EPPO Global Database

EPPO Reporting Service no. 09 - 2015 Num. article: 2015/178

Myriophyllum heterophyllum recommended for regulation in the EPPO region

A pest risk analysis (PRA) was conducted on Myriophyllum heterophyllum (Haloragaceae: EPPO A2 List) for the EPPO region in 2014. Following approval of the PRA in September 2015, M. heterophyllum was recommended for regulation in the EPPO region.

M. heterophyllum is an aquatic plant native to the Eastern United States where it often forms dense stands. 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, including aquatic plant species displacement, habitat dominance and effects on other aquatic organisms. Dense mats of M. heterophyllum reduce light reaching other submerged plants and can affect water quality by reducing oxygen levels resulting in fish avoiding the infested area. Many rivers and lakes within the PRA area are either protected areas or contain protected species that are likely to be adversely affected by dense mats of M. heterophyllum. The presence of M. heterophyllum in rivers and lakes in the EPPO region will act to degrade such habitats reducing the ecological status of water bodies.

The pest risk analysis concluded that M. heterophyllum presents a high phytosanitary risk for the EPPO region with a low uncertainty rating.


EPPO (2015) Pest risk analysis for Myriophyllum heterophyllum. EPPO Paris. http://www.eppo.int/QUARANTINE/Pest_Risk_Analysis/PRA_intro.htm