Rapid Pest Risk Analysis Xyleborinus attenuatus
This rapid pest risk analysis (PRA) provides a quick assessment of the risks posed by the pest to Sweden, which is the PRA area being assessed. The format is an adapted version of the EPPO Express PRA scheme (EPPO 2012). Definition ofterms used as well as the rating scheme and assessments are done in line with the guidance given in the EPPO CAPRA system (EPPO 2011). The likelihood of entry and establishment are assessed considering the current phytosanitary regulation in place with respect to the EU legislation (Council Directive 2000/29/EC). The definition of a quarantine pest follows the regulation (EU) 2016/2031.
Xyleborinus attenuatus is established in Sweden. The ambrosia beetle originates from Japan and eastern Russia and has until now spread to 13 European countries as well as to USA and Canada.
Entry, establishment and spread
The likelihood of entry of Xyleborinus attenuatus into Sweden is assessed to be very likely. The main pathways of entry are “Wood and wood products” and “Natural spread”. X. attenuatus is already established and further spread is assessed to be very likely since suitable host are widely distributed in Sweden, the climate is suitable and the species have a track record of being able to establish in different environments. The rate of spread is assessed to be high based on the species presumed high flight capacity and the high likelihood of spread through transportation of colonized wood material.
Both the economic, environmental and social impact was assessed to be small since there currently is little support in the easily accessible literature that the pest cause significant damage. Nevertheless, there is a risk for a similar shift towards increased impact as have been recorded for closely related ambrosia beetle species.
It is assessed to be difficult to prevent further introductions of X. attenuatus to Sweden. Current phytosanitary measures such as barking and heat treatment does not completely prevent entry of ambrosia beetles with wood and there is also a risk of natural spread from Denmark.
Assessment in relation to the definition of quarantine pests
The results presented in this rapid PRA shows that Xyleborinus attenuatus does not fulfil all of the criteria for a union quarantine pest, e.g. it is widely distributedwithin the EU territory. In addition, it indicates that X. attenuatus does not fulfil allcriteria for a protected zone quarantine pest for any part of Sweden, e.g. due tolimited possibilities to prevent natural spread from areas where the pest isestablished and that the impact was assessed to be small.
Key uncertainties and further investigation needed
There is a large uncertainty in the assessment of the future impact of Xyleborinus attenuatus due to the potential risk that it may shift from colonizing dead trees to colonizing live trees as has been observed for other closely related beetle-fungus symbioses (Hulcr and Dunn 2011). It would therefore be desirable if the development of X. attenuatus, both nationally and internationally, is followed to detect any shift towards increased impact.
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