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Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum
Leptospermum laevigatum is one of the top five invading species in the fynbos biome and its biocontrol is of high conservation priority in the Western Cape. The first species used as a biocontrol agent was a leaf-mining moth Parectopa thalassias that became established and wide-spread. The second ag...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2017
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| _version_ | 1867613301480882176 |
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| access_status_str | Open Access |
| author | Evans, Adrian |
| author_browse | Evans, Adrian |
| author_facet | Evans, Adrian |
| author_sort | Evans, Adrian |
| collection | Thesis |
| description | Leptospermum laevigatum is one of the top five invading species in the fynbos biome and its biocontrol is of high conservation priority in the Western Cape. The first species used as a biocontrol agent was a leaf-mining moth Parectopa thalassias that became established and wide-spread. The second agent a Dasineura sp (Cecidomyiidae) gall midge whose origin in unknown but was probably introduced accidentally. As it was not screened before release an investigation into the effect of parasitism on its effectiveness as a control agent is important. Midges were found to select plants for oviposition that have high growth rates and result in large galls. This results in plants with lots of large galls. These plants are conspicuous to parasites and levels of parasitism are highest at these sites. Once the plant has been selected by the parasitoid, gall selection for oviposition was not related to density of the midges within. The spatial scale showed the dispersal of the midge was primarily related to the prevailing westerly wind. Parasitism levels followed the spread of the midge and increased as midge densities increased. The midge is still spreading and indications show parasitiods do not prevent establishment into new areas. As this is the midges most vulnerable phase, once they are established they should persist. However even at the sites with high number of galls the plants still produced fruits with seeds. Thus high parasitism levels could reduce the population densities of the midge and inhibit is usefulness as a biocontrol agent. A further biocontrol agent that attacks these reproductive parts could result in the successful control of this invasive species. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/25779 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:57.504Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/25779 Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum Evans, Adrian Botany Leptospermum laevigatum is one of the top five invading species in the fynbos biome and its biocontrol is of high conservation priority in the Western Cape. The first species used as a biocontrol agent was a leaf-mining moth Parectopa thalassias that became established and wide-spread. The second agent a Dasineura sp (Cecidomyiidae) gall midge whose origin in unknown but was probably introduced accidentally. As it was not screened before release an investigation into the effect of parasitism on its effectiveness as a control agent is important. Midges were found to select plants for oviposition that have high growth rates and result in large galls. This results in plants with lots of large galls. These plants are conspicuous to parasites and levels of parasitism are highest at these sites. Once the plant has been selected by the parasitoid, gall selection for oviposition was not related to density of the midges within. The spatial scale showed the dispersal of the midge was primarily related to the prevailing westerly wind. Parasitism levels followed the spread of the midge and increased as midge densities increased. The midge is still spreading and indications show parasitiods do not prevent establishment into new areas. As this is the midges most vulnerable phase, once they are established they should persist. However even at the sites with high number of galls the plants still produced fruits with seeds. Thus high parasitism levels could reduce the population densities of the midge and inhibit is usefulness as a biocontrol agent. A further biocontrol agent that attacks these reproductive parts could result in the successful control of this invasive species. 2017-10-25T08:18:43Z 2017-10-25T08:18:43Z 2001 2017-02-21T10:15:15Z Bachelor Thesis Honours BSc (Hons) http://hdl.handle.net/11427/25779 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Botany Evans, Adrian Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| thesis_degree_str | Bachelor's / Honours |
| title | Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| title_full | Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| title_fullStr | Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| title_full_unstemmed | Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| title_short | Investigation into the effects of parasitoids on a gall midge Dasineura sp. (Cecidomyiidae), a biological control agent of Australian myrtle, Leptospermum laevigatum |
| title_sort | investigation into the effects of parasitoids on a gall midge dasineura sp cecidomyiidae a biological control agent of australian myrtle leptospermum laevigatum |
| topic | Botany |
| url | http://hdl.handle.net/11427/25779 |
| work_keys_str_mv | AT evansadrian investigationintotheeffectsofparasitoidsonagallmidgedasineuraspcecidomyiidaeabiologicalcontrolagentofaustralianmyrtleleptospermumlaevigatum |