Show simple item record

dc.contributor.authorLavandero, B.en
dc.date.accessioned2010-05-13T02:37:48Z
dc.date.issued2004en
dc.identifier.urihttps://hdl.handle.net/10182/1851
dc.description.abstractIn this thesis, conservation biological control experiments have been conducted in the broccoli agro-ecosystem in New Zealand, to target the diamondback moth (Plutella xylostella (L.) (Lepidoptera: Hyponomeutidae)) and its key parasitoid Diadegma semiclausum (Helen) (Hymenoptera: Ichneumonidae). From a suite of flowering plants chosen for their ability in other studies to enhance parasitoid longevity and fecundity, a series of experiments in the laboratory was conducted to determine the plant's effects on the parasitoid and its host. Two plant species were chosen on the basis of their selectivity in favour of the parasitoid's fitness, rather than that of the host. These plants were buckwheat (Fagopyrum esculentum) and phacelia (Phacelia tanacetifolia). Results were compared with other parasitoid-pest systems. Buckwheat was then studied as a resource subsidy in the field. The effect of the deployment of buckwheat on parasitism rates, physiological state and abundance of the parasitoid at distances from the buckwheat was studied. Parasitism rates were doubled when buckwheat was present in the field, compared with plots with no flowers. Nevertheless, the percentage of parasitoids which had fed on nectar did not differ between flower and non-flower plots. The need for studying parasitoid movement and the associated use of markers was apparent from the field studies. Therefore, the need for effective marking and tracking techniques for studying predator and parasitoid movement was reviewed. The usefulness and limitations of marking and tracking techniques for predator and parasitoid studies was analysed. Aspects of predator and parasitoid movement are relevant to the role refugia could play in influencing, via natural enemy movements, a reduction in pest populations. Following this review, a more detailed one was conducted to determine the most promising techniques to study movement for habitat manipulation and conservation biological control studies. From the possible techniques, rubidium, a trace element was chosen to study movement after feeding on nectar of buckwheat. The marker proved useful in the field to confirm nectar feeding and movement of D. semiclausum after feeding on nectar of rubidium-sprayed buckwheat plants. Although results suggested that the parasitoids moved up to 80 m in a short period of time, parasitism rates were lower in a non-flower plot separated from a flower plot by just 60 m. It seemed clear that mobility studies alone would not give an indication of the spatial arrangement to follow in order to produce enhanced parasitism rates. Finally, the behaviour of fed and unfed parasitoids in the laboratory was studied to determine if searching behaviour could be enhanced after patch encounter. D. semiclausum spent a considerable amount of time displaying characteristic behaviours related to active searching, irrespective of the treatment. This suggests that well-fed parasitoids do not search more actively for hosts once they encounter a host-patch. However, whether the parasitoid in the field would search for more host patches and therefore parasitise more hosts when fed, as has been suggested in the literature, needs further consideration. It is clear from the results of this study and others that careful laboratory screening can increase the chances of success in conservation biological control. Further studies should not only consider the use of selective resources, but the role of these in the pattern of movement and parasitism of the parasitoid. The use of selective resource subsidies in the broccoli system can increase parasitism rates, therefore constituting an important tool to help manage P. xylostella in these conditions.en
dc.format.extent1-110en
dc.language.isoenen
dc.publisherLincoln Universityen
dc.subjectparasitoidsen
dc.subjectDiadegma semiclausumen
dc.subjectPlutella xylostellaen
dc.subjectFagopyrum esculentumen
dc.subjectPhacelia tanacetifoliaen
dc.subjectselective resource subsidiesen
dc.subjectparasitoid movementen
dc.subjectrefuge typesen
dc.subjectmarking and tracking techniquesen
dc.subjectparasitism ratesen
dc.subjectsearching behaviouren
dc.subjectrubidiumen
dc.subjectbiological controlen
dc.titleFloral resources for the enhancement of the efficacy of Diadegma semiclausum (Helen) (Hymenoptera: Ichneumonidae), a parasitoid of Plutella xylostella (L.) (Lepidoptera: Hyponomeutidae) in broccoli (Brassica oleracea L. var. italica)en
dc.typeThesis
thesis.degree.grantorLincoln Universityen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
dc.subject.marsdenFields of Research::270000 Biological Sciences::270700 Ecology and Evolution::270703 Terrestrial ecologyen
dc.subject.marsdenFields of Research::270000 Biological Sciences::270500 Zoology::270505 Entomologyen
dc.subject.marsdenFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300300 Horticulture::300303 Plant protection (pests, diseases and weeds)en
lu.contributor.unitLincoln Universityen
lu.contributor.unitFaculty of Agriculture and Life Sciencesen
lu.contributor.unitDepartment of Pest Management and Conservationen
lu.contributor.unitSoil, Plants and Ecological Sciencesen
dc.rights.accessRightsDigital thesis can be viewed by current staff and students of Lincoln University only. Print copy available for reading in Lincoln University Library. en
pubs.organisational-group/LU
pubs.organisational-group/LU/Agriculture and Life Sciences
pubs.organisational-group/LU/Agriculture and Life Sciences/ECOL
pubs.organisational-group/LU/SPES
pubs.publication-statusPublisheden
dc.publisher.placeCanterburyen


Files in this item

Default Thumbnail

This item appears in the following Collection(s)

Show simple item record