Knowledge Gaps, Training Needs and Bio-ecological Studies on Fruit-infesting Flies (Diptera: Tephritidae) in Northern Ghana
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.
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,
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.
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,
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 fasciventris), and Dacus Fabricius
(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
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.
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
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:
- Knowledge gaps, perceptions and practices of fruit growers on fruit fly pests
- In-service training needs of Agricultural Extension Agents (AEAs) on fruit fly pests
- Species diversity and host range of fruit fly pests
- Seasonal phenology of major fruit fly pests
- Native parasitoids associated with fruit fly pests
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