This rapid PRA was requested as Lycorma delicatula has been spreading rapidly in the northeast states of the United States of America (USA) having first been reported there in 2014. The pest, which is of Asian origin, has been added to Great Britain (GB) legislation as a Provisional Quarantine Pest, and this PRA has been developed to determine if it should become a Regulated Quarantine Pest. It is already regulated in Northern Ireland.

Risk of entry 

The main pathways of entry are hitchhiking, plants for planting and wood products from countries with L. delicatula (USA and east Asia). Due to the nature of hitchhiking in the inconspicuous egg stage especially, the risk is rated very likely with high confidence as this has been the main mode of large-scale movement of L. delicatula. The second pathway on plants for planting, is moderately likely with low confidence. It could be a future pathway if countries that trade in large volumes of plants for planting with the United Kingdom (UK) become infested but this is uncertain and so it is rated with low confidence. The last pathway is wood products, and this risk is rated as unlikely with low confidence as some wood products that come into the UK have to undergo certain treatments that would kill most stages of L. delicatula. However, L. delicatula  is not being specifically targeted and it would be mitigated against along with other pests where there is a specific regulation in place and only specific wood products would be treated. Whereas L. delicatula lays eggs indiscriminately on wood substrate.

Risk of establishment

 The temperate climate of the UK, more specifically the cool summers, is thought to be a slight barrier to establishment. However, climate change will likely increase the number of hot days in summer months, which might increase population growth. Ailanthus altissima, commonly called tree of heaven, is the preferred host and is found throughout the south of the UK. Therefore, if L. delicatula enters into the south of the UK, then establishment outdoors has been judged unlikely with low confidence and under protection it is very unlikely with medium confidence.

Economic, environmental and social impact 

Based on uncertainty about climatically suitable conditions for L. delicatula to reach maturity and lay eggs, as well as potential quarantine and management practices that industries may have to comply to, the potential economic impact is rated small with low confidence. The environmental impacts are very small with low confidence and social impacts are medium with medium confidence.

Endangered area 

The UK is on the edge of climatic suitability, but there are suitable hosts for L. delicatula present throughout the southern more temperate areas of the UK.

Risk management options

 There are many different options, including exclusion, eradication, containment, and management with chemicals and biocontrol.  

Key uncertainties and topics that would benefit from further investigation

 • The lower temperature threshold for reproduction and egg development 

• Ability to reach high population levels in UK climate 

• Is the number of A. altissima (tree of heaven) in south of England enough to support high population numbers 

• Biocontrol options