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Wanted egg parasitoids: Ooctonus vulgatus parasitizes Philaenus spumarius in Corsica and is probably widely distributed in Europe
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International audience. Current management of Xylella fastidiosa (Xf) epidemics worldwide predominantly involves plant uprooting, soil tillage or insecticide use. Improving vector biological control may be an interesting environmentally friendly lever to help lower vector density, but this research field has been overlooked until very recently.Three types of natural enemies of Philaenus spumarius have been described: egg parasitoids, larval and adult predators, and adult parasitoids. In the present study, we tried to identify egg parasitoids of P. spumarius in Corsica and to give a first assessment of their efficiency in natura. For that purpose, we collected bunches of branches of Cistus monspeliensis in winter, checked for the presence of eggs of P. spumarius on leaf underside, and monitored insect emergence.Ooctonus vulgatus Haliday, 1833 was identified by morphological and molecular methods as emerging from 255 P. spumarius eggs, out of 808 emerged individuals (total sample size = 1107 eggs). This was the only parasitoid species found and it was recorded on 7 out of 9 sampling sites, with parasitism rates ranging from 4 to 69 %. Species distribution models fitted on all available occurrences of O. vulgatus worldwide show that this species is likely to be found commonly in northwestern Europe.Among known natural enemies of P. spumarius, egg parasitoids have a unique combination of features: they kill the pest before it reaches the most harmful stage, and usually exhibit a high level of host specialization. Consequently, we can expect that spatially restricted mass releases in host habitats could decrease Xf transmission without side effects on the local fauna. Egg parasitoids are promising biocontrol agents for the Xf vectors and, provided that we gain more information on their level of specialization and establish mass-rearings, they can be a tool of an IPM strategy for the management of the Xf pathosystem.
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