The adults spread by flight as suggested by the local expansion of damage in Europe. However, wood packaging material and wooden objects can also be a pathway as suggested by interceptions in Germany and the USA. In Greece and Spain, hundreds of Morus trees have already been attacked within a few years, and often killed. The infested area has been observed to expand from 44 to 380 km2 within 2 years in Spain (Catalonia). Phytosanitary measures are available to inhibit further introductions and slow the spread within the EU. X. chinensis satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.
More information: EFSA