This rapid PRA shows that: Popillia japonica is a highly polyphagous scarab beetle with root feeding larvae and foliage feeding adults. It is native to Japan, and has been an invasive alien pest in North America for around 100 years. In Europe, it has been present in the Azores since the 1970s. In the summer of 2014, P. japonica was reported for the first time in mainland Europe, from a valley in Italy near Milan, where it is present in very high numbers. Following this finding in mainland Europe, this PRA was requested to reassess the potential risk P. japonica poses to the UK. 

Risk of entry: Plants for planting and hitchhiking were considered the pathways of highest risk, supported by these being suspected as the pathways for previous introductions to the Azores and to some parts of North America. Overall, hitchhiking was considered to be moderately likely with medium confidence, while entry in association with plants for planting with roots were considered to be moderately likely, also with medium confidence, as the larvae are cryptic and will be hidden in the soil. Entry in association with harvested parts of plants, such as fruit or cut foliage, is considered unlikely with medium confidence: while adults are relatively conspicuous, their behaviour (at cooler temperatures) of dropping to the ground when disturbed may contaminate products such as harvested fruit. Soil on its own was considered very unlikely with high confidence, as soil from outside the EU is prohibited, and P. japonica is only present in a tiny area within the EU.

Risk of establishment: The climate mapping based on degree days undertaken in this PRA suggests that P. japonica may be able to establish outdoors in southern parts of the UK, though it is likely to require two years to complete a generation and there is some uncertainty over whether summer temperatures will be warm enough. Overall, establishment outdoors is considered likely with medium confidence. There have been some very old records of this beetle in glasshouses, but overall establishment in protected cultivation is considered unlikely with medium confidence. Semi-protected cultivation of soft fruits is also potentially at risk. 

Economic, environmental and social impact 

Within the current range, impacts in southern parts of the USA were considered large, with high confidence. Impacts in cooler parts of North America, such as southern Canada, were considered small, and P. japonica is usually not considered to be a significant pest in Japan. Due to the climatic limitations the beetle is likely to face in the UK, all potential impacts were considered small with medium confidence. 

Endangered area 

Southern parts of the UK, especially sheltered areas and urban heat islands, though damage might only be seen in the warmest years.