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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 (MSc)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867614009090375680 |
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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 (MSc)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136243 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:13.015Z |
| 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. Thesis (MSc)--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 Unpublished masters thesis.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 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. 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 81 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | 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 |
| url | https://scholar.sun.ac.za/handle/10019.1/136243 |
| work_keys_str_mv | AT mehlwanaathandile assessinginsectinvasionriskviatheshippingpathwaypotentiallytransportinglymantriadisparspongymothtosouthafricaasacasestudy |