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Pest Risk Analysis for Hymenoscyphus pseudoalbidus for the UK and the Republic of Ireland


H. pseudoalbidus, the cause of ash dieback, a lethal disease of Fraxinus spp. in at least 24 European countries and also now known to be present in Japan, has entered the PRA area where it was found to have caused disease, mainly on F. excelsior, in Great Britain (GB) in 2012. Evidence from an affected wood in Norfolk indicates that It may have here since at least 2008 (Hendry, 2013, unpublished). Plants on nurseries, recent plantings and trees in the wider environment have been found affected. In Wales, at the time of production of version 1.3 of this PRA, there were no wider environment sites affected. It has also been found in Northern Ireland (NI) and the Republic of Ireland (ROI) on nurseries and planted sites. GB is currently the most badly-affected part of the PRA area and the pest is considered to be established here, with a higher concentration of trees affected in wider environment sites in the east and south-east of England than elsewhere. NFI studies indicate that, overall, the levels of the disease in woodlands >0.5ha in GB which have been subject to FC inspection is low. However, there are clearly hotspots, as indicated by the findings reported from separate systematic and targeted surveillance studies. In NI and the ROI all of the findings are associated with imported planting material. The pest is considered to be transient in NI/ROI where it is subject to eradication measures. All parts of the PRA area continue to be subject to surveillance. The status of the pest in NI and the ROI will be better verified now that trees have broken dormancy since symptoms on trees may be more obvious at this time. Eradication is not being attempted in GB. As a result of the 2012 findings, emergency phytosanitary legislation was implemented in late 2012. This has effectively prevented the unrestricted import and movement of planting material (seeds and plants) of Fraxinus spp. from countries where the pest is known to occur as well as regulating movement of such material in the PRA area. Additionally, in NI and the ROI, imports and movement of wood of Fraxinus from countries where the pest is known to occur are now regulated. This will help reduce the risk of further entry of the pest, as well as movement of the pest on planting material from affected sites in all of the PRA area, as well as on wood into NI/ROI.


  • Hymenoscyphus fraxineus


  • Fraxinus


Type File Size
Pest Risk Analysis Download 5,26MB

PRA Area

  • United Kingdom