DRAFT PRA subject to stakeholder comments

Litylenchus crenatae is a nematode pest and causative agent of beech leaf disease (BLD) in Japan, Canada and the USA. Since the detection of BLD in the USA in 2012, this foliar nematode pest has spread quickly across beech (Fagus) forests in North America (in 3 years the spread covered an area the size of the UK) where it is causing significant environmental damage. There can be a high disease incidence in infected areas causing concern about the impacts to ecosystems resulting from its establishment, and about possible future economic impact in American beech timber production valued for flooring, veneer and furniture. The mortality rate is generally higher on smaller trees, but large trees can die after a number of years, suggesting cumulative effects. The PRA has considered pathways involving plants for planting, imported plant parts such as branches, wood with bark, seeds, contamination on clothing, footwear or baggage and natural spread. Most pathways are considered very unlikely, though with some uncertainty due to lack of knowledge. However, the greatest risk is associated with the import of plants for planting from areas where the pest is present, even though this is partially mitigated by current legislation. 

This PRA shows that relevant hosts are widely distributed across the UK and wider EPPO region. Secondly, some parts of the UK and the wider EPPO region have a climate that based on the evidence available, would be highly suitable for the pest. Therefore, the nematode is likely to be able to establish within the UK and EPPO region should it enter the territory. The pest is causing damage within a climate very similar to the PRA area and there are no clear abiotic or climatic barriers to its establishment, spread or damage potential within the UK or the wider EPPO region. The cryptic nature of the first years of infection and the nematode’s presence within the buds of dormant trees means once detected the pest is likely to have spread within a wide region of the initial finding. In the UK Fagus is used less for timber and more for specialist use such as for flooring, veneer and furniture, and economic impacts were rated as moderate. 

Environmental impacts are a key concern however. Tree mortality, as reported in the USA, is likely to be seen if L. crenatae were to establish in the UK and Fagus is a keystone species playing an important part in ecosystems. Social impacts are also rated highly as beech is the fifth most important broadleaf tree in the UK and is found in parks and gardens throughout the UK. Because of the very visible and distinctive symptoms the disease presents, public awareness and concern is likely to be high, and the outbreak in the USA has already been reported in major news outlets in the UK. 

Recommendations for action 

While there are still many unknowns about this recently identified pest, there is concern that similar damage to that caused in North America on American beech could be seen on European beech should the pest establish in the UK. It is recommended that statutory action be taken on any findings, and that consideration be given to addressing open pathways relating to imports of plants for planting and plant parts.