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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

The ecology of key arthropods for the management of Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) in Coonawarra vineyards, South Australia.

Paull, Cate January 2008 (has links)
There is currently little knowledge about the dynamics of invertebrates in Australian viticultural ecosystems. This study was conducted in Coonawarra vineyards over three seasons (years) and has focused on identifying natural enemies, their seasonal phenology, multiple species interactions, and potential for the suppression of the pest lepidopteran Epiphyas postvittana (Tortricidae). The work presented in this thesis shows that endemic natural enemies have far greater potential to control E. postvittana than has been realised. An initial survey identified a diverse and abundant range of potential natural enemies. Of these, the species most likely to attack E. postvittana include a predatory mite Anystis baccarum and a number of hymenopteran parasitoids. The most abundant parasitoid in the vineyards was a braconid, Dolichogenidea tasmanica. Understanding the characteristic behaviour of parasitoids in response to host density can help to gauge their potential for pest suppression. The results of large-scale field experiments showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that parasitism was consistently higher in Cabernet Sauvignon compared with Chardonnay varieties. Despite the fact that interactions among multiple species of natural enemies can increase or decrease pest suppression, particularly when they share a common prey/host, few multispecies interactions have been investigated. Laboratory studies identified a novel interaction between the predatory mite A. baccarum an abundant predator in the vine canopy, the parasitoid D. tasmanica and host E. postvittana larvae. Although A. baccarum readily ate E. postvittana eggs and free roaming larvae, they could not access larva in their silk leaf rolls. However, the addition of D. tasmanica significantly increased predation of E. postvittana larvae, by altering the behaviour of host larvae and increasing their vulnerability to the mite. Experiments conducted at a landscape level in the Coonawarra showed that D. tasmanica was also present in habitat other than vineyards including native vegetation. However, it was not present in highly disturbed habitats. Although the exact mechanism for this remains unknown, results indicate that viticultural practices and resources in the surrounding landscape can influence the presence of parasitoids. Together, the findings presented in this thesis make a significant contribution towards developing sustainable pest management in Australian viticulture. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320930 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008
72

Patch exploitation by the parasitoids of Plutella xylostella (L.): from individual behaviour to population dynamics / Xin-geng Wang.

Wang, Xin-geng January 2001 (has links)
Includes bibliographical references (leaves 204-230). / xvi, 230 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the behaviour and ecology of the two major larval parasitoids of the diamondback moth, Plutella xylostella; Cotesia plutellae and Diadegma semiclausum. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2001
73

The ecology of key arthropods for the management of Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) in Coonawarra vineyards, South Australia.

Paull, Cate January 2008 (has links)
There is currently little knowledge about the dynamics of invertebrates in Australian viticultural ecosystems. This study was conducted in Coonawarra vineyards over three seasons (years) and has focused on identifying natural enemies, their seasonal phenology, multiple species interactions, and potential for the suppression of the pest lepidopteran Epiphyas postvittana (Tortricidae). The work presented in this thesis shows that endemic natural enemies have far greater potential to control E. postvittana than has been realised. An initial survey identified a diverse and abundant range of potential natural enemies. Of these, the species most likely to attack E. postvittana include a predatory mite Anystis baccarum and a number of hymenopteran parasitoids. The most abundant parasitoid in the vineyards was a braconid, Dolichogenidea tasmanica. Understanding the characteristic behaviour of parasitoids in response to host density can help to gauge their potential for pest suppression. The results of large-scale field experiments showed that the response of D. tasmanica to the density of E. postvittana was inversely density-dependent, and that parasitism was consistently higher in Cabernet Sauvignon compared with Chardonnay varieties. Despite the fact that interactions among multiple species of natural enemies can increase or decrease pest suppression, particularly when they share a common prey/host, few multispecies interactions have been investigated. Laboratory studies identified a novel interaction between the predatory mite A. baccarum an abundant predator in the vine canopy, the parasitoid D. tasmanica and host E. postvittana larvae. Although A. baccarum readily ate E. postvittana eggs and free roaming larvae, they could not access larva in their silk leaf rolls. However, the addition of D. tasmanica significantly increased predation of E. postvittana larvae, by altering the behaviour of host larvae and increasing their vulnerability to the mite. Experiments conducted at a landscape level in the Coonawarra showed that D. tasmanica was also present in habitat other than vineyards including native vegetation. However, it was not present in highly disturbed habitats. Although the exact mechanism for this remains unknown, results indicate that viticultural practices and resources in the surrounding landscape can influence the presence of parasitoids. Together, the findings presented in this thesis make a significant contribution towards developing sustainable pest management in Australian viticulture. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320930 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008
74

The molecular mechanism of immune evasion by the eggs and larvae of the Endoparasitoid Venturia canescens in its host, Ephestia kühniella

Kinuthia, Wanja. January 1996 (has links) (PDF)
Bibliography: leaves 82-111. This thesis analyses the molecular composition of the surface components of the Endoparasitoid "Venturia canescens" using serological methods and specific sugar-binding lectins as diagnostic tools. The data reveals that the protective layer consists of at least two parts: a mucin-like glycoprotein and additional components from the wasp calyx fluid and the host hemolymph. The study suggests that the wasp larval cuticle is protected in a similar fashion to the egg chorion, except that the calyx-specific VLPs are probably replaced on the larval cuticle by host hemolymph proteins. The findings suggest that the mechanism of passive immune evasion could emerge during the evolution of the wasp-host interactions. The implication is that structurally conserved components may have similar functions in the parasitic and non parasitic species and could constitute a useful pre-adaptations for an endoparasitoid lifestyle.
75

Differential growth of roots and shoots of Douglas-fir (Pseudotsuga menziesii) seedlings infested with Cinara pseudotsugae, and population dynamics of a parasitoid wasp (Pauesia sp.) of C. pseudotsugae

Smith, Julia P. 03 July 1997 (has links)
Aphids are a widespread family of plant pests, whose abilities to suppress shoot and root growth are well documented for many terrestrial plants. Only a few studies have been conducted on conifer aphids of the genus Cinara. Cinara pseudotsugae are known to attack Douglas-fir seedlings, an important crop in the Pacific Northwest. Douglas-fir are most susceptible to aphid damage as seedlings, especially in nurseries where conditions favor aphid outbreaks. A parasitoid wasp (Pauesia sp.) attacks C. pseudotsugae, and may be useful as a biological control agent. Studies of its natural history and host interactions are needed to assess its potential as a bio-control agent. This study examined the effects of an experimental range of aphid densities on the growth of total shoot and root volume and biomass and shoot morphology of Douglas-fir seedlings. Eighteen-week tests explored short term effects of different aphid feeding intensities in both the greenhouse and field. Long term effects were tested by exposing greenhouse seedlings to 16 months of aphid feeding. The ability of the plants to recover was tested by allowing one set of seedlings to grow aphid free for one year, after being exposed to aphid feeding for 18 weeks. The success rate of parasitoids over an 18 week period was compared to aphid density in both greenhouse and field tests. Increasing aphid destiny was significantly related to decreasing root and shoot dry weights in greenhouse tests. Growth suppression increased slightly during the second year of testing, regardless of whether or not aphid feeding continued. The results for root and shoot volumes were highly variable. However, root tissue density was significantly reduced after the second year of testing. Few shoot characteristics showed consistently significant aphid effects among the trials. Stem diameter and height decreased and needle density of new buds increased significantly with aphid feeding in most tests. Root and shoot growth of field plants did not show any significant aphid effects. Percentage of parasitoid success was independent of aphid density except at the lowest aphid densities. There was a block effect on parasitoid success in the field test, that may have been a result of varying environmental conditions. These results indicate that even short term aphid feeding can have long lasting effects on plant growth and structure. The effect on shoot and root growth was small, but there were no signs of recovery. The long term effects of the reduced root tissue density on Douglas-fir is unknown. / Graduation date: 1998
76

Classical biological control of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), (Diptera:Tephritidae): natural enemy exploration and nontarget testing

Trostle Duke, Marcia Katherine 16 August 2006 (has links)
This work covers stages one through seven (of nine stages) of a classical biological control program for Mediterranean fruit fly (=medfly), Ceratitis capitata (Wiedemann). Major research objectives concentrate on stage five (exploration and collection of natural enemies), and stage seven (testing and selecting natural enemies for additional work). Coffee was collected monthly from three locations in Kenya from November 1997 through July 1999. Four species of tephritid flies and ten parasitoid species were recovered. Four guilds of parasitoids were recorded, and two egg-prepupal endoparasitoids, Fopius caudatus (Szépligeti) and F. ceratitivorus (Wharton), were discovered. The oviposition behavior of these two species is contrasted. Domination of this tropical parasitoid assemblage by koinobionts is discussed relative to the dominance of temperate fruit-infesting tephritid systems by idiobionts. Fruit handling procedures were examined for impact on overall percent emergence and specifically percent emergence of flies versus parasitoids. It was determined that stirring samples had a significant positive effect on overall emergence, however daily misting of fruit did not. The only treatment without a significant bias in fly emergence over parasitoids was the stirred/dry treatment. Effects of these results on rearing procedures are discussed. Host specificity and host suitability of parasitoids reared from coffee were examined via: (1) association of parasitoids with host flies based on characteristics of the fly puparia from which parasitoids emerged, (2) rearing of cucurbit infesting tephritids and their parasitoids in Kenya, (3) rearing of flowerhead infesting tephritids and their parasitoids in Kenya and Hawaii, and (4) host range testing of Psyttalia species in Kenya and Hawaii. These results are discussed in terms of their utility for predicting nontarget effects. Psyttalia concolor (Szépligeti) was shipped to Hawaii and tested against the nontarget gall forming tephritid Procecidochares utilis Stone introduced to control the weed Ageretina adenophora (Maui pamakani). Psyttalia concolor failed to attack the gall-forming P. utilis both in choice and no-choice tests, but readily attacked tephritid larvae offered in fruit in choice tests. Recommendations for further testing and release of the parasitoids from Kenya are discussed for Hawaii and Latin America.
77

Physiological and evolutionary consequences to Drosophila melanogaster of immune response to parasitism by the wasp Asobara tabida /

Hoang, Anhthu. January 2001 (has links)
Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 117-134).
78

Bottom-up and top-down effects on insects herbivores along a natural salinity gradient in a florida salt marsh

Albarracin, Maria Teresa 01 June 2005 (has links)
I compared the strength of bottom- up and top-down effects on insect herbivores along a natural salinity gradient in salt marsh communities in West - Central, Florida. I used a 2x2 factorial design with plots divided into four different treatments: 1) fertilizer applied to increase plant quality 2) sticky traps added to remove natural enemies (parasitoids) 3) fertilizer applied and sticky traps added and 4) control plots. These plots were placed on 7 different sites containing the salt marsh plant Borrichia frutescens along a natural stress salinity gradient. In each plot I determined the abundance of the sap sucker Pissonotus quadripustulatus, the gall maker Asphondylia borrichiae, spiders and the number of chewed leaves and bored stems. I also recorded leaf area, plant density, plant height and foliar nitrogen. Plants in fertilized plots exhibited increased height, density and leaf area.
79

The biology and ecology of Mussidia spp. (Lepidoptera : Pyralidae) and associated natural enemies in Kenya / Benjamin Kimwele Muli

Muli, Benjamin Kimwele January 2009 (has links)
Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae), an important pest of maize, cotton and Phaseolus bean in West Africa, has never been described as a crop pest from East and southern Africa (ESA). It was hypothesized that in ESA it was either kept under control by natural enemies or that there exist several populations of M. nigrivenella with different host plant ranges. Another possibility is the mis-identification of the Mussidia species in ESA. Studies were conducted in Kenya between 2005 and 2007 to assess the species diversity and host plant range of Mussidia spp. and spatial distribution studies were done on selected host plants. Later, based on the results of host plant range, surveys were conducted between 2006 and 2007 in mid-altitude coastal Kenya to establish a catalogue of parasitoids associated with Mussidia spp. The suitability of stem borers found in Kenya for development of Trichogrammatoidea sp. nr lutea Girault (Hymenoptera: Trichogrammatoidea) and the factors affecting the bionomics of Mussidia sp. in the laboratory were examined. Eight plant species were found to host two Mussidia spp. and six putative morphospecies, which occur sympatrically in the coastal region. The two Mussidia spp. were Mussidia fiorii Ceconni and de Joannis and M. nr nigrivenella. Only one Mussidia sp., M.Jiorii, was found attacking one host plant species in the mid-altitude regions. In general, the host plant range was much narrower than in West Africa. Mussidia nr nigrivenella and Mussidia "madagascariensis" larval distribution was aggregated on Canavalia cathartica Thouars. (Fabaceae) and Strychnos madagascariensis Poir. (Loganiaceae), respectively, while the distribution of M. fiorii adults on Kigelia africana (Lam.) Benth. (Bignoniaceae) was regular. Eight parasitoid species were recovered from Mussidia spp. eggs and larvae and include the trichogrammatid egg parasitoid Trichogrammatoidea sp. nr lutea Girault, a braconid egg-larval parasitoid, Phanerotoma sp., the bethylid Goniozus sp. and the braconid Apanteles sp. Moreover, the ichneumonid larval parasitoid Syzeuctus sp. was obtained from M. fiorii, while the tachinid Leskia sp. was obtained from M, "madagascariensis". Trichogrammatoidea sp. nr lutea, the only parasitoid species which was successfully reared in the laboratory, successfully attacked and developed on eggs of six lepidopteran hosts indicating its potential to exploit other alternate lepidopteran pests of maize in West Africa. Like the parasitoid species, only one Mussidia sp., M.fiorii, was successfully reared in the laboratory and it developed on maize seed-, Canavalia enseiformes L. DC (Fabaceae) seed- and maize leaf-based diets while it could not develop on Mucuna pruriens L. DC (Fabaceae) seed- and C. cathartica seed-based diets. The lower developmental thresholds for M. fiorii eggs, larvae, pupae and egg to adult were found to be 12.8±0.25°C, 14.4±0.27°C, 11.0±0.03°C and 13.5i0.2rc, respectively, while the thermal constants were 82.0±1.61, 384.6±9.43, 144.9±6.84 and 588.2±10.81 degree days, respectively. Adults started emerging during the last hour of photophase and peak emergence was observed in the 2nd hour of scotophase. Mating activity largely took place between the 4th and 5th hour of scotophase. It can be concluded that there exist several Mussidia spp. in Africa that vary in their host plant range. Overall, mortality caused by parasitoids was negligible hence they were unlikely to explain the population dynamics of the Mussidia spp. in Kenya. The fact that Trichogrammatoidea sp. nr lutea successfully attacks and develops in six lepidopteran hosts, including two Mussidia spp. indicates its potential for use as a biological agent against M. nigrivenella in West Africa. Mussidia fiorii was able to develop on diets based on maize and C. enseiformes. The knowledge on dietary and thermal requirements would optimize mass production of the host and natural enemies. The present study revealed again a serious bottleneck for biocontrol worldwide, namely the proper identification of the pest and natural enemy species as a result of an ever dwindling number of taxonomists. We therefore suggest that molecular (DNA) techniques should be used in addition to detailed morphological examination. In view of the fact that natural control will not be effective in case of accidental introduction of the West African M. nigrivenella into Kenya, we suggest stringent precautions during movement of grains especially maize between the West Africa region and Kenya. / Thesis (Ph.D. (Environmental Sciences and Management))--North-West University, Potchefstroom Campus, 2009.
80

The biology and ecology of Mussidia spp. (Lepidoptera : Pyralidae) and associated natural enemies in Kenya / Benjamin Kimwele Muli

Muli, Benjamin Kimwele January 2009 (has links)
Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae), an important pest of maize, cotton and Phaseolus bean in West Africa, has never been described as a crop pest from East and southern Africa (ESA). It was hypothesized that in ESA it was either kept under control by natural enemies or that there exist several populations of M. nigrivenella with different host plant ranges. Another possibility is the mis-identification of the Mussidia species in ESA. Studies were conducted in Kenya between 2005 and 2007 to assess the species diversity and host plant range of Mussidia spp. and spatial distribution studies were done on selected host plants. Later, based on the results of host plant range, surveys were conducted between 2006 and 2007 in mid-altitude coastal Kenya to establish a catalogue of parasitoids associated with Mussidia spp. The suitability of stem borers found in Kenya for development of Trichogrammatoidea sp. nr lutea Girault (Hymenoptera: Trichogrammatoidea) and the factors affecting the bionomics of Mussidia sp. in the laboratory were examined. Eight plant species were found to host two Mussidia spp. and six putative morphospecies, which occur sympatrically in the coastal region. The two Mussidia spp. were Mussidia fiorii Ceconni and de Joannis and M. nr nigrivenella. Only one Mussidia sp., M.Jiorii, was found attacking one host plant species in the mid-altitude regions. In general, the host plant range was much narrower than in West Africa. Mussidia nr nigrivenella and Mussidia "madagascariensis" larval distribution was aggregated on Canavalia cathartica Thouars. (Fabaceae) and Strychnos madagascariensis Poir. (Loganiaceae), respectively, while the distribution of M. fiorii adults on Kigelia africana (Lam.) Benth. (Bignoniaceae) was regular. Eight parasitoid species were recovered from Mussidia spp. eggs and larvae and include the trichogrammatid egg parasitoid Trichogrammatoidea sp. nr lutea Girault, a braconid egg-larval parasitoid, Phanerotoma sp., the bethylid Goniozus sp. and the braconid Apanteles sp. Moreover, the ichneumonid larval parasitoid Syzeuctus sp. was obtained from M. fiorii, while the tachinid Leskia sp. was obtained from M, "madagascariensis". Trichogrammatoidea sp. nr lutea, the only parasitoid species which was successfully reared in the laboratory, successfully attacked and developed on eggs of six lepidopteran hosts indicating its potential to exploit other alternate lepidopteran pests of maize in West Africa. Like the parasitoid species, only one Mussidia sp., M.fiorii, was successfully reared in the laboratory and it developed on maize seed-, Canavalia enseiformes L. DC (Fabaceae) seed- and maize leaf-based diets while it could not develop on Mucuna pruriens L. DC (Fabaceae) seed- and C. cathartica seed-based diets. The lower developmental thresholds for M. fiorii eggs, larvae, pupae and egg to adult were found to be 12.8±0.25°C, 14.4±0.27°C, 11.0±0.03°C and 13.5i0.2rc, respectively, while the thermal constants were 82.0±1.61, 384.6±9.43, 144.9±6.84 and 588.2±10.81 degree days, respectively. Adults started emerging during the last hour of photophase and peak emergence was observed in the 2nd hour of scotophase. Mating activity largely took place between the 4th and 5th hour of scotophase. It can be concluded that there exist several Mussidia spp. in Africa that vary in their host plant range. Overall, mortality caused by parasitoids was negligible hence they were unlikely to explain the population dynamics of the Mussidia spp. in Kenya. The fact that Trichogrammatoidea sp. nr lutea successfully attacks and develops in six lepidopteran hosts, including two Mussidia spp. indicates its potential for use as a biological agent against M. nigrivenella in West Africa. Mussidia fiorii was able to develop on diets based on maize and C. enseiformes. The knowledge on dietary and thermal requirements would optimize mass production of the host and natural enemies. The present study revealed again a serious bottleneck for biocontrol worldwide, namely the proper identification of the pest and natural enemy species as a result of an ever dwindling number of taxonomists. We therefore suggest that molecular (DNA) techniques should be used in addition to detailed morphological examination. In view of the fact that natural control will not be effective in case of accidental introduction of the West African M. nigrivenella into Kenya, we suggest stringent precautions during movement of grains especially maize between the West Africa region and Kenya. / Thesis (Ph.D. (Environmental Sciences and Management))--North-West University, Potchefstroom Campus, 2009.

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