Commodity risk assessment of Alnus cordata and Alnus glutinosa specimen trees from the UK

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as ‘high risk plants, plant products and other objects’. This Scientific Opinion covers the plant health risks posed by the following commodities: Alnus cordata and A. glutinosa as specimen trees (from 7 to 25 years old) in pots imported into the EU from the UK. A list of pests potentially associated with the commodities was compiled. The relevance of each pest was assessed based on evidence following defined criteria. Three pests were selected for further evaluation: one EU-protected zone quarantine pest (Entoleuca mammata), one EU quarantine pest (Phytophthora ramorum (non-EU isolates)) and one non-quarantine pest (Phytophthora siskiyouensis). For the selected pests, the risk mitigation measures implemented in the UK and specified in the technical dossier were evaluated. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. In the assessment of risk, the age of the plants was considered, as larger trees are more likely to be infested mainly due to longer time grown in the field. In addition, large canopies and root systems are more difficult to inspect, thereby making the detection of pests more challenging on large trees. The degree of pest freedom varies between the pests evaluated, with E. mammata being the pest most frequently expected on imported Alnus spp. specimen trees. Expert Knowledge Elicitation indicated, with 95% certainty, that between 9905 and 10,000 per 10,000 Alnus spp. specimen trees would be free from E. mammata.