Establishment of oak processionary moth <i>Thaumetopoea processionea</i> (Lepidoptera: Notodontidae) in Odense, Denmark

Abstract The oak processionary moth ( Thaumetopoea processionea ) has recently established a significant presence in Odense, Denmark, a city characterized by its substantial population of oak trees. This study provides details on the current situation (as of April 2025), examines potential introduction pathways, and outlines the challenges associated with eradicating or limiting the pest's spread due to its pest status within the European Union. Following the report of a confirmed breeding population in August 2024, extensive surveys identified over 1250 nests in crowns or on trunks of 664 trees. The observed spread, based on nests in 2022 identified via Google Street View, and males captured in a light trap from 2022 to 2024, suggests an introduction around 2020/2021, likely facilitated by human activities.