UNDERSTANDING THE FITNESS, PREFERENCE AND PERFORMANCE OF SPECIALIST HERBIVORES OF THE SOUTHERN AFRICAN BIOTYPE OF CHROMOLAENA ODORATA (ASTERACEAE), AND IMPACTS ON PHYTOCHEMISTRY AND GROWTH RATE OF THE PLANT By NONTEMBEKO DUBE Submitted in fulfillment of the academic requirement of Doctorate of Philosophy In The Discipline of Entomology School of Life Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg South Africa 2019 PREFACE The research contained in this thesis was completed by the candidate while based in the Discipline of Entomology, School of Life Sciences of the College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Pietermaritzburg campus, South Africa, under the supervision of Dr Caswell Munyai, Dr Costas Zachariades, Dr Osariyekemwen Uyi and the guidance of Prof Fanie van Heerden. The research was financially supported by the Natural Resource Management Programmes of the Department of Environmental Affairs, and Plant Health and Protection of the Agricultural Research Council. The contents of this work have not been submitted in any form to another university and, except where the work of others is acknowledged in the text, the results reported are due to investigations by the candidate. _________________________ Signed: N. Dube (Candidate) Date: 08 August 2019 __________________________ Signed: C. Munyai (Supervisor) Date: 08August 8, 2019 ________________________________ Signed: C. Zachariades (Co-supervisor) Date: 08 August 2019 _________________________________ Signed: O. Uyi (Co-supervisor) Date: 08 August 2019 ii DECLARATION 1: PLAGIARISM I, Nontembeko Dube, declare that: (i) the research reported in this dissertation, except where otherwise indicated or acknowledged, is my original work; (ii) this dissertation has not been submitted in full or in part for any degree or examination to any other university; (iii) this dissertation does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons; (iv) this dissertation does not contain other persons’ writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a) their words have been re-written but the general information attributed to them has been referenced; b) where their exact words have been used, their writing has been placed inside quotation marks, and referenced; (v) where I have used material for which publications followed, I have indicated in detail my role in the work; (vi) this dissertation is primarily a collection of material, prepared by myself, published as journal articles or presented as a poster and oral presentations at conferences. In some cases, additional material has been included; (vii) this dissertation does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the dissertation and in the References sections. _______________________ Signed: Nontembeko Dube Date: 08 August 2019 iii DECLARATION 2: PUBLICATIONS For the six experimental chapters (Chapters 3-8) in this thesis, Chapters 3 and 4 are published and Chapters 5-8 are in preparation for submission for publication to an appropriate scientific journal. My three or sometimes 4 co-authors have been included as my supervisors or because of their significant scientific input. My role in each paper and presentation is indicated. The * indicates corresponding author. Chapter 3 Dube N*, Zachariades C, Uyi OO, Munyai TC. 2017. Laboratory studies on the biology and host range of Dichrorampha odorata (Lepidoptera: Tortricidae), a biological control agent for Chromolaena odorata (Asteraceae). Biocontrol Science and Technology 27: 222-236. Dube N, Zachariades C, Munyai T, Uyi O. 2017. Biology and host range of Dichrorampha odorata (Lepidoptera: Tortricidae), a biocontrol agent of Chromolaena odorata (Asteraceae). Poster Presentation. University of KwaZulu Natal Research Day, 26 October 2017, Westville, Durban, South Africa. Chapter 4 Dube N*, Uyi O, Zachariades C, Munyai TC, Whitwell M. 2019. Impact of the shoot- boring moth Dichrorampha odorata (Lepidoptera: Tortricidae) on growth and reproductive potential of Chromolaena odorata (Asteraceae) in the laboratory. Biocontrol Science and Technology 29: 350-364. Chapter 5 Dube N, Zachariades C. 2016. Host suitability testing of a gall forming fly Polymorphomyia basilica (Diptera: Tephritidae), a potential biological control agent of Siam weed Chromolaena odorata (Asteraceae) in South Africa. 20th Australasian Weeds Conference 11-15 September 2016-Perth, Western Australia. Chapter 6-8 Dube N, Zachariades C, Uyi OO, van Heerden F, Munyai TC. 2017. Comparison of secondary compounds as influenced by Pareuchaetes insulata (Lepidoptera: Arctiidae; Erebidae) on Chromolaena odorata. 44th Annual Workshop on Biological Control of Weeds Research and Implementation, 30 October -01 November 2017, Grahamstown, South Africa. Dube N, Zachariades C, Uyi OO, van Heerden F, Munyai TC. 2018. Impact of Pareuchaetes insulata on Chromolaena odorata respective to EICA hypothesis. 45th Annual Workshop on Biological Control of Weeds Research and Implementation, 29-31 October 2018, Salt Rock, Dolphin Coast, South Africa. _______________________ iv Signed: Nontembeko Dube ABSTRACT The invasiveness and negative impacts of the alien shrub, Chromolaena odorata (L.) (Asteraceae) in South Africa resulted in the initiation of a biological control programme against the weed in the late 1980s. After the release of seven biocontrol agents, only two have successfully established to date viz. a leaf mining fly, Calycomyza eupatorivora Spencer (Diptera: Agromyzidae) and a moth with defoliating larvae, Pareuchaetes insulata Walker (Lepidoptera: Erebidae: Arctiinae). Surveys conducted suggested that C. odorata densities seem to be low in KwaZulu-Natal (KZN) province where P. insulata is present whilst its infestation is increasing in other places such as Limpopo province where the moth is absent. This study aimed to examine the life history traits, preference and performance of two biocontrol agents, viz. Dichrorampha odorata (Lepidoptera: Tortricidae) and Polymorphomyia basilica (Diptera: Tephritidae). A further objective of the study was to measure the effects of one of the established agents, P. insulata, on the competitive ability and defence mechanism of C. odorata by indirectly testing the predictions of the Evolution of Increased Competitive Ability (EICA). Studies of life history traits of D. odorata in the laboratory indicated that the moth possesses good biological control attributes such as short-lived adults with high mating success, fecundity and egg hatchability. Of the 34 asteraceous plants subjected to larval no-choice tests, only C. odorata could sustain complete development of D. odorata to adulthood, although there was slight initial boring on 14 test species (plus C. odorata). Adult no-choice tests using seven test-plant species that were damaged in larval no-choice tests were consistent with the earlier trials, with larval damage, pupae and adults of D. odorata recorded from only C. odorata. This demonstrated that only C. odorata is a suitable host for D. odorata in South Africa and permission for the release of this first shoot-tip attacking agent was granted for biocontrol of C. odorata in South Africa. To predict the efficacy of D. odorata as a biological control of C. odorata, a 9-month laboratory study was carried out. Plant growth metrics were compared across three treatments i.e. 0, 50 and 100% where newly hatched D. odorata larvae were inoculated v onto the shoot tips of C. odorata. At all treatment levels, the basal stem diameter of C. odorata was not affected by D. odorata larval feeding whilst the height of the main shoot and flower production of C. odorata were reduced at 50 and 100% relative to the control treatment. In general, the impacts of D. odorata on the weed were relatively small even though statistically significant, suggesting that the moth will modestly reduce the height and flower production of C. odorata. Positive biological characteristics of P. basilica include a high rate of increase, long-lived and mobile adults, the ability of females to produce viable offspring without repeated mating, the ability of adults to eclose from galls on dry stems and the production of several generations per year. Thirty-two asteraceous plants were investigated to determine host specificity of P. basilica in single-choice adult tests and using single pairs of adults in no- choice tests, under laboratory conditions. Oviposition and larval development through to adulthood occurred on three other South American and on two South African species; one in the same tribe Eupatorieae, closely related to C. odorata and another one in the Astereae, less closely related to the weed, but both at a lower and slower rate. Females tended to retain their eggs under no-choice conditions in the presence of an unsuitable host, and to compensate by ovipositing at a higher rate when presented later with a C. odorata plant. Overall, this study predicts the ability of P. basilica to stretch to areas where P. insulata has failed to establish and supports the suitability of P. basilica for release in South Africa. To determine the mechanism behind the decrease of C. odorata densities in KZN province, where the specialist herbivore P. insulata is present, compared to Limpopo