Assessment of Fruit Fly Damage and Implications for the Dissemination of Management Practices for Mango Production in the Upper West Region of Ghana

Abstract

Ghana's mango (Mangifera indica) industry is facing potentially serious problems with fruit flies (Diptera: Tephritidae), which endanger the industry's contribution to the national economy. Asian fruit flies in the genus Bactrocera are destructive pests of fruits and vegetables worldwide, but little is known about their prevalence in Ghana since the first detection of Bactrocera invadens in 2005. This paper reports the results of a study of the occurrence of B. invadens in Ghana's Upper West Region and assesses the pest's distribution, the damage it causes, and potential management options. Despite limited collections of B. invadens in 2007 (the first formal survey of this pest), the results of weekly trapping provide a good preliminary understanding of its presence in the region. Systematic trapping and host fruits surveys confirmed its presence in all eight districts and at three experimental stations. The highest density (10.8 flies per trap per day) was recorded in Nadawli district and the lowest (1.6 flies per trap per day) in Lawra district. In total, 10,349 flies were captured during the study period which lasted for 6 months. The counts were highest in August, when the flies attack developed fruits. Late-maturing cultivars (mostly exotics) were more severely attacked than early (local) cultivars, and B. invadens also attacked cashew (Anacardium occidentale) and shea tree (Vitellaria paradoxa) in the study area.
Mango farmers were interviewed to obtain information about the pest. Sixty percent reported that the fruit fly, although a recent pest on mangoes in the study area, had decreased fruit production. Mealybugs (Rastrococcus invadens) accounted for 13% of the pests in mango fields, but ants (Oecophylla longinoda) and termites (Microtermes spp.) were also important pests that negatively affected mango production. Fruit fly control is still at an experimental stage in Ghana. Therefore, control should focus on integrated pest management to protect important crops. Training of agricultural extension officers, mango farmers, and other stakeholders, and international cooperation, will be imperative to ensure effective management of this invasive pest.