When exotic biocontrol agents travel without passport: first record of Quadrastichus mendeli, parasitoid of the blue-gum chalcid Leptocybe invasa, in Italy

The larval parasitoid Quadrastichus mendeli (Hymenoptera: Eulophidae: Tetrastichinae), a highly effective parasitoid of the invasive blue-gum chalcid Leptocybe invasa (Tetrastichinae) was discovered to have been accidentally introduced to Italy, where it was never released. Over the last three years, Q. mendeli has become widespread in central and southern Italy, determining in some places the almost complete disappearance of the gall wasp pest. We genetically characterized the parasitoid, confirmed its placement within the genus Quadrastichus by phylogenetic analysis, and evaluated the percentage of parasitisation at three localities. We provide other examples of parasitoids that crossed country boundaries without being released, ignoring long and expensive risk assessment aimed at limiting the importation and release of exotic natural enemies.