{"id":{"repo_id":"stellenbosch","oai_identifier":"oai:scholar.sun.ac.za:10019.1/135656"},"canonical_url":"https://search.dev.ndltd.org/etd/stellenbosch/oai:scholar.sun.ac.za:10019.1/135656","repository":{"repo_id":"stellenbosch","name":"Stellenbosch University","base_url":"https://scholar.sun.ac.za/server/oai/request"},"display":{"title":"The bioecology of Dacus ciliatus (Diptera: Tephritidae) in a butternut squash production system within the Western Cape of South Africa","abstract":"ENGLISH ABSTRACT: The lesser pumpkin fly, Dacus ciliatus (Loew), is a major pest of butternut squash (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in the Western Cape Province of South Africa. Despite its economic significance, limited research on its bioecology and the absence of effective monitoring protocols have constrained the development of sustainable Integrated Pest Management (IPM). This thesis investigated the bioecology of D. ciliatus in a commercial butternut production system with the primary aims of optimising an adult monitoring protocol using commercially available tools and characterising its seasonal population dynamics and its relationship to crop damage. Field studies demonstrated that a monitoring system using McPhail traps baited with Questlure™ and placed above crop canopy height (approximately 50 cm above ground surface) was the most effective, capturing significantly more flies than traps baited with Biolure™ or those placed higher (150 cm). In the Questlure™ + 50 cm treatment, females predominated, with a male-to-female ratio of approximately 1:3. Using this optimised system, seasonal population dynamics were found to be strongly influenced by host availability and sowing dates, with fly populations at two sites peaking late summer (February) and mid-autumn (April), respectively. The most vulnerable crop stage was identified as small, immature butternuts (<200 g), which accounted for over 80% of recorded infestations. These small fruit act as the primary breeding substrate, producing approximately 20 flies per 100 g of infested tissue and fuelling population growth. Crucially, a statistically significant positive relationship was established between trap captures, measured as flies per trap per day (FTD), and the probability of fruit damage. The odds of damage increase by approximately 10.6% for each one-unit increase in FTD. This model demonstrates that as trap captures rise from 0 to 20 FTD, the probability of fruit damage increases to approximately 40%, providing a clear, quantitative early-warning signal for growers. Collectively, these findings provide a foundational understanding of the bioecology of D. ciliatus and present the first evidence-based, quantitative tool for predicting infestation risk in the region’s commercial butternut systems. This work validates a practical monitoring protocol and provides the predictive model necessary for the future development of data-driven economic thresholds and more effective IPM strategies for this pest.","abstract_html":"ENGLISH ABSTRACT: The lesser pumpkin fly, Dacus ciliatus (Loew), is a major pest of butternut squash (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in the Western Cape Province of South Africa. Despite its economic significance, limited research on its bioecology and the absence of effective monitoring protocols have constrained the development of sustainable Integrated Pest Management (IPM). This thesis investigated the bioecology of D. ciliatus in a commercial butternut production system with the primary aims of optimising an adult monitoring protocol using commercially available tools and characterising its seasonal population dynamics and its relationship to crop damage. Field studies demonstrated that a monitoring system using McPhail traps baited with Questlure™ and placed above crop canopy height (approximately 50 cm above ground surface) was the most effective, capturing significantly more flies than traps baited with Biolure™ or those placed higher (150 cm). In the Questlure™ + 50 cm treatment, females predominated, with a male-to-female ratio of approximately 1:3. Using this optimised system, seasonal population dynamics were found to be strongly influenced by host availability and sowing dates, with fly populations at two sites peaking late summer (February) and mid-autumn (April), respectively. The most vulnerable crop stage was identified as small, immature butternuts (&lt;200 g), which accounted for over 80% of recorded infestations. These small fruit act as the primary breeding substrate, producing approximately 20 flies per 100 g of infested tissue and fuelling population growth. Crucially, a statistically significant positive relationship was established between trap captures, measured as flies per trap per day (FTD), and the probability of fruit damage. The odds of damage increase by approximately 10.6% for each one-unit increase in FTD. This model demonstrates that as trap captures rise from 0 to 20 FTD, the probability of fruit damage increases to approximately 40%, providing a clear, quantitative early-warning signal for growers. Collectively, these findings provide a foundational understanding of the bioecology of D. ciliatus and present the first evidence-based, quantitative tool for predicting infestation risk in the region’s commercial butternut systems. This work validates a practical monitoring protocol and provides the predictive model necessary for the future development of data-driven economic thresholds and more effective IPM strategies for this pest.","abstract_has_math":false,"creators":["Van Rooyen, Rigardt Johan"],"institution":"Stellenbosch : Stellenbosch University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Addison, Pia","Bekker, Gerard Francois Hermanus van Ginkel"],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-03","date_published":"2026-03","updated_at":"2026-07-24T04:40:12Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholar.sun.ac.za/handle/10019.1/135656","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Addison, Pia","Bekker, Gerard Francois Hermanus van Ginkel"]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology."]},{"key":"dc:creator","label":"Author","values":["Van Rooyen, Rigardt Johan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-04-07T09:03:41Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-04-07T09:03:41Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-03"]},{"key":"dc:publisher","label":"Institution","values":["Stellenbosch : Stellenbosch University"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://scholar.sun.ac.za/handle/10019.1/135656"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis (MScConsEcol)--Stellenbosch University, 2026.","Van Rooyen, R. J. 2026. The bioecology of Dacus ciliatus (Diptera: Tephritidae) in a butternut squash production system within the Western Cape of South Africa. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/a4a45fee-062f-4d78-b9b2-368266557259"]},{"key":"dc:description.abstract","label":"Abstract","values":["ENGLISH ABSTRACT: The lesser pumpkin fly, Dacus ciliatus (Loew), is a major pest of butternut squash (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in the Western Cape Province of South Africa. Despite its economic significance, limited research on its bioecology and the absence of effective monitoring protocols have constrained the development of sustainable Integrated Pest Management (IPM). This thesis investigated the bioecology of D. ciliatus in a commercial butternut production system with the primary aims of optimising an adult monitoring protocol using commercially available tools and characterising its seasonal population dynamics and its relationship to crop damage. Field studies demonstrated that a monitoring system using McPhail traps baited with Questlure™ and placed above crop canopy height (approximately 50 cm above ground surface) was the most effective, capturing significantly more flies than traps baited with Biolure™ or those placed higher (150 cm). In the Questlure™ + 50 cm treatment, females predominated, with a male-to-female ratio of approximately 1:3. Using this optimised system, seasonal population dynamics were found to be strongly influenced by host availability and sowing dates, with fly populations at two sites peaking late summer (February) and mid-autumn (April), respectively. The most vulnerable crop stage was identified as small, immature butternuts (<200 g), which accounted for over 80% of recorded infestations. These small fruit act as the primary breeding substrate, producing approximately 20 flies per 100 g of infested tissue and fuelling population growth. Crucially, a statistically significant positive relationship was established between trap captures, measured as flies per trap per day (FTD), and the probability of fruit damage. The odds of damage increase by approximately 10.6% for each one-unit increase in FTD. This model demonstrates that as trap captures rise from 0 to 20 FTD, the probability of fruit damage increases to approximately 40%, providing a clear, quantitative early-warning signal for growers. Collectively, these findings provide a foundational understanding of the bioecology of D. ciliatus and present the first evidence-based, quantitative tool for predicting infestation risk in the region’s commercial butternut systems. This work validates a practical monitoring protocol and provides the predictive model necessary for the future development of data-driven economic thresholds and more effective IPM strategies for this pest.","AFRIKAANSE OPSOMMING: Die pampoenvlieg, Dacus ciliatus (Loew), is ‘n belangrike plaag van botterskorsies (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in die Wes-Kaap van Suid-Afrika. Ten spyte van sy ekonomiese belang het beperkte navorsing oor sy bio-ekologie en die afwesigheid van doeltreffende volwasse moniteringsprotokolle die ontwikkeling van volhoubare Geïntegreerde Plaagbestuur (“Integrated Pest Management” – IPM) belemmer. Hierdie tesis het die bio-ekologie van D. ciliatus in ‘n kommersiële botterskorsie-produksiestelsel ondersoek, met die hoofdoel om ‘n moniteringsprotokol te optimaliseer deur kommersieel-beskikbare moniteringshulpmiddels te gebruik, asook om die plaag se seisoenale bevolkingsdinamika en die verband met gewasskade te bepaal. Veldstudies het getoon dat ‘n moniteringstelsel wat McPhail-lokvalle gebruik, met Questlure™–lokaas en geplaas bokant die blare van die botterskorsieplant (ongeveer 50 cm bo grondvlak), die doeltreffendste was en beduidend meer vlieë gevang het as lokvalle met Biolure™–lokaas of lokvalle wat hoër geplaas is (150 cm). Met hierdie geoptimaliseerde stelsel is bevind dat die seisoenale bevolkingsdinamika sterk beïvloed word deur gasheerbeskikbaarheid en saaidatums, met vliegpopulasies wat op twee plase onderskeidelik laat somer (Februarie) en middel herfs (April) hul hoogtepunte bereik het. Klein, onvolwasse botterskorsies (<200 g), is geïdentifiseer as die mees kwesbare gewasstadium, waarvan meer as 80% van skade in hierdie stadium geval het. Hierdie klein vruggrootte maak ‘n noemenswaardige bydra tot populasiegroei, siende dat ongeveer 20 vlieë per 100 g besmette botterskorsie kan ontwikkel. ‘n Statisties beduidende positiewe verband is vasgestel tussen lokvaltellings, gemeet as vlieë per lokval per dag (FTD (flies per trap per day)), en die waarskynlikheid van skade. Die kans op skade neem met ongeveer 10.6% toe vir elke eenheid toename in FTD. Hierdie model toon dat, namate vangsyfers van lae vlakke tot 20 FTD styg, die waarskynlikheid van vrugskade tot ongeveer 40% verhoog, wat ‘n duidelike, kwantitatiewe vroeë-waarskuwingsein vir produsente bied. Gesamentlik verskaf hierdie bevindings ‘n fundamentele begrip van die bio-ekologie van D. ciliatus en bied dit die eerste kwantitatiewe hulpmiddel om die risiko van besmetting van botterskorsies deur D. ciliatus in kommersiële produksiestelsels te voorspel. Hierdie werk het ‘n praktiese moniteringsprotokol vasgestel en voorsien die voorspellende model wat nodig is vir die toekomstige ontwikkeling van databestuurde ekonomiese drempelwaardes en meer doeltreffende IPM-strategieë vir hierdie plaag."]},{"key":"dc:title","label":"Title","values":["The bioecology of Dacus ciliatus (Diptera: Tephritidae) in a butternut squash production system within the Western Cape of South Africa"]}]}],"canonical_facts":{"dc:contributor.advisor":["Addison, Pia","Bekker, Gerard Francois Hermanus van Ginkel"],"dc:contributor.other":["Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology."],"dc:creator":["Van Rooyen, Rigardt Johan"],"dc:date.accessioned":["2026-04-07T09:03:41Z"],"dc:date.available":["2026-04-07T09:03:41Z"],"dc:date.issued":["2026-03"],"dc:description":["Thesis (MScConsEcol)--Stellenbosch University, 2026.","Van Rooyen, R. J. 2026. The bioecology of Dacus ciliatus (Diptera: Tephritidae) in a butternut squash production system within the Western Cape of South Africa. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/a4a45fee-062f-4d78-b9b2-368266557259"],"dc:description.abstract":["ENGLISH ABSTRACT: The lesser pumpkin fly, Dacus ciliatus (Loew), is a major pest of butternut squash (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in the Western Cape Province of South Africa. Despite its economic significance, limited research on its bioecology and the absence of effective monitoring protocols have constrained the development of sustainable Integrated Pest Management (IPM). This thesis investigated the bioecology of D. ciliatus in a commercial butternut production system with the primary aims of optimising an adult monitoring protocol using commercially available tools and characterising its seasonal population dynamics and its relationship to crop damage. Field studies demonstrated that a monitoring system using McPhail traps baited with Questlure™ and placed above crop canopy height (approximately 50 cm above ground surface) was the most effective, capturing significantly more flies than traps baited with Biolure™ or those placed higher (150 cm). In the Questlure™ + 50 cm treatment, females predominated, with a male-to-female ratio of approximately 1:3. Using this optimised system, seasonal population dynamics were found to be strongly influenced by host availability and sowing dates, with fly populations at two sites peaking late summer (February) and mid-autumn (April), respectively. The most vulnerable crop stage was identified as small, immature butternuts (<200 g), which accounted for over 80% of recorded infestations. These small fruit act as the primary breeding substrate, producing approximately 20 flies per 100 g of infested tissue and fuelling population growth. Crucially, a statistically significant positive relationship was established between trap captures, measured as flies per trap per day (FTD), and the probability of fruit damage. The odds of damage increase by approximately 10.6% for each one-unit increase in FTD. This model demonstrates that as trap captures rise from 0 to 20 FTD, the probability of fruit damage increases to approximately 40%, providing a clear, quantitative early-warning signal for growers. Collectively, these findings provide a foundational understanding of the bioecology of D. ciliatus and present the first evidence-based, quantitative tool for predicting infestation risk in the region’s commercial butternut systems. This work validates a practical monitoring protocol and provides the predictive model necessary for the future development of data-driven economic thresholds and more effective IPM strategies for this pest.","AFRIKAANSE OPSOMMING: Die pampoenvlieg, Dacus ciliatus (Loew), is ‘n belangrike plaag van botterskorsies (Cucurbita moschata Duchesne, 1786 (Cucurbitaceae)) in die Wes-Kaap van Suid-Afrika. Ten spyte van sy ekonomiese belang het beperkte navorsing oor sy bio-ekologie en die afwesigheid van doeltreffende volwasse moniteringsprotokolle die ontwikkeling van volhoubare Geïntegreerde Plaagbestuur (“Integrated Pest Management” – IPM) belemmer. Hierdie tesis het die bio-ekologie van D. ciliatus in ‘n kommersiële botterskorsie-produksiestelsel ondersoek, met die hoofdoel om ‘n moniteringsprotokol te optimaliseer deur kommersieel-beskikbare moniteringshulpmiddels te gebruik, asook om die plaag se seisoenale bevolkingsdinamika en die verband met gewasskade te bepaal. Veldstudies het getoon dat ‘n moniteringstelsel wat McPhail-lokvalle gebruik, met Questlure™–lokaas en geplaas bokant die blare van die botterskorsieplant (ongeveer 50 cm bo grondvlak), die doeltreffendste was en beduidend meer vlieë gevang het as lokvalle met Biolure™–lokaas of lokvalle wat hoër geplaas is (150 cm). Met hierdie geoptimaliseerde stelsel is bevind dat die seisoenale bevolkingsdinamika sterk beïvloed word deur gasheerbeskikbaarheid en saaidatums, met vliegpopulasies wat op twee plase onderskeidelik laat somer (Februarie) en middel herfs (April) hul hoogtepunte bereik het. Klein, onvolwasse botterskorsies (<200 g), is geïdentifiseer as die mees kwesbare gewasstadium, waarvan meer as 80% van skade in hierdie stadium geval het. Hierdie klein vruggrootte maak ‘n noemenswaardige bydra tot populasiegroei, siende dat ongeveer 20 vlieë per 100 g besmette botterskorsie kan ontwikkel. ‘n Statisties beduidende positiewe verband is vasgestel tussen lokvaltellings, gemeet as vlieë per lokval per dag (FTD (flies per trap per day)), en die waarskynlikheid van skade. Die kans op skade neem met ongeveer 10.6% toe vir elke eenheid toename in FTD. Hierdie model toon dat, namate vangsyfers van lae vlakke tot 20 FTD styg, die waarskynlikheid van vrugskade tot ongeveer 40% verhoog, wat ‘n duidelike, kwantitatiewe vroeë-waarskuwingsein vir produsente bied. Gesamentlik verskaf hierdie bevindings ‘n fundamentele begrip van die bio-ekologie van D. ciliatus en bied dit die eerste kwantitatiewe hulpmiddel om die risiko van besmetting van botterskorsies deur D. ciliatus in kommersiële produksiestelsels te voorspel. Hierdie werk het ‘n praktiese moniteringsprotokol vasgestel en voorsien die voorspellende model wat nodig is vir die toekomstige ontwikkeling van databestuurde ekonomiese drempelwaardes en meer doeltreffende IPM-strategieë vir hierdie plaag."],"dc:identifier.uri":["https://scholar.sun.ac.za/handle/10019.1/135656"],"dc:language.iso":["en"],"dc:publisher":["Stellenbosch : Stellenbosch University"],"dc:title":["The bioecology of Dacus ciliatus (Diptera: Tephritidae) in a butternut squash production system within the Western Cape of South Africa"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T04:40:12Z"}