Identification and Abundance of Fruit Fly Species Responsible for Fruit Drop of Sweet Orange (Citrus sinensis L. Osbeck) in Benue State, Nigeria

Background and Objective: Citrus is one of the most important and among the top ten widely cultivated fruits in Nigeria. It is produced more in the Guinea and Sudan Savanna zones of the country with Benue State having the highest annual production. In the South of Savanna region of Africa, particularly in Nigeria; despite the economic, nutritional and health benefits of citrus, limited research work has been carried out on the identification and control of fruit flies of economic importance to the crop. The objectives of this study are to identify and determine the abundance of the fruit fly species responsible for fruit drop of citrus in Benue State, Nigeria. Materials and Methods: Fruit fly identification was done through fruit culture experiment carried out in the College of Agronomy Teaching and Research Farm, Federal University of Agriculture, Makurdi in October 2014 and October 2015.The experiment was a 2 x 3 factorial in a completely randomized design with four replications. The two factors were Zones (Zone A and B) and Varieties (Ibadan Sweet, Valencia and Washington Navel). Ten naturally infested orange fruits from four randomly selected citrus trees of each variety in each zone were weighed and placed in each plastic rearing box with dimension 39 x 27 x 26 cm containing sterilized moist soil securely covered with 1 mm mesh net for pupation and adult insect emergence. Emerged adults were killed using Mobil insecticide (Cyphenothrin), counted, sexed and stored in specimen bottles with 70% alcohol for preservation and later identification. Results: Fruit fly species identified from citrus fruit culture were: Bactrocera invadens (Drew), Ceratitis capitata (Weid) and Dacus bivittata (Biggot). Bactrocera invadens were the most abundant species and accounted for 63.70% in Washington navel and 63.10% in Valencia in 2014 and 2015 respectively. The varieties showed no significant differences (p>0.05) on the abundance of Ceratitis capitata and Dacus bivittata in 2014. In 2015 however, Ibadan Sweet variety showed significant difference (p < 0.05) on the abundance of Ceratitis capitata (28.30%) when compared with other varieties (15.8%) each. Conclusion: Fruit fly species responsible for citrus fruit drop in Benue State were Bactrocera invadens (Drew), Ceratitis capitata (Weid) and Dacus bivittata (Biggot) with Bactrocera invadens (Drew) recorded as the most abundant species.

The potential distribution of Bactrocera dorsalis: considering phenology and irrigation patterns

A species in the Bactrocera dorsalis (Hendel) complex was detected in Kenya during 2003 and classified as Bactrocera invadens Drew, Tsuruta & White. Having spread rapidly throughout Africa, it threatens agriculture due to crop damage and loss of market access. In a recent revision of the B. dorsalis complex, B. invadens was incorporated into the species B. dorsalis. The potential distribution of B. dorsalis has been previously modelled. However, previous models were based on presence data and did not incorporate information on the seasonal phenology of B. dorsalis, nor on the possible influence that irrigation may have on its distribution. Methyl eugenol-baited traps were used to collect B. dorsalis in Africa. Seasonal phenology data, measured as fly abundance throughout the year, was related to each location's climate to infer climatic growth response parameters. These functions were used along with African distribution records and development studies to fit the niche model for B. dorsalis, using independent global distribution records outside Africa for model validation. Areas at greatest risk of invasion by B. dorsalis are South and Central America, Mexico, southernmost USA, parts of the Mediterranean coast, parts of Southern and Eastern Australia and New Zealand's North Island. Under irrigation, most of Africa and Australia appear climatically suitable.

Species composition and community structure of fruit flies (Diptera: Tephritidae) across major mango-growing regions in Uganda

The species diversity of tephritid fruit flies in major mango-growing regions in Uganda was monitored over a 2-year period (2010–2012) using fruit bait and lure traps. A total of 368,332 specimens belonging to 10 species in four genera (Bactrocera,Ceratitis,TrirhithrumandDacus) were collected. Of these, 98.9% belonged toBactrocera invadens, while the second and third most common species wereDacus bivittatus(0.4%) andCeratitis anonae(0.3%), respectively. Significant differences in the evenness and diversity of fruit fly species were noted across the regions. Fruit fly community structure was significantly different across the three regions. The Lake Victoria Crescent and Mbale Farmlands harboured significantly moreD. ciliatus,T. coffeae,D. bivittatusandB. cucurbitaein contrast to the Northern Moist Farmlands and the Western Medium High Farmlands.Ceratitis rosacontributed the highest difference in regional structure, followed byC. fasciventrisandC. cosyra. Rank abundance curves depicted a geometric series distribution of the species composition in the three regions, confirming a scenario of competitive displacement of native fruit fly species byB. invadens. A comprehensive and sustainable response strategy toB. invadensand other fruit flies needs to be urgently devised to protect the horticulture industry in Uganda.