Drosophila suzukii interactions with sympatric and allopatric parasitoids

Abstract

The Spotted Wing Drosophila, D. suzukii, a native pest fly from Asia, has recently invaded USA and Europe. The female uses a serrated ovipositor to pierce the skin and lays eggs in a wide range of ripening fruits. Fruit damages result from subsequent pathogen infections and larval feeding. We have characterized the outcome of D. suzukii interactions with parasitoid species/strains, whether allopatric (three Leptopilina boulardi strains, one French strain of L. heterotoma Gotheron) or sympatric (Asobara japonica, L. japonica and a Japanese strain of L. heterotoma), with the aim of developing a biological control method. It strongly differed depending on the parasitoid species/strain, with successful emergence of A. japonica and L. heterotoma parasitoids only (>50 % for A. japonica, only 2-7% for L. heterotoma). We then tested the efficiency and specificity of A. japonica japanese strains either in laboratory or in “semi-natural” conditions (i.e on infested fruits). In parallel, a time-course analysis of D.suzukii physiological interaction with parasitoids evidenced a different timing of its immune response compared to D. melanogaster. For instance, L. heterotoma Gotheron developed larvae (instead of egg) were encapsulated, emerging flies thus harboring large melanized capsules. As a fitness cost of capsule-containing D. melanogaster flies was reported, we finally investigated the fitness cost induced by mounting a late immune response in D. suzukii. Altogether, our results provide insights for the possible use of Asian or local parasitoids to control populations of this fly pest.