Based on this PRA, Solanum viarum was added to the EPPO Observation List (Invasive Alien Plants).

Main conclusions 

Solanum viarum presents a moderate phytosanitary risk for the endangered area with high uncertainty.

The overall likelihood of S. viarum entering the EPPO region is very low with a moderate uncertainty. Several pathways were assessed in the PRA but there was no strong association with any pathways. The likelihood of further establishment outdoors is high with high uncertainty. The high uncertainty reflects the small area of potential establishment in the EPPO region. The only population in the EPPO region is in France and it is on the limits of climatic suitability and unclear if the population is established or transient. Establishment in protected conditions is very low with low uncertainty. Temperature within protected conditions would be suitable for the establishment however, other conditions, e.g., the intense management of the system are likely to reduce the likelihood of establishment. The potential for spread within the EPPO region is high with a high uncertainty. S. viarum can spread both naturally and via human assisted spread. The species is shown to spread via human assisted mechanisms which would potentially move the species over long distances. However, all spread data is taken from North America which is speculative, hence the high uncertainty score. 

The magnitude of impact in the current area of distribution (North America) is moderate with a moderate uncertainty. The species has had an impact on pasture production and cattle in North America in the late 1990s and early 2000s, but improved management (biological and chemical control) has reduced the impact. The EWG considered the potential socio-economic impacts in the EPPO region will be low with a high uncertainty. The high uncertainty reflects the unknowns relating to the plasticity of S. viarum and its ability to adapt to climatic and environmental parameters in the EPPO region. This in turn gives uncertainty to the level and type of impacts the species may have in the EPPO region.