Invasions by the palm borer moth Paysandisia archon in Italy and assessment of its trophic spectrum

The palm borer Paysandisia archon is a moth of South American origin, which has been introduced to most of Europe and the Caucasian areas of Asia. This insect is responsible for severe damage to palm trees (Arecaceae), as its larvae eat palm apical meristem and dig galleries into the stipe, resulting in plant death. The first records of P. archon in Europe date back to the early 2000s in Spain, where it arrived through the international plant trade. Despite the invasiveness of this moth, little is known about its distribution, particularly in Italy, and the range of palm species it may affect. Therefore, we summarised the distribution range of P. archon in Italy using a citizen-science project and predicted the climatic suitability for this moth in Italy under two future climate change scenarios through a Species Distribution Modelling approach. Furthermore, palm trees of the richest palm collection in Italy (Orto Botanico “Giardino dei Semplici”, Florence) were surveyed for P. archon attack to determine the trophic spectrum of this moth and to determine predictors of palm species vulnerability. We found that P. archon is widespread in Italy, occurring in 18 out of 20 Regions, and that the climatic suitability for this moth will strongly increase in the next decades because of global warming, enhancing its potential spread in Italy. We also identified 13 previously unreported palm species as potential host for P. archon. The model indicated that P. archon shows a preference for host plants with palmate leaves and that potted palms are more vulnerable to P. archon attack with respect to those with fan-shaped/pinnate/bifid leaves and non-potted ones. The extent of damage by P. archon within palm nurseries in Mediterranean areas may result in major economic costs to nursers and threaten endemic palm species in the region, thus highlighting the importance of continuous monitoring to prevent further impacts.