DIVERSITY AND POPULATION DYNAMICS OF Bactrocera invadens AND OTHER TEPHRITID FRUIT FLY SPECIES INFESTING MANGO (Mangifera indica) IN ZIMBABWE AND RELATIVE EFFICACIES OF SELECTED INSECTICIDES INCORPORATED IN FOOD BAITS BY VENGAI COLLEN MAFIRAKUREWA A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Tropical Entomology University of Zimbabwe Faculty of Science Department of Biological Sciences December 2014 DECLARATION I hereby declare that this thesis is my own original work and has not been submitted for a degree in any other university. Vengai Collen Mafirakurewa Date I, as the supervisor, confirm that the work reported in this thesis was carried out by the student under my supervision. The thesis was examined and I approved it for final submission. Dr. P. Chinwada Date ii DEDICATION This study is dedicated to parents, my wife, Joyce, our two children, Tawonga and Tadiwa and all the farmers who were gracious enough to let me into their homes and lives. iii ACKNOWLEDGEMENTS I wish to extend my profound gratitude, appreciation and deepest respect to all the mango growers in Mutoko (Mrs Mudzonga, Mrs Mudzengerere and Mrs Machita) Murewa (Mr and Mrs Mukurazhizha, Mrs Magirivha and Mr Chiwanza), Domboshava (Mr and Mrs Magama, Mr and Mrs Parirewa and Mrs Chogugudza) and Seke (Mr and Mrs Chiruwa, Mr and Mrs Muronzi and Mrs Chimanikire) who allowed me — a total stranger — to carry out my study in their orchards and backyards. I will forever be indebted to my supervisor, Dr. P. Chinwada for his valuable advice and guidance during the course of this study and the many hours he spent correcting my work. Your way of doing things will always have a lasting impression in my scientific work. You taught me well and for that I will always be thankful. I also want to thank the Director of the Research Services Division, Dr C. Mguni, and the Head of Plant Protection Research Institute (PPRI), Dr. G.P. Chikwenhere, for allowing me to use the laboratory and equipment at PPRI during my study. Their advice and comments during the course of the study were highly valuable. I am also very grateful to the following people from PPRI: Miss T. Makanza (Research Officer) for her valuable advice and support and Mrs Mary Nyamangodo (Research technician) for the long hours she had to be out with me in the field and laboratory. I also wish to acknowledge the assistance of Messrs Pawandiwa and Ngara who helped me with part of the data analysis. I also thank Mr O. Chipfunde (Research Officer, Gene Bank) for his efforts with drawing the map of the study areas. Last, but by no means least, I wish to thank and appreciate my wife Joyce, for allowing me to finance a greater part of this work from our personal savings. Words fail me, many thanks for your support, sacrifice and understanding throughout my study period. May the gracious Lord richly bless you all. iv ABSTRACT Studies were conducted from November 2013 to October 2014 in Zimbabwe to determine the temporal population dynamics of the invasive fruit fly pest Bactrocera invadens (Diptera: Tephritidae), to determine the pest’s host range and incidence and to evaluate its control using a food bait consisting of protein hydrolysate and each of the insecticides dimethoate (Dimethoate 40® EC), malathion (Malathion 50® EC), trichlorforn (Trichlorfon 90® SP), deltamethrin (Deltamethrin 2.5%® SC) and lambda-cyhalothrin (Lambda-cyhalothrin 50® EC). Fruit fly temporal dynamics studies were conducted in Mutoko, Murewa, Domboshava and Seke using methyl eugenol-baited traps while host range and incidence were assessed through “fruit rearing”. At each of the four locations (intensive study sites), fruits sampled from mixed mango varieties every two weeks were held in the laboratory at room temperature to determine the associated fruit fly species spectrum. As further confirmatory tests on host fruit and fruit fly species associations, a once-off extensive fruit survey covering the areas in which traps were located as well as outside them was conducted. Overall, there was a significant site x month interaction, with the highest catches of (over 3,400 in February 2014) being recorded in Murewa between February and April 2014. The lowest catches (below 25) were recorded in Seke and Domboshava in October 2014. The highest fruit fly diversity was recorded in Murewa, Seke and Domboshava where, in addition to B. invadens, Ceratitis cosyra and Ceratitis rosa were also recorded infesting mangoes. In the extensive surveys, Harare and Mahusekwa had the highest fruit fly diversity, recording three fruit fly species (B. invadens, C. cosyra and C. rosa). The highest B. invadens fruit infestations were recorded from stringless mango fruits collected in Guruve, which had an infestation rate of 80.5%. No B. invadens infestations were recorded from fruits collected in Chegutu, Zvimba and Buhera. The mango seed weevil, Sternochaetus mangifera, which is a quarantine pest of mangoes worldwide, was also recorded from all the four trapping locations, with Mutoko having the highest infestation rate of 22.5%. In laboratory studies to assess B. invadens control using various insecticides incorporated in hydrolysed protein food baits, Trichlorfon 90® SP (a.i. trichloforn) gave the highest adult fruit fly mortality (87.5%) while Dimethoate 40® EC (a.i. dimethoate) was the least effective with mortality of 40%. v In conclusion, this study demonstrated that though B. invadens occurs throughout the year, populations are at their highest from January to April. Its abundance is greatly influenced by location. Trichlorfon 90® SP and Deltamethrin 2.5%® SC (a.i. deltamethrin) have the potential to be used as fruit fly killing agents in case of non- availability of malathion which is the traditional fruit fly insecticide that is incorporated in food baits in Zimbabwe. Further local studies on B. invadens biology, overwintering mechanisms and behaviour are recommended so as to generate information that, when combined with results from the present study, could be useful in coming up with ‘smart’ strategies for the management of the pest in specific localities. vi TABLE OF CONTENTS DECLARATION ............................................................................................................................ ii DEDICATION ............................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................................... iv ABSTRACT .................................................................................................................................... v TABLE OF CONTENTS .............................................................................................................. vii LIST OF TABLES .......................................................................................................................... x LIST OF FIGURES ........................................................................................................................ xi LIST OF PLATES ......................................................................................................................... xii CHAPTER 1 .................................................................................................................................... 1 INTRODUCTION ........................................................................................................................... 1 1.1 Overview ................................................................................................................... 1 1.2 Justification ............................................................................................................... 3 1.3 Objectives ................................................................................................................. 5 1.4 Hypotheses ................................................................................................................ 5 CHAPTER 2 .................................................................................................................................... 6 LITERATURE REVIEW ................................................................................................................ 6 2.1 Mango Production Overview .................................................................................... 6 2.2 General Overview of Mango Pests and Diseases ..................................................... 6 2.3 Tephritid Fruit Flies .................................................................................................. 7 2.3.1 General classification ................................................................................................. 7 2.3.2 Biology and ecology .................................................................................................. 7 2.3.3 Some economically important fruit fly pests of mango ............................................. 8 2.4 Economic Impact of Tephritid Fruit Flies ............................................................... 10 2.5 Bactrocera invadens Spread in Africa and Zimbabwe ............................................ 12 2.6 Host Range of B. invadens ....................................................................................... 13 2.7 Species Status of B. invadens Inferred from Morphometrics, Molecular, Cytogenetic and Behavioural and Chemoecological Data ....................................