Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa

 

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dc.contributor.advisor Richardson, David Mark en_ZA
dc.contributor.advisor Hoffmann, John H en_ZA
dc.contributor.author Wheat, Nicola M en_ZA
dc.date.accessioned 2017-10-23T06:30:13Z
dc.date.available 2017-10-23T06:30:13Z
dc.date.issued 2004 en_ZA
dc.identifier.citation Wheat, N. 2004. Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/25722
dc.description.abstract 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. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Botany en_ZA
dc.subject.other Plant Conservation en_ZA
dc.title Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa en_ZA
dc.type Bachelor Thesis
dc.date.updated 2017-02-22T12:52:46Z
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Biological Sciences en_ZA
dc.type.qualificationlevel Honours
dc.type.qualificationname BSc (Hons) en_ZA
uct.type.filetype
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Wheat, N. M. (2004). <i>Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/25722 en_ZA
dc.identifier.chicagocitation Wheat, Nicola M. <i>"Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2004. http://hdl.handle.net/11427/25722 en_ZA
dc.identifier.vancouvercitation Wheat NM. Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2004 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/25722 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Wheat, Nicola M AB - 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. DA - 2004 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2004 T1 - Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa TI - Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa UR - http://hdl.handle.net/11427/25722 ER - en_ZA


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