The parasitoid complex of D. suzukii and other fruit feeding Drosophila species in Asia

Abstract

Drosophila suzukii is an invasive fly of East Asian origin that has become a serious fruit pest worldwide. Classical biological control through the introduction of parasitoids from Asia could help reduce populations of D. suzukii in invaded regions. Little is known about the native parasitoids of the fly in Asia. Therefore, surveys for larval parasitoids of D. suzukii were carried out in China and Japan between 2015 and 2017. Parasitoids of D. suzukii and other fruit-inhabiting drosophilids (D. pulchrella and D. subpulchrella) that are probably attacked by the same parasitoid complex were found in four Chinese provinces and four Japanese prefectures. Larval parasitoids were obtained at most sites where D. suzukii was found, with parasitism varying from 0.0 to 75.6%. At least eight parasitoid species were reared. The most abundant and frequent parasitoids were the Figitidae Ganaspis cf. brasiliensis and Leptopilina japonica, but another Leptopilina species and at least five Braconidae species belonging to the genera Areotetes, Asobara and Tanycarpa were obtained in low numbers. Due to its likely restricted host range, the most promising parasitoid for biological control is Ganaspis cf. brasiliensis. However, its exact specificity and taxonomic status require future research.

Evidence for a cryptic parasitoid species reveals its suitability as a biological control agent

“…for control of D. suzukii 18,19 , in particular in unmanaged areas, such as wild habitats, public or private gardens, which act as reservoirs 15,17 due to the current lack of local control methods.…”

“…In recent years, several research groups carried out surveys in Asia to find potential biological control agents against D. suzukii [18][19][20][21][22][23] . On the basis of these surveys, several species were identified as attacking D. suzukii in Asia, the most abundant ones belonging in Ganaspis (Hymenoptera: Figitidae).…”

“…We therefore adopt here the term "Ganaspis cf. brasiliensis" to consider this taxonomic uncertainty, as proposed by Girod et al 19 .…”

New records of Leptopilina, Ganaspis, and Asobara species associated with Drosophila suzukii in North America, including detections of L. japonica and G. brasiliensis

“…Larval parasitism of D. suzukii in invaded areas appears to be particularly uncommon, probably due to the inability of most genotypes of native larval parasitoids to overcome the immune defenses of D. suzukii (Lee et al 2019;Kacsoh and Schlenke 2012;Poyet et al 2013). Thus, soon after the introduction and spread of D. suzukii in invaded areas, exploration for potential classical biological control agents in China, South Korea, and Japan began with the goal of identifying parasitoid species that could be evaluated as potential classical biological control agents (Daane et al 2016;Girod et al 2018a;Giorgini et al 2019). These surveys found several parasitoid species attacking D. suzukii larvae and pupae, but two larval parasitoids were responsible for the greatest levels of parasitism: Ganaspis brasiliensis (Ihering) and Leptopilina japonica Novkovic & Kimura (Hymenoptera: Figitidae).…”

“…Leptopilina japonica is known to attack Drosophilidae other than D. suzukii in the field in Asia (Novković et al 2011). Ganaspis brasiliensis has only been reared from fresh fruits infested by D. suzukii and other closely related, microsympatric frugivorous Drosophilidae and thus appears to have a more restricted host range than L. japonica (Daane et al 2016;Girod et al 2018a;Giorgini et al 2019). The host specificity of G. brasiliensis may also vary significantly among genetic lineages (Nomano et al 2017;Girod et al 2018b).…”