Invasive Populations of the Emerald Ash Borer Fairmaire, 1888 (Coleoptera: Buprestidae) in Saint Petersburg, Russia: A Hitchhiker?

The emerald ash borer (EAB), , is an invasive beetle of East Asian origin that has killed millions of ash trees ( spp.) in North America and Russia. In September 2020, EAB was detected in Saint Petersburg, a notable event for the metropolitan city. The aim of the present study was to investigate the occurrence and ecology of EAB in Saint Petersburg. The presence of two distinct enclave populations of EAB was revealed, each of which has, most likely, been established through separate events of "hitchhiking" via transport vehicles. Following the invasion, the further spread of EAB in Saint Petersburg was slow and locally restricted, most likely due to climatic factors. This spread by "hitchhiking" suggests that the possibility of the further long-distance geographic spread of EAB in the Baltic Sea region (the EU) is high, both by ground transport (120-130 km distance from EU borders) and ferries that transport cars across the Baltic Sea. In certain cases, the development of EAB on based on the stem portion colonized, larval densities, number of galleries, exit holes, viable larvae, and emerged adult beetles, was more successful than in trees. The observed relatively high sensitivity of to EAB, therefore, casts doubt on the efficacy and benefits of the currently ongoing selection and breeding projects against ash dieback (ADB) disease, which is caused by the fungus . Inventory, mapping, and monitoring of surviving trees infested by both ADB and EAB are necessary to acquire genetic resources for work on the strategic long-term restoration of , tackling the probable invasion of EAB to the EU.