Increasing threat: Rhynchophorus ferrugineus invaded mainland America through Uruguay.

Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is one of the most dangerous palm pests worldwide. Here we report the invasion process of R. ferrugineus in Uruguay. Beyond morphological and molecular identification, we infer the geographic origin of the invasive population, describe the succession of introduced and native palms attacked, provide an easy-to-use key to differentiate the invader R. ferrugineus from the native Rhynchophorus palmarum, and model the ecological niche of R. ferrugineus in Uruguay and neighboring countries. First detected in 2022, the Uruguayan population of the weevil is the first to establish on mainland America, following the earlier island records from Curacao and Aruba. Phylogenetic analysis showed that the Uruguayan R. ferrugineus sequences clustered within a single clade, most closely related to sequences from southern China, and clearly distinct from the sequences of Curacao and Aruba, indicating at least two independent introduction events into the Americas from different source regions. After four years, R. ferrugineus has spread across an area of nearly 80,000 square kilometers and in January 2026 it reached Argentina, invading two points near the border with Uruguay. Over the first two years after the invasion, attacks focused on Phoenix canariensis, yet the three most common native palms in Uruguay, Butia odorata, Butia yatay, and Syagrus romanzoffiana, are currently being attacked. The diagnostic key to differentiate the pair R. palmarum / R. ferrugineus is based on three characters: the tip of the rostrum, the tegminal plate, and the ratio between the interocular space and the width of the rostrum at the base. Niche models showed that Uruguay and the neighboring areas of Argentina and Brazil are suitable for R. ferrugineus, and these are precisely the areas where both the highly susceptible P. canariensis and the native B. odorata, B. yatay, and S. romanzoffiana are present. Neighboring countries should therefore be prepared for the expansion of R. ferrugineus in the short term.