Origin of Popillia japonica specimens found in Switzerland
In Switzerland, Popillia japonica (Coleoptera: Scarabaeidae – EPPO A2 List) was first recorded in 2017 in Ticino and specimens have been caught in traps in other parts of the country (EPPO RS 2017/160, RS 2023/184, RS 2025/170).
Scientists recently conducted phylogenetic and population structure analyses on 42 specimens collected in several sites of Switzerland and compared sequences with specimens from Japan, North America, the Azores (PT), Italy, and southern Switzerland. They showed that populations in Basel, Valais, and central Switzerland (Luzern, Schwyz, Uri) likely originated from Ticino or northern Italy and correspond to local spread facilitated by road or rail transport. Conversely, the population near Zürich Airport (Kloten) was identified as an independent introduction from North America, likely through unintentional air transport.
This study showed that P. japonica may be introduced to new areas in association with road/ rail or air transport, and sites at a high risk of introduction should be monitored to detect any introduction early.
Sources
Pedrazzini C, Funari R, Cucini C, Nardi F, Grabenweger G, Widmer F, Enkerli J (2026) Population genomics identifies Italian and North American origins of Popillia japonica in Switzerland. Scientific Reports 16(1), 8445. https://doi.org/10.1038/s41598-026-39440-4