Risk assessment of the beetle Agrilus planipennis that attacks ash trees
Report no: 2014: 13
Should Agrilus planipennis reach Norway by imported trees or timber, there is a high probability of establishment and spread. The potential damage is considered high, since ash trees in forests, parks and urban areas of Norway may be killed within a few years after infestation.
Agrilus planipennis is native to eastern Asia. The beetle is also introduced in the US, Canada and European Russia, where it has done great damage to ash trees. In Michigan, USA, the mortality of ash exceeds 99 percent.
Probability of entry
The Norwegian Scientific Committee for Food Safety (VKM) considers the probability of entry of Agrilus planipennis by natural spread low, mainly because of the geographical distance and sea barriers between Norway and the infested areas.
Among the human-assisted pathways of entry, via commodities containing ash wood, the probability of entry is considered to be: moderate for wood chips, wood in the rough and plants for planting; low-to-moderate for fuel wood; and low for waste wood and wood sawn or chipped lengthwise.
Risk reducing measures
VKM is of the opinion that the risk-reduction measures in the EPPO PRA, as well as in the EU legislation, can be considered safe under Norwegian conditions.
• VKM suggests squaring of wood, with removal of at least 3.5 cm of the outer sapwood. EPPO recommended at least 2.5 cm, but this regarded by VKM as a measure that may be ineffective at preventing entry because prepupae and pupae could be located more deeply in the wood.
• Ionizing radiation of 1 kGy for disinfestation of wood is proposed in the EPPO standard. VKM assumes that this would be an effective phytosanitary measure, but more specific research on irradiation tolerance of the pest is needed.
• VKM is of the opinion that chipping and heat treatment are not regarded as reliable risk-reduction measures due to lack of documented information on efficiency.
Missions from the NFSA
VKM has been asked by NFSA to assess the probability of entry of Agrilus planipennis into Norway through different pathways, establishment in Norway and the further spread and potential damage on ash trees in Norway. In addition, an evaluation of the effectiveness of the risk-reduction measures described by the European and Mediterranean Plant Protection Organization (EPPO) and the European Union (EU) has been requested.
The risk assessment is performed by VKM’s Panel on Plant Health.