Species identification of figitid parasitoids associated with Drosophila suzukii using near infrared spectroscopy

Authors: Hougardy, Evelyne; Liang, Peishih; Haff, Ronald; DAANE, KENT - University Of California Berkeley; Wang, Xingeng; Hogg, Brian

Submitted to: Entomologia Generalis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: The spotted wing drosophila (SWD) is a worldwide pest of berries and soft-skinned stone fruit. Control measures using insecticides are ineffective because they do not kill SWD larvae in fruits. Also, SWD can survive in untreated natural habitats surrounding crop fields. A parasitic wasp from SWD’s native range in Asia is currently being released in Europe and the USA to help control SWD. This wasp looks very similar to other wasp species that attack SWD in Asia, Europe and the USA. Current methods for differentiating these species are time consuming and expensive. This study aimed to demonstrate near-infrared spectroscopy (NIRS) as a rapid and convenient method for discriminating between the parasitic wasp that is being released and other similar-looking parasitic wasps associated with SWD. The four species tested were successfully distinguished using NIRS with an accuracy of 94 – 99%. The ability to rapidly distinguish lookalike wasp species would facilitate the sorting of wasps captured in regions infested with SWD and would allow the impacts of wasp releases to be more accurately and efficiently assessed. This methodology increases the efficiency of university and government researchers working to develop enhanced biocontrol methods for damaging insect pests including SWD which currently causes over four billion dollars in annual US crop losses alone. The research effort on biological control of SWD is global, with one recent review article covering the last decade of such research reporting that of 184 publications reviewed, “most” focused on parasitic wasps. Thus, the research reported here impacts a very large international research community with the potential for significant impact, both in terms of efficiency and economy, to researchers and growers alike

Technical Abstract: Drosophila suzukii, the spotted wing drosophila (SWD) is a worldwide pest attacking berries and soft-skinned stone fruit. Insecticides are the primary control tool but often ineffective because they do not impact SWD larvae in fruit, and SWD is a polyphagous species that can persist in natural habitats surrounding crop fields. The larval parasitoid Ganaspis kimorum (Hymenoptera: Figitidae) has been identified as highly specialized on SWD and is currently being released in Europe and the USA against SWD. Ganaspis kimorum is one of two cryptic species that coexist as natural enemies of SWD in the fly’s native range. Its cryptic counterpart, G. lupini, is morphologically indistinguishable but has a broader host range and has not been approved for release. This study aimed to investigate the feasibility of Near-infrared spectroscopy (NIRS) as a more rapid and convenient alternative to molecular diagnostics for discriminating G. kimorum from G. lupini and other similar-looking figitid species (e.g., Leptopilina japonica and L. heterotoma) associated with SWD in its region of origin or in newly invaded regions. Results showed that the four species can be differentiated by applying canonical discriminant analysis to their spectral signatures, with total classification rates varying between 94 and 99% depending on the samples selected. Our results also show that NIRS could be used for age and sex differentiation.