First report of Phytophthora megasperma causing decline and death on Celtis australis in Italy.
European hackberry (Celtis australis) is a popular shade tree mainly planted in southern Europe and known to be tolerant to dry and poor soils. In early autumn 2013, hackberry plants grown in soil in a commercial nursery located in the floodplain in Umbria region (Italy) showed symptoms of wilting, dieback, and death. Up to 100% of the canopy was affected, and over 60% of the plants were symptomatic or dead. Based on morphological characteristics, molecular data (sequencing of the cytochrome-c oxidase subunit II and internal transcribed spacer region) and pathogenicity tests, the causal agent was identified as P. megasperma sensu stricto. This is thought to be the first report of P. megasperma sensu stricto on C. australis and its family Ulmaceae/Cannabaceae.