This PRA supported the addition of the plant to the EPPO A2 list.

Myriophyllum heterophyllum presents an overall high phytosanitary risk for the EPPO region with a low uncertainty rating. The overall likelihood of M. heterophyllum continuing to enter the EPPO region is high. 

The plant is imported into the EPPO region as a misidentified aquatic species for aquaria and ponds and is already established in Austria, Belgium, France, Germany, Hungary, the Netherlands, Spain and Switzerland. 

The risk of entry into other EPPO countries through import is considered high. 

The risk of the species establishing in additional countries is high as movement through irrigation and river systems acts to connect countries, facilitating spread regionally. 

Spread may be accelerated by recreational activities in water bodies invaded by the weed. Impacts of the species within the EPPO region are likely to be severe (high score rating), including aquatic plant species displacement, habitat dominance and effects on other aquatic organisms.