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Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study
Thesis (MScConsEcol)--Stellenbosch University, 2026.
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1869484251950350336 |
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| access_status_str | Open Access |
| author | Mehlwana, Athandile |
| author2 | Veldtman, Ruan |
| author_browse | Mehlwana, Athandile Veldtman, Ruan |
| author_facet | Veldtman, Ruan Mehlwana, Athandile |
| author_sort | Mehlwana, Athandile |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScConsEcol)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136243 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-07-01T04:11:56.010Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/136243 Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study Mehlwana, Athandile Veldtman, Ruan Jubase-Tshali, Nolwethu Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. Lymantria dispar -- Geographical distribution Introduced insects -- South Africa Ships -- Inspection Biological invasions -- South Africa -- Prevention Insects -- Host plants -- Africa, Southern Risk assessment Harbors -- South Africa -- Management UCTD Thesis (MScConsEcol)--Stellenbosch University, 2026. Mehlwana, A. 2026. Assessing insect invasion risk via the shipping pathway: Potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/afd2166d-12de-4604-be3f-66e5d1efdda6 ENGLISH ABSTRACT: Lymantria dispar (Spongy moth) is a highly invasive insect species native to Eurasia and invasive in North America, and it feeds on thousands of hectares of forest and can completely defoliate forests. It is listed among the 100 worst invasive species globally. Although the species has not yet been discovered in South Africa, the country is at risk due to increasing maritime trade and travel with countries with established spongy moth populations. This study aimed to investigate how L. dispar could be accidentally introduced to South Africa through which ports, and which foreign ports would be the source of the introduction and assess the probability of establishment after transport. To determine which South African ports could be at risk of L. dispar introduction, shipping records from 2014 were analysed to determine the volume and origin of ships arriving at South Africa's five main ports. Countries were grouped based on the presence of spongy moth and flighted spongy moth populations. High-risk ships were defined as those from countries with known populations of spongy moth or flighted populations, and the proportion of ships originating from these countries was compared across ports using chi-square tests. The findings revealed that the ports of Durban and Cape Town are vulnerable entry points for invasive insect species introduced via the shipping pathway, such as L. dispar. In contrast, ports of Saldanha Bay, Richards Bay, and Port Elizabeth pose relatively lower threats, but the probability of introduction through contaminated ships or containers remains. In the second part of the study, vegetation cover around foreign ports was mapped using Sentinel-2 NDVI satellite imagery. NDVI values were extracted within a 15 km radius to estimate the probability of L. dispar females flying to ports and laying their eggs on ships or containers. Furthermore, the probability of establishment after egg transport was evaluated within a 2 km radius of the five main South African ports, also using Sentinel-2 NDVI data, and host plant surveys were conducted using Google Street View images. The findings revealed that many foreign ports sending ships to South African ports are surrounded by moderate vegetation cover, allowing for the possibility of female L. dispar flying from nearby forests to oviposit on ships or containers. This increases the probability of viable egg masses being transported to South African ports. However, vegetation cover and host plant availability around the South African ports were low. Only about 2 % of the tree genera identified around the ports were known host plants for the spongy moth. The lack of these host plants reduces the likelihood that a ballooning larva would come across suitable host plants. This is despite climatic studies indicating that coastal regions in South Africa are climatically suitable for the development of this species. In conclusion, this study shows that while the introduction risk through the international shipping pathway is high in ports of Durban and Cape Town, the likelihood of establishment near these ports is unlikely, mainly due to the lack of host trees in the immediate areas surrounding South African ports. This is because L. dispar larvae cannot complete its development without suitable host plants. Additionally, this study highlights the importance of ongoing surveillance and monitoring at both ports of Durban and Cape Town to prevent the entry of invasive insect species. AFRIKAANSE OPSOMMING: Lymantria dispar (Sponsmot) is 'n hoogs indringende insekspesie inheems aan Eurasië en indringend in Noord-Amerika, waar dit voed op duisende hektaar woud wat heeltemal ontblaar kan word. Dit word gelys onder die 100 ergste indringerspesies ter wêreld. Alhoewel die spesie nog nie in Suid-Afrika ontdek is nie, is die land in gevaar as gevolg van toenemende maritieme reis en handel met lande wat wel gevestigde sponsmotbevolkings het. Hierdie studie het ten doel gehad om te ondersoek hoe L. dispar per ongeluk in Suid-Afrika ingebring kon word. Spesiale klem is gesit op deur watter hawens, en watter buitelandse hawens die bron van die invoer sou wees en die waarskynlikheid van vestiging na vervoer te bepaal. Om te bepaal watter Suid-Afrikaanse hawens 'n risiko vir die invoer van L. dispar kan loop, is verskepingsrekords vanaf 2014 ontleed om die volume en oorsprong van skepe wat by Suid-Afrika se vyf hoofhawens aankom, te bepaal. Lande is gegroepeer op grond van die teenwoordigheid van sponsmot- en gevlieënde sponsmotbevolkings. Hoërisiko-skepe is gedefinieer as dié van lande met bekende populasies van sponsmot of gevlugte populasies. Die proporsie skepe van oorsprong uit hierdie lande is tussen hawens vergelyk met behulp van chi-kwadraattoetse. Die bevindinge het aan die lig gebring dat die hawens van Durban en Kaapstad kwesbare toegangspunte is vir indringerspesies wat via die skeepsroete ingebring word, soos L. dispar. In teenstelling hiermee hou hawens van Saldanha Bay, Richards Bay en Port Elizabeth relatief laer bedreigings in, maar die waarskynlikheid van invoer deur besmette skepe of houers bly bestaan. In die tweede deel van die studie is plantegroei rondom buitelandse hawens gekarteer met behulp van Sentinel-2 NDVI-satellietbeelde. NDVI-waardes is binne 'n radius van 15 km onttrek om die waarskynlikheid te skat dat L. dispar-wyfies na hawens vlieg en hul eiers op skepe of houers lê. Verder is die waarskynlikheid van vestiging na eiervervoer binne 'n radius van 2 km van die vyf hoof Suid-Afrikaanse hawens geëvalueer. Dit was ook met behulp van Sentinel-2 NDVI-data bepaal, en verder aangevul met gasheerplantopnames met behulp van Google Street View-beelde. Die bevindinge het aan die lig gebring dat baie buitelandse hawens wat skepe na Suid-Afrikaanse hawens stuur, omring word deur matige plantegroei, wat die moontlikheid bied dat vroulike L. dispar van nabygeleë woude kan vlieg om eier te lê op skepe of houers. Dit verhoog die waarskynlikheid dat lewensvatbare eiermassas na Suid-Afrikaanse hawens vervoer word. Die plantegroeibedekking en gasheerplantbeskikbaarheid rondom die Suid-Afrikaanse hawens was egter laag. Verder was slegs ongeveer 2 % van die geïdentifiseerde boomgenera was bekende gasheerplante vir die sponsmot. Die gebrek aan gasheerplante rondom hierdie hawens verminder die waarskynlikheid dat 'n ballonende larwes op geskikte gasheerplante sal afkom. Dit is ten spyte van klimaatstudies wat aandui dat kusstreke in Suid-Afrika klimaats geskik is vir die ontwikkeling van hierdie spesie. Ten slotte toon hierdie studie dat hoewel die invoer-risiko deur die internasionale skeepvaartroete hoog is in Durban en Kaapstad hawens, is die waarskynlikheid van vestiging naby hierdie hawens onwaarskynlik is. Dit is hoofsaaklik as gevolg van die gebrek aan gasheerbome in die onmiddellike gebiede rondom Suid-Afrikaanse hawens en omdat L. dispar-larwes nie ontwikkeling kan voltooi sonder geskikte gasheerplante nie. Daarbenewens beklemtoon hierdie studie die belangrikheid van voortdurende toesig en monitering by beide hawens van Durban en Kaapstad om die toetreding van indringerspesies te voorkom. Masters 2026-04-29T09:43:44Z 2026-04-29T09:43:44Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/136243 en Stellenbosch University xii, 68 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lymantria dispar -- Geographical distribution Introduced insects -- South Africa Ships -- Inspection Biological invasions -- South Africa -- Prevention Insects -- Host plants -- Africa, Southern Risk assessment Harbors -- South Africa -- Management UCTD Mehlwana, Athandile Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title | Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title_full | Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title_fullStr | Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title_full_unstemmed | Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title_short | Assessing insect invasion risk via the shipping pathway: potentially transporting Lymantria dispar (spongy moth) to South Africa as a case study |
| title_sort | assessing insect invasion risk via the shipping pathway potentially transporting lymantria dispar spongy moth to south africa as a case study |
| topic | Lymantria dispar -- Geographical distribution Introduced insects -- South Africa Ships -- Inspection Biological invasions -- South Africa -- Prevention Insects -- Host plants -- Africa, Southern Risk assessment Harbors -- South Africa -- Management UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/136243 |
| work_keys_str_mv | AT mehlwanaathandile assessinginsectinvasionriskviatheshippingpathwaypotentiallytransportinglymantriadisparspongymothtosouthafricaasacasestudy |