Host use of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in South Africa

The highly invasive oriental fruit fly, Bactrocera dorsalis (Hendel), has been declared present in the northern parts of South Africa since 2013. A study was thus initiated in July 2014 to determine the host range and field population of the pest species in the region. Fruit were collected from commercial fruit production, interface (smaller commercial blocks surrounded by natural savannah vegetation) and natural areas (savannah vegetation) throughout Limpopo and Mpumalanga provinces, South Africa. Field sites consisted of five commercial fruit production sites, two interface sites and two natural areas. Fruit samples from the tree and the ground were collected and incubated separately to determine infesting fruit fly species and the degree of infestation. Adult B.dorsalis populations were monitored at each field site using three methyl eugenol-baited bucket traps to estimate population pressure and to determine with the use of time series analysis if monthly trap captures were correlated with fruit infestation. Bactrocera dorsalis was reared from seven plant species: two from commercial orchards (Mangifera indica cv. [Tommy Atkins, Sensation], Citrus sinensis cv. [Valencia]), and five from other plant species (Psidium guajava, Anacardium occidentale, Solanum mauritianum, Xylotheca kraussiana, Vangueria infausta). Fruit utilized by B.dorsalis was also infested or damaged by other species, which may indicate opportunism by the pest, and the potential for competitive interactions. Time series analyses show adult population increased 2months after an increase in mean temperature in all sites, 4months after rainfall in natural and interface sites, and 1month and 3months after fruit infestation in commercial and natural and interface sites, respectively. This study shows B.dorsalis utilizing a limited range of hosts in South Africa. However, the host range of B.dorsalis may expand as it may not yet have encountered all potential hosts.