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The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production
Thesis (MScConsEcol)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613881863503872 |
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| access_status_str | Open Access |
| author | Neethling, Emma Cecile |
| author2 | Crous, Casparus J. |
| author_browse | Crous, Casparus J. Neethling, Emma Cecile |
| author_facet | Crous, Casparus J. Neethling, Emma Cecile |
| author_sort | Neethling, Emma Cecile |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScConsEcol)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131858 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:11.727Z |
| 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:10019.1/131858 The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production Neethling, Emma Cecile Crous, Casparus J. Roets, Francois Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. Pears -- Breeding -- South Africa -- Western Cape Pears -- Quality Pears -- Diseases and pests -- Control -- South Africa -- Western Cape Polyphagous shot hole borer Fruit trees -- Water requirements -- Physiological effect Phenotypic plasticity -- Effect of temperature on Orchards -- Management Beetles UCTD Thesis (MScConsEcol)--Stellenbosch University, 2024. ENGLISH ABSTRACT: This thesis investigates the impact of the invasive polyphagous shot hole borer (PSHB) beetle and its fungal symbiont Fusarium euwallaceae (FE) (together PSHB-FE) on commercial pear production, specifically focusing on the Packham's Triumph cultivar in the Western Cape, South Africa. PSHB-FE is recognized globally as a destructive pest–disease complex affecting a vast range of hardwood tree species, many of which are important to agriculture, forestry, and urban landscaping. The presence of such a destructive pest in the economically vital fruit production industry, where its full impact is yet unknown, is alarming. The study primarily evaluates the physiological and phenological responses of commercial pear trees to different levels of infestation and explores how these responses affect fruit quality, water-use efficiency (WUE), and leaf traits. After the first year of invasion, we assess the early impact of PSHB-FE on fruit quality and WUE and examines the phenotypic plasticity of tree responses to infestation. It highlights that high PSHB attack density is associated with smaller, sweeter, and duller-coloured fruit, along with reduced WUE, even in asymptomatic trees. In the second year of invasion, the assessment zoomed into the physiological and phenological changes in the host trees due to PSHB-FE infestation. Here no significant physiological stress or disruption to phenological timing was detected. The research also evaluates the potential of multispectral vegetation indices (VIs) for early detection and monitoring of PSHB-FE invasion in commercial pear crops, highlighting their application in agricultural settings. While VI results aligned with the physiological assessments, the absence of clear physiological stress in the trees limited the ability to correlate VIs with specific PSHB-FE-induced stress parameters. Overall, the risk of PSHB-FE to commercial pear production appears lower than initially anticipated. However, early stages of invasion may still significantly impact production and the continued presence of PSHB-FE in orchards cannot be disregarded. The study highlights underlying inconsistency in the water-use dynamics of highly infested trees, suggesting potential management challenges if water use becomes more variable during hot, dry productive seasons. Monitoring PSHB populations during these periods will be critical. Invasion in this orchard was likely opportunistic, facilitated by prolific hosts in surrounding vegetation, since PSHB breeding in Packham’s Triumph pears is poor and infrequent, and PSHB activity seemingly declined in the second year. We propose that any resulting stress to pear host trees closely mirrors prevailing climatic conditions and PSHB-FE activity, rather than compounding over consecutive seasons of invasion. This response may extend to other deciduous fruit species with low breeding susceptibility. Our observations emphasize the importance of safely removing infested breeding hosts surrounding orchards and call for continued research on the susceptibility of various fruit species and cultivars to PSHBFE. The findings from this study are expected to inform future research and orchard management and pest monitoring strategies to mitigate and better understand the threat posed by this invasive pest complex. AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die impak van die indringende polifagiese stompneuskewer (PSHB) en sy swamsimbiont, Fusarium euwallaceae (FE) (saam PSHB-FE), op kommersiële peerproduksie. Daar word spesefiek gefokus op die Packham’s Triumph kultivar in die Wes-Kaap, Suid-Afrika. PSHB-FE word wêreldwyd erken as 'n vernietigende plaag-siektekompleks wat 'n wye verskeidenheid hardehoutboomspesies affekteer, waarvan baie van groot belang is vir landbou, bosbou en stedelike landskapbestuur. Die teenwoordigheid van so 'n vernietigende plaag in die ekonomies belangrike vrugteproduksiebedryf, waar die volle impak daarvan nog onbekend is, is kommerwekkend. Die studie evalueer hoofsaaklik die fisiologiese en fenologiese reaksies van kommersiële peerbome tot verskillende vlakke van besmetting (aanvalsdigthede) en ondersoek hoe hierdie reaksies die vrugkwaliteit, waterverbruikdoeltreffendheid (WGD) en blaar eienskappe beïnvloed. Na die eerste jaar van inval evalueer ons die vroeë impak van PSHB-FE op vrugkwaliteit en WGD, en ondersoek die fenotipiese plastisiteit van bome se reaksies tot besmetting. Dit beklemtoon dat hoë PSHB-aanvalsdigtheid selfs in asimptomatiese bome geassosieer word met kleiner, soeter en dowwer-gekleurde vrugte, sowel as verminderde WUD. In die tweede jaar van inval is die fisiologiese en fenologiese veranderinge in die gasheerbome weens PSHB-FE- besmetting in meer diepte bestudeer. Hier is geen betekenisvolle fisiologiese stres of ontwrigting van fenologiese tydsberekening waargeneem nie. Die navorsing evalueer ook die potensiaal van multispektrale plantegroei-indekse (PGIs) vir die vroeë opsporing en monitering van PSHB-FE-inval in kommersiële peregewasse, met klem op hul toepassing in landboubestekke. Terwyl die PGI-resultate ooreenstem met die fisiologiese assesserings, word die vermoë om PGIs met spesifieke PSHB-FE-geïnduseerde stresparameters te korreleer, beperk deur die afwesigheid van duidelike fisiologiese spanning in die gasheerbome. Oor die algemeen lyk die risiko van PSHB-FE vir kommersiële pereproduksie laer as wat aanvanklik verwag is. Nietemin, die vroeë fases van indringing kan steeds 'n beduidende impak op produksie hê, en die voortgesette teenwoordigheid van PSHB-FE in vrugteboorde kan nie verontagsaam word nie. Die studie beklemtoon onderliggende onreëlmatigheid in die watergebruiksdinamika van hoogs besmette bome, wat moontlike bestuursuitdagings mag inhou as watergebruik meer wisselvallig raak gedurende warm, droë produksieseisoene. Monitering van PSHB-populasies gedurende hierdie periodes sal van kritieke belang wees. Aangesien PSHB broei in Packham’s Triumph pere swak en selde is, en PSHB-aktiwiteit skynbaar in die tweede jaar afgeneem het, was indringing in hierdie boord waarskynlik opportunisties en gefasiliteer deur besmette broei-gasheerbome in die omliggende plantegroei. Klaarblyklik weerspieël spanning op peer- gasheerbome die heersende klimaatstoestande en PSHB-FE aktiwiteit, eerder as om op te bou oor opeenvolgende invalseisoene. Hierdie reaksiepatroon mag van toepassing wees op ander bladwisselende vrugtebome met 'n lae broeisikbaarheid. Ons waarnemings beklemtoon die belang van die veilige verwydering van besmette broei-gasheere rondom boorde en doen 'n beroep op voortgesette navorsing oor die vatbaarheid van verskeie vrugte-spesies en kultivars vir PSHB-FE. Die bevindings van hierdie studie ondersteun toekomstige navorsing en boordbestuur, sowel as plaagmoniteringstrategieë, om die bedreiging van hierdie indringende plaagkompleks te verminder en beter te verstaan. Masters 2025-04-03T10:31:04Z 2025-04-03T10:31:04Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131858 Stellenbosch University 65 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Pears -- Breeding -- South Africa -- Western Cape Pears -- Quality Pears -- Diseases and pests -- Control -- South Africa -- Western Cape Polyphagous shot hole borer Fruit trees -- Water requirements -- Physiological effect Phenotypic plasticity -- Effect of temperature on Orchards -- Management Beetles UCTD Neethling, Emma Cecile The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title | The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title_full | The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title_fullStr | The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title_full_unstemmed | The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title_short | The impact of the polyphagous shot hole borer beetle and its fungal symbiont, Fusarium euwallaceae, on commercial pear production |
| title_sort | impact of the polyphagous shot hole borer beetle and its fungal symbiont fusarium euwallaceae on commercial pear production |
| topic | Pears -- Breeding -- South Africa -- Western Cape Pears -- Quality Pears -- Diseases and pests -- Control -- South Africa -- Western Cape Polyphagous shot hole borer Fruit trees -- Water requirements -- Physiological effect Phenotypic plasticity -- Effect of temperature on Orchards -- Management Beetles UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131858 |
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