A New Species of Invasive <i>Ophelimus</i> (Hymenoptera: Eulophidae: Opheliminae) Gall Wasp on <scp> <i>Eucalyptus globulus</i> </scp> in Portugal

ABSTRACT We describe a new species of Australian gall wasp of the genus Ophelimus Haliday (Hym: Eulophidae) found in Portugal, Southern Europe, forming galls on Eucalyptus globulus Labill. The identity of the new species, Ophelimus ramorum sp. nov., was confirmed by an integrative approach combining biological, morphological and molecular evidence. The new species is described and illustrated. Ophelimus ramorum sp. nov. induces galls mainly on stems and branches of young eucalypts, and occasionally also on the leaf's petiole and midrib but never on the limb of leaves. Attacks cause stem deformation, premature leaf senescence, branch dieback and reduced tree growth. The wasp is present in the most important eucalypt‐producing regions of northern and central Portugal, but attacks are restricted to E. globulus and do not occur on other eucalypts from the sections Maidenaria, Adnataria, Bolites and Exsertaria. No males of O . ramorum sp. nov. were recovered. A critical comparison between species and an updated key to the world species of Ophelimus with forestry interest is presented. A small number of females of the endoparasitoid Closterocerus chamaeleon (Girault) were reared from galls of O . ramorum sp. nov. in 2022 and 2023. As O. ramorum sp. nov. represents an additional threat to the productivity of E. globulus plantations in South‐Western Europe, control strategies against this pest are currently being developed, with the testing of E. globulus clones and families with lower susceptibility to the insect and an assessment of the efficiency of C. chamaeleon .