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.