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Mesmin X, Chartois M, Genson G, Rossi J, Cruaud A, Rasplus J.2019. Ooctonus vulgatus (Hymenoptera, Mymaridae), a potential biocontrol agent to reduce populationsof Philaenus spumarius (Hemiptera, Aphrophoridae) the main vector of Xylella fastidiosa in Europe. PeerJ Preprints7:e27941v1https://doi.org/10.7287/peerj.preprints.27941v1
As vector of Xylella fastidiosa (Wells, 1987) in Europe, the meadow spittlebug, Philaenus spumarius (Linnaeus, 1758) (Hemiptera: Aphrophoridae) is a species of major concern. Therefore, tools and agents to control this ubiquitous insect that develops and feeds on hundreds of plant species are wanted. We conducted a field survey of P. spumarius eggs in Corsica and provide a first report of Ooctonus vulgatus Haliday, 1833 (Hymenoptera, Mymaridae) as a potential biocontrol agent of P. spumarius in Europe. To allow species identification, we summarized the main characters distinguishing O. vulgatus from other European species of Ooctonus and generated COI DNA barcodes. We also assessed parasitism rates in several sampling sites, highlighting the top-down impact of O. vulgatus on populations of P. spumarius. Based on the geographic occurrences of O. vulgatus mined in the literature, we calibrated an ecological niche model to assess its potential distribution in the Holarctic. Our results showed that O. vulgatus potential distribution overlaps that of P. spumarius. Hence, O. vulgatus appears to be a promising biocontrol agent of the meadow spittlebugin Europe and it seems advisable to conduct research on this small parasitoid wasp to assess whether it could contribute to reduce the spread and impact of X. fastidiosa in Europe.
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Illustration of the hatching experiment to quantify parasitism rates in four sampling sites
After inspection of the back of each leaf of C. monspeliensis collected in the Corsican maquis, parts of leaf containing whitish clusters were cut and put on moistened filter paper in Petri dishes (A). Panel B shows a zoom on the leaf, the white arrow pointing to the P. spumarius egg cluster. Leaf cuttings were observed under a binocular microscope to confirm the presence of P. spumarius eggs. Panels C, D and E show several groups of P. spumarius eggs. The orange pigmented spots and the black shields that can both be seen especially in panels C and D are respectively the future eyes of the larva and the characteristic “egg burster” used by the larva to break the egg shell (Weaver and King 1954). Panel E shows an egg cluster embedded in the frothy cement described by Weaver and King (1954). In panel D, the egg on the right has already hatched whereas the egg on the left hasn’t. Finally, panel F shows a first instar larva of P. spumarius in dorsal view while panel G show a male of O. vulgatus in ventral view