Occurrence of the non-native species ophraella communa on ambrosia artemisiifolia in north-eastern italy, with records from slovenia and croatia

The ragweed leaf beetle, Ophraella communa LeSage (Coleoptera Chrysomelidae), is of North American origin and is associated with the Asteraceae, and especially with the invasive neophyte Ambrosia artemisiifolia L., which is native to North and Central America and currently naturalized in many parts of Europe, including Italy. The presence of the beetle in northern Italy and southern Switzerland was first noted in 2013. In 2017 it was first reported for Veneto region (north-eastern Italy) and Slovenia, and in 2018 for Croatia. An extensive survey was carried out in summer and autumn 2017 in Friuli Venezia Giulia, after the first accidental finding of some O. communa specimens on A. artemisiifolia plants at a site on the High Friulian Plain in July. To determine a possible pathway of O. communa entry, sites from the nearby eastern Veneto, western Slovenia and north-western Croatia were also inspected. O. communa was detected on A. artemisiifolia in 70 out of the 77 sampled sites in Friuli Venezia Giulia (54 sites), Veneto (5 sites), Slovenia (7 sites) and Croatia (4 sites). The distribution of O. communa on the Friulian and Veneto plains seems to be continuous. In 20% of cases, A. artemisiifolia defoliated plants or completely dried plants, lacking reproductive structures and with stem tissues seriously damaged were observed. In some cases, O. communa was found on other three Asteraceae, namely Xanthium orientale italicum (Moretti) Greuter, Erigeron canadensis (L.) Cronquist and Helianthus annuus L. The pathway of colonization by the beetle in the study area seems to be from west to east. These are the first records of the beetle for Friuli Venezia Giulia. The beetle seems to spread very rapidly across large areas and is very capable of effective control of the invasive weed, A. artemisiifolia.