Impact of biocontrol agents on Lantana camara L. (Verbenaceae) in the lowveld region of Mpumalanga, South Africa By Naweji Katembo A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the academic requirements for the degree of Doctor of Philosophy School of Animal, Plant and Environmental Sciences, Johannesburg June 2018 Declaration I declare that this thesis is my own, unaided work. It is being submitted for the Degree of Doctor of Philosophy at the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination at any other University. 1st__day of __June_____2018______at Johannesburg, South Africa i Abstract Lantana camara L. (sensu lato) (Verbenaceae) remains one of the worst invasive alien plants in most tropical and subtropical parts of the world, including South Africa. Despite a concerted biological control (biocontrol) effort, with 45 biocontrol agents released against the weed worldwide since the early 1900s to date, L. camara control is far from satisfactory in most areas, including the study area. In 2012, during the initial stage of this work, a plant-ecological survey was conducted in riparian areas along the Sabie River, across an altitudinal gradient, and also in the adjacent forest plantation areas, in the province of Mpumalanga (South Africa). As a follow-up to two separate previous studies in the same area (1996/7 and 2005), aimed at determining the effectiveness of the ‘Working for Water’s (WfW) invasive alien plant (IAP) control programme, this work is another milestone in a long-term monitoring study. However, despite 16 years (1996/7-2012) of integrated IAP-control operations in the area, the WfW programme was only able to successfully remove larger overstorey IAPs, which opened-up the canopy and reduced competition, creating a conducive growing environment for an amalgamation of understorey IAPs, including L. camara, whose spread and densification were still on the rise. Biocontrol is regarded as a better alternative for long-term, sustainable and environmentally friendly IAP control, compared to the conventional mechanical and chemical methods. Most L. camara biocontrol agents introduced into South Africa have not yet had their full impact quantified under field conditions. This work is novel in that, for the first time, it quantifies the combined impact of the ‘old plus new’ suite of L. camara biocontrol agents, on the growth, reproduction and biomass of the weed under field conditions, in an inland area, through an insecticidal exclusion experiment, using carbofuran. Five prominent biocontrol agents occur on L. camara at the study sites, namely the fruit-mining fly, Ophiomyia lantanae (Froggatt) (Diptera: Agromyzidae); the shoot-sucking bug, Teleonemia scrupulosa Stål (Hemiptera: Tingidae); the defoliating moth, Hypena laceratalis Walker (Lepidoptera: Noctuidae); the leaf-mining beetle, Octotoma scabripennis Guèrin-Mèneville (Coleoptera: Chrysomelidae); and the fungal leaf-spot pathogen, cf. Passalora sp. ii (Chupp) U. Braun & Crous var. lantanae. During the course of this study, an additional agent, the flower-galling mite, Aceria lantanae (Cook) (Acari: Trombidiformes: Eriophyidae), was released and successfully established at lower altitudes (~843 m), showing an affinity for the dark-pink L. camara variety over others in the study area, namely light-pink and red-orange. Agent impact was difficult to measure because the activity of carbofuran in exclusion plants (carbofuran-treated L. camara plants) was short-lived; and therefore the impact of biocontrol agents on L. camara, which appeared to be negligible, may have been underestimated. Despite failing to maintain the ‘exclusion’ plants biocontrol agent-free through the application of carbofuran, there were reductions of 28% in the number of side-stems per plant, 31% fewer seeds in the soil seedbank, and 29% lower seed production, in ‘biocontrol’ plants compared to ‘exclusion’ plants. Although these differences were not statistically significant, they suggest that the present suite of biocontrol agents slightly reduces the vegetative and reproductive growth of L. camara. To achieve significant biocontrol of L. camara in inland areas, it seems necessary to introduce additional agents, which are well adapted to inland climatic conditions. The effects of micro-environmental factors, namely altitude and the degree of shading, were also investigated. Some biocontrol agents, such as T. scrupulosa, exhibited feeding phenological plasticity, resulting in it maintaining its presence at different altitudinal levels throughout the seasons. The performance of the suite of biocontrol agents, except A. lantanae, was, also, not limited by plant varietal differences. Additional research on biological and integrated control of L. camara is required. Keywords: Biocontrol; Biological invasion; Carbofuran; Insecticidal exclusion; Invasive alien plants; Lantana camara; Post-release evaluation. iii Acknowledgements Foremost, I would like to thank my supervisors, Prof. Marcus Byrne and Prof. Ed Witkowski, as well as my co-supervisor, Dr David Simelane, for their advice, push, and support during this wonderful journey. I am particularly grateful to Prof. Marcus Byrne, for being my teacher and mentor, for over a decade. I would also like to thank Dr Alan Urban, for taking a keen interest in my work - his valuable comments and suggestions influenced the shaping of this thesis. To my partner, Zanele Katembo (Mamu), thank you for your support and love. It will be remiss of me not to acknowledge Lindiwe Ncube (Mamiza). Thank you for loving me and believing in me throughout this journey. To my parents, mwanta Katembo Kainda and mama Kashala Omba Katembo, and my entire family, particularly my big brother Dr K. Katembo, thank you so very much for providing a solid family support system. I am so grateful to each and every one of you. “…na sakilili hama kud’eyi Katembo, Mwini Kansas Kazol, Mweni Ngidju, Ngidju ya panshi, yakwiulu ya yeni, ami Mwin’amwana, Chinga namwana Kajiba, Kajiba ka mwinshinda, Ngoni wa milemba ntenkantenka…” To my comrades-in-arms, most of whom assisted in my field work, Samalesu Mayonde (‘Dr Blood)’, Dr Lutendo Mugwedi (‘Munna’), Tafuma Sasa (‘Muammar’), Kaddy Kalima (‘Sportif’), Dr Solomon Newete (‘Uncle’), and Lusa Kalumba (‘le frère’), thank you for being my witnesses. I would like to thank the South African Forestry Company Ltd (SAFCOL), formerly known as Komatiland Forests Pty Ltd, for allowing this study to be conducted in and around their plantations. This work would not have been possible without financial support from the Working for Water (WfW), for which I am very grateful. Lastly, I would like to express my gratitude to the University of the Witwatersrand for providing research facilities, without which this work would not have been completed. iv Table of Contents Declaration ......................................................................................................................... i Abstract.............................................................................................................................. ii Acknowledgements ........................................................................................................... iv Table of Contents ...............................................................................................................v List of Figures .................................................................................................................. viii List of Tables ................................................................................................................... xiii Glossary ............................................................................................................................ xv Chapter One: General Introduction ............................................................................... 1 1.1 Background ........................................................................................................... 2 1.2 Lantana camara L. (sensu lato) (Verbenaceae) .................................................. 3 1.2.1 Lantana camara taxonomy and varieties ..................................................... 3 1.2.2 Impacts of Lantana camara .......................................................................... 4 1.2.3 Lantana camara in South Africa .................................................................. 5 1.3 Biocontrol .............................................................................................................. 6 1.3.1 Biocontrol of Lantana camara in South Africa ........................................... 7 1.3.2 Some factors limiting biocontrol ................................................................ 10 1.4 Post-release evaluation of biocontrol agents ..................................................... 11 1.5 Choosing insecticides to use in an exclusion experiment ................................. 12 1.6 Rationale for the study ....................................................................................... 14 1.7 Field sites ............................................................................................................. 15 1.8 Aims and objectives ............................................................................................ 16 1.8.1 Research questions ...................................................................................... 16 1.9