Maxwell Kelvin Billah

Cross mating studies among five fruit fly parasitoid populations: potential biological control implications for tephritid pests

The reproductive compatibility between four different species/populations of the tephritid parasitoid Psyttalia (Walker) species from Kenya and individuals of the morphologically identical Psyttaliaconcolor (Szépligeti) (Hymenoptera: Braconidae) from a laboratory culture in Italy used in augmentative biological control of olive fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae) was assessed through cross mating tests using single-pair and group mating methods. Reciprocal crosses among the species resulted in the production of viable offsprings up to the second generation. In spite of the successful production of viable offspring in the laboratory, Psyttalia species are known to have specific host fruit and/or host fly preferences and populations/species may be isolated in one way or the other. However, it is not known whether these populations/species interbreed in the field. We discuss the ability of these parasitoids to interbreed and the potential effects of that on their use as biological control agents, especially in environments where other closely related species are present or in situations where multiple parasitoid introductions are intended.

Species composition and host range of fruit-infesting flies (Diptera: Tephritidae) in northern Ghana.

An important aspect of fruit fly management is accurate information on the species and their host spectrum. Studies were conducted between October 2011 and September 2013 to determine the host range and species diversity of pest fruit flies in the northern savannah ecology of Ghana. Fruit samples from 80 potential host plants (wild and cultivated) were collected and incubated for fly emergence; 65 (81.5%) of the plant species were positive to fruit flies. From records in Africa, 11 plant species were reported to be new hosts to the African invader fly, Bactrocera invadens (Drew, Tsuruta and White, 2005). This study documented the first records of Dacus ciliatus (Loew) and Trirhithrum nigerrimum (Bezzi) in northern Ghana although both species have been previously reported in other parts of the country. Infestation by B. invadens was higher in the cultivated fruits; Ceratitis cosyra dominated in most wild fruits. Cucurbitaceae were mainly infested by three species of Dacus and Bactrocera Cucurbitae, a specialized cucurbit feeder. Among the commercial fruit species, the highest infestations were observed in mango, tomato, sweet pepper and watermelon, whereas marula plum, soursop, tropical almond, sycamore fig, African peach, shea nut, persimmon, icacina and albarillo dominated the wild host flora. The widespread availability of host plants and the incidence of diverse fly species in the ecology call for particular attention to their impact on commercial fruits and the development of sustainable management strategies against these economically important pests in Ghana.

Species composition of fruit flies (Diptera: Tephritidae) in the Citrus Museum at the Agricultural Research Centre (ARC), Kade, Ghana

To determine species composition of fruit flies on six cultivated varieties of citrus (Late Valencia orange, Pineapple orange, Ovaleto, Mediterranean sweet lemon, Satsuma tangerine and Ortanique orange), a study was conducted at the Agricultural Research Centre, Kade, Ghana. Improvised Lynfield baited traps (methyl eugenol (ME) and citrus juice (CJ)) and McPhail baited traps (trimedlure (TML)) were used. Ripe infested fruits from the selected varieties were also collected and incubated. Tephritid fruit fly species from trapping were identified as Bactrocera invadens Drew, Tsuruta & White, Bactrocera Cucurbitae (Coquillet), Ceratitis ditissima Munro, C. anonae Graham, C. capitata (Wiedemann), C. bremii Guerin-Meneville, Dacus bivittatus (Bigot), D. punctatifrons Karsch and Trirhithrum Bezzi. A total of 35,247 fruit flies were collected from the traps, with densities of 10.38, 1.00 and 0.27 flies/trap/day for ME, CJ and TML traps, respectively. All incubated fruit varieties showed co-habitation of three different species (C. ditissima, C. anonae and B. invadens) in each of them. In addition, one Dacus vertebratus was obtained from dropped Late Valencia fruits. Moreover, three individual Fopius caudatus (Szèpligeti) parasitoids were recorded from the infested incubated fruits. Ranking of the different fruit fly species from infested incubated host fruits was as follows: C. ditissima (476) > C. anonae (74) > B. invadens (71) and D. vertebratus (1). Competitive ability among the invasive flies in their process to infest the six citrus varieties was observed. These findings could serve as a useful starting point for the development of a reliable catalogue of host diversity, fruit fly species diversity and associated natural enemy records in Ghana.

Risk of heavy metal ingestion from the consumption of two commercially valuable species of fish from the fresh and coastal waters of Ghana

Background The need to evaluate the human health safety of fishery resources remain urgent in the mist of the ever-increasing fear of heavy metal toxicity from the consumption of Ghana’s fisheries resource, as a consequence of pollution from several anthropogenic activities including artisanal gold mining. Nevertheless, the bigeye grunt (Brachydeuterus auritus) and Bagrid catfish (Chrysichthys nigrodigitatus) remain commercially valuable fish species in West Africa and continue to attract high patronage. Method Forty-five specimens each of C. nigrodigitatus and B. auritus collected from the Weija Dam and the Tema Fishing Habour in Ghana, between June and September 2016, were analysed for seven heavy metals using Atomic Absorption Spectrometry. Result Lead and Cadmium were below detection in all samples while Cu was not detected in B. auritus. Levels of the remaining metals (mg kg-1) were below FAO/WHO maximum permissible limits in fish and occurred in the rank order Se (3.5) > Zn (2.34) > Cu (0.59) > As (0.37) > Hg (0.19) in C. nigrodigitatus and Se (2.97) > Zn (2.28) > Hg (0.31) > As (0.21) in B. auritus. Only As in C. nigrodigitatus recorded Estimated Weekly Intake (EWI) greater than FAO/WHO Provisional Tolerable Weekly Intake (PTWI). Also, As in C. nigrodigitatus and Hg in B. auritus had Targeted Hazard Quotient (THQ) greater than 1 for individuals consuming the fishes on daily basis and therefore, raising concerns. However, for both species of fish, cancer risk of As was 1 in 10,000,000,000 and modified Health Benefits values of Se (HBVSe) were positive indicating the health risks that might accompany Hg exposure would be negated. Since toxicity depends on the concentration and quantity of a pollutant consumed, safe maximum consumption rate of C. nigrodigitatus based on As concentrations was 0.21 mg per day and that of B. auritus was 0.058 mg per day for Hg. With an average of 0.227 kg fish per meal of an adult human, these translated into not more than 24 C. nigrodigitatus and nine (9) B. auritus meals in a month but because fish is consumed at 0.0685 kg per person per day in Ghana, these values respectively translates to 93 and 30 safe days of consumption per month. Conclusion At the rate of 0.0685 kg fish per person per day that fish is consumed in Ghana, the consumption of the two species of fish in Ghana would essentially be of little or no consequence to consumers.

Integrated Management of Fruit Flies: Case Studies from Ghana

This case study is an overview of the general fruit fly situation in Ghana, starting with a historical background on fruit fly studies in Ghana, through the period when Bactrocera dorsalis invaded Africa in the early- to mid-2000s, to the present. We focus on the importance and contribution of agriculture to the economy of Ghana, the effect of fruit flies on agricultural production, the local and export markets (especially of horticultural produce), and attempts made to manage fruit fly populations. These attempts include the initial acceptance that the challenge of fruit flies was a national issue requiring the development of strategic action plans by the Ghana National fruit fly Management Committee (NFFMC) to understand the biology and ecology of the pest and implement effective management. The strategies include a four-point plan consisting of three main management strategies: (1) Bait application technique (BAT), (2) Male annihilation technique (MAT) and (3) Orchard Sanitation/Farm Hygiene, and a fourth non-management strategy: (4) Capacity Building, Awareness Creation and Information Dissemination. The latter ensured that there was a highly knowledgeable human capital base, well-equipped with the necessary information to undertake the management actions. This has resulted in the development of some innovative tools such as the development of the Fruit Fly Resource Box, which is widely used in Ghana and gradually gaining recognition in neighbouring countries.

Preliminary inventory of hymenopteran parasitoids associated with fruit-infesting flies (Diptera: Tephritidae) in Northern Ghana

ABSTRACT Baseline studies were conducted to determine the parasitoids associated with fruit flies in the northern savanna ecology of Ghana. Fruit fly puparia obtained from incubation of 17 host fruit species were maintained in rearing cages for the emergence of parasitoid wasps. Four species of braconid parasitoids namely, Fopius caudatus (Szépligeti), Psyttalia cosyrae (Wilkinson), Psyttalia concolor (Szépligeti) and Diachasmimorpha fullawayi (Silvestri) were recovered. F. caudatus was the most abundant parasitoid (61.0%) reared from most host fruits while D. fullawayi was the least abundant (7.7%). The overall mean parasitism rate was 7.1% with the highest record in Annona senegalensis Pers., Sarcocepholus latifolium S. Bruce and Icacina senegalensis Juss. Ceratitis cosyra and Bactrocera invadens were the fruit fly species most commonly reared that produced F. caudatus, and to a lesser extent, P. cosyrae. The peak occurrence of the parasitoids coincided with the peak of the rains and the maturity period of many of the host fruits. This first inventory of tephritid parasitoids in Ghana provides critical baseline data for biological control efforts in the future.