Ecology and biocontrol options of the leaf miner, liriomyza huidobrensis, on potatoes in the Western Cape province
| dc.contributor.advisor | Addison, Pia | en_ZA |
| dc.contributor.advisor | Malan, Antoinette P. | en_ZA |
| dc.contributor.advisor | Visser, Diedrich | en_ZA |
| dc.contributor.author | Mugala, Thabu | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology. | en_ZA |
| dc.date.accessioned | 2021-03-01T13:31:31Z | |
| dc.date.accessioned | 2021-04-22T10:13:44Z | |
| dc.date.available | 2021-09-01T03:00:12Z | |
| dc.date.issued | 2021-04 | |
| dc.description | Thesis (MScConsEcol)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The potato leaf miner, Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae), is a devastating pest of potatoes, worldwide. However, little knowledge of the biology and ecology of this pest in South Africa exists, with both factors being cardinal elements in implementing an effective integrated pest management (IPM) programme. Control of the pest relies on the extensive use of chemical insecticides. Concerns regarding insect resistance, human safety and environmental impacts have, however, encouraged the development and use of alternative environmental control strategies, including the use of entomopathogenic nematodes (EPNs) and fungi (EPF). The present study focuses on the population dynamics of L. huidobrensis during the winter and summer period, a parasitoid survey and biological control using EPNs and EPF. The study showed differences in adult leaf miner populations in both the potato fields and the natural vegetation for both the winter and summer monitoring periods. The abundance and population densities of leaf miners increased during summer, while being very low during the winter monitoring period. The observed trend was that the leaf miner populations increased during crop development, with damage regularly being spotted on the potato leaves two weeks after plant emergence. Five parasitoid species associated with L. huidobrensis were identified during the monitoring periods, with Diglyphus isaea being the most abundant species. After assessing the occurrence of entomopathogens in the soil samples collected from the potato fields, one EPN species Heterorhabditis zealandica, one insect-associated nematode Acrobeloides sp. and two EPF species, Metarhizium robertsii and Metarhizium majus were isolated from the 16 surveyed potato fields. Four EPN species were screened for pathogenicity against the larval and pupal stages using different concentrations of infective juveniles (IJs) in the laboratory, which included Heterorhabditis bacteriophora, Heterorhabditis baujardi and Steinernema yirgalemense and which were obtained from the collection of the Department of Conservation Ecology and Entomology, Stellenbosch University, with the fourth species Heterorhabditis zealandica being isolated from the potato fields. The pathogenicity results of all the EPNs at 200 IJs/50 μl of distilled water solution indicated insect mortality of > 40 % for both the leaf mining larvae and the pupae. However, pupae and larvae trials indicated that the best performing treatment was found to be H. baujardi with more than 57 % of pupae mortality and > 71 % larvae mortality. The findings, thus, indicate the EPNs potential for adoption as part of an IPM strategy. On the other hand, two different species of EPF, namely Metarhizium robertsii and Beauveria bassiana, were tested for pathogenicity against the pupae of the potato leaf miner. The EPF were able to cause 67 % mortality. The study also screened five different isolates of M. robertsii found during the monitoring period, with the results obtained indicating very high pupae mortality of more than 80 % of pupae. The study provided a positive forecast for the management of potentially damaging populations using entomopathogens as biocontrol agents against L. huidobrensis, in potato cultivation, in South Africa. This study was a laboratory assessment and thus a first step towards further development of a management strategy. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die aartappelblaarmyner, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), is 'n ernstige pes van aartappels wêreldwyd. Daar is egter min bekend oor die biologie en ekologie van hierdie pes in Suid-Afrika en beide hierdie faktore is van kardinale belang vir die implementering van ʼn effektiewe geïntegreerde pesbeheerstelsel (IPM). Die bestryding van die L. huidobrensis is afhanklik die gebruik van chemiese insekdoders. Insekweerstand, menslike veiligheid en die effek op die omgewing het egter die ontwikkeling en gebruik van alternatiewe omgewingsbeheerstrategieë aangemoedig, insluitend die gebruik van entomopatogeniese nematodes (EPNs) en entomopatogeniese fungi (EPF). Hierdie studie fokus op die bevolkingsdinamika van L. huidobrensis gedurende die winter en somer, 'n parasitoïed opname en biologiese beheer met behulp van EPNs en EPF. Die studie het verskille getoon in die populasies van blaarmyners by volwassenes, in beide die aartappellande en die natuurlike plantegroei gedurende die winter- en somer moniterings periodes. Die bevolkingsgetalle en digtheid van blaarmyners het gedurende die somer toegeneem, terwyl dit gedurende die winter moniterings periode baie laag was. Die waargenome tendens was dat die blaarmynerpopulasies toegeneem het tydens gewas ontwikkeling, met skade wat gereeld op die aartappelblare opgemerk is twee weke na die opkoms van plante. Vyf parasitoïed spesies, wat verband hou met L. Huidobrensis, is tydens die moniteringstydperke geïdentifiseer, met Diglyphus isaea wat die mees algemeen waargeneem is. Nadat die voorkoms van entomopatogene in grondmonsters wat van 16 aartappellande versamel is, vasgestel is, is die volgende spesies geïsoleer: een EPN spesie naamlik, Heterorhabditis zealandica, een insek geassosieerde nematode, Acrobeloides sp. en twee EPF spesies, Metarhizium robertsii en Metarhizium majus. Vier EPN spesies is in die laboratorium vir patogenisiteit teen die larwale- en papiestadia getoets deur verskillende konsentrasies van infektiewe larwes (IJ's) te gebruik. Hierdie spesies sluit in: Heterorhabditis bacteriophora, Heterorhabditis baujardi en Steinernema yirgalemense wat verkry is uit die versameling van die Departement van Bewaringsekologie en Entomologie, Universiteit Stellenbosch. Die vierde spesie, H. zealandica is van die aartappellande geïsoleer. Die patogenisiteitsresultate van al die EPNs met ʼn konsentrasie van 200 IJs / 50 μl gedistilleerde water dui op insekmortaliteit van >40% vir beide die blaarmyner larwes en die papies. Papie- en larfproewe het egter aangedui dat H. baujardi die beste behandeling is met meer as 57% van die papiesterftes en >71% larvale mortaliteit. Die bevindinge dui dus op die potensiaal vir aanvaarding van EPNs as deel van 'n IPM-strategie. Twee verskillende soorte EPF, naamlik Metarhizium robertsii en Beauveria bassiana, is ook getoets vir hul vatbaarheid teen die papies van die aartappelblaarmyner. Die EPF kon tot 67% mortaliteit veroorsaak. Vyf verskillende isolate van M. robertsii, wat gedurende die moniteringstydperk gevind is, getoets en die resultate dui op 'n baie hoë papiemortaliteit van meer as 80%. Die studie dui daarop dat entomopatogene as biobeheermiddels die potensiaal het om baie suksesvol te wees vir die beheer van skadelike populasies van L. huidobrensis in aartappelverbouing in Suid-Afrika. Hierdie studie was 'n laboratorium assessering, en dus 'n eerste stap in die verdere ontwikkeling van 'n bestuurstrategie vir L. huidobrensis. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2021-09-01 | |
| dc.format.extent | (12 unnumbered pages) vii, 113 pages : illustrations (some color), maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110316 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Potatoes -- South Africa -- Western Cape | en_ZA |
| dc.subject | Entomopathogenic nematodes -- Biocontrol agents | en_ZA |
| dc.subject | Entomopathogenic fungi | en_ZA |
| dc.subject | Liriomyza huidobrensis | en_ZA |
| dc.subject | Parasitoids | en_ZA |
| dc.subject | Potato leaf miner | en_ZA |
| dc.subject | Potatoes -- Disease and pest resistance | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Ecology and biocontrol options of the leaf miner, liriomyza huidobrensis, on potatoes in the Western Cape province | en_ZA |
| dc.type | Thesis | en_ZA |