Exploration for native parasitoids of Drosophila suzukii in China reveals a diversity of parasitoid species and narrow host range of the dominant parasitoid

Drosophila suzukii is native to East Asia and an invasive pest of fruit crops widely established in the Americas and Europe. The lack of effective indigenous parasitoids of D. suzukii in the invaded regions prompted surveys for co-evolved parasitoids in Yunnan Province, China, from 2013 to 2016. From banana-baited traps (2013-2015), 458 parasitoids of drosophilids were reared, comprised of Braconidae (49.56%), Figitidae (37.55%), Diapriidae (7.42%), and Pteromalidae (5.46%). Larval parasitoids included seven braconid species, all Asobara and primarily Asobara mesocauda, and five figitid species, primarily Leptopilina japonica japonica. Pupal parasitoids were the diapriid Trichopria drosophilae and the pteromalid Pachycrepoideus vindemiae. Collections from wild fruits (2016) provided more interesting results. From the puparia of drosophilids collected, comprised of D. suzukii and Drosophila pulchrella, emerged 1354 parasitoids. The larval parasitoids Ganaspis brasiliensis and L. j. japonica were the prevalent species, reaching a fairly high percentage parasitism of fly puparia collected from berries of Rubus foliosus (22.35%), R. niveus (18.81%), Fragaria moupinensis (19.75%), and Sambucus adnata (63.46%). Ganaspis brasiliensis was the dominant species and was collected only from D. suzukii and D. pulchrella-infested fruits and never from banana-baited traps. Molecular analysis showed two G. brasiliensis lineages, which are discussed with respect to previous Japanese collections. Quarantine tests showed that G. brasiliensis developed from D. suzukii and two closely related hosts (Drosophila melanogaster and Drosophila simulans) but did not develop from seven non-target drosophilid species. Our results suggest that G. brasiliensis is a promising classical biocontrol agent for release in invaded regions.