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Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa
Thesis (PhDConsEcol)--Stellenbosch University, 2021.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867613943618338816 |
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| access_status_str | Open Access |
| author | Huisamen, Elizabeth Johanna |
| author2 | Karsten, Minette |
| author_browse | Huisamen, Elizabeth Johanna Karsten, Minette |
| author_facet | Karsten, Minette Huisamen, Elizabeth Johanna |
| author_sort | Huisamen, Elizabeth Johanna |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhDConsEcol)--Stellenbosch University, 2021. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124278 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:10.803Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124278 Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa Huisamen, Elizabeth Johanna Karsten, Minette Terblanche, J. S. Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology. Crop losses -- Developing countries Insect pests -- Biological control Sterile insect technique Biological pest control agents -- South Africa False codling moth -- Biological control Codling moth Insects -- Physiology Insects -- Effect of temperature on Climatic changes Trace elements in nutrition UCTD Thesis (PhDConsEcol)--Stellenbosch University, 2021. ENGLISH ABSTRACT: Agricultural insect pests lead to substantial crop losses worldwide, with the highest losses in the developing world. With the demand for food expected to rise in the coming decades, effective solutions for pest management are urgently needed. This dissertation presents research work examining the impact of environmental factors on insect physiology in an attempt to improve the efficacy of two commonly used control measures (Sterile Insect Technique (SIT) and Insecticide use) using False codling moth (FCM; Thaumatotibia leucotreta) and Drosophila melanogaster. Firstly, I tested the impact of different rearing temperatures (constant 15°C, Fluctuating Thermal Regime (FTR): 15°C for 12h:25°C for 12h, and constant 25°C) and transport conditions (cold and engine vibration) used in the SIT programme on the life history, cold tolerance, and flight ability of FCM in the laboratory. These experiments allowed new insights into insect performance in an SIT programme. Secondly, to understand the effects of dietary salts on insect quality and performance, I tested the impact of a combination of dietary salt supplementation (either NaCL or KCL) and developmental temperature acclimation (15°C and 22°C) on flight ability in D. melanogaster. Lastly, I tested the impact of a sub-lethal dosage of the insecticide spinetoram (4mg/100ml) on developmental temperature acclimation (22°C and 28°C) and metabolic rate, life history and body composition of FCM in order to inform decisions on insecticide use. Research presented in this dissertation generated novel insights on several fronts. First, I found that FTR significantly improves flight ability, cold tolerance, and fecundity in FCM with no apparent trade-offs. In addition, transport conditions (cold temperature and vibration) used during the SIT programme for FCM did not have a significant effect on either flight ability or cold tolerance. Second, the presence of a salt (KCL) in the diet significantly reduced the benefits of cold acclimation on flight performance in D. melanogaster at least partly due to morphological changes (body size and wing size). Lastly, the insecticide spinetoram had a sub-lethal effect on FCM leading to a lower emergence rate, smaller pupal mass and a slower metabolic rate. Additionally, the sub-lethal concentration interacted with temperature in complex ways, with higher amounts of body water, body lipids and body proteins in FCM exposed to a lower acclimation temperature (22°C) compared to the warmer acclimation (28°C). In conclusion, this study provides valuable information on the impacts of biotic and abiotic factors on insect pest management strategies. The results suggest that the implementation of a FTR during rearing in the SIT programme for FCM will be beneficial. In addition, as dietary salt supplementation influences cold acclimation of flight performance in the model species D. melanogaster it suggests that the impact of dietary ions might have profound effects for insect quality in mass-rearing programmes. Lastly, as sub-lethal exposure to spinetoram has deleterious effects on FCM, spinetoram application can suppress the population into the next generation, however since a sub-lethal exposure was found to have complex interactions with temperature, these effects need to be studied in more detail in the field, particularly in relation to insecticide resistance. AFRIKAANSE OPSOMMING: Insek peste veroorsaak aansienlike verliese in gewasse wêreldwyd, waarvan die meerderheid van dié verliese in ontwikkelende lande plaasvind. Effektiewe oplossings vir pesbeheer word dringend benodig, veral met die verwagte toename in aanvraag na voedsel in die komende dekades. Hierdie verhandeling ondersoek die impak van omgewingsfaktore op insek fisiologie, met die doel om die doeltreffendheid van twee algemeen toegepaste beheermaatreëls (die Steriele Insek Tegniek (SIT) en die gebruik van insekdoders) te verbeter, deur te fokus op Valskodlingmot (VKM; Thaumatotibia leucotreta) en Drosophila melanogaster. Eerstens, is die impak van verskillende ontwikkelingstemperature (konstante 15°C, Wisselende temperature (FTR): 15°C vir 12h:25°C vir 12h, en ‘n konstante 25°C) en vervoer kondisies (koue en vibrasie van ‘n enjin) wat tans gebruik word in die SIT program getoets op die lewensgeskiedenis, weerstand teen koue en vlug vermoë van VKM in die laboratorium. Hierdie eksperimente het gelei na nuwe insig in die prestasie van insekte in ‘n SIT program. Tweedens, in ‘n poging om die effek van soute in die dieet van insekte op gevolglike kwaliteit en optrede te bepaal, is die impak van ‘n kombinasie van sout aanvullings tot die insek dieet (NaCL of KCL) en temperatuur akklimasie (15°C en 22°C) tydens ontwikkeling op die vlug vermoë van D. melanogaster getoets. Laastens, is die impak van ‘n sub-dodelike dosering van die insekdoder spinetoram (4mg/100ml) op termiese akklimasie tydens ontwikkeling (22°C en 28°C), metaboliesetempo, lewensgeskiedenis en liggaamsamestelling van VKM getoets, in ‘n poging om meer ingeligte besluite oor die gebruik van insekdoders te kan maak. Die navorsing wat in hierdie verhandeling voorgelê word, het nuwe inligting gelewer op verskeie gebiede. Eerstens het ek gevind dat FTR ‘n beduidende positiewe impak op vlug vermoë, koue toleransie en vrugbaarheid in VKM het, sonder enige beduidende nagevolge. Vervoer kondisies (koue en die vibrasie van ‘n enjin) het ook nie ‘n beduidende impak gehad op vlug vermoë of koue toleransie in VKM nie. Tweedens, het die byvoeging van ‘n sout (KCL) tot die dieet van D. melanogaster die voordele van koue akklimasie tydens vlug verlaag, deels as gevolg van gepaardgaande morfologiese veranderinge (liggaamsgrootte en vlerkgrootte). Laastens het die insekdoder Spinetoram ‘n sub-dodelike uitwerking gehad op VKM, wat gelei het tot ‘n laer uitbroei syfer, laer papie massa en ‘n stadiger metaboliese tempo. Verder het die sub-dodelike konsentrasie ‘n komplekse interaksie gehad met temperatuur met laer liggaamswater, liggaamslipiede en liggaamsproteïene in die VKM wat aan die laer akklimasie temperatuur (22°C) blootgestel is, in vergelyking met die warmer akklimasie temperatuur (28°C). Ter afsluiting, die studie het belangrike inligting voorsien oor die impak van biotiese en abiotiese faktore op insek pesbeheer strategieë. Die resultate stel voor dat die implementering van FTR tydens ontwikkeling in die SIT program vir VKM voordelig sal wees. Addisioneel, aangesien die byvoeging van ‘n sout ‘n nadelige invloed het op die koue akklimasie vir vlug vermoë in die model spesies, D. melanogaster, stel dit voor dat ione in die dieet ‘n aansienlike effek kan hê op insek kwaliteit in massa produksie programme. Laastens, aangesien ‘n sub-dodelike blootstelling aan Spinetoram negatiewe impakte op VKM gehad het, kan die toediening van Spinetoram die insek populasie moontlik tot in die volgende generasie onderdruk. Die bogenoemde effekte moet egter in meer diepte in die veld ondersoek word as gevolg van die komplekse interaksies tussen die sub-dodelike konsentrasie en temperatuur veral t.o.v. weerstandigheid tot insekdoders. Doctorate 2021-11-19T09:41:59Z 2022-02-22T10:22:45Z 2021-11-19T09:41:59Z 2021-12 Thesis http://hdl.handle.net/10019.1/124278 en_ZA Stellenbosch University xiv, 123 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Crop losses -- Developing countries Insect pests -- Biological control Sterile insect technique Biological pest control agents -- South Africa False codling moth -- Biological control Codling moth Insects -- Physiology Insects -- Effect of temperature on Climatic changes Trace elements in nutrition UCTD Huisamen, Elizabeth Johanna Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title | Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title_full | Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title_fullStr | Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title_full_unstemmed | Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title_short | Understanding interactions between environmental conditions and insect physiology to inform pest management in South Africa |
| title_sort | understanding interactions between environmental conditions and insect physiology to inform pest management in south africa |
| topic | Crop losses -- Developing countries Insect pests -- Biological control Sterile insect technique Biological pest control agents -- South Africa False codling moth -- Biological control Codling moth Insects -- Physiology Insects -- Effect of temperature on Climatic changes Trace elements in nutrition UCTD |
| url | http://hdl.handle.net/10019.1/124278 |
| work_keys_str_mv | AT huisamenelizabethjohanna understandinginteractionsbetweenenvironmentalconditionsandinsectphysiologytoinformpestmanagementinsouthafrica |