Distribution pattern and host preference of African invader fly, Bactrocera invadens (Drew, Tsuruta and White) [Diptera: Tephritidae] in Akure and its environs  

Raphael Abiodun Adebayo , S. T. Akinbola
Federal University of Technology, Akure, Ondo State, PMB 704, Nigeria
Author    Correspondence author
Molecular Entomology, 2014, Vol. 5, No. 7   doi: 10.5376/me.2014.05.0007
Received: 13 Aug., 2014    Accepted: 19 Sep., 2014    Published: 28 Oct., 2014
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Adebayo and Akinbola, 2014, Distribution pattern and host preference of African invader fly, Bactrocera invadens (Drew, Tsuruta and White) [Diptera: Tephritidae] in Akure and its environs, Molecular Entomology, Vol.5, No.7 1-6 (doi: 10.5376/me.2014.05.0007)

Abstract

The presence, distribution pattern and host preference of the African Invader Fly, Bactrocera invadens (Drew, Tsuruta and White) was studied in three different locations in Akure and its environs, Federal University of Technology Akure (FUTA), Federal College of Agriculture (FECA) and Ipogun (Ondo State, southwestern Nigeria) on mango, citrus and pawpaw for a period of eight weeks. Trapping of the fruit flies was done using fabricated plastic bottle traps baited with Methyl Eugenol (ME) (4-allyl-1,2-dimethoxybenzen) pre-mixed with insecticide, Plan D. The flywas present in the three locations sampled throughout the study period. Average value of the fly obtained revealed that Bactrocera invadens was most abundant at Ipogun village compared with FECA and FUTA and was significantly different at p > 0.05. The result also showed no significant difference in the number of catches at FECA and FUTA, but showed significant difference in Ipogun throughout the period of the study (p > 0.05). Pattern of catches was also observed to increase with the number of weeks on all the hosts at the three locations. The computed mean density of the fly in the various locations showed that number of fly caught was most on the mango host than citrus and pawpaw, though, no significant difference was observed between the three hosts at the end of the eight weeks. This study has provided information on the presence, distribution pattern and preference for already identified hosts within the region. It is therefore recommended that continuous monitoring of the fly’s population be initiated, while the comprehensive control measure is urgently required.

Keywords
Bactrocera invadens; Fruit fly; Methyl eugenol; Plan D

Fruit production and export is one of the fastest growing agricultural sectors in Africa, providing income and employment. Mangoes, citrus, pawpaw, apple, pineapple and tomatoes are among the commonest ones grown both for domestic, urban markets and for exports that target large markets in Europe and the Middle East. Besides export, is the changing dietary patterns leading to increased consumption of fruits (Lux et al., 2002). Successful fruit production depends on maintaining high productivity and meeting ever-increasing quality and quarantine standards required on the local and export markets. This entails coping with the local insect pests and diseases. Both the producers and authorities are aware that new exotic pests, once introduced to, and established in the country, may ruin thriving fruit industries (Lux et al., 2002).

Different types of insect pests afflict fruit production in Africa, but perhaps none has gained greater notoriety than the group known as fruit flies (Diptera: Tephritidae). They cause enormous losses through direct damage to fruits and loss of market opportunities through imposition of strict quarantine regulations (Drew et al., 2005). An assessment reveals that of the 1.9 million mangoes produced in Africa annually, about 40% is loss due to fruit flies. Fruit infestation rates vary among countries and seasons, ranging from 5% to 100%. The recent introduction of a uniform and strict quarantine and the maximum residue level regulations in the European Union (EU) are other factors compounding the problem and jeopardizing the lucrative export of fresh mangoes from Africa (Lux et al., 2002). Bactrocera invadens (Drew, Tsuruta and White) is a recentlydescribed species of Tephritidae commonly known as African invader fly, Asian fruit fly, Mouche des fruits, or Tephritid fruit fly (Drew et al., 2005). It is highly invasive and polyphagous with high reproductive potential. The female pierces the fruit using their ovipositor to lay an average of 700 eggs depending on the host. Bactrocera invadens is multivoltine and reproduces with an average life span of about 3 months (White, 2006).
Billah et al. (2005) obtained high concentrations (more than 10 specimens per trap per day) not only from sites with cultivated crops, but also from either indigenous forest or forest reserves. This shows that the pest could be capable of reproducing in wild fruits and hence, has sufficient reproductive base even off the main hosts fruiting season for them to thrive. White et al. (1992) had also reported that Bactrocera species are multivoltine (i.e producing several generations per year) and attack fruits belonging to several unrelated families of plants.B. invadens is a polyphagous species and has to date been recorded from 25 host species belonging to 13 plant families (Aruna et al., 2009). Bactrocera invadens has brought a major economic challenge to sub-Sharan African farmers as a result of the heavy fruit losses that it causes and also the restrictions in fruit trade from quarantine measures to control it. There exist a gap in available information on the presence, extent of spread and pattern of distribution of this fly in Nigeria. Therefore, this study seeks to investigate the presence, distribution and density of Bactrocera invadens in Akure and its environs.
1 Results
Results from this work indicated that Bactrocera invadens was present in all the locations sampled throughout the period of monitoring, i.e from May to July, 2011. During the sampling period, a total of sixty thousand and sixty four flies were caught. Considering the average value of the pest density obtained for each of the study locations throughout the study period, B. invadens appears to be most abundant at Ipogun, followed by Federal College of Agriculture (FECA) and least at Federal University of Technology Akure (FUTA).
The study also revealed that number of catches on all the hosts were not significantly different at p > 0.05 for the eight weeks of trapping at FUTA (Table 1). However, number of flies trapped at FUTA was higher on mango, followed by pawpaw, while citrus recorded the least. It was also observed that number of the trapped flies increased with the number of weeks on the hosts sampled.
Table 2 below presented the result from FECA site and the same trend was observed as in the case of FUTA site (Table 1). On the contrary, number of flies was least on pawpaw, as the least host at FUTA was citrus.


Table 1 Mean number of fly catches on hosts at FUTA for 8weeks


Table 2 Mean number of fly catches on hosts at FECA for 8weeks

At Ipogun, there were significant differences in the number of flies caught per week, except for week 2 and 6. Significantly lower number (326) was recorded on pawpaw at week 1, while the highest (421) was recorded for citrus. The same trend was observed at week 3, 4, 5 and 7 where least number of catches was recorded for pawpaw. However, there were significant differences at p > 0.05 in the numbers of flies trapped on all the hosts at week 8, though mango produced highest number of trapped flies (575) [Table 3].


Table 3 Mean number of fly catches on hosts at Ipogun village for 8weeks

Table 4 revealed a significant difference for hosts and location for the eight weeks period. At FUTA, significantly lower number of catches was obtained on citrus (3825), while mango recorded highest (4809). FECA result also showed that mango recorded highest number of trapped flies (5749), while pawpaw pooled least (4751). The result obtained at Ipogun was similar to that at FECA.


Table 4 Mean number of fly catches on hosts at FUTA, FECA and Ipogun for 8weeks

Results of the total number of flies caught on the hosts at the three locations were presented in the Table 5. Number of catches at FUTA and FECA showed no significant difference at p > 0.05 when compared, though highest number was recorded at FECA. However, Ipogun was significantly different from all other locations with the highest number of trapped flies (32,947). Number of catches on hosts for the three locations were not significantly different at p > 0.05 with highest number of trapped flies recorded on mango (22,463), followed by citrus (19,723) and least on pawpaw (17,878).


Table 5 Mean number of flies caught at the locations and on hosts for 8weeks

2 Discussion
The results from this study were consistent with the results obtained by earlier workers that methyl eugenol is an effective and efficient lure for B. invadens (Lux et al., 2003; Mwatawala et al., 2004; Billah et al., 2005; Drew et al., 2005; Vayssieres 2005). The effectiveness and efficiency of the traps shows their importance in surveillance and detection programs involving B. invadens.This study clearly revealed the presence of B. invadens in Akure and its environs, and shows that the pest is well distributed in all locations studied. This observation is in agreement with works of other researchers. Lux et al., 2003 reported the detection of B. invadens in East Africa. Ekesi et al. in 2006 reported Bactrocera invadens to be rapidly spreading across tropical Africa, while Billah et al. (2005) reported the presence of the fly in Ghana. In Nigeria, B. invadens has been recorded on mangoes and citrus (Umeh et al., 2008). All the hosts used in the study were infested B. invadens as various numbers of flies were trapped on them. This result agrees with the work of Aruna et al., 2009 who reported some horticultural crops as hosts of B. invadens and also confirms that the fly is highly polyphagous as reported by Copeland et al., (2002). It was also indicated by the study that mango produces highest number of catches compared to other hosts studied. This is in agreement with the studies carried out by Utomi (2006), Ekesi et al. (2006), and Aruna et al. (2009) where mango was listed as a major and most preferred host of B. invadens.
The relative pest density of the flies at the different locations appeared to be influenced by the characteristics of the ecological zones where they are situated. On the average, Ipogun is situated in denser forest than the other locations has the highest observed pest density (32,947) of the fly. This was expected because of the large diversity of plants, hence the hosts in the zone. This finding agrees with the results of Vargas et al., (1990) and Harris and Lee (1989) who in their works on the distribution and abundance of various tropical Tephritids, found that availability of the host fruits has a major effect on the distribution and abundance of fruit flies.
Furthermore, in the forest zone, due to the diversity of plants, there are greater chances of finding orchids from which Methyl Eugenol is sequestered. FUTA had the least pest density (12,942). This was expected as it is situated in scattered and sparse vegetation unlike Ipogun situated in more dense vegetation. The high catches at Ipogun confirms that B. invadens is a low land pest as shown by previous studies (Ekesi et al., 2006). It was also observed in this study that pattern of catches increased with time of trapping during the present study in the locations surveyed. This corresponds with the work of Hanna et al. (2008) who stated that B. invadens reinvades with increasing density after the beginning of the raining season. The high rainfall, relative humidity and cloudy skies reduce the effect of the heat of the sun which might reduce the flies’ activity. It was thus suspected that they find refuge in moist and humid environments especially in places with thick canopy covers.
3 Conclusion
This study has contributed to the knowledge of B. invadens in Africa and Nigeria in general, and Akure in particular (south-western Nigeria). This is important for the development of efficient management strategies against the pest. Furthermore, the data could serve as baseline data for future studies on the pest.The strong and selective response of the new invasive fruit fly species to Methyl Eugenol, and the capacity to infest and develop in mango fruits and other hosts, typical of Asian fruit flies from the genus Bactrocera Macquart were confirmed by this study.
Evidence from this research has shown that, Bactrocera invadens is well distributed in Akure, Ondo State, in the south-western part of Nigeria. The study on the distribution of the pest has shown a distribution pattern that corresponds with environmental conditions, being more abundant in areas that are forested and humid (as in the case of Ipogun). Host availability depends on how diverse an environment can be in terms of vegetation.The result also showed that mango was most preferred, followed by citrus and pawpaw. It was also observed that trapped number of flies increases with the number of weeks.
3.1 Recommendations
Based on the findings of this study, it is recommended that; Further studies should be carried out on the distribution of the pest for a longer period of time.Thus, the government and other stakeholders should make the lure, Methyl Eugenol available in the country to facilitate fruit flies monitoring research.For the purpose of preventing the spread of B. invadens and other fruit flies in the country, a system approach should be adopted in the management of B. invadens. Effective phytosanitary measures should also be developed to safeguard trade of commodities suspected to be the hosts of B. invadens.More hosts should be further screened for the detection of B. invadens, while year round trapping should also be carried out to determine the population dynamics of B. invadens.
4 Materials and Methods
4.1 Study Area
The study was conducted in Akure, south-western Nigeria, from May 19 to July 14, 2011. Three locations in the rainforest ecological zone surveyed include campuses of the Federal University of Technology Akure (FUTA), Federal College of Agriculture Akure (FECA) and Ipogun, a village in Ifedore Local Government Area of Ondo State. However, the thickness of the existing vegetation in the three selected locations varies. Fruit crops are grown in these locations, thereby making the locations suitable environment for the study. The fruits, mango, citrus and pawpaw selected are reported as major hosts of fruit flies. FUTA lies within the tropical rainforest belt, between latitude 7015’N and longitude 5015E (Adekayode and Olojugba, 2009). Akure has an average annual rainfall of about 1,613mm per annum, and annual mean temperature of about 270C. The dry season is usually witnessed in Akure between November and March, while the rainy season occurs from April to October.
The sites selected at FUTA for survey include crop type museum and Akindeko hall of Obekekere, Southgate of the campus. The host trees in these sites are mainly homestead and orchard. The plantations of host fruits on the Eastside of the campus were sampled at FECA, while mango, citrus and pawpaw plantations were sampled at Ipogun village.
4.2 Fabrication of Traps
Local traps were fabricated according to that of Billah et al. (2005). Bottle traps were used for the sampling of the fruits flies. These were made from a clear cylindrical recyclable plastic container (8cm diameter and 15cm height), with four holes (2.7cm diameter each), evenly spaced around the upper half of the container, and perforated at the underneath for water drainage. A ball of cotton wool wick was made and tied with string of length 45cm with a knot on the string serving as a stopper. The bottle was closed with the string passing through lid, hanging the cotton beneath the four holes to prevent insects from falling off the container when trapped.
4.3 Trapping Procedures
The lure used was Methyl Eugenol (4-allyl-1,2- dimethoxybenzen) (ME) (Agri-Mat®, England). This has been pre-mixed with insecticide, Plan D or Akape in ratio 4:1 (that is, 4 parts ME:1 part Plan D or Akape). Cotton wicks were soaked in the mixture for 5seconds (to near saturation and avoiding dripping) and suspended in the trap from one end of a piece of string that passes through the lid of the trap from which the trap was hanged on the tree. Care was taken to avoid contamination of the outer parts of the traps.
4.4 Sampling for B. invadens on Mango, Citrus and Pawpaw
The sampling was carried out within a period of eight weeks (May-July, 2011). Hosts from orchard/homestead or plantation (as in the case of Ipogun site) were sampled at a distance of 25m between the trees as recommended by the standard. Each trap was replicated three times per site. An interval of seven days was allowed between the placement of traps and the recovery of trapped insects. Collected insects were preserved in 70% ethanol for identification in the laboratory, using morphological keys as described by Billah (2003). This was done after the flies have been counted and recorded.
4.5 Statistical Analysis
Data collected on the number of catches were square root transformed and Analysis of Variance performed. Where statistical difference existed, means were separated using Duncan Multiple Range Test (DMRT) at (p>0.05).
Acknowledgement
The authors are thankful to Mr. O. O. Ogunfunmilayo of Nigeria Agricultural Quarantine Service, Moor Plantation Ibadan for his assistance at sourcing the lure used for this project.
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