Ragweed leaf beetle Ophraella communa LeSage, 1986 (Coleoptera, Chrysomelidae) successfully crossing the Slovenian–Austrian border

In the past two decades, several alien insect species have been introduced to Europe.One of these is the chrysomelid beetle Ophraella communa, a promising biocontrol agent against its host plant, Ambrosia artemisiifolia.Ambrosia artemisiifolia produces highly allergenic pollen that causes significant health issues, leading to substantial healthcare costs.Since its first recorded occurrence in Italy and Switzerland in 2013, O. communa has been rapidly spreading across Europe.In 2023 and 2024, we monitored 27 populations of A. artemisiifolia in various habitats in northeastern Slovenia and one population across the border in Austria.We recorded the presence of O. communa, its developmental stages, herbivory damage, and associated fauna.Ambrosia artemisiifolia population sizes ranged from a single plant to entire fields with over 100 individuals.We confirmed the presence of O. communa in 89% of the monitored Slovenian populations as well as in the Austrian site.Ophraella communa was observed in Radkersburg, Austria, on July 31, 2024, with a single adult specimen found in a large A. artemisiifolia population growing in a pumpkin field.One week later, eggs were detected, and by the end of August, all developmental stages of O. communa were present.Despite this, the herbivory rate remained relatively low in all monitored populations.The accompanying fauna of A. artemisiifolia in agricultural fields included several specimens of Corythucha arcuata.In an urban environment, at a ruderal parking lot in Maribor, we observed one adult Cicadella viridis on an A. artemisiifolia stem and a final instar of Zicrona caerulea preying on a larva of O. communa.This research provides valuable insights into the dynamics of invasive species and their rapid range expansion.