect of genetically modified maize meal, containing the Bacillus thuringiensis gene, in an artificial medium for codling moth rearing, is determined. The use of even a small amount of Bacillus thuringiensis resulted in larval mortality and prolonged development. These results are detrimental to a mass-rearing facility and must be considered by any rearing facility that uses genetically modified maize meal if the insect is sensitive to the gene. An alternative to maize meal in the artificial medium was tested and whole wheat flour was considered to be a suitable replacement. Agar agar is an expensive gelling agent used in the artificial medium. An alternative for agar agar (Kelcogel, Elastigel and carrageenen) is tested and the biological effect on codling moth is determined. Factors such as mortality, pupal and moth weight, longevity, fecundity and development time were used as quality parameters. Results showed that Elastigel was a suitable replacement for agar agar, with bigger pupae and moths, higher fecundity and increased longevity. The economical advantage of the replacement is a 40.91% reduction of the diet cost. The other gelling agents tested also gave acceptable results and can be considered if shortages of agar agar or Elastigel occur. A new method of mass-rearing codling moth larvae in a closed rearing system using large trays placed in a ventilated box is designed. This method is more cost and space effective as a smaller area is needed to rear a large number of moths. The risk of diet contamination is less because of the closed environment and more economical and effective air handling. This is the first report of its kind to describe the mass-rearing of codling moth in a closed environment and the risks involved in using genetically modified maize meal in an artificial diet for the codling moth. These results should be incorporated into existing mass-rearing facilities or taking into consideration when designing new mass-rearing facilities.
AFRIKAANSE OPSOMMING: Die kodlingmot, Cydia pomonella, is van ekonomiese belang vir die Suid-Afrikaanse kernvrugte bedryf. Die steriele insek tegniek word gebruik as ‘n komponent in area-wye geïntegreerde plaagbeheer en sluit in die massa-aanteel, sterilisering en vrylaat van steriele insekte. Vir die steriele insek tegniek is die verbetering van die massa-aanteel van die kodlingmot in terme van kwaliteit van die dieet en die ekonomiese aspek van die aanteel metode ondersoek. Die effek van genetiese gemanipuleerde mieliemeel wat die Bacillus thuringiensis geen bevat, in ‘n kunsmatige voedselmedium vir die aanteel van kodlingmot, is bepaal. Daar is gevind dat die gebruik van selfs ‘n klein persentasie Bacillus thuringiensis in die mieliemeel, mortaliteit en ‘n verlengde lewenssiklus in kodlingmot veroorsaak. Die gevolge is nadelig vir ‘n massa-aanteel fasiliteit en behoort in ag geneem te word vir enige insek wat op ‘n kunsmatige medium, wat mieliemeel bevat, geteel word, mits die insek sensitief is vir Bacillus thuringiensis. ‘n Alternatiewe bestanddeel vir mieliemeel, volkoringmeel, word aanbeveel. Agar agar is ‘n duur verdikkingsagent wat in kunsmatige mediums gebruik word. ‘n Alternatief vir agar agar (Kelcogel, Elastigel en carrageenen) is getoets en die biologiese effek op die kodlingmot is bepaal. Faktore soos mortaliteit, papie en mot gewig, langlewendheid, vrugbaarheid en lengte van lewenssiklus was gebruik as kwaliteit parameters. Resultate het getoon dat Elastigel ‘n geskikte plaasvevanger is van agar agar, met groter papies en motte, groter vrugbaarheid en langlewendheid. Die ekonomiese gevolg van die plaasvervanger, is ‘n vermindering van 40.91% van die dieetkoste. Die ander verdikkingagente wat is getoets is, het aanvaarbare resultate gelewer wat noodsaaklik is indien daar ‘n tekort van Elastigel of agar agar ontwikkel. ‘n Nuwe metode van massa-aanteel van kodlingmot larwes is bepaal. Die metode behels ‘n geslote sisteem, waar groter aanteel bakke in ‘n geslote, geventileerde boks geplaas word. Die metode is koste en spasie effektief en ‘n kleiner area word benodig om ‘n groter aantal motte te lewer. Die risiko van kontaminasie van die dieet word verminder as gevolg van die geslote sisteem wat gebruik word en meer ekonomiese en effektiewe lugversorging word gebruik. Hierdie is die eerste verslag van sy soort wat die massa-aanteel van kodlingmot in ‘n geslote sisteem beskryf en wat die risiko aandui van geneties gemanipuleerde mieliemeel in ‘n kunsmatige medium vir die kodlingmot. Hierdie resultate behoort in ag geneem te word vir reeds bestaande massa-aanteel fasiliteite of met die ontwerp van nuwe massa-aanteel fasiliteite.

Mid-Atlantic crop producers are increasingly transitioning to soil conservation methods that include reducing or eliminating tillage and planting high residue cover crops. These practices are associated with an increase in moderate to severe damage to field crops by slugs. Conserving, and even enhancing, natural enemy populations is a desirable way to manage slug infestations because remedial control measures are limited. To better understand how cover crop usage and tillage practices affect slug and natural enemy populations, 43 Virginia fields with different combinations of tillage practices and cover crop use were intensively sampled in 2018 and 2019. Fields were sampled over a six-week period during the early planting season when slugs are most problematic. Shingle traps and pitfall traps were used to sample slugs and natural enemies, respectively. To determine how multiple farming practices, soil composition, landscape features, and field history affect slug feeding injury to seedling plants, over 1,000 hectares of commercial production fields in the Shenandoah Region of Virginia were scouted for slug feeding injury to seedling plants. Corresponding crop producers were then surveyed on management methods. Our goal was to determine if slug feeding risk could be predicted by a single factor and or a combination of factors. Behavioral assays were performed with a common slug pest, Deroceras laeve, to determine if this species prefers feeding on maize, soybean, daikon radish, crimson clover, rye, or hairy vetch leaf tissue. Our sampling study found that cover crop use and conservation tillage type did not affect slug presence and damage, but that these factors affected various slug predators in different ways. We also observed that fields with more Phalangiidae and total predators overall had fewer slugs. Average slug feeding injury in both years was low and no factor or interaction of factors in our broader survey affected slug feeding injury ratings in fields. Behavioral assays indicated that slugs fed more on soybean tissue compared with maize, slugs consumed less maize when it was offered with hairy vetch or crimson clover, and slugs consumed less soybean when it was offered with hairy vetch or daikon radish.
Master of Science in Life Sciences
Invasive slug species the gray field slug, Deroceras reticulatum (Muller), and the marsh slug, Deroceras laeve, are major pests of maize and soybean grown in Virginia no-till systems. Slug feeding causes injury to young plants that, when severe, can reduce crop yield and necessitate replanting a field. Chemical control options are limited, and farmers may not be willing to use tillage as a control measure. Conserving arthropod slug predators may suppress pest populations below economic levels. Research is needed to understand how farming methods such as tillage type (e.g., no-till, strip tillage, vertical tillage) and cover crop use affect slugs and their predators. Our study investigated 1) how tillage type and cover crop use affected slug and slug predators, 2) if certain farming practices and field characteristics can be used to predict slug injury, and 3) if slugs preferred feeding on commonly-used cover crop species when offered with maize or soybean seedlings. Commercial production fields with different combinations of no tillage or reduced tillage, and planted with or without cover crops, were sampled to evaluate how these farming practices affect slugs and slug predators. Shingle traps and frames were used before planting and during early plant growth stages to collect and identify slug species; pitfall traps were used throughout the growing season to collect and identify slug predator species. To determine if slug feeding risk could be predicted, a survey of commercial production fields in the Shenandoah area was conducted and used to identify factors, if any, that influence slug feeding. Laboratory assays were used to determine feeding preference by offering slugs opportunity to feed on leaf tissue from a maize or soybean seedling or a mature cover crop species. We found that tillage type and use of cover crops did not affect the abundance of slugs, but that they did influence predator populations. The highest number of total predators were found in fields with reduced tillage, cover crops, and no insecticide use prior to crop emergence. Harvestmen were potentially the most impactful slug predator in the region. Field surveys suggested that no tested factor or interaction of factors affected slug injury to plants in commercial fields. Finally, we observed that slugs fed differently on soybean and maize tissue depending on cover crop species present.

Agricultural intensification is widely considered a major threat to biodiversity and ecosystem services. To better protect biological communities, it is necessary to gain a more detailed understanding of the way species use habitats and move across increasingly simplified landscapes. Traditional landscape ecology approaches are mainly based on the dichotomy between focal semi-natural habitat patches and the surrounding agricultural matrix. While the advances made possible by the landscape mosaic model are undeniable, this approach fails to account for real-world complexity, as many species are known to use multiple habitat types (natural and disturbed) during their life cycle. In addition to landscape changes, many local factors (including management such as soil disturbance or pest control) can impact biodiversity, often interacting with each other. In order to inform efficient biodiversity management actions in the future, it is crucial to increase our knowledge on the way local and landscape factors can impact biodiversity at multiple spatial scales. The general aim of this thesis was to develop a novel approach to the study of species-habitat interactions, and to apply the approach to answer some pressing questions about the way landscape simplification influences important arthropod functional groups. Additionally, we studied the effects of local factors on an arthropodmediated ecosystem service (weed seed predation) in the same area. Arthropods were chosen as they are among the most abundant and ecologically relevant organisms in agroecosystems, providing a wide variety of pivotal services. The new approach, based on network theory, showed that landscape simplification reduces habitat specialization in low-mobility insect groups, and allowed us to pinpoint the most important habitat types for the facilitation of arthropod movement through the landscape mosaics. Our local-level study, on the other hand, highlighted how multiple factors can interact in a complex way in shaping ecosystem services. This study demonstrates the potential of the novel species-habitat network approach as a complementary tool for investigating landscape-biodiversity interactions, while simultaneously unveiling new information on the way landscape changes and local factors influence key arthropod groups. This enabled us to provide a series of recommendations for biodiversity management actions, varying depending on the target group. Overall, our research is a reminder of the importance of taking into account multiple potentially interacting factors at different spatial scales to correctly understand and manage biodiversity-related processes.

In our ever more populated world, the rapid expansion and intensification of agriculture is driving worldwide biodiversity loss, and the interactions between production landscapes and wildlife conservation are becoming increasingly important. Farming systems depend on ecosystem services such as biological control, while conservationists are calling for the establishment of conservation initiatives in non-preserve landscapes. Despite this, the goals of agriculture and the goals of predator-conservation are rarely mutual. Here, I demonstrate one of the first examples of a mutually beneficial scenario between agriculture and predator conservation. I used, as a case study, a reintroduction project that translocated individuals of the threatened New Zealand falcon (Falco novaeseelandiae) from the hills of Marlborough into vineyards, to determine if predators can survive within an agricultural landscape while simultaneously providing that landscape with biological control services. Examples of vertebrates providing biological control to agriculture are rare. I show that the presence of falcons in vineyards caused an economically important reduction in grape damage worth over US $230/ ha. Falcon presence caused a 78- 83% reduction in the number of introduced European pest birds, which resulted in a 95% reduction in the damage caused by these species. Falcon presence did not cause a reduction in the abundance of the native silvereye (Zosterops lateralis), but did halve the damage caused by this species. To assess the conservation value of the falcon translocations, I used remote videography, direct observations and prey analysis to measure the behavioural changes associated with the relocation of falcons from their natural habitat in the hills and into vineyards. Falcons in vineyard nests had higher nest attendance, higher brooding rates, and higher feeding rates than falcons in hill nests. Additionally, parents in vineyard nests fed their chicks a greater amount of total prey and larger prey items compared to parents in hill nests. I also found an absence of any significant diet differences between falcons in hill and vineyard habitats, suggesting that the latter may be a suitable alternative habitat for falcons. Because reintroduced juvenile falcons were released in areas devoid of adult falcons, it was possible that they were missing essential training normally provided by their parents. I used direct observations to demonstrate that the presence of siblings had similar effects to the presence of parents on the development of juvenile behaviour, with individuals flying, hunting, and playing more often when conspecifics were present. Finally, through the use of artificial nests and remote videography, I identified that falcons nesting in vineyards are likely to suffer lower predation rates. I also found that falcons in vineyards are predated by a less dangerous suite of animals (such as hedgehogs, Erinaceus europaeus, and avian predators), than their counterparts in the hills, which are predated by more voracious species (such as stoats, Mustela erminea, and feral cats, Felis catus). The work presented in this thesis has also added to the current knowledge of New Zealand falcon breeding behaviour, prey preferences, and behavioural development. Although agricultural regions globally are rarely associated with raptor conservation, and the ability of raptors to control the pests of agricultural crops has not been previously quantified, these results suggest that translocating New Zealand falcons into vineyards has potential for both the conservation of this species, and for providing biological control services to agriculture

Thesis (MScAgric (Conservation Ecology and Entomology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The banded fruit weevil, Phlyctinus callosus (Schönherr), is a key pest of apples, nectarines and grapevines in the southern areas of the Western Cape. The control of P. callosus is not satisfactory and the insecticides used to control this insect have not proved to be effective since the development of tolerance to pyrethroids and acephate. A control method that can be used, despite it being very labour-intensive, is that of tree trunk barriers. The use of such a method will prevent the weevils from reaching the fruit, as they are unable to fly. Alternative control options, such as the use of entomopathogenic nematodes, are urgently needed for the control of P. callosus. Entomopathogenic nematodes belonging to the Steinernematidae and Heterorhabditidae are ideal biocontrol agents for incorporation into an integrated pest management programme. In order to develop control strategies for P. callosus, large numbers and a predictable quantity of different weevil stages are needed. Especially large numbers of larvae are needed, as this is the stage that will be targeted with nematodes. One of the aims of the current study was to assess various artificial diets for rearing larvae of P. callosus. Though adult weevils were easily collected from orchards, it was very difficult to obtain large numbers of larvae. Modified versions of an agar diet, as well as different carrot based diets, were tested at 21°C. The highest percentage survival obtained for the agar diet was 50% and 60% for one type of carrot diet. A better rearing method proved to be that of planting full-grown carrots in pots, kept at 25°C, resulting in the attainment of the highest percentage survival rate of 90%. A study was undertaken to assess how long, and at what temperature, P. callosus eggs could be stored. A mean percentage hatch of 45.7% was obtained when eggs were stored at 4°C for 70 days. Eggs started hatching after 47 days and 10 days, when stored at temperatures of 11°C and 14°C, respectively. If the aim of the employment of such a method is only to delay egg hatching, the two temperatures (11°C and 14°C) will be suitable. For the following part of the study, several entomopathogenic nematode isolates were evaluated for their potential use as biological control agents against P. callosus. The susceptibility of P. callosus larvae and adults to nematode infection was assessed in the laboratory by screening for their mortality, using different nematode isolates. Larvae were found to be more susceptible to nematode infection than adults. Heterorhabditis isolates were found to cause higher levels of mortality than the Steinernema isolates during screening, when a concentration of 400 infective juveniles (IJ) per insect V was used. Biological characteristics, such as the effect of different temperatures on nematode activity and the minimum concentration of nematodes needed to obtain acceptable levels of control for P. callosus, were also investigated. The percentage mortality ranged from no infection to 75% after four days for the larvae, and the SF41 isolate of Heterohabditis zealandica was selected as the most promising isolate for further laboratory experiments. The vertical movement of nematodes in sand, compared with such movement in sandy loam soil, and the biology of H. zealandica in P. callosus larvae was also investigated in laboratory bioassays. After four days, the LD50 and LD90 values were 96 IJ/50 μl and 278 IJ/50 μl, respectively. Nematodes were found to be inactive at 11°C, with the highest mortality rate of P. callosus resulting from nematode infection being recorded at 25°C. A higher percentage mortality rate was obtained with the sandy loam soil (95.2%) than with the sand (77.5%). Heterorhabditis zealandica could successfully complete its life cycle in 6th instar P. callosus larvae. The study showed that P. callosus larvae are suitable hosts for H. zealandica, and that the control of P. callosus in the field by the selected isolate holds promise. The persistence of the SF41 isolate of H. zealandica at different concentrations was investigated in the last part of the study. The experiment took place in a blueberry orchard, subject to a high rate of infestation by P. callosus. Concentrations of 0, 20, 30 and 45 IJ/cm2 were topically applied, with persistence being evaluated for days 1, 35 and 84. Percentage persistence for 30 IJ/cm2 was calculated as 87.5% for days 35 and 84. The persistence of soil samples taken on day one, and kept in plastic containers at room temperature, was again evaluated on day 128, with the finding that both 30 IJ/cm2 and 45 IJ/cm2 caused 100% mortality of Tenebrio molitor (L.). Results indicated good persistence of H. zealandica after 84 days in field conditions, with a high maintenance of P. callosus populations. The study indicated the potential use of H. zealandica for the control of P. callosus, with the possibility of persistence for at least three months. Future research into the control of P. callosus with nematodes should aim to investigate the technical aspects of field application. The current study shows that entomopathogenic nematodes have potential for controlling the soil stages of P. callosus. The capacity to rear large numbers of P. callosus larvae in the laboratory, for later use in laboratory and field trials, is of key importance.
AFRIKAANSE OPSOMMING: Die gebande vrugtekalander, Phlyctinus callosus (Schönherr), is ʼn groot plaag in appel- en nektarienboorde sowel as wingerde in die suidelike gebiede van die Wes-Kaap. Phlyctinus callosus word nie voldoende beheer nie, en plaagdoders wat voorheen gebruik is om dié insek in toom te hou, het doeltreffendheid ingeboet weens weerstandontwikkeling teen piretroϊede en asefaat. ʼn Alternatiewe beheermetode is stamsperbande. Omdat die kalanders nie kan vlieg nie, moet hulle teen stamme uitklim om die vrugte te bereik. Stamsperbande versper dus die insekte se toegang tot die vrugte, maar is baie arbeidsintensief. Meer haalbare metodes vir die beheer van P. callosus is daarom dringend nodig, en die gebruik van entomopatogeniese nematodes blyk ʼn besliste moontlikheid te wees. Entomopatogeniese nematodes, wat tot die Steinernematidae en Heterorhabditidae behoort, is uitstekende biobeheermiddels vir insluiting by geϊntegreerde plaagbeheerprogramme. Om doeltreffende beheerstrategieë vir P. callosus te bedink, is groot en voorspelbare hoeveelhede kalanders nodig veral groot hoeveelhede larwes, aangesien nematodes op hierdie ontwikkelingstadium gemik sal wees. Die eerste doel met die studie was dus om ʼn kunsmatige dieet vir die teling van P. callosus larwes te ontwikkel. Volwasse kalanders kon maklik in vrugteboorde ingesamel word, maar groot hoeveelhede larwes was moeiliker bekombaar. Aangepaste weergawes van ʼn agardieet sowel as verskillende worteldiëte is by 21°C beproef. Die hoogste persentasie larwale groei en -oorlewing op die agardieet was 50%, en 60% op een bepaalde soort worteldieet. Die beste teelmetode blyk egter volgroeide wortels te wees wat in potte geplant is en by 25°C gehou word. Dié metode het ʼn oorlewingspersentasie van 90% opgelewer. ʼn Studie is onderneem om te bepaal hoe lank en by watter temperature P. callosus eiers vir toekomstige gebruik geberg kan word. ʼn Gemiddelde uitbroeipersentasie van 45.7% is verkry toe eiers vir 70 dae by 4°C geberg is. Eiers wat onderskeidelik by 11°C en 14°C geberg is, het ná 47 en 10 dae onderskeidelik begin uitbroei. Indien die doel is om die eiers slegs stadiger te laat uitbroei, sal hierdie twee temperature dus geskik wees. VII Hierna is verskeie entomopatogeniese nematode-isolate vir moontlike gebruik as biologiese beheermiddels vir P. callosus beoordeel. Phlyctinus callosus larwes en volwassenes se vatbaarheid vir nematode infeksie is in die laboratorium bepaal deur dit met behulp van verskillende nematodeisolate vir mortaliteit te toets. Dié toetse het getoon dat larwes meer vatbaar is vir nematode infeksie as volwassenes. In die proefnemings het die Heterorhabditis-isolate hoër mortaliteit as die Steinernema-isolate veroorsaak teen ʼn konsentrasie van 400 infektiewe larwes (IJ) per insek. Biologiese eienskappe, soos die uitwerking van verskillende temperature op nematode aktiwiteit, sowel as die minimum konsentrasie nematodes om aanvaarbare vlakke van beheer uit te oefen, is ondersoek. Die persentasie mortaliteit vir die larwes het ná vier dae tussen 0% en 75% gewissel, en die SF41-isolaat van Heterohabditis zealandica is as die belowendste isolaat vir die res van die proefnemings gekies. Die vertikale beweging van nematodes in sand teenoor leemgrond, sowel as die biologie van H. zealandica in P. callosus larwes, is ook bestudeer. Ná vier dae was die LD50- en LD90-waardes onderskeidelik 96 en 278 IJ/50 μl. Wat temperatuur betref, is daar bevind dat nematodes onaktief is by 15°C, terwyl die hoogste mortaliteit van P. callosus larwes as gevolg van nematode infeksie by 25°C aangeteken is. Die mortaliteit was hoër in die leemgrond (95.2%) as in die sandgrond (77.5%). Heterorhabditis zealandica kon sy lewensiklus suksesvol in 6de instar P. callosus larwes voltooi. Die studie het derhalwe getoon dat P. callosus larwes geskikte gashere is vir H. zealandica, en dat hierdie isolaat dus in die praktyk ʼn doeltreffende beheermiddel vir P. callosus kan wees. Die oorlewing van verskillende konsentrasies H. zealandica is ten slotte bestudeer. Die proefneming is in ʼn bloubessieboord met ʼn groot populasie P. callosus uitgevoer. Konsentrasies van 0, 20, 30 en 45 IJ/cm2 is op die grond (uitwendig) toegedien, en oorlewing is op dag 1, 35 en 84 gemeet. Die persentasie oorlewing vir die 30 IJ/ cm2 konsentrasie was 87.5% op sowel dag 35 as 84. Oorlewing in grondmonsters wat op dag een ingesamel en by kamertemperatuur in plastiekhouers geberg is, is weer op dag 128 beoordeel. Daar is bevind dat sowel die 30 IJ/cm2 as die 45 IJ/cm2 konsentrasie 100% mortaliteit by T. molitor veroorsaak het. Heterorhabditis zealandica blyk ʼn goeie oorlewing te hê ná 84 dae in veld kondisies wat erg met P. callosus besmet is, en is dus ʼn moontlike beheermiddel vir P. callosus, met potensiële oorlewing vir minstens drie maande.

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: The obscure mealybug, Pseudococcus viburni (Signoret) (Pseudococcidae), is one of the common and serious pests of apples and pears in South Africa. The management of this pest in South Africa is dominated by the use of insecticides, while research into using natural enemies for biological control of mealybugs is still ongoing. Increasing concern over the environmental impact, pesticide residues in fruits, resistance, and expense associated with frequent use of insecticides make it necessary to investigate alternative biological control methods, such as the use of entomopathogenic nematodes, for the control of mealybugs. Entomopathogenic nematodes have proven comparable or even superior to chemicals in controlling certain insect pests, without residue problems or a harmful effect on the environment. An important aspect of using endemic nematodes includes the identification of species of nematodes and their symbiotic bacterial cells. A study was carried out to describe a new species of Steinernema, which was recovered during a previous survey in citrus orchards in three provinces of South Africa. Morphometrics, morphology, crossbreeding, drawings, light microscopy and Scanning Electron Microscopy (SEM) photographs were used to describe the new species. A cryopreservation method has been simplified and optimised for the long-term storage of Steinernema khoisanae (SF87) and Heterorhabditis zealandica (J34). Different cryoprotectants used included 15% glycerol, 8% ethylene glycol and 8% dimethyl sulfoxide (DMSO), in which S. khoisanae was incubated at room temperature for periods of two, three, four and five days, followed by a methanol wash. An optimum survival rate of 69% was obtained for S. khoisanae after a four-day incubation period in 15% glycerol. This technique has been used for the cryopreservation of H. zealandica, with a 78% survival rate. The thawed nematodes of both species were able to infect Galleria mellonella larvae after 42 days of cryopreservation (-196ºC) and were able to complete their life cycles.
AFRIKAANSE OPSOMMING: Die ligrooswitluis, Pseudococcus viburni (Signoret) (Pseudococcidae), is een van die algemene en ernstige peste van appels en pere in Suid-Afrika. Die bestuur van hierdie pes word tans in Suid-Afrika deur die gebruik van insekdoders gedomineer terwyl navorsing oor die gebruik van natuurlike vyande vir die beheer van P. viburni nog aan die gang is. Die verhoogde kommer oor die omgewing, residue in vrugte, weerstand, en die koste verbonde aan die gereelde gebruik van chemiese middels maak dit nodig om alternatiewe biologiese metodes van beheer, soos die gebruik van entomopatogeniese nematodes vir die beheer van witluis, te ondersoek. In ander lande is reeds aangetoon dat entomopatogeniese nematodes onder sekere omstandighede en vir sekere insekte gelykwaardige of selfs beter beheer kan gee as chemiese middels. ʼn Belangrike aspek van die gebruik van endemiese nematodes vir die beheer van insekte sluit die korrekte identifikasie van die spesies met hul geassosieerde bakteriese simbionte in. ʼn Nuwe spesie van Steinernema is uit ʼn vorige opname van entomopatogeniese nematodes in sitrusboorde in drie provinsies van Suid-Afrika geïsoleer. Morfometrie, morfologie, kruisteling, ligmikroskoop en SEM fotografie is gebruik om ʼn nuwe spesies te beskryf. ʼn Kriopreserveringsmetode is ontwikkel en ge-optimaliseer vir die langtermyn bewaring van Steinernema khoisanae (SF87) en Heterorhabditis zealandica (J34). Verskillende kriobeskermingsmiddels insluitend 15% gliserol, 8% dimetiel sulfokied (DMSO) en 8% etileen glikol, waarin S. khoisanae vir periodes van twee, drie, vier, en vyf dae geïnkubeer is, is teen kamertemperatuur, getoets, gevolg deur ʼn metanolbad. Optimum oorlewing van 69% is verkry vir S. khoisanae nadat die infektiewe larwes (IJ) vir vier dae in 15% gliserol gehou is. Hierdie tegniek is ook toegepas op H. zealandica, met 78% oorlewing van die IJ. Die ontvriesde nematodes van beide spesies was in staat om Galleria mellonella larwes suksesvol te infekteer en hulle lewensiklus te voltooi nadat hulle vir 45 dae onder kriopreservering gehou is teen -196ºC.

Brown stink bug, Euschistus servus (Heteroptera: Pentatomidae), is a recently re-emerged pest of cotton in Arizona. It has been present in southwestern desert-grown cotton since at least the early 1900’s, but dropped from primary pest status in the latter half of the twentieth century. Farmers and pest managers did not perceive it as a primary or economic pest until 2011, when elevated numbers of brown stink bugs were reported in isolated valleys of Arizona and southeastern California. Reports increased and became more widespread in the following years. In response to increased abundance of brown stink bug and corresponding cotton boll injury, research was needed to provide information to cotton farmers. First, pest managers needed information on which factors affect the susceptibility of cotton bolls to stink bug feeding (chapter 1). Young bolls are most vulnerable to stink bug injury, and injury is sustained in the first four days of feeding. In addition, research was needed to determine the effects of currently available brown stink bug chemical controls on the broader integrated pest management system in Arizona cotton (chapter 2). Current chemical control options disrupt natural enemy communities, which results in outbreaks and resurgences of other cotton pests. The negative outcomes and additional costs outweigh the benefits of brown stink bug management.

Thesis (PhD)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) is a devastating pest of pome fruit in temperate regions of the world. Control of this pest, previously involved the extensive use of broad-spectrum insecticides. However, concerns over human safety, environmental impact, widespread dispersal of resistant populations of codling moth and the sustainability of synthetic pesticides in agroecosystems, has encouraged the development and use of alternative environmentally-friendly pest management technologies including the use of entomopathogenic nematodes. These nematodes are lethal pathogens of insects and belong to the families Steinernematidae and Heterorhabditidae, and are ideal candidates for incorporation into the integrated pest management programme currently being developed for residue-free pome fruit production in South Africa. The biological and ecological factors pertaining to the successful use of these nematodes for the control of codling moth were investigated in this study. Their use for bin-disinfestations was evaluated, focusing on the optimum handling conditions to ensure the survival and subsequent efficacy of the nematodes. The study proved that the local isolate SF41 of Heterorhabditis zealandica Poinar 1990 could be used for successful bin-disinfestation. The use of the same nematode isolate was also investigated for the disinfestation of mulch layers of diapausing codling moth larvae. An insect containment device which allowed for direct trial efficacy evaluation was identified and ecological factors pertaining to the successful use of nematodes for mulch disinfestation were investigated. The biological control potential of local nematode isolates, which had previously never been tested against codling moth larvae, was investigated in the laboratory under conditions as can be expected during orchard applications. The efficacy of the selected isolates was confirmed in field experiments. Innovative insect containment methods for above-ground trial efficacy evaluation in the field were investigated. Desiccation proved to be the most limiting factor to the survival and subsequent efficacy of the nematodes during field applications in temperate regions. The effect of low moisture levels on H. zealandica’s efficacy to control diapausing codling moth larvae was subsequently investigated and a starch-based formulation was further tested to overcome the issue of desiccation. Conclusive results indicated that there were several biological and ecological factors influencing the survival of nematodes and illustrated how these factors could be manipulated to overcome these issues and thereby ensure the efficacy of treatments. This is the first report of its kind to comprehensively investigate the use of South African entomopathogenic nematodes for the control of diapausing codling moth larvae and all results emanating from the study can be integrated into a framework for the commercial use of these nematodes in this regard in future.
AFRIKAANSE OPSOMMING: Kodlingmot, Cydia pomonella (L.) is ‘n ernstige sleutelplaag in appel- en peerboorde in gematigde klimaats gebiede wêreldwyd. In die verlede is hoofsaaklik breëspektrum insektedoders gebruik vir die beheer van hierdie plaaginsek. Maar, kommer oor veiligheid vir die mens, impak op die omgewing, verspreiding van weerstandbiedende populasies van kodlingmot en beperkte volhoubaarheid van sintetiese plaagdoders het die ontwikkeling en gebruik van alternatiewe plaagbeheer tegnologieë, insluitend die gebruik van entomopatogeniese nematodes, genoodsaak. Entomopatogeniese nematodese horende tot die families Steinernematidae en Heterorhabditidae, is ideale kandidate vir insluiting in die geïntegreerde plaagbestuur programme wat huidiglik ontwikkel word vir gebruik in plaaslike boorde met die uiteindelike doel om residu-vrye vrugte te produseer. In hierdie studie word die biologiese en ekologiese faktore bestudeer wat die sukses van ‘n nematode-toediening gemik op kodlingmot beïnvloed. Hierdie studie het bewys dat die lokale SF41 isolaat van Heterorhabditis zealandica Poinar 1990 gebruik kan word om vrugtekratte te disinfesteer van kodlingmot. Die gebruik van dieselfde isolaat vir die disinfestasie van deklae is ook ondersoek. ‘n Metode van insek-inkamping is ook ontwikkel wat die evaluering van toedienings vergemaklik en meer effektief maak. Die omgewings-toestande wat ook bydrae tot die oorlewing en gevolglike sukses van ‘n toediening is ook ondersoek. Die biologiese beheer potensiaal van ‘n paar lokale isolate wat nog nooit voorheen teen kodlingmot getoets is nie, is ook bestudeer. Die isolate se effektiwiteit is ook bevestig in veldproewe en insek-bekampings metodes wat meer van toepassing is vir bogrondse plaaginsekte is ook geïdentifiseer. Resultate dui daarop dat vogverlies en gevolglike uitdroging van nematodes die grootste beperkende faktor is vir hierdie tipe toedienings in gematigde gebiede en ‘n stysel-gebaseerde formulasie is dus ondersoek om hierdie probleem te oorkom. Die uiteindelike gevolgtrekking van die studie was, dat alhoewel daar verskeie biologiese en ekologiese faktore is wat die oorlewing van nematodes beperk, daar tog verskeie maniere is om hierdie faktore te manipuleer en sodoende te oorkom, wat bydrae tot die uiteindelike sukses van ‘n toediening. Hierdie is die eerste studie wat werklik die praktiese gebruik van lokale entomopatogeniese nematodes vir die beheer van kodlingmot ondersoek en alle bevindinge kan geïntegreer word in toekomende riglyne vir die kommeriële gebruik van nematodes vir die beheer van kodlingmot.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The states of Rio Grande do Norte and Ceará are the main producers of melons from Brazil. They account for about 90% of national production, which makes the growth of melon Cucumis melo L. one of the main segments of agribusiness in these states. Despite the high technology used for the cultivation of this vegetable crop, this crop has suffered serious damage due to attack of the leafminer Liriomyza sativae (Diptera: Agromyzidae). The control method used by manufacturers to control this pest is basically the use of chemical insecticide, however, the exclusive use of this method has not been satisfactory for suppressing the population of insect biological control and using the parasitoid Opius sp. (Hymenoptera: Braconidae) has been shown to be a promising technique for controlling this pest in melon. Thus, this study aimed to estimate the number of parasitoids to be released in the field and evaluate the effect of insecticides on it, under field conditions. Among the ratios evaluated the proportion of 1:10 (one every ten parasitoid larvae) was the one with the highest rate of emergence of parasitoid 33.13%. Among the insecticides evaluated in the first trial, was observed at all doses of Neem Oil that the rate of emergence of the parasitoid Opius sp. was not different from control, whereas treatment with the lowest Abamectin rate was verified emergency 2.24%, differing from all other treatments. In the second experiment, we observed that treatment with the active Deltamethrin was the highest rate of reduction in population of the parasitoid Opius sp. (71.4%), followed by Abamectin and Cartap Hydrochloride (50.5 and 14.4% respectively)
Os estados do Rio Grande do Norte e Ceará são os principais produtores de melão do Brasil. São responsáveis por cerca de 90% da produção nacional, o que faz do cultivo do meloeiro Cucumis melo L. um dos principais segmentos da cadeia do agronegócio nesses estados. Apesar da alta tecnologia empregada para o cultivo desta olerícola, essa cultura vem sofrendo sérios danos devido ao ataque da mosca minadora Liriomyza sativae (Diptera: Agromyzidae). O método de controle utilizado pelos produtores para o controle desta praga é basicamente o uso de inseticida químico, no entanto, o uso exclusivo deste método não tem sido satisfatório para supressão da população desse inseto, e o controle biológico através da utilização do parasitoide Opius sp. (Hymenoptera: Braconidae) tem se mostrado uma técnica promissora no controle dessa praga na cultura do meloeiro. Sendo assim, o presente trabalho teve como objetivo, estimar o número de parasitoides a serem liberado em campo e avaliar o efeito de inseticidas sobre o mesmo, em condições de campo. Dentre as proporções avaliadas a proporção de 1:10 (um parasitoide a cada dez larvas vivas) foi a que apresentou a maior taxa de emergência deste parasitoide 33,13%. Dentre os inseticidas avaliados no primeiro ensaio, foi verificado em todas as dosagens do Oléo de Neem que a taxa de emergência do parasitoide Opius sp. não diferiu da testemunha, enquanto que no tratamento com a Abamectina foi verificado a menor taxa de emergência 2,24%, diferindo de todos os outros tratamentos. No segundo ensaio, foi observado que no tratamento com o ativo Deltametrina ocorreu a maior taxa de redução na população do parasitoide Opius sp. (71,4%), seguido da Abamectina e do Cloridrato de Cartape (50,5 e 14,4%, respectivamente)

Les syrphes aphidiphages et les hyménoptères parasitoïdes sont impliqués dans la régulation des ravageurs du pommier, notamment du puceron cendré et du carpocapse. Une fois adulte, ils s'alimentent principalement de ressources florales. Renforcer la fourniture en nectar et pollen devrait donc favoriser les syrphes et les parasitoïdes, et contribuer au contrôle biologique. L'objectif de cette thèse est de mieux comprendre la contribution des espèces végétales au service de régulation fourni par les syrphes aphidiphages et les hyménoptères parasitoïdes, en vergers de pommiers. Nos travaux s'appuient sur des relevés floristiques, des échantillonnages de syrphes et de parasitoïdes et des observations d'insectes ravageurs et de leurs dégâts, en vergers commerciaux et expérimentaux. Des analyses de barcoding et metabarcoding ont permis d'étudier plus finement les relations des syrphes et des parasitoïdes avec les plantes à fleurs. Seulement 6 % des parasitoïdes collectés sur les plantes à fleurs en vergers appartiennent à des espèces impliquées dans la régulation du puceron cendré. Parmi les syrphes collectés sur la végétation des vergers, trois genres ont été identifiés comme des contributeurs principaux à la régulation du puceron cendré, car ils ont également été observés au stade larvaire dans des colonies, et représentaient 20% de l'abondance totale de syrphes collectés sur la flore des vergers. D'autres taxons de syrphes visitant la flore des vergers sont aussi susceptibles de prédater les pucerons du pommier, mais de façon moins constante. En conséquence, seule l'abondance des syrphes observés sur la végétation des vergers a un effet significatif sur l'infestation du puceron cendré. Concernant les parasitoïdes, nous avons observé une amélioration du taux de parasitisme du carpocapse et du puceron cendré en présence de certaines espèces végétales installées en pied d'arbre (i.e. Veronica persica, Ocimum basilicum), mais qui ne se traduit pas par une réduction du nombre d'insectes ravageurs ou des dégâts associés. Préserver la flore spontanée et intégrer des aménagements fleuris dans les vergers favorise donc les syrphes aphidiphages et les hyménoptères parasitoïdes. Cependant, les effets de cascade sur la régulation des insectes ravageurs et la réduction des dégâts sont limités, soulignant la nécessité de combiner ces approches entre elles, et avec d'autres stratégies, pour assurer une protection durable des pommiers
Aphidiphagous hoverflies and parasitoid wasps are involved in the regulation of two main apple pests, the rosy apple aphid (RAA) and the codling moth (CM). Once adult, they feed mainly on floral resources. Providing nectar and pollen may thus favour hoverflies and parasitoid wasps, and improve pest biological control. Here, we studied the contribution of flowering plant species to biological control services provided by hoverflies and parasitoid wasps in apple orchards. Botanical and entomological surveys were conducted in commercial and experimental orchards: floristic surveys, hoverfly and parasitoid sampling, and observations of apple pests and associated damages. Barcoding and metabarcoding were used to characterise the relationships between flowering plants and hoverflies or parasitoid wasps. Only 6% of parasitoid wasps collected on flowering plants belonged to species involved in RAA regulation. Among the hoverflies collected on orchard vegetation, three genera were identified as major contributors to RAA regulation, as their larvae were also observed in RAA colonies. These three taxa accounted for 20% of the total adult hoverfly abundance. Other hoverfly taxa collected on flowering plants also predate apple aphids, but less consistently. Moreover, only the abundance of hoverflies observed on spontaneous vegetation had a significant effect on the infestation of RAA. Concerning parasitoid wasps, we observed a higher parasitism rate of CM and RAA on apple trees associated with some flowering plant species (i.e. Veronica persica, Ocimum basilicum). However, the higher parasitism rates did not translate into a reduction in the number of apple pests or apple damage. Preserving spontaneous vegetation or adding flowering infrastructures in apple orchards may promote parasitoid wasp and hoverfly abundances, but cascading effects on insect pest regulation and damage reduction remain low. Further studies are needed to better understand interactions between these two strategies and other crop management practices to promote sustainable apple pest regulation

Thesis (MScAgric)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The agricultural industry in South Africa is dominated by the use of insecticides. Producers rely heavily on chemicals that cause increased risk to health, the environment and ecology, rapid resistance development in key insect pests and pesticide residues on crops. The increased concern regarding the impact of these pest management practices on the environment and alternative pest management strategies are being investigated. Entomopathogenic nematodes (EPNs) have been identified as being promising biological control agents of key insect pests. The two EPN genera that have shown promise for use as biological control agents within an integrated pest management programme areSteinernema and Heterorhabditis. Commercialisation and the successful use of EPNs to control pests in North America, Australia, Europe and Asia have confirmed the effectiveness of these organisms as biological control agents. Unfortunately, EPNs in large enough numbers for commercial field applications are not yet available on the South African market. Large numbers of EPNs can be produced through either in vivo or in vitro culturing practices. The objective of this study was to streamline the in vivo production process by using two endemic EPN species, Heterorhabditis zealandica (SF41) and H. bacteriophora (SF351). These EPN isolates have been shown to be effective control agents of codling moth Cydia pomonella, false codling moth Thaumatotibia leucotreta, obscure mealybug Pseudococcus viburni, and the banded fruit weevil Phlyctinus callosus. A comparative study was conducted to identify suitable host insects for EPN production of local H. zealandica (SF41) and H. bacteriophora (SF351) strains. Hosts were selected according to their susceptibility to the two EPN species used, their general availability and the ease and cost of rearing. Wax moth larvae Galleria mellonella (WML) and mealworms Tenebrio molitor (MW) were selected as hosts. In order to produce nematodes of consistent quality, a continuous source of host insects reared on a standardised diet was required. WML and MW were each reared on five different diets in the dark at ±26°C. A superior diet for each host was selected according to the diet that produced, on average, the larvae with the highest body mass within a specific timeframe. The heaviest WML, at an average weight of 0.19 g per larva, were produced on a diet consisting of 118 g wheat flour, 206 g wheat bran, 118 g milk powder, 88 g brewer‟s yeast, 24 g wax powder, 175 ml honey and 175 ml glycerol. The heaviest MW larvae weighed, on average, 0.0154 g per larva, and were produced on a diet consisting of 100% wheat bran. To confirm the hypothesis that a linear relationship exists between the weight of a host and the number of nematodes produced from that host, a study was conducted to determine the number of H. zealandica and H. bacteriophora produced per g of host. WML, MW, codling moth larvae and false codling moth larvae were weighed individually and inoculated with the two nematode species respectively. In addition, nematode production in frozen MW and WML was tested. The number of nematodes harvested from each host was counted, and the average number of nematode progeny produced in each host was calculated. A significant linear correlation between the weight of WML and MW and the number of H. zealandica and H. bacteriophora respectively produced confirmed the hypothesis that nematode production within the specified host increases with an increase in host weight. WML produced the highest number of H. zealandica and H. bacteriophora per g of host (1 459 205 ± 113 670 and 1 898 512 ± 94 355), followed by MW larvae (836 690 ± 121 252 and 414 566 ± 67 017). Lower numbers of H. zealandica and H. bacteriophora per g codling moth (57 582 ± 10 026 and 39 653 ± 8 276) and per g false codling moth (192 867 ± 13 488 and 97 652 ± 23 404) were produced. Successful infection of a suitable insect host is one of the key factors in an efficient in vivo nematode production process. Three inoculation techniques were compared using H. zealandica and H. bacteriophora: inoculation with a pipette; shaking of hosts in the nematode inoculum; and immersion of hosts in the nematode suspension. With each inoculation technique, WML and MW were used as host larvae and were inoculated with nematodes at a concentration of 200 infective juveniles (IJs) / larva. The percentage mortality of insect hosts was determined after two days, and EPN infectivity, confirmed by colour change and dissection, after seven days. The highest percentage EPN infection was obtained using pipetting for both nematode isolates and hosts. Nematode infection rates for all nematode-host combinations obtained with pipetting were above 90%, with the exception of MW inoculation with H. bacteriophora, where the percentage of infection obtained was 76%. The current study conclusively demonstrated that variations in infection levels occur, depending on the inoculation technique used. In an additional effort to enhance infectivity during inoculation, H. zealandica, H. bacteriophora and MW were subjected to host-stressor regimes and to nematode- infectivity-enhancing additives. Three treatments, plus a control treatment, were compared. Exposing MW to 70°C tap water prior to inoculation did not increase infection levels. On the contrary, reduced infection levels were observed with host immersion in 70°C tap water followed by inoculation with H. bacteriophora, compared to the control. Only 12% infection was obtained compared to the 48% infection achieved in the control. Infection obtained using H. zealandica was 21%. Treating H. zealandica and H. bacteriophora IJs withMn2+SO4.H20 in a suspension, prior to inoculating MW, did not significantly enhance nematode virulence. Inoculation of MW with treated H. zealandica IJs led to an infection rate of 81%, compared to the control, with which 80% infection rate was obtained. Heterorhabditis bacteriophora caused 47% MW infection, compared to the control, which was subject to 48% infection. A combination of the two above-mentioned treatments did not enhance the infection levels either. Immersing MW into 70°C tap water prior to inoculation with nematodes treated with Mn2+SO4.H20 led to infection levels of 13% and 9% respectively when H. bacteriophora and H. zealandica were used. Future research is required to optimise the protocol used in this study of subjecting MW and local nematode isolates to stressor regimes. The ability of two formulations to maintain biological activity and virulence of H. zealandica was investigated. A quality standard control measure was used to measure the percentage survival and virulence of formulated H. zealandica over a period of 21 days. IJs were formulated into Pesta granules and coconut fibres, while nematodes stored in tap water served as the control. The numbers of live H. zealandica in Pesta granules and coconut fibres decreased drastically after seven days of storage. The survival of nematodes in Pesta granules dropped to 9.79% after 21 days compared to the control, where the survival rate was 79.79%. Nematode survival in coconut fibres was even lower, at 25.84% after seven days and 2.25% after 21 days. After 21 days in storage, 100%+of nematodes survived in the control for coconut fibres. The application of the standard quality control measure, which was used to determine the virulence of formulated H. zealandica, proved to be ineffective. Higher MW mortality rates were obtained in the control where no nematodes were added to larvae, compared to where nematodes were added in varying dosages. However, adjusting certain aspects in the protocol of this quality control measure specifically to accommodate local conditions could possibly make it a more effective tool for measuring endemic nematode virulence.
AFRIKAANSE OPSOMMING: Die landboubedryf in Suid-Afrika word oorheers deur die gebruik van insekdoders. Vervaardigers steun swaar op chemikalieë wat toenemend gesondheids-, omgewings- en ekologiese risiko's, asook die snelle ontwikkeling van weerstand in sleutelinsekteplae veroorsaak, en wat reste van plaagdoders op gewasse laat. Na aanleiding van toenemende besorgdheid oor die impak van hierdie plaagbestuurspraktyke op die omgewing, word alternatiewe plaagbestuurstrategieë ondersoek. Entomopatogeniese nematodes (EPNs) is geïdentifiseer as belowende biologiese beheeragente van sleutelinsekteplae. Die twee EPN genera wat belofte inhou vir gebruik as biologiese beheeragente binne 'n geïntegreerde plaagbestuursprogram is Steinernema en Heterorhabditis. Kommersialisering en die geslaagde gebruik van EPNs om insekplae te beheer in Noord-Amerika, Australië, Europa en Asië, het die doeltreffendheid van hierdie organismes as biologiese beheeragente bevestig. Ongelukkig is EPNs in groot genoeg getalle vir kommersiële aanwending in die veld nog nie op die Suid-Afrikaanse mark beskikbaar nie. Groot getalle EPNs kan deur in vivo en in vitro teling verkry word. Die doelwit van hierdie studie was om die in vivo produksieproses te stroomlyn deur die gebruik van twee endemiese EPN spesies, Heterorhabditis zealandica (SF41) en H. bacteriophora (SF351). Hierdie EPN isolate is deur navorsing bewys om doeltreffende beheeragente van kodlingmot Cydia pomonella, vals kodlingmot Thaumatotibia leucotreta, ligrooswitluis Pseudococcus viburni, en gebande vrugtekalanders Phlyctinus callosus te wees. 'n Vergelykende studie is gedoen om geskikte gasheerinsekte vir EPN produksie van plaaslike H. zealandica (SF41) en H. bacteriophora (SF351) isolate te vind. Gashere is geselekteer op grond van vatbaarheid vir die EPN spesie wat gebruik word, en algemene beskikbaarheid en gemak en koste van teling. Wasmotlarwes Galleria mellonella (WML) en meelwurms Tenebrio molitor (MW) is as gashere gekies. Ten einde nematodes van konsekwente kwaliteit te teel, word 'n deurlopende bron van gasheerinsekte benodig wat op 'n gestandaardiseerde dieet voed. WML en MW is onderskeidelik op vyf verskillende diëte geteel by ±26°C in die donker. Die beste dieet vir elke gasheer is gekies op grond van die dieet wat, gemiddeld, die swaarste larwes binne 'n spesifieke tydsraamwerk opgelewer het. Die swaarste WML, teen 'n gemiddelde massa van 0.19 g per larwe, is geteel op 'n dieet wat bestaan het uit 118 g koringmeel, 206 g semels, 118 g melkpoeier, 88 g brouersgis, 24 g verpoeierde was, 175 ml heuning en 175 ml gliserol. Die swaarste MW larwes het gemiddeld 0.0154 g per larwe geweeg en is geteel op 'n dieet van 100% semels. Ten einde die hipotese te bevestig dat 'n lineêre verwantskap bestaan tussen die massa van 'n insekgasheer en die aantal nematodes wat deur daardie gasheer geproduseer word, is 'n studie gedoen om die aantal H. zealandica en H. bacteriophora per gasheergram te bepaal. WML, MW, kodlingmotlarwes en vals kodlingmotlarwes is individueel geweeg en met infektiewe larwes van die twee onderskeidelike EPN spesies geïnokuleer. Daarbenewens is die vermeerdering van nematodes in bevrore MW en WML ook getoets. Die aantal nematodes wat in elke gasheer geoes is, is getel, en die gemiddelde nematode-afstammelinge in elke gasheer bereken. 'n Beduidende lineêre korrelasie tussen die massa van WML en MW en die aantal H. zealandica en H. bacteriophora wat onderskeidelik geproduseer is, het die hipotese bevestig dat nematode-vermeerdering binne hierdie gashere toeneem namate die gasheermassa toeneem. WML het die meeste H. zealandica en H. bacteriophera per gasheergram opgelewer (1 459 205± 113 670 en 1 898 512± 94 355 onderskeidelik), gevolg deur MW larwes (836 690± 121 252 en 414 566± 67 017 onderskeidelik). Laer getalle H. zealandica and H. bacteriophora per gram kodlingmot (57 582 ± 10 026 en 39 653 ± 8 276) en per gram vals kodlingmot (192 867 ± 13 488 en 97 652 ± 23 404) is egter geproduseer. Een van die sleutelfaktore vir die doeltreffendheid van die in vivo vermeerdering van nematodes is geslaagde gasheerinfeksie. Drie inokulasietegnieke is dus geëvalueer en vergelyk deur H. zealandica en H. bacteriophora te gebruik: inokulasie met 'n pipet, skud van gashere in 'n nematode-inokulum, en gasheerindompeling in 'n nematode-suspensie. WML en MW is as gashere gebruik vir elke inokulasietegniek, en is geïnokuleer met nematodes wat uit 'n konsentrasie van 200 infektiewe larwes (ILs) / insek larwe bestaan het. Die persentasie dooie insekgashere is na twee dae bepaal, en infeksie soos bevestig deur kleurverandering en disseksie, na sewe dae. Die hoogste persentasie infeksie deur sowel nematode-isolate as gashere te gebruik, was met die pipet-tegniek. Die infeksiekoerse vir alle nematode-gasheerkombinasies met die pipet-tegniek was hoër as 90%, met die uitsondering van MW-inokulasie met H. bacteriophora, waar die infeksie 76% was. Hierdie studie toon dat afwykings voorkom in die mate van gasheerinfeksie, na gelang van die inokulasietegniek wat gebruik is. In 'n bykomende poging om infeksie na inokulasie te verhoog, is H. zealandica, H. bacteriophora en MW onderwerp aan stressors en bymiddels om nematode-infeksie te bevorder. Drie behandelings, asook 'n kontrole-behandeling, is vergelyk. Infeksievlakke het nie verhoog deur MW voor inokulasie aan kraanwater van 70°C bloot te stel nie. Inteendeel, laer infeksievlakke is opgemerk waar gashere in kraanwater van 70°C gedompel is en daarna met H. bacteriophora geïnokuleer is, vergelyke met die kontrole. Gasheerinfeksie van slegs 12% is verkry, vergelyke met 48% in die kontrole. Infeksie van 21% is met H. zealandica verkry. Die virulensie van nematodes het nie beduidend toegeneem deur H. zealandica en H. bacteriophora IL in 'n suspensie met Mn2+SO4H20 te behandel voor MW geïnokuleer is nie. Inokulasie van MW met behandelde H. zealandica IL het tot 'n infeksie van 81% gelei, vergelyke met die kontrole waar 'n infeksie van 80% behaal is. H. bacteriophora het 'n MW-infeksie van 47% veroorsaak, vergelyke met die kontrole se infeksiekoers van 48%. 'n Kombinasie van die twee bogenoemde behandelings het eweneens nie gasheerinfeksievlakke verhoog nie. Die indompeling van meelwurms in kraanwater van 70°C voor inokulasie met nematodes wat met Mn2+SO4H20 behandel is, het tot gasheerinfeksie van 13% en 9% onderskeidelik gelei wanneer H. bacteriophora en H. zealandica gebruik is. Toekomstige navorsing is nodig om die protokol te verbeter wat in hierdie studie gebruik is om MW en plaaslike nematode-isolate aan stressors te onderwerp. 'n Ondersoek is gedoen na die vermoë van twee formulasies om biologiese aktiwiteit en virulensie van H. zealandica te onderhou. 'n Kwaliteitsstandaardtegniekis gebruik om weekliks die persentasie oorlewing en virulensie van geformuleerde H. zealandica oor 'n tydperk van 21 dae te meet. IL is in Pesta korrels en klappervesel geformuleer, terwyl nematodes in kraanwater gedien het as kontrole. Die aantal lewende H. zealandica in Pesta korrels en klappervesel het drasties verminder na sewe dae in die formulasie. Oorlewing van nematodes in Pesta korrels het gedaal tot 9.79% na 21 dae vergyleke met die kontrole, waar 79.79% oorleef het. Nog minder nematodes - 25.84% - het na sewe dae in die klappervesel oorleef, en slegs 2.25% na 21 dae. Na 21 dae van berging het 100%+ van nematodes oorleef in die kontrole vir klappervesel. Die toepassing van die kwaliteitsstandaardtegniek om die virulensie van geformuleerde H. zealandica te bepaal, het ondoeltreffend geblyk. Verhoogde MW sterftesyfers is verkry in die kontrole waar geen nematodes by die inseklarwes gevoeg is nie, vergelyke met die byvoeging van hoër dosisse nematodes. Nietemin, die aanpassing van sekere aspekte in die protokol van hierdie kwaliteitsbeheermeting om spesifiek plaaslike toestande in ag te neem, sou dit moontlik 'n meer doeltreffende middel kon maak om die virulensie van endemiese nematodes te bepaal.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Among the natural enemies of agriculture pests, the Coccinellidae predators are detached. Some coccinellids only complete their development and produce viable eggs and progenies when they consume their preferred prey. However, when this prey is scarce or in presence of a prey of low quality, certain coccinellids feed on alternative food resources, such as extra floral nectar and pollen, to guarantee their survivorship. Thus, the absence of these floral resources limits the occurrence and abundance of ladybeetles in the agroecosystems. Due to these characteristics, the coccinellids have great potential for being managed by the three strategies of biological control: classic, augmentative and conservation. However, to use the coccinellids as biological control agent, more information about their biology and ecology are still necessary. In this context, the present work was conducted with the general objective of producing information about ecological and biological aspects of the Coccinellidae. These approaches are in the Chapters I and II, respectively. In the Chapter I, the studies aimed to determine if Anethum graveolens (dill), Coriandrum sativum (coriander) and Foeniculum vulgare (sweet fennel) favor the abundance of Coccinellidae; to evaluate the potential of these aromatic plants to provide vital resources for these predators; to determine the species diversity of these insects attracted by these plants; and to characterize their community structure. The experiment was carried out in an integrated crop-livestock organic production area (Seropedica/RJ, Brazil) in a completely randomized design with three treatments (aromatic plants) and three replicates. From September 14th, 2007 to January 21st, 2008, samplings of adults and immature stages of ladybeetles were realized. Besides an unidentified species of Chilocorini, Coleomegilla maculata, Coleomegilla quadrifasciata, Cycloneda sanguinea, Eriopis connexa, Harmonia axyridis, Olla v-nigrum and Hippodamia convergens were collected. The dill provided significant increase in the abundance of coccinellids in relation to the coriander and sweet fennel. These three aromatic vegetal species were used as ovipositon sites and shelter for immature forms and adults of ladybeetles. The dill and sweet fennel were also used as mating sites and proved food resources (pollen and/or alternative prey). The principal species visiting these aromatic plants were C. sanguinea, H. convergens, and E. connexa (more frequent, constant and dominant). In the Chapter II, the studies aimed to determine biology aspects of Coleomegilla maculata and Eriopis connexa feed on two diets: ultraviolet-unviable and frozen eggs of Anagasta kuehniella (Lepidoptera: Pyralidae) and the alive aphids of Lipaphis erysimi (Hemiptera: Aphididae) under laboratory condition (25 ? 1?C, relative humidity of 70 ? 10%, and photophase of 12 hours). The experimental design was complete randomized in a 2x2 split-plot arrangement (two ladybeetle species and two diets). In general, the biological characteristics of C. maculata and E. connexa were similar, when their larvae and adults fed on the two diets. Both diets were suitable for C. maculata and E. connexa, keeping their development and oviposition for a generation, and the eggs of A. kuehniella still maintained the rearing of these ladybeetles for one more generation.
Entre os inimigos naturais de pragas agr?colas, destacam-se os Coccinellidae predadores. Alguns coccinel?deos s? completam seu desenvolvimento e produzem ovos e prog?nie vi?vel quando consomem sua presa preferencial. Todavia, quando esta presa est? escassa ou na presen?a de uma presa de qualidade inferior, certos coccinel?deos alimentam-se de alimentos alternativos, tais como n?ctar extrafloral e p?len, para garantir sua sobreviv?ncia. Desse modo, a aus?ncia desses recursos florais limita a ocorr?ncia e abund?ncia de joaninhas nos agroecossistemas. Devido essas caracter?sticas, os coccinel?deos apresentam grande potencial para serem manejados por meio do controle biol?gico cl?ssico, aumentativo e conservativo. Todavia, para usar os coccinel?deos como agente de controle biol?gico, mais informa??es sobre sua biologia e ecologia s?o ainda necess?rias. Neste contexto, o presente trabalho foi realizado com o objetivo geral de gerar informa??es sobre aspectos ecol?gicos e biol?gicos dos Coccinellidae, sendo esses temas abordados nos Cap?tulos I e II, respectivamente. No cap?tulo I, os estudos foram conduzidos com os seguintes objetivos: determinar se Anethum graveolens (endro), Coriandrum sativum (coentro) e Foeniculum vulgare (erva-doce) favorecem a abund?ncia de Coccinellidae; avaliar o potencial dessas esp?cies arom?ticas como provedoras de recursos vitais para esses predadores; determinar a diversidade de esp?cies desses insetos atra?dos por essas plantas; e caracterizar a estrutura de sua comunidade. O experimento foi conduzido em ?rea de produ??o org?nica integrada animalvegetal (Serop?dica/RJ), em delineamento de blocos casualizados, com tr?s tratamentos (esp?cies arom?ticas) e tr?s repeti??es. De 14 de setembro de 2007 a 21 de janeiro de 2008, foram realizadas amostragens de adultos e formas imaturas de joaninhas. Al?m de uma esp?cie n?o identificada da tribo Chilocorini, coletou-se Coleomegilla maculata, Coleomegilla quadrifasciata, Cycloneda sanguinea, Eriopis connexa, Harmonia axyridis, Olla v-nigrum e Hippodamia convergens. O endro proporcionou aumento significativo na abund?ncia de coccinel?deos em compara??o ao coentro e ? erva-doce. Essas tr?s esp?cies arom?ticas foram usadas como s?tios de oviposi??o e abrigo para formas imaturas e adultas de joaninhas. O endro e a erva-doce tamb?m foram utilizados como s?tios de acasalamento e de alimenta??o pelas joaninhas. As principais esp?cies visitantes das arom?ticas foram C. sanguinea, H. convergens e E. connexa (mais freq?entes, constantes e dominantes). No cap?tulo II, os estudos foram conduzidos com os seguintes objetivos: 1) determinar aspectos biol?gicos de C. maculata e E. connexa alimentadas com duas dietas: ovos de Anagasta kuehniella (Lepidoptera: Pyralidae) inviabilizados com ultravioleta e congelados e pulg?es vivos de Lipaphis erysimi (Hemiptera: Aphididae), em condi??es de laborat?rio (25?1?C, 70?10% UR e fotofase de 12 horas). O delineamento foi inteiramente casualizado em arranjo fatorial 2 x 2 (duas esp?cies de joaninhas e duas dietas). No geral, as caracter?sticas biol?gicas de C. maculata e E. connexa foram bem semelhantes, quando suas larvas e adultos se alimentaram das duas dietas. Ambas as dietas foram adequadas para C. maculata e E. connexa, assegurando seu desenvolvimento e oviposi??o por uma gera??o e os ovos de A. kuehniella permitiram ainda manter a cria??o dessas joaninhas por mais uma gera??o.

Paropsis atomaria Olivier (Coleoptera: Chrysomelidae: Paropsini), is a major pest of commercially grown eucalypts in South-East Queensland. Current management of paropsine beetles involves regular inspection and the application of chemical sprays if defoliation is severe. However, non-chemical control of plantation pests is highly desirable given the requirement to certify forest practices for sustainability, and community concerns over the use of pesticides. One way of reducing pesticide use is through conservation biological control, which requires detailed knowledge of the life history of the pest and its natural enemies. This thesis documents aspects of P. atomaria phenology, including life tables, sex ratios and damage estimates; identifies the predators, parasites, and egg and larval parasitoids of P. atomaria; and examines the ecology of the most promising natural enemy, Neopolycystus Girault sp. (Hymenoptera: Pteromalidae) in South-East Queensland. P. atomaria adults are active from September until April and can complete up to four generations in a season. Field mortality between egg and fourth instar larvae is approximately 94%. A large proportion of this mortality can be attributed to natural enemies. The most abundant predators in eucalypt plantations were spiders, comprising 88% of all predators encountered. Egg parasitoids exerted the greatest influence on P. atomaria populations, emerging from around 50% of all egg batches, and were responsible for mortality of almost one third of all eggs in the field. Only about one percent of larvae were parasitised in the field, in contrast to paropsine pests in temperate Australia, where egg parasitism rates are low and larval parasitism rates high. Neopolycystus sp. was the only primary parasitoid reared from P. atomaria eggs, along with three hyperparasitoid species; Baeoanusia albifunicle Girault (Encyrtidae), Neblatticida sp. (Encyrtidae) and Aphaneromella sp. (Platygasteridae). This is the first record of B. albifunicle hyperparasitising Neopolycystus spp. B. albifunicle emerged from one-third of all parasitised egg batches and could pose a potential problem to the efficacy of Neopolycystus sp. as a biological control agent. However, within egg batches, hyperparasitoids rarely killed all Neopolycystus sp. with only 9% of hyperparasitised egg batches failing to produce any primary parasitoids. Total field mortality of P. atomaria through direct and indirect effects of parasitism by Neopolycystus sp. was 28%. The proportion of egg batches parasitised increased with exposure time in the field, but within-batch parasitism rate did not. In general, there was no significant correlation between parasitism rates and distance from landscape features (viz. water sources and native forest).

Paropsis atomaria Olivier (Coleoptera: Chrysomelidae: Paropsini), is a major pest of commercially grown eucalypts in South-East Queensland. Current management of paropsine beetles involves regular inspection and the application of chemical sprays if defoliation is severe. However, non-chemical control of plantation pests is highly desirable given the requirement to certify forest practices for sustainability, and community concerns over the use of pesticides. One way of reducing pesticide use is through conservation biological control, which requires detailed knowledge of the life history of the pest and its natural enemies. This thesis documents aspects of P. atomaria phenology, including life tables, sex ratios and damage estimates; identifies the predators, parasites, and egg and larval parasitoids of P. atomaria; and examines the ecology of the most promising natural enemy, Neopolycystus Girault sp. (Hymenoptera: Pteromalidae) in South-East Queensland. P. atomaria adults are active from September until April and can complete up to four generations in a season. Field mortality between egg and fourth instar larvae is approximately 94%. A large proportion of this mortality can be attributed to natural enemies. The most abundant predators in eucalypt plantations were spiders, comprising 88% of all predators encountered. Egg parasitoids exerted the greatest influence on P. atomaria populations, emerging from around 50% of all egg batches, and were responsible for mortality of almost one third of all eggs in the field. Only about one percent of larvae were parasitised in the field, in contrast to paropsine pests in temperate Australia, where egg parasitism rates are low and larval parasitism rates high. Neopolycystus sp. was the only primary parasitoid reared from P. atomaria eggs, along with three hyperparasitoid species; Baeoanusia albifunicle Girault (Encyrtidae), Neblatticida sp. (Encyrtidae) and Aphaneromella sp. (Platygasteridae). This is the first record of B. albifunicle hyperparasitising Neopolycystus spp. B. albifunicle emerged from one-third of all parasitised egg batches and could pose a potential problem to the efficacy of Neopolycystus sp. as a biological control agent. However, within egg batches, hyperparasitoids rarely killed all Neopolycystus sp. with only 9% of hyperparasitised egg batches failing to produce any primary parasitoids. Total field mortality of P. atomaria through direct and indirect effects of parasitism by Neopolycystus sp. was 28%. The proportion of egg batches parasitised increased with exposure time in the field, but within-batch parasitism rate did not. In general, there was no significant correlation between parasitism rates and distance from landscape features (viz. water sources and native forest).

Species of Prosopis (Mimosaceae), or mesquite, are native to the Americas and introduced in South Africa as agro forestry trees to provide wood, fodder and shade in the late 1800s. In the Northern Cape Province, these trees have been particularly used for their pods by local farmers and local industry. However due to Prosopis’ ability to spread rapidly there has been increasing pressure to step up control of the tree. Due to the costs associated with most control methods biological control has been singled out as the most viable control method worth pursuing. This thesis attempts to explain and shed light on the effects that increased biological control of Prosopis would have on the farming community and Prosopis based businesses in the area. Two hypothetical scenarios were used, the first being a possible 50% reduction in available pods and the other a possible 100% reduction. In an effort to explain these effects data was collected from a series of collection activities in the form of a pilot study and two unique questionnaire surveys. Twenty-seven farmers and one Prosopis based business were interviewed at random with the data analysed and documented. Results showed that the business community is the main user of pods incurring crippling losses in the event of a 50% or 100% decrease in available pods. Using control costs from working for water De Aar long term costs of the presence of Prosopis were estimated and compared to the estimated provincial cost of losing pods giving a cost comparison ratio of (α)270 million : Y(N(15.7million)). Only 48% of the respondents valued pods and 11% had traded in pods, the top concern resulting from the invasion was the loss of underground water. With a 50% decline in available pods, all respondents indicated unchanged effects. However empirical results showed that with a 100% decline in pods estimate losses of R 5 818 per farm are expected. The cost comparison ratio showing the losses farmers bore with Prosopis in the area and the losses they would suffer with a 100% decline in pods was R11 389 + (K): R5 818. In light of the empirical results, policy recommendations that support the introduction of more effective biological control agents have been made with areas for further research identified and discussed.

Thesis (MScConEcol)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Acacia saligna, or Port Jackson, is an Australian Acacia which has spread throughout the Western and Eastern Cape provinces of South Africa where it has become invasive and a prominent feature of the vegetation. In areas where A. saligna establishes it replaces natural vegetation, alters ecosystem processes and interferes with agricultural practices. Consequently large management efforts have been made to eradicate this invasive alien tree. However, its large and persistent soil stored seed bank, even in the presence of management and biological control agents, poses a serious obstacle to its successful removal. Furthermore the reproductive output and the size of the seed bank of A. saligna over its whole distribution as well as the variation of seed production and the seed bank with environmental conditions in time and space is poorly known. Understanding the seed bank dynamics of A. saligna in time and space is essential for reducing invasive success and achieving management objectives. This study has filled this knowledge gap through studying the seed production and seed bank of A. saligna over its invaded range in South Africa, including how environmental factors influence these factors in time and space. The seed rain of A. saligna was assessed at 10 sites across its distribution in South Africa. The seed rain of A. saligna at the sites was determined through the use of seed rain traps. Twenty five traps were placed out at every site during November 2010 (pre-dehiscence) which was collected again during April 2011 (postdehiscence). The seed bank of A. saligna was estimated through sampling at 25 sites across its distribution range in South Africa. The seed bank was sampled during April 2010 (postdehiscence), November 2010 (pre-dehiscence) and April 2011 (post-dehiscence) through taking 50 litter and soil samples at every site which gave a total sampling size of 3 750 for both the seed in the soil and litter over its distribution in South Africa. In addition the average tree diameter, tree density, average number of Uromycladium tepperianum induced galls per tree, the summer aridity index, De Martonne aridity index, winter concentration of precipitation, temperature of coldest month and the soil texture for every site was determined. The damage done by the seed feeding weevil, Melanterius compactus, was also estimated for the seed rain study sites. Water availability during the hot summer months was assessed as the most important factor governing seed production and seed bank size. Riparian and non-riparian water regimes were shown to be important in understanding the seed bank dynamics of A. saligna over its distribution range in the Cape Floristic Region. In non-riparian A. saligna populations the seed production and consequently the size of the seed bank and its rate of accumulation is limited by both water and temperature and in riparian A. saligna populations, only by temperature. Therefore, two environmental gradients influence the seed bank dynamics of Port Jackson in South Africa. In non-riparian A. saligna populations the number of seed produced and the accumulation of seed in the seed bank generally increases along the west coast of South Africa from Clanwilliam towards Cape Town and along the south coast from Cape Town towards Port Elizabeth. Seed banks are larger closer to the coast, when A. saligna populations of similar age are compared. In riparian A. saligna populations, the number of seed produced generally increases from Port Elizabeth towards Cape Town and from Cape Town towards Clanwilliam, again, with larger seed banks being accumulated closer to the coast, when populations of similar age are compared. This study provides managers with a useful tool for prioritising management efforts.
AFRIKAANSE OPSOMMING: Acacia saligna of Port Jackson is ‘n indringerplant in Suid-Afrika wat afkomstig is uit Suid-Wes Australië. Acacia saligna is ‘n onmisbare kenmerk van die plantegroei in die Wes en Oos-Kaap. Waar Port Jackson vestig, verplaas dit natuurlike plantegroei, verander dit ekosisteem prossesse en verhinder dit landbou praktyke. Gevolglik is groot bestuurspogings aangewend om hierdie indringer plant uit te roei. In die teenwoordigheid van bestuursprogramme en biologiese beheer bly A. saligna lewensvatbaar as ‘n gevolg van die plant se groot blywende grond saadreserwes. Verder is die saad produksie en saadbank grootte van A. saligna oor sy verspreiding bereike asook hoe dit met omgewingstoestande in tyd en ruimte interreageer en varieer grootendeels onbekend. ‘n Goeie en omvattende begrip van die saadbankdinamika is belangrik om die indringings vermoë van die plant te verlaag en om bestuursdoelwitte te bereik. Hierdie studie vul die bestaande gaping in die kennis aangaande die saadbank dinamika van A. saligna aan deur die saadproduksie en die saadreserves van die indringerplant oor sy verspreiding in Suid-Afrika te bestudeer, insluitend hoe omgewingstoestande die saadbankdinamika beïnvloed in tyd en ruimte. Die saadreën vir 10 A. saligna populasies was bepaal deur die gebruik van saadlokvalle. Vyf-entwintig lokvalle was uitgeplaas in elke bestudeerde Port Jackson perseel gedurende November 2010 (voor-saadval) wat weer gaan haal is gedurende April 2011 (na-saadval). Die saadbank van A. saligna was bepaal in 25 populasies van die boom gedurende April 2010 (na-saadval), November 2010 (voor-saadval) en April 2011 (na-saadval) deur die neem van 50 blaar- en grondmonsters by elke perseel wat ‘n totaal van 3 750 blaar- en grondmonster gee oor die hele verspreiding van A. saligna in Suid-Afrika. Verder is die gemiddelde boomdeursnee, boomdigtheid, gemiddelde Uromycladium tepperianum geinduseerde galle per boom, die somers droogtheids indeks, De Martonnes droogtheids indeks, die winter konsentrasie van presipitasie, die temperatuur van die koudste maand en die grond tekstuur van elke Port Jackson stand bepaal. Die skade wat die saad voedende kewer, Melanterius compactus, aanrig aan die sade van A. saligna is ook vir die persele waar die saadreën eksperiment uitgevoer is, bepaal. Die beskikbaarheid van water vir A. saligna in die droë somermaande is bepaal as die belangrikste faktor wat die grootte van die saadproduksie en saadbank beïnvloed. Oewer en nie-oewer water omgewings is bevind as noodsaaklik om die saadbank dinamika van A. saligna oor die indringerplant se verspreidingareas in die Kaap Floristiese Streek te verstaan. In nie-oewer A. saligna populasies word saadproduksie en gevolglik die grootte en tempo van akkumulasie van die saadbank deur beide water en temperatuur omstandighede beperk, terwyl in oewer A. saligna populasies word die indringerplant slegs deur temperatuur omstandighede beperk. Gevolglik blyk dit dat twee water beskikbaarheids gradiënte bestaan waarop die plant reageer wat dan uitgedruk word in die plant se saad produksie en gevolglik ook die plant se saadbank. In nie-oewer Port Jackson populasies neem die saadproduksie en die tempo waarteen die saadbank akkumuleer algemeen toe langs die weskus van Clanwilliam na Kaapstad en van Kaapstad na Port Elizabeth, met grootter saadproduksie en saadbank akkumulasie nader aan die kusgebiede, wanneer A. saligna populasies van dieselfde ouderdom vergelyk word. In oewer Port Jackson populasies neem die saadproduksie en die tempo waarteen die saadbank akkumuleer algemeen toe van Port Elizabeth na Kaapstad en van Kaapstad na Clanwilliam, met grootter saadproduksie en saadbank akkumulasie nader aan die kusgebiede, wanneer A. saligna populasies van dieselfde ouderdom vergelyk word. Hierdie studie verskaf bestuursplanne met ‘n nuttige raamwerk waarvolgens uitroeiing en beheer programme vir A. saligna beplan kan word.

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CAPES
The biological control is as important method to regulate the pest populations in a system of sustainable agricultural production, because it is a promising alternative to the use of the organic synthetic pesticides that cause great ecotoxicological impacts. The predator ladybeetles are part of the biological control agents of agricultural pests, could be management by the three biocontrol strategies: classical, conservative and augmentative. In the present work, it was tried to generate knowledge for using the aphidophagous predator ladybeetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) under the perspective of the last two strategies. The conservative biological control involving predator insects bases on the fact that in the absence or scarceness of their preferential prey or in the presence of the other preys with inferior nutritional quality, they may use alternative foods, such as pollen, to guarantee their survivorship and, sometimes, their reproduction, and because of that botanical species that provide this floral resource might integrate the agricultural landscape, inside and/or around the agricultural property; meanwhile the augmentative control requests the multiplication of the predator in the laboratory, using natural or artificial preys. Even though some authors proved the visitation of the flowers of some species of Apiaceae by C. maculata, there are no records in the literature of the ingestion of pollen grains of this botanical family by this ladybeetle. In this context, this work was carried out with the aim to select the plant species whose flowers are source of pollen as alternative or complementary food to C. maculata in the perspective to compose the vegetation of the agroecosystems to contribute in the conservation of this ladybeetle, and /or to aid in its mass rearing in the laboratory conditions. The objective of the chapter I was to prove the ingestion of pollen of three species of the family Apiaceae [coriander (Coriandrum sativum L.), dill (Anethum graveolens L.), and fennel (Foeniculum vulgare Mill.)] from the provision of their flowers to the larvae of the 4th instar and adults of C. maculata. It was observed the presence of pollen grains in the five replicates of all treatments, proving the ingestion of the pollen of these three species of Apiaceae from their flowers by C. maculata. At 24 hours of exposition, adults fed on average more pollen of dill than pollens of coriander and fennel, while the larvae consumed more pollen of fennel. The objective of the chapter II was to determine the suitability of nine diets to C. maculata, including provision of pollen of the two species of Apiaceae (coriander and dill), under controlled conditions of the laboratory. Even though the diets with only flowers of these two Apiaceae did not provided the full development of C. maculata, they used as complementary food with eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) resulted in reduction of larval period, increased the egg number by cluster, and increased the body weight. The diet with alive larvae of Drosophila melanogaster Meigen (Diptera: Drosophilidae) was proved to be an essential food as well as resulted in adults with higher body weight, and the number of eggs per cluster increased in comparison with the feeding with only eggs of A. kuehniella.
O controle biol?gico ? um importante m?todo para regular as populac?es de pragas em um sistema de produ??o agr?cola sustent?vel, pois ? uma alternativa promissora ao uso de agrot?xicos org?nicos sint?ticos que causam grandes impactos ecotoxicol?gicos. As joaninhas predadoras fazem parte dos agentes de controle biol?gico de pragas agr?colas, podendo ser manejadas pelas tr?s estrat?gias de controle biol?gico: cl?ssico, conservativo e aumentativo. No presente trabalho, buscou-se gerar conhecimento para uso da joaninha predadora afid?faga Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) sob a perspectiva das duas ?ltimas estrat?gias. O controle biol?gico conservativo envolvendo insetos predadores baseia-se no fato de que, na aus?ncia ou escassez da presa preferencial ou na presen?a de outras presas de qualidade inferior, podem usar alimentos alternativos, tais como p?len, para garantir sua sobreviv?ncia e, por vezes, sua reprodu??o e, por isso, esp?cies bot?nicas provedoras desse recurso floral devem integrar a paisagem agr?cola, dentro e/ou no entorno da propriedade agr?cola; enquanto o controle aumentativo requer a multiplica??o do predador no laborat?rio, podendo se valer de presas naturais ou artificiais. Apesar de alguns autores comprovarem a visita??o das flores de algumas esp?cies de Apiaceae por C. maculata, n?o h? relatos na literatura da ingest?o de gr?os de p?len dessa fam?lia bot?nica por essa joaninha. Nesse contexto, este trabalho foi conduzido a fim de selecionar esp?cies de plantas cujas flores sejam fonte de p?len como alimento alternativo ou complementar para C. maculata na perspectiva de compor a vegeta??o dos agroecossistemas para contribuir na conserva??o dessa joaninha, e/ou auxiliar na cria??o massal da mesma em condi??es de laborat?rio. O objetivo do cap?tulo I foi comprovar a ingest?o de p?len de tr?s esp?cies da fam?lia Apiaceae [coentro (Coriandrum sativum L.), endro (Anethum graveolens L.) e erva-doce (Foeniculum vulgare Mill.)] a partir da oferta de suas flores para larvas de 4? instar e adultos de C. maculata. Constatou-se a presen?a de gr?os de p?len nas cinco repeti??es de todos os tratamentos, comprovando a ingest?o de p?len dessas tr?s Apiaceae a partir de suas flores por C. maculata. Em 24 horas de exposi??o, os adultos consumiram em m?dia mais p?len de endro em compara??o aos polens de coentro e erva-doce, enquanto que as larvas consumiram mais p?len de erva-doce. O objetivo do capitulo II foi determinar a adequabilidade de nove dietas para C. maculata, incluindo oferta de p?len de duas esp?cies de Apiaceae (coentro e endro), em condi??es controladas de laborat?rio. Apesar das dietas apenas com flores dessas duas Apiaceae n?o proporcionarem o desenvolvimento completo de C. maculata, elas usadas com complementa??o da alimenta??o com ovos de Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) possibilitam a redu??o do per?odo larval, aumento no n?mero de ovos por postura e aumento do peso corp?reo. A dieta com larvas vivas de Drosophila melanogaster Meigen (Diptera: Drosophilidae) n?o foi s? comprovada como alimento essencial como tamb?m resultou em adultos de maior peso corp?reo e um aumento no n?mero de ovos por postura em compara??o ? alimenta??o apenas com ovos de A. kuehniella.

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Invasive species are among the most important global conservation threats. Their management is one of the key conservation challenges that will have to be addressed in the next few decades. The study of real invasions and their management in natural ecosystems provides an opportunity to gain important information on theoretical and applied aspects of biological invasions. This project focuses on the broader ecological context of invasive ant management in an ecologically sensitive island habitat. The thesis has three main components: 1) assessing the role of the invasive ant Pheidole megacephala in the ecosystem and evaluating its threat to the system, 2) evaluating a low-impact management program for the ant, and 3) using a community-level approach to assess ecosystem response to ant removal. The ant occupied almost 30% of the island‘s total land area and reached extremely high densities in some areas. The ant was associated with exotic hemipteran scale insects through trophobiotic mutualisms that facilitated high ant and hemipteran abundances. The highly destructive scale insect Pulvinaria urbicola was among the hemipterans that benefited from ant attendance. High levels of hemipteran feeding resulted in dieback of functionally important and threatened native Pisonia trees, which represented a significant threat to the forest ecosystem. A management program was initiated in response to this threat, consisting of baiting with selective hydramethylnon-based bait delivered in bait stations, accompanied by detailed pre-and post-baiting monitoring. The method was highly effective at suppressing the ants, whilst preventing bait uptake by non-target organisms. It was also cost-effective and adaptable to ant density in the field, but was only effective over short distances. The method may be applicable to other sensitive environments with similar challenges. After ant control, the ant-scale mutualism was decoupled and the Pu. urbicola population collapsed. There were variable responses in different taxa to the removal of these highly abundant exotic species, the most important of which was the recovery in Pisonia trees. Shoot condition and foliage density improved and there was a decrease in sooty mold. Herbivory on Pisonia increased due to recovery of native canopy herbivores, but the overall impact was far less than that of the exotic hemipterans. Soil surface arthropods, a group that may have been vulnerable to the treatment method, were unaffected by baiting. Instead, they increased significantly after ant removal, confirming the ant‘s impact on other arthropods. Other ant diversity and non-ant arthropod abundance increased post-baiting, including the endemic ant Pheidole flavens farquharensis and some functionally important insects such as the Indian cockroach. Natural enemies that interacted predictably with the mutualists were influenced by management. Predators of hemipterans increased significantly after ant removal and were instrumental in the scale population collapse, whereas parasitoids of hemipterans that benefited from the mutualism declined. Additionally, groups that were unrelated to the mutualism were indirectly influenced by management. The natural enemy assemblage as a whole showed recovery to pre-invasion conditions. The study shows how widely interconnected and influential the ant was in the ecosystem. It highlights the threat of the species in natural systems as well as the complex responses following invasive ant removal. Yet, it also demonstrates the potential to safely and effectively manage the species, thereby raising the opportunity for ecosystem recovery.
AFRIKAANSE OPSOMMING: Indringerspesies is van die belangrikste globale bedreigings vir natuurbewaring. Hulle bestuur is van die grootste bewaringsuitdagings wat in die volgende paar dekades aangespreek moet word. Die studie van werklike invalle en hul bestuur in natuurlike ekosisteme bied 'n geleentheid om belangrike inligting te verkry oor teoretiese en toegepaste aspekte van biologiese indringing. Hierdie projek fokus op die breër ekologiese konteks van uitheemse mier bestuur in 'n ekologies sensitiewe eiland habitat. Die tesis het drie hoofkomponente: 1) die beoordeling van die rol van die indringer mier Pheidole megacephala in die ekosisteem en evaluering van sy bedreiging vir die sisteem, 2) die evaluering van 'n lae-impak bestuursprogram vir die mier, en 3) die gebruik van 'n gemeenskaps-vlak benadering om ekosisteem reaksie op mierverwydering te assesseer. Die mier het byna 30% van die totale landoppervlak van die eiland beslaan en het in party areas baie hoë digthede bereik. Die mier was geassosieer met uitheemse dopluis spesies in mutualismes wat hoë mier en dopluis getalle gefasiliteer het. Die hoogs beskadigende dopluis Pulvinaria urbicola was een van die spesies wat bevoordeel is deur die mutualisme. Hoë vlakke van dopluis voeding het die terugsterwe van funksioneel belangrike, bedreidge inheemse Pisonia bome veroorsaak, wat ʼn groot bedreiging vir die ekosisteem verteenwoordig het. ‗n Bestuursprogram is geïmplimenteer as gevolg van hierdie bedreiging, wat bestaan het uit selektiewe hidrametielnoon-gebaseerde lokaas wat in die veld geplaas is in lokaashouers, vergesel deur intensiewe monitering voor en na lokaasplasing. Die metode was hoogs effektief in die onderdrukking van die miere en het lokaasinname deur nie-teiken organismes verhoed. Dit was ook koste-effektief en aanpasbaar volgens mierdigtheid in die veld, maar was slegs effektief oor kort afstande. Die metode mag van toepassing wees in ander sensitiewe omgewings met soortgelyke uitdagings. Na mierbeheer is die mier-dopluis mutualisme ontkoppel en die Pu. urbicola bevolking het drasties verminder. Daar was verskillende reaksies in verskillende taxa tot die verwydering van die oorvloedryke eksotiese spesies, maar die belangrikste reaksie was die herstel van Pisonia bome. Spruittoestand en blaardigtheid het verbeter en daar was ʼn afname in roetskimmel. Herbivorie op Pisonia het toegeneem as gevolg van ʼn herstel in inheemse herbivore, maar die algehele impak was veel minder as dié van die eksotiese dopluis. Grondoppervlak gelidpotiges, 'n groep wat kwesbaar kon wees vir die behandelingsmetode, was onaangeraak deur die lokaas, maar het beduidend na mierverwydering vermeerder. Mierdiversiteit het vermeerder en die Seychelles endemiese mier Pheidole flavens farquharensis is hervestig. Ander gelidpotiges het ook vermeerder, insluitend funksioneel belangrike spesies soos die Indiese kakkerlak. Natuurlike vyande wat geassosieer was met die mutualiste is beïnvloed deur die mierbestuur. Predatore van dopluis het beduidend toegeneem na mierverwydering en was hoogs betrokke by die vermindering van dopluis, terwyl parasiete van dopluis, wat voordeel getrek het uit die mutualisme, gedaal het. Daarbenewens is groepe wat onverwant was aan die mutualisme indirek beïnvloed deur mierbestuur. Die algehele natuurlike vyand gemeenskap het herstel na pre-indringing toestand. Die studie toon hoe wydverbind en invloedryk die mier was in die ekosisteem. Dit beklemtoon die bedreiging van die spesies in natuurlike stelsels asook die komplekse reaksies wat uitheemse mierverwydering volg. Tog demonstreer dit die potensiaal om die spesies veilig en doeltreffend te bestuur, en sodoende die geleentheid vir ekosisteemherstel te skep.

Augmenter la diversité végétale au sein même du champ permet de réguler les populations de ravageurs dans de nombreux agroécosystèmes. Les mélanges variétaux (diversité intraspécifique) ou les associations de cultures avec une plante compagne (diversité interspécifique) sont considérées comme des pratiques agroécologiques prometteuses pour les systèmes de culture à bas intrants ou l'agriculture biologique. En effet, ces pratiques favorisent de nombreux services écosystémiques tels que la régulation des ravageurs, des maladies ou des adventices, ainsi que la fertilisation azotée. Cependant, le potentiel de régulation des ravageurs du blé par la combinaison de ces deux pratiques de diversification n'a pas encore été étudié.Nous avons combiné ces deux pratiques dans le cadre d'expérimentations menées en plein champ et sur deux saisons de culture, afin d'examiner leurs impacts sur les populations de pucerons et d'ennemis naturels. Nous avons également évalué le potentiel de régulation des ravageurs en mesurant les taux de prédation de proies sentinelles.La combinaison des diversités intra- et interspécifique n'est pas plus performante pour réduire les populations de pucerons que les pratiques prises séparément. L'association de culture blé-trèfle tend à être moins infestée par les pucerons, tandis que le mélange variétal est plus infesté que la variété la moins sensible. Les variations annuelles des conditions climatiques impactent fortement le développement du blé et du trèfle, ainsi que la date d'apparition du pic de puceron. Le rendement du blé, ainsi que le taux d'azote du grain sont réduits par l'association de culture par 7 à 10%, mais pas par le mélange variétal. La présence d'un couvert de trèfle dans les champs de blé, semble avoir favorisé la biodiversité fonctionnelle, particulièrement les ennemis naturels tels que les carabes, mais pas le mélange variétal. Les résultats sont variables selon la famille d'arthropodes concernée et leur position au sein du couvert végétal (au sol ou dans le feuillage). Le couvert de trèfle et le champ ont influencé la composition de la communauté de carabes prédateurs. Les taux de prédation des proies sentinelles n'ont pas été impactés par les pratiques de diversifications.En laboratoire, nous avons évalué comment l'association du blé avec des légumineuses (trèfle ou pois) pouvait modifier le comportement du puceron du blé Sitobion avenae en terme de location de sa plante hôte et du développement de la population. Les pucerons ont résidé moins de temps sur le blé quand il était associé à du trèfle. Les populations de pucerons se sont moins développées dans les associations du blé avec une légumineuse par rapport à du blé seul, mais si l'on prend en compte la biomasse du blé, seulement l'association blé-trèfle a considérablement réduit les densités de pucerons sur le blé. Ainsi l'espèce associée et sa densité sont des paramètres importants qui devraient être pris en compte dans les études sur la diversité interspécifique, car ils pourraient expliquer la grande variation dans les résultats rapportés par les analyses bibliographiques.Nos résultats suggèrent qu'augmenter la diversité cultivée au sein du champ peut aider à réguler les pucerons dans une certaine mesure, mais la combinaison des deux pratiques de diversification ne résultent pas en un trade-off entre la régulation des ravageurs et les performances agronomiques particulièrement attractifs pour les agriculteurs
Increasing intrafield plant diversity has been shown to regulate pest populations in various agroecosystems. Polyvarietal mixtures of a crop species (intraspecific diversity) or associations of a crop and a companion plant (interspecific diversity) are both considered as promising agroecological practices for low-input or organic agriculture systems by providing several ecosystem services such as pest, disease and weed control, and nitrogen fertilization. However, combining both diversification practices has not been studied yet in perspective of winter wheat pest control.In organic field experiments over two growing seasons, we combined both practices and examined the direct impact on aphid and natural enemy populations and on wheat production. We also investigated the potential pest regulation service through the assessment of the rate of predation by using sentinel preys.Results show that combining intra- and interspecific diversity did not outperform each practice individually in reducing aphid populations, thus not clearly showing synergetic effects. Taken separately, intercropping tended to have lower aphid infestation, while it the cultivar mixtures was more infested by aphids than the least susceptible cultivar. Yearly variation in climatic conditions strongly impacted wheat and clover development, as well as the appearance of aphid peaks. Wheat yields and grain nitrogen content were reduced in intercropping by 7 to 10%, but not in cultivar mixtures. Functional biodiversity, especially natural enemies such as ground beetles, tended to be positively correlated to the presence of a clover cover in the wheat fields (interspecific diversification), but did not respond to the wheat cultivar mixture (intraspecific diversification). Results varied according to the family of arthropods concerned and their position within the vegetation layer (ground dwelling or foliage dwelling arthropods). The cover of white clover and the field context influenced the community composition of predatory ground dwelling beetles. Rates of predation on sentinel preys were not influenced by any of the diversification practices.Under laboratory conditions, we evaluated how combining wheat and legumes (clover or pea) modifies the behaviour of the cereal aphid Sitobion avenae in terms of host-plant location, and population growth. We observed that aphids’ residence time on wheat was decreased when this host-plant was intercropped with clover. At the population level, wheat-legume intercrops reduced the number of aphids on wheat plants compared to wheat sole crops but if we take into account plant biomass, only intercropping clover with wheat significantly reduced aphid densities on wheat. The species used as non-host plants and their density are important parameters that should be taken into account in studies on intercropping systems and that may explain the large variability in the results observed in the literature.Our findings suggest that intrafield diversification may regulate wheat aphids to some extent, but combining the two diversification practices did not result in an interesting trade-off between pest regulation and wheat production in real farming conditions

In this thesis, experiments were conducted in the laboratory and the field to determine whether the provision of floral resources to hoverflies could enhance the biological control of aphids. The overall aim was to clarify hoverfly behaviour and ecology in an agroecosystem in order to understand the potential of these insects for biocontrol under a conservation biological control (CBC) regime. A preliminary experiment in New Zealand compared the effect of different coloured water-traps on catches of the hoverflies Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart). Significantly more individuals were caught in completely yellow traps than in traps with green outer walls and yellow inner walls or in completely green traps. This suggested that if a measure of hoverfly numbers relating to a particular distance along a transect is required, consideration should be given to the ability of hoverflies to detect yellow traps from a distance. The use of traps that are green outside would more accurately reflect the local abundance of hoverflies, as the insect would be likely to see the yellow stimulus only when above or close to the trap. Also, the addition of rose water significantly increased the number of M. fasciatum caught. From a suite of flowering plants chosen for their ability in other studies to increase hoverfly visit frequencies, laboratory experiments were conducted in France to determine the plant’s effectiveness at enhancing Episyrphus balteatus (De Geer) ‘fitness’, and to evaluate whether adult feeding on flowers was related to performance. Phacelia (Phacelia tanacetifolia Bentham cv. Balo), followed by buckwheat (Fagopyrum esculentum Moench cv. Katowase) and coriander (Coriandrum sativum L.) gave the optimal reproductive potential of female E. balteatus. There was no correlation between pollen and nectar consumption, and there was no discernible positive correlation between the quantity of pollen ingested and the resulting female performance. Phacelia and buckwheat were then studied as resource subsidies in the field in New Zealand. The effect of incorporating phacelia or buckwheat in the margins of 5 m x 5 m broccoli plots was tested for hoverfly activity and floral ‘preferences’. Hoverflies which had fed on phacelia and buckwheat pollen were found up to 17.5 m from the floral strips and females of M. fasciatum and M. novaezelandiae consumed more phacelia pollen than that of buckwheat in the field. These results support the choice of phacelia as an ideal floral resource subsidy in crops for enhanced biological control by these New Zealand species. The need for studying hoverfly movement in a large-scale field experiment was apparent from the field studies, so the next experiment was carried out in a field 450 × 270 m and flies were marked via their ingestion of the pollen of phacelia. The focus was on the proportion of flies having consumed the pollen. Although large quantities of pollen were found in some hoverfly guts, most did not contain phacelia pollen and very few were captured at 50 m from phacelia, compared with numbers at the border of the floral strip. A possible explanation was that hoverflies feed on a large variety of pollen species, reducing the relative attraction of phacelia flowers. Another possibility was that hoverflies dispersed from the phacelia away from the crop. Also, pollen digestion rates are likely to be a factor. Finally, a series of experiments was conducted in the field and laboratory to study hoverfly efficacy through oviposition and larval behaviour. In field experiments, female M. fasciatum and M. novaezelandiae laid more eggs where buckwheat patches were larger; however higher oviposition rates did not lead to improved aphid population suppression. In greenhouse experiments, larvae of E. balteatus could initiate a decline in aphid numbers at the predator: prey ratio 1: 8.3, however this control did not persist. Experiments in the laboratory showed that hoverfly larvae became more active and left the system while aphid numbers declined or numbers of larvae increased. This behaviour was caused by two factors: hunger and avoidance of conspecific larvae. Further experiments showed that the avoidance of conspecifics was caused by mutual interference rather than cannibalism. The results of this work highlight the importance of hoverfly dispersal ability. Given the observations of foraging behaviour of females and mutual interference observed between larvae, and the lack of success in CBC by hoverflies in experiments at the crop scale, it is essential to assess the impact of insect predators and parasitoids at a landscape scale.