Commodity risk assessment of oak and walnut logs from the US

The European Commission submitted to the EFSA Panel on Plant Health a Dossier from the United States proposing the use of a vacuum-steam-heat treatment as a stand-alone phytosanitary measure to mitigate the risk of entry of Bretziella fagacearum, Geosmithia morbida and its vector Pityophthorus juglandis (thousand cankers disease complex) into the EU when trading oak (Quercus alba, Q. rubra) and walnut (Juglans nigra) logs with bark from the US. The proposed treatment consists of heating the sapwood to 56°C for 30 min at a depth of 5 cm from the cambium under vacuum and steam conditions. EFSA assessed the likelihood that logs of oak and walnut target species would be free from EU quarantine pests, basing its evaluation solely on the efficacy of the proposed treatment. In addition to B. fagacearum, G. morbida and P. juglandis, 14 other EU quarantine pests were identified as relevant because they are present in the US and are potentially associated with the commodities. The assessment was based on the information provided by the applicant country and on systematic literature reviews conducted by EFSA to determine the survival temperature and wood colonisation depth of the target pests. The evidence gathered was evaluated through an Expert Knowledge Elicitation (EKE) to estimate the likelihood of pest freedom of logs after the treatment assuming that all logs were infested. The vacuum-steam-heat treatment substantially reduces the presence of target pests infesting the sapwood. The EKE indicated with 95% certainty that between 9021 and 10,000 treated Q. alba logs per 10,000 and that between 9347 and 10,000 treated Q. rubra logs per 10,000 will be free from B. fagacearum. The EKE indicated with 95% certainty that between 9862 and 10,000 treated J. nigra logs per 10,000 will be free from G. morbida and that between 9948 and 10,000 treated J. nigra logs per 10,000 will be free from P. juglandis. However, the treatment is expected to be much less effective against pests which infest wood deeper than 5 cm from the cambium such as the species Arrhenodes minutus. The EKE indicated with 95% certainty that between 1109 and 10,000 logs per 10,000 will be free from A. minutus.