Exploring the range expansion of the yellow-spotted longhorn beetle Psacothea hilaris hilaris in northern Italy

Psacothea hilaris hilaris is an exotic cerambycid detected in Lombardy (northern Italy) in 2005 and now established and undergoing an expansion phase. The species constitutes a serious pest for Ficus spp. and Morus spp. The aim of this work is to update the distribution area of the species in Italy, investigating its expansion over 16 years. Data were acquired through the authors' direct field records and community science, by data mining on national and international web platforms and social networks. Reports were analysed and GPS points plotted in ArcMap 10.8.1 to obtain distribution maps. Of the records collected, 34% were acquired during field surveys, 22% via e-mail and 44% through on-line forums and social networks. Adults of P. h. hilaris showed a long period of activity, from April to the beginning of December, with a peak of presence from June to September. The presence of the pest has been ascertained over six provinces in Lombardy covering an area estimated at more than 1750 km2 in 2021. New detections occurred within 2 km of a known infestation from the previous year in 41.6% of cases, and between 2 and 4 km away in 37.7% of cases. The mean rate of range expansion estimated from reported records was 3.17 ± 0.33 km/year from 2010 to 2021. After an initial phase of settlement, the insect is now spreading southward. Given the relevant phytosanitary interest that the species may have for fig plants in Italy and in the Mediterranean Basin, it is fundamental to deepen the knowledge about its flight biology, dynamics and active dispersal capabilities in order to estimate the future range expansion.