First record of the invasive sawfly Aproceros leucopoda infesting elms in Italy

The occurrence of an East Asian sawfly, Aproceros leucopoda Takeuchi (Hymenoptera Argidae), in Italy is reported here for the first time. In 2009, this invasive species was observed in five sites in the Friuli Venezia Giulia region (north-eastern Italy) along the Alpe-Adria A23 motorway. A survey carried out in 2010 has enabled verification that the sawfly has spread across an area of more than 1,200 km2 (68 infested sites out of 132 investigated), covering part of Friuli Venezia Giulia (Udine and Pordenone districts) and the neighbouring Veneto region (Treviso district). Only female adults were observed, suggesting that the species reproduces parthenogenetically. The species is multivoltine and most likely produces at least four generations per year in lowlands of north-eastern Italy. The larvae have severely defoliated different elm species, mainly field elm (Ulmus minor Mill.) and Siberian elm (Ulmus pumila L.). Also, wych elm (Ulmus glabra Huds.), monitored at a mountain site, has been attacked by the sawfly. The repeated defoliations could dramatically aggravate the phytosanitary state of elms already stressed from Dutch elm disease, which is transmitted by bark beetles, and elm yellows transmitted by leafhoppers.