KNOWLEDGE GAPS, TRAINING NEEDS AND BIO-ECOLOGICAL STUDIES ON FRUIT-INFESTING FLIES (DIPTERA: TEPHRITIDAE) IN NORTHERN GHANA BY BADII KONGYELI BENJAMIN MASTER OF PHILOSOPHY IN ENTOMOLOGY UNIVERSITY OF GHANA, LEGON, GHANA THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF DOCTOR OF PHILOSOPHY CROP SCIENCE (ENTOMOLOGY) DEGREE JULY, 2014 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh DECLARATION I hereby declare that this thesis is the result of my own original research, and that it has neither in whole nor in part been presented for a degree elsewhere. Works of others which served as sources of information have been duly acknowledged by reference to the authors. Candidate ………………………… Badii Kongyeli Benjamin Principal Supervisor …………………. Co-supervisor ………………….. Prof. Daniel Obeng-Ofori Prof. Kwame Afreh-Nuamah Co-supervisor …………………… Dr. Maxwell Kevin Billah University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENTS This thesis could not have been accomplished without the guidance of my dear supervisors and academic mentors. My supervisors (Prof. Daniel Obeng-Ofori, Prof. Kwame Afreh-Nuamah and Dr. Maxwell K. Billah) offered me the needed encouragement, support and guidance throughout the study. Also, Prof. Gebriel A. Teye (Pro-Vice Chancellor), Prof. George Nyarko (Dean, Faculty of Agriculture), Dr. Elias N. K. Sowley (Director, Academic Quality Assurance Directorate) and Dr. Isaac K. Addai (Head, Department of Agronomy) all of the University for Development Studies (UDS) approved of my leave of study, supported and encouraged me throughout my study. The Head of Department (Mrs. Dr C. Amoatey), Lecturers and research colleagues of the Department of Crop Science, University of Ghana offered constructive criticisms and suggestions especially during seminars which helped to improve the work. I am grateful to the Ghana Education Trust Fund (GETFUND) for financially supporting the research project. I am also grateful to the Market-Oriented Agricultural Program of the German International Co-operation (GIZ-MOAP), Tamale for subsidizing the cost of transportation during the survey work. I am thankful to the National Fruit Fly Management Committee of Ghana for giving me letters of introduction which facilitated my access and work in the study districts and fruit sampling localities. Many thanks also go to the Regional Plant Protection Officers, District Directors of Agriculture, Agricultural Extension Agents and all the fruit growers for their kind co-operation, support and assistance throughout the data collection process. I thank my Field and Laboratory Assistants at the UDS for helping me in the questionnaire administration, fruit collection and incubation procedures. Finally, I thank the Almighty God for my life, health and abundant knowledge. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh DEDICATION To my dear wife, Mrs Rose B. Badii for her time-tested loyalty. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh ABSTRACT Tephritid fruit flies are a major threat to the horticultural industry in sub-Saharan Africa owing to the heavy losses they cause to fruit and vegetable crops, and the resultant quarantine restrictions. Addressing the fruit fly menace in Ghana requires effective stakeholder training along the fruit value chain, coupled with adequate research information on management strategies. Baseline studies were conducted in northern Ghana to determine the priority management training needs of fruit growers and Agricultural Extension Agents (AEAs), and to document the host range, species composition, seasonal phenology and parasitoid fauna of the pests. The studies involved the use of questionnaire for surveys coupled with a two-year collection and incubation of wild and cultivated fruits from selected sites in the Northern, Upper West and Upper East regions of the country. Fruit growers in all the regions were generally aware that fruit flies were serious horticultural pests responsible for the high losses in their fruit and vegetable production. Fruit growers in the Northern Region were more familiar with the economically important fruit fly species (especially the African invasive fruit fly, Bactrocera invadens) and their damage impact, compared with those in the other regions. Even though basic control practices were adopted by some farmers, a significant proportion of the growers took no action to control the pests. Recommended fruit fly control strategies such as pheromone trapping, bait application, soil inoculation and biological control were virtually unknown to the growers, with the majority of them resorting to the application of unprescribed chemicals with potential environmental and health risks. AEAs demonstrated fair knowledge in majority of the competency aspects of the pests. The top 5 competency areas in need for further training of AEAs included; knowledge of the economically important species, their economic impact, life cycle, host plant associations and control strategies. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh Out of 80 plant species studied, 65 (81.5%) of them were positive to 10 different fruit fly species. Eleven (11) plant species were reported for the first time as hosts to B. invadens, while two fruit fly species (Dacus ciliatus and Trirhithrum nigerrimum) were identified for the first time in the area. Ceratitis cosyra and B. invadens were the dominant fruit fly species recorded. Infestation by B. invadens was higher in commercial fruits while C. cosyra dominated in the wild hosts. Among the commercial fruits, infestation was highest in mango (Mangefera indica L), green pepper (Capsicum anuum L.) and water melon (Citrulus lunatus Thunb.), whereas sour sop (Annona senegalensis Pers.), tropical almond (Terminalia catapa L.), syncomore fig (Ficus syncomosus L.), African peach (Sarcocepholus latifolium Smith.), sheanut (Vitellaria paradoxa C.F. Gaertn.), persimmon (Diospyros mespiliformis A. DC.), icacina (Icacina senegalensis Juss.) and albarillo (Ximenia americana L.) dominated the wild host flora. The dynamics of emergence of B. invadens and C. cosyra fluctuated at various levels in response to the availability of host fruits and the influence of air temperature, relative humidity (RH) and precipitation, with precipitation showing the strongest influence. Four species of larva-pupal braconid parasitoids were reared from 14 fruit species that hosted C. cosyra and B. invadens. The parasitoids included Fopius caudatus (Szépligeti), Psyttalia cosyrae (Wilkinson), P. concolor (Szépligeti) and Diachasmimorpha fullawayi (Silvestri). The most abundant and diverse parasitoid was F. caudatus (61.0 %) while the least abundant was D. fullawayi (7.7 %). The overall mean parasitism level was 7.1 % with the highest record in sour sop, African peach and icacina. The peak occurrence of the parasitoids was on June and July, which coincided with the peak of the rains and maturity period of many of the surveyed crops. It is important to train fruit growers on the basic expertise to help address the fruit fly menace in the area. Also, professional capacity development programmes for AEAs should look into how the 5 critical educational needs on fruit fly pests (namely knowledge of the economically important species, University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh their economic impact, life cycle, host associations and control strategies) can be addressed in training workshops. The widespread availability of host plants and the diverse fruit fly species call for particular attention to their impact on commercial fruits, and development of management strategies against these economically important pests. An understanding of the occurrence periods of the different potential hosts and their influence on the population patterns of B. invadens and C. cosyra is also necessary for the development of sustainable IPM programmes. Finally, this study presents the first inventory of parasitoid fauna of major tephritid pests in the area, providing critical baseline data for future conservation or introduction of parasitoids for biological control efforts in the Ghana. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS ITEM PAGE TITLE PAGE …………………………………………………………………………………………...i DECLARATION ……………………………………………………………………………………….ii ACKNOWLEDGEMENTS ………………………………………………………………...………….iii DEDICATION ……………………………………………………………………………...………….iv TABLE OF CONTENTS …………………………………………………………………………......viii LIST OF TABLES ……………………………………………………………………………….….....xi LIST OF FIGURES ………………………………………………………………………….………..xii LIST OF PLATES ………………………………………………………………………….....……...xiii CHAPTER ONE 1.0 GENERAL INTRODUCTION …………………………….………………………..………...….1 1.1 Background ……………………………………………………………………………………...…..1 1.2 Problem statement ………………………………………………………………………..............…2 1.3 Justification ……………………………………………………………………………………….....5 1.4 Objectives ………………………………………………………………………..………….............6 CHAPTER TWO 2.0 LITERARURE REVIEW ……………………………………….………………..………………7 2.1 Phylogeny of fruit flies ……………………………………………………………………...……7 2.1.1 The order Diptera …………………………………………………………………………...…….7 2.1.2 The super family Tephritoidea ……………………………………………………………………8 2.1.3 The family Tephritidae ………………………………………………………………….….……10 2.1.4 True fruit flies ……………………………………………………………………………..……..12 2.2.0 Functional morphology of fruit flies ……….……………………………………………..…..…13 2.2.1 The adult ……………………………………………………………………………………...….13 2.1.2 The egg …………………………………………………………………………..………...…….14 2.2.3 The larvae …………………………………………………………………………………...…...15 2.2.4 The pupa …………………………………………………………………………………………16 2.3.0 General biology of fruit flies …………………………….…………………...........................….17 2.3.1 Life cycle …………………………………………………………………………...………...….17 2.3.2 Nutrition ……………………………………………………………………………………...….20 2.3.3 Host associations …… ………………………………………………...………………………..20 2.3.4 Symbiotic associations …………………………………………………………………………..23 2.3.5 Natural enemies …………………………………………………………………..………….…..24 2.4.0 Ecology of fruit flies ……………………………………………………………………………..28 2.4.1 Life history strategies ……………………………………………………………………..……. 28 2.4.2 Determinants of abundance ……………………………………………………………..…….…30 2.4.3 Demography and population dynamics ……………………………..…………………...………40 2.5.0 Behaviour of fruit flies ……………………………………………………………...........……...42 2.5.1 Host finding behavior ……………………………………………………………………………42 2.5.2 Feeding behavior …………………………………………………………………………...……43 2.5.3 Mating behavior ………………………………………………………………………………….44 2.5.4 Oviposition behavior ………………………………………………………………………….…47 2.5.5 Movements………………………………………………………………………………...……..49 2.5.6 Rhythms of activity and resource utilization patterns …………………………………..……….52 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 2.5.7 Response to lures …………………………………………………………………….…………..53 2.5.8 Larval behavior …………………………………………………………………………………..55 2.6.0 Economic importance of fruit flies ……………………………………...……………………….56 2.6.1 Beneficial fruit flies …………………………………………………………..………………….56 2.6.2 Pest species of fruit flies …………………………………………………………...…………….57 2.6.3 Damage caused by fruit flies ……………………………………………………….……………61 2.6.4 Economic impact of fruit flies …………………………………………………...………………62 2.7.0 Management strategies of fruit flies …………………………………………….……………….66 2.7.1 The eradication approach ………………………………………………………..………………67 2.7.2 The IPM approach …………………………………………………………………...…………..69 CHAPTER THREE 3.0 GENERAL MATERIALS AND METHODS ……………………….…………………………89 3.1 Study area ………………………………………………………………………………………….89 3.1.1 Location and size …………………………………………………………………………...……89 3.1.2 Agro-ecological conditions ……………………………………………………...………………90 3.2 Survey studies ……..………………………………………………………………………………92 3.3 Bio-ecological studies …………………………………………………………..…………………93 CHAPTER FOUR 4.1 FARMERS’ KNOWLEDGE, PERCEPTIONS AND PRACTICES IN THE MANAGEMENT OF FRUIT FLY PESTS IN NORTHERN GHANA …………………………………...……..94 4.2 Introduction …………………………………………………………………………….......…….94 4.3 .0 Materials and methods …………..……………………………………………………………95 4.3.1 Selection of respondents ………………………………………………………..…………….95 4.3.2 Survey methods ………………………………………………………………………………96 4.4 .0 Results …………..……………………………………………………………………………98 4.4.1 Demographic and production profile of fruit growers ……………………………………….98 4.4.2 Fruit fly awareness and identification by fruit growers …………………………………..…102 4.4.3 Fruit fly damage and economic impact ……………………………………………………..104 4.4.4 Fruit fly management practices and way forward …………………………………………..105 4.5 Discussion ………………………………………………………………………………………109 CHAPTER FIVE 5.0 INSERVICE TRAINING NEEDS OF AGRICULTURAL EXTENSION AGENTS IN THE MANAGEMENT OF FRUIT FLIES IN NORTHERN GHANA ………….....…………..113 5.1 Introduction ……………………………………………………………………………………123 5.2 Materials and methods ………………………………………………………...……………….115 5.2.1 Theoretical framework ……………………………………………………………….……115 5.2.2 Survey methods ……………………………………………………………………………116 5.3 .0 Results ……..……………………………………………………………………………....118 5.3.1 Demographic information of AEAs ……………………………………………….………118 5.3.2 AEAs’ perceived knowledge of fruit fly pests ………………………………………….…120 5.3.3 AEAs’ perceived importance of fruit fly pests ……………………………….……………121 5.3.4 AEAs’ perceived competence of fruit fly pests…………………………………………….122 5.3.5 Inservice training needs of AEAs for fruit fly pests …………………………...…………..124 5.4 Discussion …………………………………………………………………………………..…125 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh CHAPTER SIX 6.0 HOST RANGE AND SPECIES COMPOSITION OF FRUIT FLIES IN NORTHERN GHANA………………………………………………………………………………………..128 6.1 Introduction ………………………………………………………………………………..…..128 6.2 Materials and methods ………………………………………………………………………...130 6.2.1 Field sites …………………………………………………………………………………..130 6.2.2 Fruit collection ……………………………………………………………………………..132 6.2.3 Fruit incubation …………………………………………………………………………....133 6.2.4 Insect monitoring …………………………………………………………………………..136 6.2.5 Plant and fly identification ………………………………………………………………....137 6.2.6 Data analysis ………………………………………………………..………………..…….138 6.3 Results ……………………………………………………………………………………….…139 6.3.1 Host plants and fruit fly species ………………………………………………………....…139 6.3.2 Incidence and infestation indices ………………………………………………………..…147 6.4 Discussion……………………………………………………………………………………....154 CHAPTER SEVEN 7.0 SEASONAL PHENOLOGY OF BACTROCERA INVADENS (DREW, TSURUTA AND WHITE) AND CERATITIS COSYRA (WALKER) (DIPTERA: TEPHRITIDAE) IN NORTHERN GHANA ……………………………………………………………………..161 7.1 Introduction ………………………………………………………………………………….161 7.2 Materials and methods ………………………………………………………………..……...163 7.2.1 Fruit collection and processing …………………………………………………………...163 7.2.2 Meteorological data ………………………………………………………….…………...164 7.2.3 Data analysis …………………………………………………………………...………....165 7.3 Results ………………………………………………………………………………………..165 7.3.1 Host infestations ……………………………………………………………………….....165 7.3.2 Seasonal fluctuations ………………………………………………………..…………....166 7.3.3 Effect of abiotic factors ……………………………………………………….………….171 7.4 Discussion …………………………………………………………………………………….173 CHAPTER EIGHT 8.0 HYMENOPTERAN PARASITOIDS ASSOCIATED WITH FRUIT-INFESTING FLIES IN NORTHERN GHANA ………………………………………………………………….....178 8.1 Introduction …………………………………..……………………………………………..178 8.2 Materials and methods ………………………………………………………………………180 8.2.1 Fruit sampling and processing …………………………………………………….……..180 8.2.2 Parasitoid identification ……………………………………………………..…………..181 8.2.3 Data analysis …………………………………………………………………………….182 8.3 Results ………………………………………………………………………………………182 8.3.1 Parasitoid diversity and abundance ……………………………………………………..182 8.3.2 Infestation and parasitism rates ………………………………………………………....187 8.4 Discussion……………………………………………………………………...……………190 CHAPTER NINE 9.0 GENERAL CONCLUSION AND RECOMMENDATIONS ………………………...196 9.1 Conclusion ……………………………………………………………………………….....196 9.2 Recommendations ………………………………………………………………………….198 REFERENCES ………………………………………..…………………………………...…201 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh LIST OF TABLES TABLE TITLE PAGE Table 2.1 Fruit fly species of economic importance in Sub-Saharan Africa …………………………..60 Table 2.2 EU interceptions of infested mangoes from Africa…………………………………..……..65 Table 2.3: Parasites and predators used against African tephritid pests………………………………81 Table 2.4: Microorganisms and microbial toxins used against African tephritid pests…………….….85 Table 4.1: Study regions, selected districts and the number of fruit growers interviewed..................97 Table 4.2: Demographic information of fruit growers in northern Ghana, 2012...................... ...........99 Table 4.3: Fruit production profile of farmers in northern Ghana, 2012...................... .......................101 Table 4.4: Awareness of fruit flies and pest identification by fruit growers in northern Ghana, 2012.....................................................................................................................................103 Table 4.5: Descriptive statistics summarizing farmers’ knowledge of fruit fly damage and economic impact in northern Ghana, 2012..........................................................................................105 Table 5.1: Demographic information of Agricultural Extension Agents (AEAs) in northern Ghana, 2012.......................................................................................................................119 Table 5.2: AEAs’ perceived level of importance of 15 competency aspects to fruit fly pests in northern Ghana, 2012.......................................................................................................120 Table 5.3: Mean scores for items comprising direct assessment of AEAs’ knowledge of 15 competency aspects of fruit fly pests in northern Ghana, 2012........................................122 Table 5.4: AEAs’ perceived level of competence in 15 competency aspects to fruit fly pests in northern Ghana, 2012..........................................................................................................123 Table 5.5: Mean weighted discrepancy scores (MWDS) for AEAs’ perceived level of importance, knowledge and competence in 15 competency aspects of fruit fly pests in northern Ghana, 2012........................................................................................................................125 Table 6.1: Fruit collection sites in northern Ghana with their approximate latitudes, longitudes and altitudes………...…………………………………………………………………….131 Table 6.2: List of fruit species collected in northern Ghana with their sample details and host status to tephritid pests ………...………………...…………………………..…...……….141 Table 6.3: Host plants of tephritid pests in northern Ghana and their infestation indices………….148 Table 7.1: List of the studied fruit species indicating their habitats and sample details…….……164 Table 7.2: Infestation data for the main hosts of B. invadens and C. cosyra in northern Ghana....166 Table 7.3; Results of the linear regression model with the poisson variance function of counts of B. invadens and C. cosyra with the covariates measured……….…………………….173 Table 8.1: Fruit flies and associated parasitoid species recovered from host fruits in northern Ghana………………………………………………………….…………………….….186 Table 8.2: Numbers of the parasitoid species in relation to periods of occurrence….…………....187 Table 8.3: Parasotoid species and their relative abundance in tephritid pupae recovered from the host fruits………….…………………..……………………………….…….……..188 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh xii LIST OF FIGURES FIGURE TITLE PAGE Figure 2.1: Generalized developmental cycle of fruit flies ………………………..………….…..19 Figure 2.2: Fruit fly damage symptoms on various types of fruit………………………………….62 Figure 3.1: Map of northern Ghana showing the study regions and districts ……………………..90 Figure 4.1: Practices adopted by fruit growers for the control of fruit fly pests in northern, Ghana, 2012...............................................................................................................................106 Figure 4.2: Farmers’ knowledge of fruit fly management strategies in northern Ghana, 2012.......108 Figure 4.3: Way forward to addressing the fruit fly menace as proposed by fruit growers in northern Ghana, 2012..................................................................................................................109 Figure 6.1: Tephritid species and their relative abundance in host fruits in northern Ghana…….147 Figure 6.2: Infestation indices (number of flies per kg fruit) of each of the fruit fly species recorded in the host plant species (pooled data) in relation to the study regions..........................….……….152 Figure 6.3: Infestation indices (number of flies per kg fruit) of the 12 most attacked plant species by the fruit fly species (pooled data) in relation to the study regions…………...153 Figure 6.4: Average infestation levels of the 12 most attacked plant species by the 2 major fruit fly species (B. invadens and C. cosyra)………………………………………………….154 Figure 7.1: Seasonal trends in infestation by B. invadens and C. cosyra (pooled data) in12 main host plants in northern Ghana…………………………………….……………………..….168 Figure 7.2: Emergence dynamics of B. invadens and C. cosyra from the 12 main hosts (pooled data) in relation to the study regions….…………………………………….……………....172 Figure 7.3: Relationship between climatic factors and infestation rates of B. invadens and C. cosyra on the 12 main host plants ………….......................……………………….………..174 Figure 8.1: Parasitoid diversity as measured by the Shnnon-Weaner Diversity Index in 14 fruit fly host plants collected in northern Ghana. ……….............……………………...………..186 Figure 8.2: Infestation and parasitism rates of fruit fly species in relation to study regions…..….191 Figure 8.3: Infestation and parasitism rate of fruit fly species in relation to host fruit species…...192 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh xiii LIST OF PLATES PLATE TITLE PAGE Plate 6.1: Sampled fruits packaged in a plastic container for transport from the field to laboratory………………………………………………………………………………..133 Plate 6.2: Fruit holding containers …………………………………………………..……….…..135 Plate 6.3: Incubators with fruit samples arranged in metal shelves for recovery of puparia……..135 Plate 6.4: A puparia holding cage for checking emergence of adult fruit flies………………..…137 Plate 6.5: Tephritid species reared from fruit samples collected in nortern Ghana………………..145 Plate 8.1: Parasitoid species reared from fruit fly puparia recovered from host fruits in northern Ghana……………………………………………………………………………........183 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh xiv LIST OF APPENDICES PLATE TITLE PAGE Appendix 1: Survey questionnaire to assess the knowledge, perceptions and practices of fruit growers in the management of fruit flies in northern Ghana……………..244 Appendix 2: Survey questionnaire to assess the in-service training needs of agricultural extension agents in the management of fruit flies in northern Ghana…………...….245 Appendix 3: Photographic vouchers of plant species in northern Ghana from which fruit samples were collected for determining the host range, species composition, seasonal phenology and parasitoid fauna of fruit flies……………………………....247 Appendix 4: ANOVA for fruit fly species reared from host fruits in northern Ghana……....254 Appendix 5: ANOVA for the host plant species infested by fruit flies in northern Ghana.....254 Appendix 6: ANOVA for the infestation indices of the 12 most attacked plant species by the 2 major fruit fly species (B. invadens and C. cosyra) in northern Ghana………..255 Appendix 7: ANOVA for parasitoids species recovered from fruit fly puparia in host fruits in northern Ghana………………………………………………………...….….255 Appendix 8: Multiple regression analysis of the effect of climatic factors on the emergence of C. cosyra from host fruits in northern Ghana…………………….……..256 Appendix 9: Multiple regression analysis of the effect of climatic factors on the emergence of B. invadens from host fruits in northern Ghana………………………..256 Appendix 10: Summary of the Mean monthly air temperature, precipitation and relative humidity (RH) recorded during October, 2011 to September, 2013 at the Meteorological Stations of the Savanna Agricultural Research Institute, Ghana…...256 University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 1 CHAPTER ONE 1.0 GENERAL INTRODUCTION 1.1 Background Over the last two decades, diversification into high value horticultural crops has been pushed as an economic development strategy of sub-Saharan Africa (Weinberger and Lumpkin, 2007). Diversification into horticulture has contributed to poverty alleviation by promoting food security while helping to restore equilibrium in the balance of payments by increasing total export earnings for African countries (World Bank, 2008). Fruit and vegetable crop production is one of the fastest growing sectors of the horticulture industry, providing food, income and employment as well as enhancing access to education and health care. The sector also provides women with economic opportunities especially in rural communities where the highest production of fruit and vegetable crops takes place (Norman, 2003). The changing dietary patterns leading to increased consumption of fruit and vegetables, may account for the fast growth of the sector. Additionally, the increasing liberal global trade arrangements have created new and lucrative production and market opportunities for fresh fruit and vegetable crops in the sub region, and thus, giving the industry more prospects for the future (Jaeger, 2008). In Ghana, several fruit and vegetable crops are grown for both domestic and export markets. The major ones include mango, citrus, pineapple, papaya, banana, tomatoes, peppers, okra, garden eggs and the cucurbits. More than 90,000 tonnes of fruit and vegetables are exported annually from the country (GEPC, 2010). There are a number of public and private sector enterprises that ensure monitoring of compliance with quality standards, access to markets, improving national goodwill, University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 2 enlisting government support and providing limited funding for research and development (Jaeger, 2008). Several constraints, however, hinder the sector from realizing its full potential. Among them include insufficient investments, inadequate basic and adaptive research, limited knowledge of the incidence and management of major pests and diseases, poor extension of existing knowledge and method of dissemination, coupled with the porous borders and weak economic policies (Norman, 2003; Jaeger, 2008). The USAID-commissioned global horticulture assessment identified the following primary issues as of core importance to the development of the horticulture industry in producer countries: (1) market systems, (2) post harvest systems and food safety, (3) genetic resources conservation and development (4) sustainable production systems and natural resource management, (5) capacity building, (6) enabling environment, (7) gender equity and (8) nutrition and human health (World Bank, 2010). A critical look at the situation in Ghana shows a similar trend, and within the constraint of sustainable production systems, biotic stresses that include pests and diseases are considered crucial to development. Currently, infestation and damage by fruit flies has been the key biotic constraint to the increased and sustainable production, and marketing of fruit and vegetable crops in the country (PPRSD, 2010). 1.2 Problem Statement Tephritid fruit flies are among the most economically important group of insects which pose serious threat to the horticultural industry worldwide (White and Elson-Harris, 1992; Ekesi, 2006). According to Thompson (1998), equatorial Africa is the aboriginal home of 915 fruit fly species from 148 genera with 299 species developing from either cultivated or wild host plants, or in both. Indigenous fruit flies in Sub-Saharan Africa belong to the genus Ceratitis MacLeay (e.g., C. cosyra, C. capitata, C. ditissima, C. anonae, C. bremii, C. rosa and C. fasciventris), and Dacus Fabricius University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 3 (e.g., D. bivitatus, D. ciliatus, D. punctatifrons. D. frontalis and D. vertebratus) (Drew, 1992; Drew et al., 2005). In addition, four Asian invasive species of the genus Bactrocera Macquart, have invaded the continent. These are B. invadens, B. cucurbitae, B. zonata and B. latifrons (Ekesi, 2006). Fruit fly species of these three genera have established resident populations in tropical Africa, causing serious concern in mango, citrus and vegetable production. In Ghana, the earlier fruit flies observed to be of major concern were C. capitata (Wiedmann) which attacked citrus (Afreh-Nuamah, 1985; 1999; 2007) and C. cosyra (Walker) which attacked mango (Lux et al., 2003a, b). However, the arrival of the African invader fly, B. invadens (Billah et al., 2006) has jeopardized the situation in the fruit and vegetable production sector (PPRSD, 2010). Fruit fly pests are known to spread through and within the West African sub-region primarily by the movement of infested commodities due to the weakness of phytosanitary surveillance and control systems for the export of fruit and vegetable crops among member countries (Mwatawala et al., 2004). Bactrocera invadens in particular, was first detected in eastern Africa, Kenya in 2003 (Drew et al., 2005: Ekesi et al., 2006), and in Ghana in 2005 (Billah et al., 2006). Fruit flies are polyphagous pests that cause extensive damage (both direct and indirect) to fruit and vegetable crops in sub-Saharan Africa (Ekesi, 2006; IITA-CIRAD, 2008). Direct fruit damage occurs when adult female fly punctures the fruit skin and lays eggs underneath it. Damage symptoms vary depending on the host fruit species. During oviposition, saprophagous bacteria from the intestinal flora of the fly are introduced into the fruit, causing rot of the fruit tissues surrounding the eggs. When eggs hatch, the rotten fruit tissues make it easier for the larvae to feed. The puncture and feeding galleries made by developing larvae also provide access for pathogens to develop, and increase the fruit decay, and thus, rendering it unmarketable. Generally, the fruit falls to the ground just before the larvae pupate (Ekesi, 2006; Afreh-Nuamah, 2007). Indirect fruit damage and losses University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 4 result from quarantine restrictions that are imposed by importing countries to prevent entry and establishment of such unwanted pest species through the border lines (Ishida et al., 2005). In Ghana, damage caused by fruit flies has been recognized as a quarantine problem for fruits destined for both international and local markets. Since the introduction of B. invadens into the country, the mango production sector has been particularly hit with heavy losses from producing communities (PPRSD, 2010). The damage to fleshy fruits is mainly caused by a limited number of highly polyphagous species, most of them likely belonging to the genera Ceratitis and Bactrocera. These losses can be very heavy or severe. For example, Lux et al. (1999) reports losses of up to 40% in mango in East Africa, while Vayssieres et al. (2005) mentioned loss averages ranging from 12 to 50% for the same host in Benin, depending on the season. Bactrocera invadens alone can cause production losses of up to 70% on mango, 40% on citrus and significant proportions on fruit and vegetable crops (White and Elson-Harris, 1992; USDA-APHIS, 2008). The presence of high populations of fruit fly species in fruit production areas can lead to severe economic losses for fruit growers, as well as a reduced source of essential dietary components especially vitamins and minerals to consumers. As a result of fruit flies, European and other international borders and airports have intercepted and destroyed large quantities of fruits from several African countries, and thus, causing major economic losses to affected nations. For example, the republic of South Africa, the Lebanon Republic and the United States have banned fruits exports from Ghana as a result of Bactrocera and Ceratitis species (STDF, 2009; PPRSD, 2010). The strict maximum residue level regulations in the European Union have further jeopardized the export market. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 5 Fruit fly research and management in Ghana is yet to be fully optimized. Although some baseline studies have been conducted on the bionomics and management of the pests (Afreh-Nuamah, 1985; Billah et al., 2006; Utomi, 2006; Foba, 2009; Appiah et al., 2009; Abdullahi et al., 2011; Ambele et al., 2012; Foba et al., 2012; Nboyine et al., 2012; Wih and Billah, 2012). These studies are mostly specific to one crop or tephritid species, and/or generally targeted at the southern ecologies of Ghana. At present, there is still limited knowledge of fruit fly pests and their economic impact among stakeholders along the fruit value chain. Also, information on the bioecology of the pests and the sustainable strategies to manage them within the different agro-ecological zones of the country still remains fragmented or inadequate, and in many situations, unavailable. The northern sector of the country seems to be the most threatened with the fruit fly problem on mango which is the major host of fruit flies, is the most potentially exportable crop gaining commercial cultivation in the area. 1.3 Justification The Economic Community of West African States (ECOWAS) has recognized the impact of fruit flies in the sub-region. At a regional validation workshop on “Study on damage inflicted by fruit flies in West African fruit production, and action plan for a regional response” held in Bamako, Mali in August, 2008, the issue of research and organizational problem, in relation to the management of fruit flies along the value chain, was identified as of major concern (STDF, 2009). In line with this, a resolution was passed directing all ECOWAS-member countries to establish national committees that would develop action plans to help address the fruit fly menace in the sub- region (COLEACP-CIRAD, 2009). In Ghana, the Plant Protection Regulatory Services Directorate (PPRSD) of the Ministry of Food and Agriculture (MoFA), in collaboration with the universities, research institutions and other University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 6 stakeholders, have initiated some fruit fly awareness campaigns and monitoring activities in some parts of the country. Moreover, in response to the resolution adopted at the ECOWAS workshop, the PPRSD of MoFA, in June, 2010, launched its Action Plan (AP) following the inauguration of the National Fruit Fly Management Committee (NFFMC) of Ghana (PPRSD, 2010). The committee seeks to set standards of public-private partnership for protecting the horticultural sector against fruit flies and other invasive pests in the country. Among the major components of the AP of the committee is to intensify stakeholder awareness, and develop and disseminate integrated management strategies for fruit fly pests in the country. This research project was designed in line with the AP of the NFFMC of Ghana to provide valuable information on fruit flies for the development of sustainable management interventions that would help address the fruit fly menace in the country. 1.4 Objectives The study sought to determine some key educational and bio-ecological aspects, and their implications for the management of fruit-infesting flies in the northern savanna ecology of Ghana. The specific objectives were to determine the: 1. Knowledge gaps, perceptions and practices of fruit growers on fruit fly pests 2. In-service training needs of Agricultural Extension Agents (AEAs) on fruit fly pests 3. Species diversity and host range of fruit fly pests 4. Seasonal phenology of major fruit fly pests 5. Native parasitoids associated with fruit fly pests University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 7 CHAPTER TWO 2.0 LITERATURE REVIEW 2.1.0 Phylogeny of fruit flies 2.1.1 The order Diptera Diptera is the fourth insect order (after Coleoptera, Lepidoptera and Hymenoptera) in terms of number of known and described species (Rull, 2008). The order contains about 120,000 named species in approximately 130 families, with thousands of species of agricultural, medical and veterinary importance (Diniz and Morias, 2008). Diptera is considered to be the most ecologically diverse order of the Insecta class (Mendes, 2008). Dipterans diet encompasses all possible ranges from blood feeders, endo- and eco-parasites of vertebrates and predators to all forms of mycetophages, saprophages and phytophages (Rull, 2008). Members of the order can be found in every zoogeographic region of the globe, inhabiting a wide diversity of habitats (Grimaldi and Engel, 2005). Dipterans are holometabolous endopterygote insects, undergoing complete metamorphosis, in which a pupal stage intervenes between the larval and adult instars. Immature stages are morphologically different from adult forms, and often have contrasting habitat and food requirements (Romoser and Stoffolano, 1994). Although some families, species, and sometimes members of one sex of flies are apterous (posses no wings), Diptera as a whole can be characterized for possessing only two functional front wings, and a pair of vestigial knob (named halters) behind the wings, that function as organs of equilibrium, helping the flies to remain stable during flight (Borror et al., 1992). Two suborders can be recognized in Diptera; Nematocera and Brachycera. The Nematocerans include cane flies, midges, mosquitoes and gnats, which have thin multisegmented antennal flagella. Larval forms generally have conspicuous head, and pass through University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 8 more than three instars before reaching the pupal stage (Mendes, 2008). The Brachycerans include higher flies, hover flies and dung flies, which possess shorter and thicker antennae with fewer flagellomer. These have robust bodies with legs shorter than the Nematocerans. Brachyceran larval forms have the posterior portion of the head capsule desclerotized and extended into the thorax (Rull, 2008). The phylogenic relationships between these two suborders are still controversial, although Nematocera is suspected to be paraphyletic (Mittelbach et al., 2007). Within Brachycera, the infraorder Muscomorpha (=Cyclorrapha) is composed of species whose larval forms are commonly known as maggots, which are mostly saprophagous, and with the exception of their sclerotized mouth hooks, are soft bodied. Cyclorrapha are also characterized by the fact that pupation occurs within the tanned cuticle (the puparium) of the last larval instar (Rull, 2008). Within the Cyclorrapha, the division Schizophora comprised the largest tertiary radiation of insects, with approximately 50,000 species (Grimaldi and Engel, 2005). Schizophora is characterized by possessing a membranous sac that expands like a balloon to rupture the puparium during adult emergence. Such structure, called ptilinum, is then invaginated into the head, and as a consequence, adult schizophorans can be identified by having a ptilinal fissure bordering the face. Within the Schizophora the section Acalyptratatae includes species of flies that possess no calypteres on wings, which are lobes at the extreme base of the wing (Borror et al., 1992). Acalyptratatae includes families in the superfamily Tephritoidea. 2.1.2 The Superfamily Tephritoidea The superfamily Tephritoidea includes eight known families of acalypterate flies: Lonchaeidae, Piophilidae, Pallopteridae, Richardiidae, Ulidiidae, Plastytomatidae, Pyrgotidae, and Tephritidae (Korneyev, 2000a). Lonchaeidae are commonly known as lance flies. There are about 500 described University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 9 species in 9 genera. Lonchaeids are generally small, robustly built flies with blue-black or metallic bodies. Lonchaeid larvae are secondary invaders of diseased bodies or injured plant tissues, adults have the rare habit among acalypterate flies to form swarms for mating, and are found mostly in wooded areas (Rull, 2008). The Piophilidae are mostly scavengers in fungi and animal products, with the family getting its common name, skipper flies, due to the fact that larvae tend to jump during their last instars before pupation. Pallopteridae or flutter-winged flies, is a little known small family, with larvae of some species feeding in flower buds, or occurring as predators of wood borer larvae under the bark of fallen trees. Over 50 species in 15 genera are found in the temperate region of the Northern and Southern hemispheres. The Richardiidae is a small family that consists of 30 genera and 175 species. It is a little known family whose adults can be captured in fruit-baited traps; the few larval feeding records of this family suggest that these flies feed on rotten vegetable matter. Most adults generally have conspicuously pictured wings, often with metallic-blue or greenish colours on bodies and legs, and a typical tephritoid ovipositor (Rull, 2008). Ulidiidae and Plastytomatidae are both pictured-winged flies. The Plastytomatids are sometimes referred to as signal flies. Both families are abundant in the tropics, occurring in decaying tissues but also sometimes feeding on plants with a few species considered as pests. Most species share with the Tephritidae an unusual elongated posteroapical projection of the anal cell in the wing, but can be differentiated by the smooth-curving subcostal veins (Korneyev 2000a). Pyrgotidae are medium to large flies with considerable colouring of the wings. They are mostly nocturnal. Unlike other tephritoids, Pyrgotids are endoparasitoids; the females pursue scarab beetles in flight, laying their eggs on the back of the beetle, under the elytra, beyond host’s reach. Developing larvae enter University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 10 the cavity of the beetle and eventually kill the host before pupation (Rull, 2008; Mendes, 2008). Phylogenetic relationships among tephritoid families have been reviewed by Korneyev (2000a). 2.1.3 The Family Tephritidae Tephritidae is a very large family, which includes more than 4,000 described species. The family can be characterized by an elaborate wing patterns and the possession of a telescopic ovipositor by the female. Tephritidae is known as one of the most ecologically diverse families of Diptera, and due to its size, it has been difficult to synthesize phylogenetic relationships among higher groups of the family (Korneyev, 2000b). Phylogenetic relationships of important genera of the family have been provided by Norrbom and Thompson (2003). Despite the lack of a conclusive phylogeny, the study of Tephritidae can be approached by looking separately at five different subfamilies; Blepharoneurinae, Phytalmiinae, Trypetinae, Dacinae and Tephritinae, all of which are well represented in the tropics. The subfamily Blepharoneurinae represents flies of the tropical group, and composed of five main genera; Ceratodacus, Problepharoneura, Blepharoneura, Baryglossa, and Hexaptilona. The first three genera consist of species of the neotropical and afrotropical regions, while the last two genera include species of the paleartic regions. Although this subfamily is composed of a reduced number of described species, recent scrutiny on flies in the genus Blepharoneura suggests that there may be more than 200 species. This subfamily is interesting as the group appears to be one of the oldest lineages in Tephritidae. All the genera for which biological data have been gathered feed on plants and parts of plants in the family Cucurbitaceae. There is suggestive evidence that these flies have undergone rapid processes of speciation, as much as more than one species can cohabit the same University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 11 plant, exploiting different parts of it and exhibiting complex courtship behaviours (Condon and Norrbom, 1994). Phytalmiinae is a subfamily comprising six genera; Diplochorda, Ortaloptera, Phytalmia, Sessilinia, Tetrastiomyia, and Sophiria. These are the flies with antenna-like head projections, sometimes referred to as antler flies or deer flies (not to be confused with Tabanidae). Decaying plant material is the larval food across this subfamily. All described species of antler flies occur between the island of Borneo and the Cape York Peninsula of Australia. The few behavioral studies on this group suggest that antler flies evolved in the context of male intrasexual competition. Resource defense mating systems for this group have been described by Dodson (1997), while Dodson (2000) provided a review on current knowledge on the Phytalmiinae. Trypetinae is a large subfamily that includes 19 known genera; Carpomya, Cryptodacus, Goniglossum, Haywardina, Myiopardalis, Rhagoletis, Rhagoletotrypeta, Zonosemata, Acidia, Euleia, Strauzia, Trypeta, Anastrepha, Toxotrypana, Epochra, Paraterellia, Chetostoma, Oedicarena, and Myoleja. The genera Rhagoletis, Anastrepha, and Toxotrypana include several species of major economic importance. While members of Rhagoletis are both holartic and neotropical in distribution, Anastrepha, and Toxotrypana are restricted to the new world, the rest of Trypetinae is especially diverse in the old world tropics, which may be the center of origin (Foote et al., 1993). Within Trypetinae, the subtribe Trypetina contains all the known leaf-mining species of tephritids, along with others with different larval feeding habits. A comprehensive account of this group of flies is provided by Han (2000). Tephritinae is considered the most specialized subfamily of Tephritidae. It is composed of six tribes with over 210 genera (Foote et al., 1993). Most species of Trypetini breed in flower heads, or form University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 12 flower, stem, or root galls in plants of the family Asteraceae. Due to this habit, many of these tephritids have been used in biological control of weeds (White and Elson-Harris, 1992; Turner 1996). Sexual behavior and biology of some members of this subfamily have been reviewed by Headrick and Goeden (1998; 2000). Dacinae is a subfamily that contains only three genera Bactrocera, Dacus, and Ceratitis all of which include many species of major economic importance. All members of this subfamily are native to the Old World, despite the fact that the Mediterranean fruit fly, C. capitata has been established in South and Central America since the beginning of the 20 th century, and there have been recurrent introductions and eradication efforts of this pest along with the Olive fruit fly, B. oleae, the Oriental fruit fly, B. dorsalis and others in North America (Foote et al., 1993). 2.1.4 True Fruit Flies The term “fruit fly” is sometimes used for two distantly related groups of flies, namely the families Drosophilidae and Tephritidae. The Drosophilidae includes “fruit flies” of the geneticists, which are in reality, micro-fungi feeders that have acquired this name because of their habit of feeding on decaying fruit (Aluja et al., 2003). The Tephritidae is generally described to include the “true fruit flies” because most species attack living plant material, and an estimated 40% of the over 5,000 described species attack intact and growing fruits. Females of fruit flies have an ovipositor, similar to the “sting” of a wasp, with which they puncture the skin of healthy fruits and lay their eggs therein. Larval development is completed within the fruit (which may become rotten as a result) and the fully grown larvae then drop into the soil and form a puparium (Aluja et al., 2003). University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 13 There are about 150 genera and 950 species of Tephritid fruit flies known in tropical Africa, most of which form a natural component of Africa’s rich and varied biodiversity. About 70 species of fruit flies are considered important agricultural pests, and many others are minor or potential pests. Fruits and vegetables are the most important crops attacked, even though some seed crops are also affected (White and Elson-Harris, 1992). 2.2.0 Functional morphology of fruit flies Morphology and anatomy of the different life stages of fruit flies, particularly characters useful for taxonomic purposes, have been described in detail by Drew (1982) and Munro (1984). Only those aspects relevant for an understanding of the group's developmental biology are considered here. 2.2.1 The adult The adult body colouration of different fruit fly species varies from black through various shades of brown to orange or yellow. Yellow marks, particularly on the thorax, give many species a somewhat wasp-like appearance. This resemblance is particularly pronounced in certain Bactrocera subgenera and Callantra spp., which have petiolate abdomens, heavily fuscated costal stripes on the wings, and a jerky, wasp-like walk (Fletcher, 1987). The paired antennae each consist of three segments. Scanning electron microscope studies on B. oleae and B. tryoni indicate that the outer segment is covered with long cuticular spines interspersed with large numbers of chemosensilla of several distinct morphological types and functional significance (Drew et al., 1983; 1984; Giannakakis and Fletcher, 1985). The general structure of dacine fruit flies is fairly typical of cyclorrhaphan Diptera. Male dacines, except those of some groups such as Gymnodacus, typically have a pair of combs (or pectins) comprised of stiff curved bristles on the lateral hind margins of the third abdominal tergite. These combs function as stridulatory organs during courtship (Drew et al., 1983). Both sexes have a pair University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 14 of tergal glands (ceromae) that open onto the surface of the fifth tergite. These consist of dense groups of minute alveolae that secrete a waxy substance, which is spread onto the body and wings during preening (Munro, 1984). In female dacines, abdominal segments 7-9 form the ovipositor, which is usually smooth and pointed but is serrated in some species. The apical segment has a number of chemosensiIla; the most prominent are the preapical setae that arise from lateral grooves on either side of the segment (Hardy, 1969). These presumably play an important role in fruit discrimination (Fletcher, 1987). 2.2.2 The egg The study of tephritid egg morphology has largely been confined to the description of surface features (Headrick and Goeden, 1993) mainly through transmission electron microscopy examination (Margaritis, 1985). Tephritid eggs are elongate ellipsoidal in shape and thus have only a single primary axis. At one end, the egg bears a pedicel. The pedicel bears the micropyle and the aeropyles. Typically, the micropyle is located on the apex of the pedicel and may have a single or multiple openings (Fletcher, 1987). The arrangement of the micropyle is similar among the nonfrugivorous species studied. The pedicel may be only a slight projection (Knio et al., 1996), but it may also occur as an elongated stalk nearly as long or longer than the body of the egg (Goeden and Teerink, 1996). The eggs of all tephritid species studied develop inside the ovariole with the pedicel oriented toward the ovary terminus. This orientation facilitates the functions of fertilization and oviposition. According to Headrick and Goeden (1994), fertilization takes place through the micropyle as the egg passes through the median oviduct. The basal end exits the gonopore first near the end of the aculeus that is inserted into plant tissues during oviposition. Embryogenesis proceeds after oviposition, and the head of the embryo develops and orients toward the pedicel. However, in many species, the embryo turns 180º before eclosion and exits the egg through the basal end. This University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 15 apparently serves to position the embryo so that the plant tissue is encountered immediately upon eclosion (Headrick and Goeden, 1991). The surfaces of eggs have polygonal, typically hexagonal, reticulations or mass-relief-type ridges. These ridges represent the outline of the follicle cells responsible for laying down the chorion (Mouzaki and Margaritis, 1991). These reticulations may be prominent and bear additional structural ornamentation, as in Tephritis baccharis (Headrick and Goeden, 1991). The surface features of the egg are most strongly developed at the pedicel end, and diminish often to a smooth surface near the basal end, as reported in Aciurina thoracica (Headrick and Goeden, 1993). Goeden and Headrick (1991) hypothesized that because the pedicel end of the egg is left exposed to facilitate gas exchange, and the basal end is inserted into plant tissues, the pedicel would need greater structural support to protect the aeropyles and associated respiratory channels from distortion. 2.2.3 The larvae Three free-living instars exist for tephritid fruit flies. The only known exceptions are Urophora jaceana and Urophora cardui, in which the first instar remains in the egg and exits as a second instar. The external anatomy of the larvae of frugivorous tephritids has been examined in detail, and at least partial descriptions based primarily on scanning electron micrographs for 25 species have been available (Knio et al., 1996). By comparison, White and Elson-Harris (1992) have developed an atlas of immature morphology based on the third instar of 34 economically important species. Several other structures including the median oral lobe, the lateral spiracles accompanied by a variable number of sensilla associated with the sensory organs of the gnathocephalon have been newly identified for various frugivorous species (Headrick and Goeden, 1993). University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 16 Tephritids have distinct anterior and posterior spiracles. With the aid of modern scanning electron microscopy, the lateral spiracles have been located on the meso- and metathoracic segments and the abdominal segments, excluding the caudal segment, which bears the posterior spiracles (Headrick and Goeden, 1990). Lateral spiracles are always located along the lateral mid-linenear the anterior portion of a segment, and they have a variable number of associated campaniform sensilla posterior of the spiracle. The number of sensilla ranges from one, in some Aciurina (Goeden and Teerink, 1996) and Trupanea (Knio et al., 1996) species to as many as four in Stenopa affinis (Goeden and Headrick, 1990). When more than one sensilla is present, they are typically arranged along a dorso- ventral axis adjacent to the spiracle. 2.2.4 The pupa The puparium is the hardened, penultimate larval integument of the developing fly. It is remarkable in its external morphology in tephritid fruit flies. When the third instar larva is ready to pupate, it leaves the medium, and its anterior spiracles evert, its body shortens and ceases to move and it attaches to a firm substrate. The cuticle then transforms into a puparium, which is initially soft and white, but soon hardens, turning tan and eventually brown and bristle. Shortly after the puparium forms, metamorphosis then takes place. The prepupal integument is shed and adheres to the inner wall of the puparium. The pupa forms within the puparium after the prepupal molt. The pupa develops independently of the puparium and has bilobed thoracic spiracles for respiration (Headrick and Goeden, 1990). The larval tracheae adjacent to the anterior and posterior spiracular openings remain open, thus allowing for gas exchange for the developing pupa within the puparium (Fletcher, 1987). Goeden and Headrick (1992) reported a pre-puparial stage in which the mouthparts are invaginated and the integument takes on a waxy appearance, but the processes of integument hardening and University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 17 darkening are delayed. The latter processes may be triggered by changing environmental conditions by overwintering prepuparia of certain Neaspilota (Goeden and Headrick, 1992) and North American Urophora species, especially those found at higher altitudes (Goeden et al., 1995). Eclosion marks the end of pupation and the beginning of the adult life. The insect cracks open the puparium anteriorly and laterally at its seams and emerges from the pupal case. This almost invariably occurs around dawn, when leaves are still dump with dew, and the emerging fly can fold its new wings and harden its cuticle without the risk of desiccation. The timing of this is controlled by circadian rhythm (Fletcher, 1987). 2.3.0 General biology of fruit flies Fruit fly biology is an extensive topic. The following account is largely based on information gathered from fruit infesting tephritids of economic importance and may not represent tephritid biology as whole. 2.3.1 Life cycle Basic life cycles of tropical pestiferous fruit flies are roughly similar. A generalized developmental cycle of typical fruit fly is shown in Figure 2.1. Eggs can be deposited singly (as in A. obliqua), in strings (as in T. curvicada), or in clutches of various sizes (as in A. ludens, C. capitata and B. cacuminata) (Headrick and Goeden, 1994). Eggs are typically deposited under the epicarp or mesocarp of ripening fruit, although some species such as A. sagittata, or T. curvicauda, possess long ovipositors that they can employ to deposit eggs in or near seeds from which their offspring feed (Robinson and Hooper, 1989; Diaz-Fleischer et al., 2000). Egg hatch, like all other developmental stages of fruit flies, is dependent on environmental conditions. For example, eggs of B. dorsalis, B. cucurbitae, and Ceratitis capitata take from one to two days to hatch. Ceratitis University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 18 capitata typically posseses 28 polytrophic ovarioles that can produce from 300 to 1000 eggs during the life of a female, and these are laid in clutches of 1 to 10 eggs (Mcpheron and Steck, 1996). Prior to pupation, late instar larvae may leave host fruit while the early instar may still be attached to the tree, or more frequently pupate within the fruit once it has fallen to the ground. Within the fruit, pupation has been observed to be common among many tephritid larvae such as in the olive fruit fly, Bactrocera oleae and the Medterranean fruit fly, C. capitata. Moreover, larvae of some species like C. capitata jump by means of a spring mechanism that may serve to evade predators. Larvae of several species of Anastrepha and Bactrocera crawl out of the host fruit and seek adequate sites to bury into the ground, usually 2.5 cm and pupate therein (Bush 1966). Larvae seem to prefer sites with loose, moist, shaded soil for pupation. Larvae exiting the fruit in search of pupation sites are susceptible to dehydration and predation by ants and beetles (Aluja et al., 2000). After completion of metamorphosis, adults exit the puparium by rupturing one end with the aid of an appendage called ptilinum, which invaginates into the head soon after emergence. Newly emerged adults are desclerotized, and require some time for their cuticle to harden by exposure to the elements of nature. Tephritid adults are anautogenous, requiring to consume protein in order to reach sexual maturity. Sexual maturation with free access to protein sources can take from 5 to 20 days or more depending on the species. At sexual maturity, flies mate, oviposit and the cycle ends (Aluja et al., 2000). University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 19 Figure 2.1: Generalized developmental cycle of fruit flies (Adapted from Ekesi, 2006) Adult longevity is variable within and across species, and between both sexes. It has been suggested that some species of Anastrepha may enter aestivation as adults during periods of adverse climatic conditions and host unavailability. Some species of Bactrocera may reabsorb eggs into the body system during host scarcity (Vargas et al., 1997). At any rate, adult longevity appears to be the strategy of monophagous tropical tephritids to cope with fruit maturation periodicity (Aluja et al., 2000). Eggs laid in batches of 3-8 and hatch between 2-5 days Sexually matured between 4-10 days Maggots pass 3 instar stages, burrow in soil (2-5 cm) to pupate Length of cycle differ with climatic conditions University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 20 2.3.2 Nutrition Essential nutrients for fruit flies (adults and larvae) are amino acids, vitamins, sugar, minerals and growth factors (Mazor et al., 1987). To meet the nutritional requirements, a large array of ingredients is used for artificial diets for larvae. Included among these are dried carrot, wheat products (germ, bran, floor), yeasts (brewer’s yeast, torula yeast, yeast extracts), proteins (amino acids or enzymatic hydrolysate, autolysate), oils, sucrose, cholesterol, choline chloride, vitamins and salts. To provide texture, products such as tissue paper, cellulose, corn grits, bagasse and cassava, have been used. Antimicrobial agents such as nipagin, potassium sorbate, butoben, sodium benzoate and formalin, are used to keep artificial diets free from spoilage by micro-organisms, at least, until after the first instar. Egg production and hatchability are significantly reduced when vitamin E, biotin, choline chloride, inositol, nicotinic acid and riboflavin, are individually omitted from diet (Heath et al., 1997; Lux et al., 2003a). Adult flies require carbohydrate source, water and a protein substance in order to reach sexual maturity. In nature, although fruit flies have been observed feeding on a large range of products, such as decaying fruits, damaged fruits, plant sap, nectar, animal faeces, and honey, their major source of protein comes from bacteria belonging to the Enterobacteriaceae, commonly referred to as the fruit fly bacteria. A combination of sugar and enxymatic hydrolysed protein smeared on cards suspended from the tops of cages, and isolates of Enterobacteriaceae on agar plates placed on the tops of cages, provide adequate nutrients for a range of fruit fly species (Drew and Lloyd, 1987). 2.3.3 Host associations Most species of Tephritidae studied are phytophagous. Host range varies considerably, often among closely related species (Norrbom and Kim, 1988). Many species are strictly monophagous. For University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 21 example, B. oleae breeds only in olives, but some pest species are remarkably polyphagous. For example, C. capitata has been reported in more than 300 hosts (Liquido et al., 1991). Probably the majority of Tephritidae, however, are oligophagous, breeding in a few related or ecologically and chemically similar hosts. Toxotrypana species, for example, breeds in similar, latex-bearing, thick- skinned fruits of Caricaceae and Asclepiadaceae, two plant families that are not closely related (Norrbom and Kim, 1988). Even many of the polyphagous pest species, although able to breed in many hosts, have preferences for certain plant families or genera. Host races are known in Rhagoletis and possibly in Eurosta and Tephritis (Hernández-Ortiz and Aluja, 1994). Although phytophagy is the predominant mode of feeding in the Tephritidae, the Tachiniscinae are all probably parasitoids (the only reared species is a moth parasitoid), and at least one adramine species (Euphranta toxoneura) is predaceous within galls. Saprophagy, which is predominant in the Platystomitidae and Otitidae, could be the primitive feeding habit for the Tephritidae. Some (probably most) Phytalmiini and Acanthonevrini are saprophagous, although many breed in damaged or recently dead tissues of limited ranges of plants. A few species have been reared from rotten fruits, decomposing tree trunks, or from under bark of live trees (Dodson and Daniels, 1988; Permkam and Hancock, 1995). Some species of Acanthonevra breed in decaying bamboo shoots (Hancock and Drew, 1995). Termitorioxa termitoxena has been reared from termite galleries in living trees as well as from under tree bark (Hancock, 2002). Although tephritids are commonly known as fruit flies, a variety of host parts and tissues are attacked, including fruits (pulp and/or seeds), flowers, stems, buds, leaves, and roots. In phytophagous species, females deposit eggs in healthy plant tissues, where the larvae feed, and sometimes causing gall formation. Fruits and flowers (of diverse plant families) are the plant parts most commonly attacked, but many Trypetini are leaf or stem miners, and some Gastrozonina and University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 22 Acanthonevrini breed in bamboo shoots (Hardy, 1988, Hancock and Drew, 1995). The members of the subfamily Tephritinae have specialized in attacking Asteraceae and a few other families (Acanthaceae, Goodeniaceae, Lamiaceae, Verbenaceae). They breed in the flower heads or form galls, although the type and stage of flower tissue attacked varies (Headrick and Goeden, 1990), and galls of varying form and complexity may be produced on stems or roots, in flowers, or rarely on leaves (Freidberg, 1984). The larvae of species of Rachiptera and Strobelia secrete a liquid that forms a globular protective structure outside of its gall (Aljaro et al., 1984). Some species of Tephritids and Campiglossa misella have alternate gall-forming or stem-mining and flower-feeding generations, and Trupanea conjuncta is a faculative gall-former (Goeden, 1993). There is no worldwide list of tephritid host plants other than that of White and Elson-Harris (1992). Liquido et al. (1998) listed and cataloged the reported hosts of C. capitata, and Copeland et al. (2002) reported numerous additional hosts. De Meyer et al. (2002) listed the hosts of all Ceratitis species recorded from the Afrotropics. Norrbom and Kim (1988) provided a list of the hosts of Anastrepha, and Norrbom (2004) provided a database of the hosts of Anastrepha and Toxotrypana. There are no comprehensive host lists for the other zoogeographic regions. For the Afrotropical Region, Munro (1984) includes numerous host data; host index for many Tephritinae, and the Dacini of the region. For the Australasian Region, the hosts of the Dacini were listed by Drew (1989), those of the Phytalmiinae, Ceratitidini, and most other non-dacine Trypetinae of Australia were listed by Permkam and Hancock (1995), and the most known hosts of the Tephritinae of Australia were included in Hardy and Drew (1996). For the Neotropical Region, host data for Rhagoletis, Anastrepha and Toxotrypana have been compiled (Norrbom and Kim 1988), and known host plants for the Brazilian and Chilean tephritid species were listed by Frías (1992). For the Oriental Region, Kapoor (1993) listed the hosts of the Indian species, and provided host indices for the species of Thailand and the Philippines. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 23 In tropical Africa, host plants of fruit-infesting flies have received extensive evaluation in a number of ecologies. Detailed checklist of host plants of some major tephritid species in East and Central Africa is provided by De Meyer et al. (2002) and Ekesi and Billah (2006). Also, differences in host range among different polyphagous pests and the importance of certain plant families in the natural history of these pests have been studied in Kenya (Copeland et al., 2002, 2006), Benin (Vayssieres et al., 2005), Tanzania (Mwatawala et al., 2006a; 2009a), Mali (Vayssieres et al., 2007). Other studies focussed on the fruit fly spectrum of one or few commercial hosts, such as mango and citrus (Vayssieres and Kalabane, 2000; Vayssieres et al., 2005). Other available records on this topic are scattered through the literature, many of which are locally- and/or species-specific and require further evaluation. 2.3.4 Symbiotic associations Mutualistic relationships with microorganisms are extremely common among tephritid species. Possibly, the relatively low concentrations of proteins and other essential chemicals in vegetable tissues, make supplementary sources of certain nutrients mandatory. The vital importance of the symbiotes to their hosts is evidenced by the morphological adaptations evolved to ensure their survival and transmission from generation to generation (Bateman, 1972; Headrick and Gorden, 1998). The most elaborate adaptations so far reported for a tephritid are those of Dacus species (Rull, 2008). They multiply in the esophageal bulb and are released as compact masses, which pass down the gut and break down at the beginning of the hind gut. Electron microscopy has indicated that the bacteria subsequently collect and multiply in the diverticula that open into the rectum, and are transferred from there to the eggs during oviposition; some enter the micropyle and others remain on the egg surface (Mazzini and Vita, 1981). The bacteria enter the larvae at the time of hatching and multiply in the four mycetomes. Small numbers remain in the pupal stage and reinvade the esophageal bulb when it forms. This elaborate system is far from typical of the University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 24 remainder of the Tephritidae. Fletcher (1987) reported evidence of increasing levels of development of the symbiotic organs, with the Trypetinae the most primitive, and the Dacinae the most highly developed. The majority of the microorganisms which have so far been established as symbiotes of tephritids have proved to be rod-like, Gram-negative bacilli. Yeasts, fungi, and Gram-positive bacteria have been cultured from a number of species (Bateman, 1972) but have usually been shown to be simply associated organisms rather than symbiotes. It is probable that the most important function of the symbiotic bacteria is the production of specific nutrients which are absent or in low concentrations in the diets of the host insects. It is usually assumed that they supplement the larval diet primarily, even though the morphological adaptations which facilitate their survival are often far more elaborate in adults (Headrick and Goeden, 1998). Symbiotes may also be involved in the degradation of toxic substances ingested by the host insect. Fletcher (1987) suggested that use might be made of D. oleae’s extreme dependence on its symbiotes to achieve suppression of field populations of this serious pest. The symbiotes are very rapidly killed by streptomycin, and of course, the resultant larvae die soon after hatching from the egg. The progeny of recombinant parents have a considerably reduced rate of survival. 2.3.5 Natural enemies Many groups of organisms have been reported to attack tephritid fruit flies, but the records are widely scattered in literature and, except for some fruit fly species, there are few lists or review publications concerning tephritid natural enemies. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 25 2.3.5.1 Predators Common larval and pupal predators of tephritid fruit flies include Formicidae, predaceous wasps, Dermaptera, Staphylinidae, Carabidae, Coccinellidae, Chrysopidae, Pentatomidae, Coreidae, mites, crickets and myriapods (Sivinski, 1996). Immature stages of tropical fruit flies are known to be heavily preyed upon by ants (Van Mele and Cuc, 2000; Peng and Christian, 2005), especially during the vulnerable moment between leaving the fruit and securing a pupation site (Aluja et al., 2005). Van Mele et al. (2007) investigated the effect of the African weaver ant, Oecophylla longinoda, in controlling fruit flies in mango in Benin agrosystems and reported that conservation biological control with this predatory ant in high-value tree crops has great potential for African and Asian farmers. Staphylinid beetles can also prey on larvae in fallen fruits (Stibick, 2004). Mordellid beetles and birds attack the immatures of Eurosta solidaginis in their galls (Abrahamson et al., 1994). A cecidomyiid is an egg predator of Bactrocera oleae (Neuenschwander et al., 1983). Utomi (2006) conducted a preliminary survey on the natural enemies of B. invadens in four locations in the forest ecology of Southern Ghana. A range of predator insects of seven families belonging to five orders were recorded. Spiders, wasps, birds, toads and gekkos have also been reported as predators of adult tephritids (Condon and Norrbom, 1994; Sivinski, 1996). Jumping spiders have been presumed to constitute a selective force on the evolution of wing patterns and wing displays of adult tephritids. Apparently, R. pomonella is able to deter spiders from pounding due to the fact that its wing patterns resemble a frontal view of a spider that conspecifics and avoid attack (Sivinski, 1996). Hendrichs and Hendrichs (1998) observed attack of vespid wasps on C. capitata, noting that calling males, females visiting leks, and ovipositing and mating couples were heavily predated upon. Drew (1987) reported University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 26 that frugivorous rodents caused the highest mortality in two species of Bactrocera, and Thomas (1993) reported predation by rodents on immatures of Blepharoneura and Anastrepha. 2.3.5.2 Parasites Over a 100 species of parasitic wasps in the family Braconiadae have been reared from fruit infesting tephritids. Parasitoids can utilize their tephritid host during the egg stage, as is the case with Fopius arisanus on eggs of C. capitata, or Utetes canaliculatus on eggs of Rhagoletis pomonella, which the parasitoids appear to find by following trails of marking pheromone of its host (Wharton, 1989). Other species parasitize tephritid larvae of different instars such as Doryctobracon areolatus and D. crawfordi, both of which attack larvae of different species of Anastrepha (Aguiar-Menexes and Menexes, (1997). Some species also attack tephritid pupae such as Pachycrepoideous vindemiae, which has been found in the pupae of C. capitata, and A. ludens (Wharton et al., 2000). Parasitoids attacking different developmental stages can specialize in single species. For instance, Utetes canaliculatus, specializes on tephritids in several genera. Also, Diachasmimorpha longicaudata has been reared from Ceratitis, Bactrocera, Anastrepha and Rhagoletis. It may parasitize dipteran insects in several families, as is the case with Pachycrepoideous vindemiae (Stibick, 2004). Several species of parasitoids have been introduced or artificially reared and used in augmentative biological control programs against tephritids (Wharton, 1989). White and Elson-Harris (1992) provided references concerning the parasitoids (mostly Hymenoptera) of the 100 most economically important species of Tephritidae. Wharton (1989) listed parasite species used in biological control of fruit flies. A great deal of useful information on parasitic wasps attacking fruit flies worldwide is provided by Stibick (2004). In Africa, Wharton et al. (2000) reared ten hymenopteran parasitoids dominated by koinobiont assemblage from C. capitata and related tephritids from coffee plantations University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 27 in Kenya. Billah et al. (2005) studied the effect of host larvae on three Psyttalia species, braconid parasitoids of fruit flies and reported that Psyttalia species are especially important in post-release sampling surveys to ascertain the establishment of the parasitoids in new environments where they may adapt to new fruit fly host species. The possibility of rearing some Opiine braconid parasitoids on four species of Ceratitis from Kenya was demonstrated by Copeland et al. (2006). In a preliminary survey in the southern ecology of Ghana, Utomi (2006) recorded range of parasitic wasps dominated by Braconidae, Opiinae and Ichneumonidae infesting fruit flies in mango and citrus plantations. The reproductive compatibility between four different species of Psyttalia from Kenya and individuals of the morphologically identical Psyttalia concolor from laboratory culture from Italy was assessed by Billah et al. (2008a) through cross-mating tests using single-pair and group mating methods. Vayssieres et al. (2011; 2012) provided update of inventory of parasitoids associated with fruit flies in cultivated and wild crops within the agrosystems of Benin and Senegal. 2.3.5.3 Pathogens A number of pathogenic microorganisms have been known to attack tephritid fruit flies. For example, the fungus, Stigmatomyces aciurae (Ascomycetes) has been reported on Anastrepha striata adults collected in the field (Goeden and Benjamin (1985). Hedstrom (1994) reported records of Stigmatomyces fungus species known to attack Tephritidae, and Laboulbeniales species have been found on abdomens of various fruit fly species. A virus is known to attack Bactrocera tryoni (Sivinski 1996). Drew and Allwood (1985) described a species of Strepsiptera that parasitizes ten species of Bactrocera. Nematodes have also been used for the control of several tephritid species (Sivinski, 1996), but naturally occurring attacks have not been reported. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 28 The use of microbial pesticides in control of fruit fly pests is generally considered as biotactical techniques. It should be remembered that nongenetic resistance may take place. This includes phenotypic changes in insect behavior or physiology and of host plant interference with pesticide action, including microbial pesticides such as entomopathogenic bacteria and viruses. These are particularly sensitive to plant chemistry because they infect through the gut. As a consequence, the composition of foliage ingested with the microbial pesticide can dramatically influence its effectiveness. (Appel and Schultz, 1994). Another factor to consider is rainfall. It has been suggested that a light rainfall may help in prolonging the period of activity of viral preparations by moving the virus downwards, towards the more shaded parts of a plant and away from light. This would help to prolong its effectiveness. No absolute proof of this hypothesis has yet been made. (D’Amico and Elkinton, 1995) 2.4.0 Ecology of fruit flies A great deal of information on the ecology of tephritid fruit flies has accumulated over the years, but most of it is scattered and fragmentary. Investigations aimed at the systematic assembly of quantitative and qualitative information, leading to an understanding of the determinants of abundance of populations of species are presented here. 2.4.1 Life history strategies The two most important parameters influencing the life history strategies of dacine fruit flies are (a) suitability of the environment for reproduction and survival and (b) host availability in time and space (Fletcher, 1987). The life history characteristics of the polyphagous species are best suited for exploiting resources that occur intermittently throughout most of the year, but are unpredictable in time and space. The adults have high mobility, relatively long life span (often more than three months), high potential fecundity (> 1000 eggs per female), scramble type competition in the larval University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 29 stages, several generations per year, and the ability to pass unfavorable periods of the year in a facultative reproductive diapause when necessary (Vargas et al., 1983). The life history characteristics of the oligophagous species are similar in many respects to those of the polyphagous species. However, the majority of oligophagous species have a lower potential fecundity (400-600 eggs) (Fletcher, 1987) and their rate of egg production is more directly influenced by the availability of suitable hosts (Fitt, 1986). The life history strategies of the monophagous and stenophagous species vary depending upon the fruiting characteristics of their hosts. In general, they have fewer ovarioles and lower potential fecundity than the other groups. The potential fecundity of B. oleae and B. latifrons is about 300 eggs per female (Vargas and Nishida, 1985). Females of D. musae, however, have about the same number of ovarioles as polyphagous females, and therefore possibly have the ability to lay a large number of eggs in a relatively short period when hosts are abundant. Bactrocera opiliae is univoltine and spends most of its life as an adult, although the actual reproductive period is quite short. Adults of B. oleae can survive several months when reproductively inactive, but during periods of intense oviposition, particularly in late summer, their longevity is markedly reduced (Kapatos and Fletcher, 1984). During much of the year, adults probably live a maximum of 1-2 months. Unlike most dacines, B. oleae lays only one egg per fruit and then marks the fruit with fruit juice. It is the only dacine known in which contest type competition normally prevents the development of more than one larva per fruit. A number of other monophagous species that infest small fruits, e.g. D. cacuminatus and B. opiliae, do not use marking compounds; overcrowding due to multiple ovipositions can result in high mortality of larvae (Fitt, 1981; Drew and Hooper, 1983), because the type of competition switches from scramble toward contest at relatively low larval densities per fruit. University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 30 The importance of dispersal also varies among monophagous species. Those that infest host plants that fruit erratically throughout the year, e.g. D. cacuminatus, appears to be highly mobile, and move around frequently in search of hosts. Bactrocera opiliae, which infests a host with a limited fruiting period, moves mainly from emergence site to dry season refuge, and then in search of fruiting host plants at the beginning of the subsequent wet season. In B. oleae the dispersive movements are determined largely by host availability in the areas where they emerge. The polyphagous dacines are the most strongly r-selected, and the monophagous species, such as B. oleae, are the least strongly r-selected, although they still fall nearer the r than the K end of the spectrum compared with most other tephritids (Fletcher, 1987). 2.4.2 Determinants of abundance The family Tephritidae divides naturally into two major groupings on the basis of physiological and ecological characteristics: (i) the univoltine species, which usually have a winter diapause and inhabit the more temperate regions of the earth (e.g., Rhagoletis species); and (ii) the multivoltine species which have no obvious diapause and inhabit warmer regions (e.g., Dacus and Anastrepha species (White and Elson-Harris, 1992). The principal components of the life systems of tephritids are moisture, temperature, light, food, natural enemies, and symbiotes (Fletcher, 1987). The part which these factors play in the determination of numbers, and the aspects of behavior which are of particular relevance to survival and multiplication, would be examined here. 2.4.2.1 Effect of moisture Environmental moisture is of special importance as a determinant of abundance for several tephritid species. The distribution of B. cucurbitae in India is largely determined by moisture. The population expands when rainfall is adequate and contracts during dry periods (Nishida, 1963). Moisture is of primary importance in the determination of abundance of the Queensland fruit fly, B. tryoni, at least University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 31 toward the southern fringe of its permanent distribution. Over a period of several years, there was a highly significant correlation between the availability of moisture as measured by summer rainfall, and the peak numbers of this pest achieved each year. The effect is apparently mediated through a reduction in the fecundity of adult females during dry periods, by greatly reduced immigration from other areas, and by high mortality among newly emerged adults which struggle upward through dry soil into air with low relative humidity (Fletcher, 1987). In Nova Scotia, R. pomonella is also less common in hot dry summers than in cool wet ones due to desiccation of pupae in dry soil (Neilson, 1990). These effects have a direct bearing on the magnitude of adult populations of this species in dry years and in dry areas (Aluja et al., 2000). The longevity of adults of the walnut husk fly, R. completa, in field cages, is also considerably reduced at low relative humidities (Foote et al., 1993). Tephritids are rarely found in extremely dry parts of the world, perhaps because of limitations on the distributions of their host plants rather than on their capacity for physiological adaptation (Aluja et al., 2000). A species which has become adapted for existence in a dry area is R. slycopersella, which is indigenous to the dry western plains of Peru. Exposure to the hottest and driest parts of the year is avoided by a pupal aestivation which delays adult emergence for as long as eight months. The pupae are resistant to desiccation, and rain induces a flush of emergence of adults (Boller and Prokopy, 1976; Pablo et al., 2008). The stages of the life cycle which appear to be most susceptible to desiccation are the mature larvae (in the interval between emergence from the fruit and pupation) and the newly emerged adults. Rain has been shown to influence the behavior of both of these forms. It stimulates the emergence of mature larvae from fruit in A. ludens and B. tryoni (Aluja, 1994), and induces an increased rate of adult emergence in R. pomonella (Boller and Prokopy, 1976; Boller, 1993). University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 32 2.4.2.2 Effect of temperature The role of temperature as a determinant of abundance in tephritids, as in all poikilothermic animals, is mediated either directly or indirectly through its effects on rates of development, mortality, and fecundity. Rates of increase (or decrease) of individual populations are dependent upon the values of these parameters, and they in turn are determined by the multiple influences impinging upon the individuals from within the life system of the population (Drew and Yuval, 2000). Temperature is one of the most important of these influences. It has the dominant role in the determination of rates of development, and is therefore, largely responsible for the timing of the population processes, and their synchronization with changes in the environment. In most parts of the world, fruit flies are distinctly seasonal in abundance, with numbers high in summer and low in winter (Hallman et al., 2011). In the univoltine (temperate) species, egg laying is usually restricted to a few weeks in summer (Bateman, 1972) but in the more tropical multivoltine forms, it may extend from early spring into late autumn, whenever suitable host fruits are available. The multivoltine species may produce up to six overlapping generations in a single season. Characteristically, their numbers buildup to a peak in late summer and early autumn, and then decline fairly rapidly (Xiaofei and Hui, 2009). Even in tropical areas such as Hawaii, where the difference between summer and winter is relatively small, there is a distinct seasonal pattern of abundance (Bateman, 1972). but this is probably more related to the availability of suitable hosts than directly to changes in temperature (Fletcher, 1989). In general, development of the immature stages of tephritids is possible between 10°C and 30°C, although post-diapause pupae of some temperate species can develop at temperatures as low as 5ºC. Survival is possible over a much wider range. A few hours at 45ºC seems to be the upper limit, regardless of the stage of development, but the lower limit is indefinite; pupae of temperate species University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 33 may be exposed in the field, to temperatures as low as -12°C, apparently without harm (Yuan et al., 2005). Fecundity is also dependent upon temperature, with maximum production of eggs within the range from 25°C to 30°C (Bateman, 1972). For oviposition, however, thresholds fall between 9°C and 16°C for various species. Upper limits are not clear, but in the field, egg-laying activity is often depressed during the hottest parts of the day (Hallman et al., 2011). More detailed information concerning the effects of temperature on survival and development has been outlined by White and Elson-Harris (1992) in their review of the bionomics of the group. 2.4.2.3 Effect of light Light plays an extremely important role in the determination of fecundity in fruit flies, but has less direct effects on rates of development and mortality. It affects fecundity in two main ways: first, by influencing the general activity of adult females (especially feeding and ovipositional activity); and, second, by its important role in the synchronization of mating behavior (Bateman, 1972). Bactrocera dorsalis females reach sexual maturity earlier, mate sooner, and lay eggs earlier when kept in bright rather than dim light (Khalid and Mishkatallah, 2007). Similarly, females of B. oleae kept in bright light lay about six times as many eggs as those kept in the same room but in relatively dull light (Tzanakakis and Economopoulos, 1967). Fecundity in D. tryoni is considerably affected by illuminance. Changes in fecundity in this species associated with changes in both illuminance and photoperiod are directly correlated with feeding activity and rate of ovarian maturation although females kept at a low illuminance, approaching that which normally initiates sexual activity, also lay increased numbers of eggs (Bateman, 1972). There are conflicting reports on the effect of increased illuminance on the age at which mating occurs. Light is one of the most important factors influencing oviposition in the temperate species. Direct radiation from the sun or from a strong artificial light source (4000 lux) directly stimulates University of Ghana http://ugspace.ug.edu.ghUniversity of Ghana http://ugspace.ug.edu.gh 34 oviposition (Boller, 1993). For many species of Tephritidae, falling illuminance at dusk acts as a stimulus for the initiation of sexual activity (Syed et al., 1970; Fletcher, 1987). In B. tryoni the direct effect of light on the daily cycle of sexual activity is reinforced by a strong endogenous rhythm (Fletcher, 1987). In temperate species, the time of mating appears to be less rigidly defined. The host fruit is often used as a point of rendezvous for the sexes, and mating occurs either on the fruit or on foliage nearby (e.g., R. pomonella). In these circumstances, an elaborate mechanism to synchronize mating activity and restrict it to a certain time of the day is probably unnecessary. The fact that it is sometimes observed more commonly in the afternoon may be related to generalized daily activity in cooler areas rather than specific synchronization of mating behavior (Fletcher, 1987). 2.4.2.4 Food availability The types of food required by the feeding stages (larvae and adults) of tephritids and available to them in nature, and in the extent to which the quantity available influences rates of development, fecundity, and mortality, is of much interest in this review. A great deal of research has been devoted to the development of larval media suitable for the maintenance of laboratory cultures of fruit flies and for the mass production of flies for use in biological control or sterile release programs. The majority of these media are based on those devised by Vargas et al. (1990) for B. dorsalis, B. cucurbitae, and C. capitata in Hawaii. Simple, efficient and relatively cheap media are now available for most of the pest species of Tephritidae (Ekesi et al., 2007). The history of the development of these media, their modifications for various species and the laboratory techniques devised for their efficient use, have been reviewed by Vargas et al. (1990). No fruit fly larvae have yet been reared on a chemically defined medium, and consequently their precise nutritional r