Efficacy, host-finding ability and application methods of entomopathogenic nematodes to control pupae of Gonipterus sp. 2 (Coleoptera: Curculionidae)

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dc.contributor.advisor Hurley, Brett P.
dc.contributor.coadvisor Katumanyane, Agil
dc.contributor.postgraduate Rakubu, Innocent Lephaswa
dc.date.accessioned 2023-06-19T06:39:06Z
dc.date.available 2023-06-19T06:39:06Z
dc.date.created 2023-09
dc.date.issued 2023
dc.description Dissertation (MSc (Entomology))--University of Pretoria, 2023. en_US
dc.description.abstract Gonipterus sp. 2 is a pest of economic importance to South Africa as it threatens the sustainability of eucalypt plantations. The adult beetles and larvae cause damage to Eucalyptus spp. through defoliation. There are currently no insecticides registered to control Gonipterus sp. 2 and only limited control is achieved by using an egg parasitoid, Anaphes nitens. It is thus necessary to explore other alternatives such as entomopathogenic nematodes (EPNs). Entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae have a symbiotic relationship with bacteria from the genus Xenorhabdus and Photorhabdus, respectively. They are obligate parasites of many soil-dwelling insect pests of economic importance. EPNs are mass-produced for commercial purposes and distributed around the world. Despite the documented efficacy however, newly identified EPN species should be tested against economically important pests. In this study, the efficacy, host-finding ability and application methods of five local EPN species, namely Heterorhabditis noenieputensis, H. safricana, Steinernema fabii, S. jeffreyense, and S. yirgalemense, to control pupae of Gonipterus sp. 2 were investigated. Results from laboratory bioassays indicated that S. yirgalemense provided the highest pupal mortality and the lethal concentration of this EPN species was determined, namely LC50 = 45.7 IJs/pupa and LC90 = 150 IJs/pupa. Steinernema yirgalemense was also confirmed to kill pupae within their pupal cases and provided high mortality of the two pupal age groups tested, namely 1-3 days old and 9-12 days old. The host-foraging strategies of the five local EPN species were investigated by studying their movement behaviour in the presence of the host and comparing the distance they travel on a rough substrate and a smooth substrate. Heterorhabditis noenieputensis, H. safricana, S. jeffreyense, and S. yirgalemense were able to locate larvae of G. mellonella buried at a depth of 10 cm, thus causing high mortality. This suggested that the four EPN species use a cruiser foraging strategy, although this result was not supported when comparing the movement of those EPNs on the xvi two substrates. Steinernema fabii was not effective at locating the larvae of G. mellonella, resulted in low larval mortality, and showed a reduced movement on a rough substrate, suggesting that it uses an ambusher foraging strategy. The infective juveniles of S. yirgalemense applied with both nematode-infected cadavers and aqueous suspension application methods were equally and highly effective at locating and infecting Gonipterus sp. 2 pupae buried at depths of 10 cm. This is the first study in South Africa to report the potential of five local EPN species as biological control agents of pupae of Gonipterus sp. 2. en_US
dc.description.availability Unrestricted en_US
dc.description.degree MSc (Entomology) en_US
dc.description.department Zoology and Entomology en_US
dc.description.sponsorship NRF grandholder linked, UID number 40945 en_US
dc.identifier.citation * en_US
dc.identifier.doi https://doi.org/10.25403/UPresearchdata.23272268.v1 en_US
dc.identifier.other S2023
dc.identifier.uri http://hdl.handle.net/2263/91141
dc.identifier.uri DOI: 10.25403/UPresearchdata.23272268.v1
dc.language.iso en en_US
dc.publisher University of Pretoria
dc.rights © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.
dc.subject UCTD en_US
dc.subject Heterorhabditis en_US
dc.subject Virulence en_US
dc.subject Bioassay en_US
dc.subject Mortality en_US
dc.subject Steinernema
dc.subject.other Natural and agricultural sciences SDG-15
dc.subject.other SDG-15: Life on land
dc.title Efficacy, host-finding ability and application methods of entomopathogenic nematodes to control pupae of Gonipterus sp. 2 (Coleoptera: Curculionidae) en_US
dc.type Dissertation en_US


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