First Report of Leptopilina japonica in Europe

Abstract

Simple Summary

The invasive spotted wing drosophila, Drosophila suzukii, is a polyphagous species that has become a serious fruit pest worldwide. Biological control plays a key role in the integrated management of invasive insect pests. With the aim to verify whether some parasitoid wasps, being considered as major mortality factors for D. suzukii, followed its host along global pathways, a field survey was conducted by sampling fruits and installing fruit-baited traps near isolated cherry trees within a wide agricultural area. Morphological and molecular analysis revealed three specimens of Leptopilina japonica in the parasitoid complex collected during the 2019 field survey; this is considered the first record of this larval parasitoid in Europe. A wider survey carried out during 2020 confirmed the presence of an adventive population of the parasitoid. In terms of reproductive biology, L. japonica shows similarity with Ganaspis brasiliensis, the best candidate for a future program of classical biological control. Interplay among indigenous parasitoids and the newly arrived Asian parasitoid, as well as the interactions of these species with G. brasiliensis, offer a unique ecological context to acquire new insights into the relationship between D. suzukii and its natural enemies and into their role in providing effective control of the pest.

Abstract

Drosophila suzukii (Matsumura; Diptera: Drosophilidae) is a key pest of sweet cherry and small fruits worldwide. Biological control remains unutilized in the framework of D. suzukii management. Nonetheless, natural enemies may play an important role in regulating this pest. We report for the first time the presence of Leptopilina japonica Novković and Kimura (Hymenoptera: Figitidae) in Europe. Two specimens emerged from ripened fruits and one was collected after direct observation on a cherry tree in June 2019. They showed the distinctive morphological traits already described and shared more than 99% sequence similarity with specimens of L. japonica collected in Asia. This first finding was confirmed by a wider survey carried out in 2020; L. japonica emerged from cherry fruit samples collected in five other sites across the Trentino region, suggesting that L. japonica has already colonized a wide area. Detection of this Asian species is relevant to the future direction in managing D. suzukii, both in Europe and North America. In fact, L. japonica showed similarity with Ganaspis brasiliensis (Ihering) (Hymenoptera: Figitidae), the most promising candidate for the classical biological control, in terms of developmental time, egg maturation, host age preference and lifetime fecundity.