First exploration of parasitoids of Drosophila suzukii in South Korea as potential classical biological agents

The invasive spotted wing drosophila, Drosophila suzukii Matsumura (Dipt.: Drosophilidae), a native of East Asia, has widely established in North America and Europe, where it is a serious pest of small and stone fruit crops. The lack of effective indigenous parasitoids of D. suzukii in the recently colonized regions prompted the first foreign exploration for co-evolved parasitoids in South Korea during 2013 and 2014. We collected the larval parasitoids Asobara japonica Belokobylskij, A. leveri (Nixon) and A.brevicauda Guerrieri & van Achterberg (Hym.: Braconidae), Ganaspisbrasiliensis (Ihering), Leptopilina japonica japonica Novkovi? & Kimura and L. j. formosana Novkovi? & Kimura (Hym.: Figitidae); and the pupal parasitoids Pachycrepoideus vindemiae (Rondani) (Hym.: Pteromalidae) and Trichopria drosophilae Perkins (Hym.: Diapriidae). From UC Berkeley quarantine records, percentage parasitism ranged from 0 to 17.1 % and varied by geography, season, and collection methods. Asobara japonica was the most common parasitoid species. Higher numbers of parasitoids were reared from field-picked fruit as opposed to traps baited with uninfested fruit. Quarantine bioassays confirmed that A. japonica, G. brasiliensis, L. j. japonica, P. vindemiae, and T. drosophilae developed from D. suzukii. Female individuals of the endoparasitoid, A. japonica, were larger when reared on the larger D. suzukii larvae compared with those reared on the smaller larvae of D. melanogaster Meigen. Larger parasitoid size was associated with longer developmental time. Several of the South Korean parasitoid species have the potential for use in classical biological control and may contribute to the suppression of D. suzukii in the newly invaded regions.