Visual and olfactory cues used in host location by the blister beetle Hycleus apicicornis (Coleoptera: Meloidae), a pest of Desmodium (Fabaceae) species Lefulesele Nteletsana Lebesa © University of Pretoria Visual and olfactory cues used in host location by the blister beetle Hycleus apicicornis (Coleoptera: Meloidae), a pest of Desmodium (Fabaceae) species by Lefulesele Nteletsana Lebesa Submitted in partial fulfilment of the requirements for the degree Philosophiae Doctor (Entomology) In the Faculty of Natural and Agricultural Science Department of Zoology & Entomology University of Pretoria December 2012 © University of Pretoria Dedication For my family My lovely daughters, Khabiso, Boitumelo and Boikhabo, this piece of work is dedicated to you. I thank you because you waited for me to come back home and be a mother after a long absence. I thank God, Almighty for sustaining you throughout the waiting period. I thank my two mothers, my late mom, ‘Maitumeleng Masakale and my mother-in law, ‘Makatleho Lebesa. My mom single-handedly raised me and it was with her trust in the Lord, her determination and encouragement that I knew any heights could be reached. Mom-in-law, ‘thank you for being the pillar of support and portraying the true qualities of a parent.’ The rest of the family, I thank you for your continued support and for standing as a united team behind me. Men love to wonder, and that is the seed of science. (Ralph Waldo Emerson) May we keep on planting the seed. i © University of Pretoria Abstract Visual and olfactory cues used in host location by the blister beetle Hycleus apicicornis (Coleoptera: Meloidae), a pest of Desmodium (Fabaceae) species Student: Lefulesele Nteletsana Lebesa Supervisors: Prof. Kerstin Krüger (University of Pretoria) Co-supervisor: Dr Zeyaur R. Khan (ICIPE) Department: Department of Zoology & Entomology, University of Pretoria Degree: Philosophiae Doctor Abstract Desmodium spp. are leguminous plants mainly used as livestock fodder. In Kenya and neighbouring countries they are also used in a „push-pull‟ strategy by smallholder farmers to protect maize (Zea mays) against two major groups of pests, stemborers (Lepidoptera) and witchweed, Striga spp., by repelling the former away from the cereal crop and suppressing growth of the latter. However, smallholder seed production of Desmodium spp. is compromised by blister beetles Hycleus spp. (Coleoptera: Meloidae) which feed on the flower petals and adversely affect seed setting. The objective of this study was to determine the behavioural responses of Hycleus apicicornis (Guér.) (Coleoptera: Meloidae) towards olfactory and visual cues from host plants, and the impact of these cues on resource-finding by this beetle. The present findings should be of future use in developing a trapping system to manage this pest. A farmer questionnaire and a field survey were used to determine the pest status and host range of blister beetles. Desmodium spp. were identified as the most preferred ii © University of Pretoria Abstract followed by beans (Phaseolus vulgaris) and sweetpotato (Ipomoea batatas). Fewer farmers mentioned cowpea (Vigna unguiculata) and maize as additional host plants. Based on the questionnaire, the field survey and a literature review on potential host plants for blister beetles, D. uncinatum, I. batatas, P. vulgaris, V. unguiculata, Abelmoschus esculentus, and Ipomoea hildebrandtii (a local wild host) were chosen for subsequent experiments. Behavioural studies were undertaken to determine i) the impact of visual cues on their host locating and landing behaviours, ii) responses of beetles towards volatiles released by individual host plants, iii) responses of beetles towards extracts of flowers of host plants and two synthetic compounds and iv) orientation and settling preferences of Hycleus apicicornis towards different host plants in the laboratory. Beetles were significantly attracted to sky blue (with maximum spectral reflectance of 73% around 450 nm), which was preferred over other colours tested (black, red, yellow, white and green) and other shades of blue (turquoise and dark blue). Beetles also showed a high preference for odours of cut flowers of D. uncinatum, I. batatas and P. vulgaris, and 2-phenylethanol and phenylacetaldehyde but not for intact flowers in olfactometer bioassays. In the orientation and settling experiment, cut flowers of A. esculentus were attractive in addition to P. vulgaris, D. uncinatum and I. batatas. Volatiles were collected from A. esculentus, D. uncinatum, P vulgaris and V. unguiculata through air-entrainment techniques and analysed with gas chromatography coupled with mass spectrometry (GC- MS) to identify volatile compounds that may be inducing behavioural responses of adult beetles. Qualitative and quantitative differences were observed between and within the chemical profiles of the four host plant species. This study provides baseline information required for the development of a trapping system for the management of blister beetles on Desmodium spp. or other potential host crops by making use of visual and olfactory cues. A stronger response was iii © University of Pretoria Abstract obtained with the visual cues compared to olfactory cues suggesting that H. apicicornis may be using visual cues for long range while the olfactory is used at close range during host location. iv © University of Pretoria Acknowledgements Acknowledgements First and foremost I am grateful to my supervisors, Dr Khan and Dr Krüger for tirelessly providing guidance throughout this study and who did not only give academic support but also provided or facilitated provision for my personal needs both in Kenya and in South Africa. I am also thankful to the rest of the supervisory team, Prof. A. Hassanali, Prof. J.A. Pickett and Dr Toby Bruce who guided me and transferred their skills to me. Prof. Hassanali and Dr Bruce, I am forever grateful for your presence because there was a time I did not want to continue but you believed in me, you were very patient with me and inspired me to move on. My sincere gratitude to the Habitat Management Project team: i) Dr D. Amudavi, Mr I. Mbeche, Dr C. Midega, Dr A. Murage, Dr E. Njuguna, Mr J. Pittchar and Dr A. Tameru for their expertise in the design of my experiments, reading and providing valuable comments and inputs and ii) Mr Paul Diela, Mr George Genga, Mr Salim Juma, Mr Elisha Kongere, Mr Samuel Mukaya, Mr Aloice Ndiege, Mr Dickens Nyagol, Mr Phillip Akelo, Mr Charles Oyugi, Mr Silas Ouko, Mr Joseph Ondiju, Mr Harrison Odhiambo and Mr Jacob Odhiambo for the support in carrying out the experimental work and many more that I came across in my practical work. I am indebted to Dr. B. Torto who allowed me to use his laboratory and resources, offered suggestions and advices in the analyses of plant volatiles for my samples as well as providing his team (Mr Onesmo Wanyama, Mr Xavier Cheseto, Ms Peris Amwayi, and Mr Vincent) for helping out and providing an enabling environment for learning. My gratitude goes to the following people (Dr M. Liphoto, Dr M. Phoofolo but most importantly Mr S. Ratšiu) who critically went through my work and helped me put it in order. v © University of Pretoria Acknowledgements I am also grateful for the financial support for the living and travel expenses provided by DAAD through the icipe Capacity Building & Instititional Development (CB&ID) Department. Some financial and logistical support provided by the University of Pretoria and the Lesotho Government when working in South Africa is also appreciated. I thank the whole CB&ID team, Lilian Igweta, Lisa Omondi & Margaret Nyagol for their dedication in facilitating and ensuring that my stay in Kenya and my exit from Kenya were a smooth process. The icipe Mbita family, friends and colleagues who saw me through this challenging period are also thanked. I would like to thank my family for being there for me and taking me tirelessly through the whole process. My mother-in-law, „me „Makatleho Lebesa, you were the pillar of strength. You stood by me during the darkest hours and encouraged me to move on. I thank all my sisters and brothers who stood in for me to help with the kids. Mr Katleho Lebesa, I thank you for being both parents to our daughters when I was away. I cannot leave out the family support I got from my church, Shofar, Pretoria. I thank you, pastor H. Titus for being my spiritual father and giving me the support of a father I never had. My friends (E.M. Njuguna, L. Serutla, A. Murage, N. Makio, K. Morobe, M. Lebete, T. Molomo, M. Mohloboli, T. Au, P. Nkhabutlane, K. Lehloenya, M. Semuli, L. Ntsane, M. Likhang, P. Mojela, L. Mashile, M. Matete and N. Tsiboho – to name a few), you displayed the true meaning of friendship, you cried with me when it was tough, laughed with me when things seemed better but most importantly you prayed with me and for me, held my hand and pushed me on. I am grateful to the Department of Agricultural Research (DAR) for providing me an opportunity in their training and capacity building program to further my studies for the vi © University of Pretoria Acknowledgements betterment of the institution. The management team (especially DAR director, Dr M. Ranthamane) is being thanked for providing an enabling atmosphere (time and resources) for completion of this work. Overall I thank God Almighty, the provider, the guide and the father who surrounded me with his tender mercies and grace and gave me the ability to go through this process to the end. vii © University of Pretoria Declaration Declaration I, Lefulesele Nteletsana Lebesa, declare that the thesis titled Visual and olfactory cues used in host location by the blister beetle Hycleus apicicornis (Coleoptera: Meloidae), a pest of Desmodium (Fabaceae) species which I hereby submit for the degree Philosophiae Doctor (Entomology) at the University of Pretoria is my own work and has not previously been submitted by me or anyone else for a degree at this or any other tertiary institution.