Based on this PRA, Celastrus orbiculatus was added to the EPPO A2 List of pests recommended for regulation as quarantine pests in 2021. Measures for C. orbiculatus are recommended. 

Main conclusions

Although the likelihood of entry of C. orbiculatus into the EPPO region via imported plants for planting is low with a high uncertainty, C. orbiculatus is already produced and widely available in trade within the EPPO region and occurs in parks and gardens throughout the EPPO region. 

Celastrus orbiculatus is established in limited areas of the EPPO region. Potential habitats that C. orbiculatus can invade are widespread and include disturbed or managed habitats (e.g. harvested forests), transportation networks (e.g. verge of railway tracks, roadsides and habitats under powerlines) and natural habitats (e.g. forests and woodlands and adjacent grassland and heathland). Further establishment is likely because the species can tolerate a wide range of climatic and other abiotic factors. Where conditions are suitable, the likelihood of further establishment outdoors is very high with low uncertainty. Likelihood of establishment in protected conditions is very low with a low uncertainty, as management practices within protected conditions would prevent establishment. The potential for spread within the EPPO region is high with a moderate uncertainty. C. orbiculatus can spread both naturally (e.g. seed via mammals and birds) and with human assistance.

The magnitude of impact in the current area of distribution is moderate with a moderate uncertainty. In North America, C. orbiculatus threatens natural habitats, and the species can act locally as an ecosystem engineer by transforming the structure of habitats and supressing native species with its dense thickets. C. orbiculatus can reduce tree growth and regeneration which can have a negative impact on timber production in forests. The EWG consider that potential impact in the PRA area will be largely the same as in the current area of distribution but with an increased uncertainty. Direct impact studies and/or comparative studies are lacking, however, taking a precautionary approach, the increased uncertainty indicates the risk may be higher than that of the current area of distribution. 

Due to the wide availability of the species in the EPPO region already, the overall risk of the species is not strongly influenced by further entry.