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Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa
Thesis (MScConsEcol)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613860625645568 |
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| access_status_str | Open Access |
| author | Engelbrecht, Karyn |
| author2 | Roets, Francois |
| author_browse | Engelbrecht, Karyn Roets, Francois |
| author_facet | Roets, Francois Engelbrecht, Karyn |
| author_sort | Engelbrecht, Karyn |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScConsEcol)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132201 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:42:51.481Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132201 Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa Engelbrecht, Karyn Roets, Francois Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. Fruit trees -- South Africa -- Western Cape Orchards -- Diseases and pests -- Control Beetles -- Genetic aspects Polyphagous shot hole borer beetle -- South Africa -- Western Cape Fungal diseases of plants Orchards -- Economic aspects UCTD Thesis (MScConsEcol)--Stellenbosch University, 2025. Engelbrecht, K. 2025. Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/48e132b6-8e71-4a7e-b342-362d84100db7 ENGLISH ABSTRACT: The spread of the polyphagous shot hole borer beetle (Euwallacea fornicatus; Coleoptera: Curculionidae: Scolytidae) in South Africa has caused many concerns due to the possible impact of this beetle and its main fungal symbiont, Fusarium euwallaceae, on key fruit species. It was previously discovered on deciduous fruit trees in nurseries and urban settings, but the study of PSHB in orchard settings was minimal. This study assessed the susceptibility of various deciduous fruit species and cultivars to PSHB, determined the pathogenicity of F. euwallaceae towards these hosts, and investigated a possible link between beetle establishment success and host preferences. Monitoring of pome and stone fruit orchards, and adjacent windbreak tree lines, was conducted in a mixed agricultural setting in the Western Cape province, South Africa where the beetle recently invaded. These included two pear cultivars (Pyrus communis), an apple cultivar (Malus domestica), four plum cultivars (Prunus salicina), and two windbreak tree species (Poplar and Beefwood). Low beetle attack levels were found in all monitored orchards, while high beetle infestation levels were recorded on the windbreak tree species. A substantial increase in the number of attacked trees for a ‘Packham’s Triumph’ pear orchard was observed over a 2-year period. Fusarium euwallaceae was pathogenic to all species and cultivars included here even though natural colonization success for the beetle was low in the field. The ‘African Delight,’ ‘Songold’ and ‘Black Pearl’ plum cultivars were more susceptible to F. euwallaceae than other hosts. ‘Early Bon Chretien’ (EBC) pear and Beefwood had the shortest lesion lengths caused by F. euwallaceae. Choice and no-choice experiments were conducted to determine whether PSHB actively chose more suitable hosts under laboratory conditions. Beetles failed to establish successful colonies in all hosts except for the ‘EBC’ pear cultivar. The total number of attacks and gallery formation length were highest in the two pear cultivars. No links were found between PSHB host preferences, the ease of growth of F. euwallaceae within hosts, and beetle establishment success. This supported the hypotheses that PSHB attacks hosts almost indiscriminately in its invaded range. This study confirms the first report of F. euwallaceae and its beetle associate in various commercial deciduous fruit tree orchards in South Africa, and globally. It raises concerns that PSHB may readily attack numerous deciduous fruit tree species and that it can establish viable colonies on some. However, attack levels are seemingly low for most hosts and propagule pressure from the surrounding windbreak trees and other hosts may be most influential in the numbers of attacks experienced. Managing PSHB in orchards will therefore need a specific focus on the surrounding vegetation. AFRIKAANSE OPSOMMING: Die verspreiding van die polifagiese stompneuskewer (Euwallacea fornicatus; Coleoptera: Curculionidae: Scolytidae) in Suid-Afrika het baie kommer veroorsaak weens die moontlike impak van hierdie kewer en sy hoof swamsimbiont, Fusarium euwallaceae, op belangrike vrugspesies. Dit is voorheen op bladwisselende sagtevrugtebome in kwekerye en stedelike gebiede ontdek, maar die studie van PSHB in boordinstellings was minimaal. Hierdie studie het die vatbaarheid van verskeie bladwisselende vrugspesies en kultivars vir PSHB geassesser, die patogenisiteit van F. euwallaceae teenoor hierdie gashere bepaal, en 'n moontlike koppeling tussen kewer-koloniseringsukses en gasheer-voorkeure ondersoek. Monitering van sagtevrug- en steenvrugboorde, asook aangrensende windskermboomlyne, is in 'n gemengde landbou-omgewing in die Wes-Kaap provinsie, Suid-Afrika, waar die kewer onlangs gevestig het. Dit het twee peerkultivars (Pyrus communis), 'n appelkultivar (Malus domestica), vier pruimkultivars (Prunus salicina), en twee windbreekboomspesies (Populier en Kasuarisboom) ingesluit. Lae aanvalvlakke deur kewers is in alle gemoniteerde boorde gevind, terwyl hoë vlakke van keweraanvalle in die windbreekboomspesies aangeteken is. 'n Beduidende toename in die aantal aangevalde bome vir die ‘Packham’s Triumph’-peerkultivar is oor 'n twee-jaar tydperk waargeneem. Fusarium euwallaceae was patogenies vir alle spesies en kultivars wat hier ingesluit is, alhoewel natuurlike koloniseringsukses van die kewer in die veld laag was. Die ‘African Delight,’ ‘Songold’ en ‘Black Pearl’ pruimkultivars was meer vatbaar vir F. euwallaceae as ander gashere. Die ‘Early Bon Chretien’ (EBC)-peerkultivar en Kasuarisboom het die kortste letsellengtes wat deur F. euwallaceae veroorsaak is, gehad. Keuse- en geen-keuse eksperimente is uitgevoer om vas te stel of PSHB aktief meer geskikte gashere onder laboratoriumtoestande kies. Kewers het nie daarin geslaag om suksesvolle kolonies in enige gasheer te vestig nie, behalwe vir die ‘EBC’-peerkultivar. Die totale aanvalle en galeryvorming was die hoogste in die twee peerkultivars. Geen koppeling is gevind tussen PSHB-gasheer-voorkeure, die groei van F. euwallaceae binne gashere, en kewer-koloniseringsukses nie, wat die hipotese ondersteun dat PSHB gashere byna lukraak in sy invalgebied aanval. Hierdie studie bevestig die eerste verslag van F. euwallaceae en sy kewer-assosiaat in verskeie kommersiële bladwisselende vrugteboorde in Suid-Afrika, en wêreldwyd. Dis kommerwekkend dat PSHB talle bladwisselende vrugteboomspesies maklik kan aanval en dat dit lewensvatbare kolonies op sommige kan vestig. Aanvalvlakke blyk egter laag te wees vir die meeste gashere, en die voortplantingsdruk vanaf omliggende windbreekbome en ander gashere die grootste invloed kan hê op die aantal aanvalle wat opgemerk word. Die bestuur van PSHB in boorde sal dus spesifieke fokus op die omliggende plantegroei verg. Masters 2025-05-29T12:12:17Z 2025-05-29T12:12:17Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132201 Stellenbosch University vii, 57, 6 unnumbered pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Fruit trees -- South Africa -- Western Cape Orchards -- Diseases and pests -- Control Beetles -- Genetic aspects Polyphagous shot hole borer beetle -- South Africa -- Western Cape Fungal diseases of plants Orchards -- Economic aspects UCTD Engelbrecht, Karyn Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title | Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title_full | Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title_fullStr | Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title_full_unstemmed | Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title_short | Assessing the threat of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and its symbiotic fungus (Fusarium euwallaceae) to deciduous fruit trees in the Western Cape Province of South Africa |
| title_sort | assessing the threat of the polyphagous shot hole borer beetle pshb euwallacea fornicatus and its symbiotic fungus fusarium euwallaceae to deciduous fruit trees in the western cape province of south africa |
| topic | Fruit trees -- South Africa -- Western Cape Orchards -- Diseases and pests -- Control Beetles -- Genetic aspects Polyphagous shot hole borer beetle -- South Africa -- Western Cape Fungal diseases of plants Orchards -- Economic aspects UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132201 |
| work_keys_str_mv | AT engelbrechtkaryn assessingthethreatofthepolyphagousshotholeborerbeetlepshbeuwallaceafornicatusanditssymbioticfungusfusariumeuwallaceaetodeciduousfruittreesinthewesterncapeprovinceofsouthafrica |