Alternanthera philoxeroides recommended for regulation in the EPPO region
A pest risk analysis (PRA) was conducted on the aquatic invasive alien Alternanthera philoxeroides (Amaranthaceae: EPPO A2 List) for the EPPO region in 2015. Following approval of the PRA in September 2015, A. philoxeroides was recommended for regulation in the EPPO region.
A. philoxeroides is an emergent aquatic perennial herb found growing in both aquatic and terrestrial habitats throughout its native (South America) and non-native range. In the EPPO region, A. philoxeroides is recorded from France and Italy only, though there are suitable habitats and climates for this species throughout Europe in particular the Mediterranean region. It is not clear how this species entered the EPPO region and there are no clear pathways of further introduction, as the species is not widely traded as an aquarium plant or as any other type of living plant material. There may be confusion with A. sessilis, or other Alternanthera species traded for aquarium, ornamental or food purposes. The risk of A. philoxeroides establishing in other EPPO countries is considered high as movement through irrigation and river systems may act to connect countries, facilitating spread regionally, especially through high energy unstable river systems that may encourage fragmentation. Spread may be significantly accelerated by water based recreational activities. The potential high impact of the species within the EPPO region is be considered similar to that seen in other countries where the species has invaded and become established; i.e. Australia and the southern states of North America. Impacts are likely to be more pronounced in countries and regions where the climate is most suited to population establishment, growth and spread. A. philoxeroides has been shown to have significant environmental and economic impacts within the invaded range (excluding the EPPO region). There is no evidence to suggest that the impacts observed will be different in the EPPO region. The potential economic impact of A. philoxeroides in the EPPO region could be highly significant if the species spreads and establishes in further areas; especially when consideration is given to the loss of earnings and costs associated with management for other aquatic species in Europe. There are no host specific natural enemies in the EPPO region to regulate the pest species, and in many EPPO countries herbicide application in or around water bodies is highly regulated or not permitted. Climate change, especially increases in temperature may extend the total area this species is able to invade.
The pest risk analysis concluded that A. philoxeroides presents a high phytosanitary risk for the EPPO region with a low uncertainty rating.
Sources
EPPO (2015) Pest risk analysis for Alternanthera philoxeroides. EPPO Paris.http://www.eppo.int/QUARANTINE/Pest_Risk_Analysis/PRA_intro.htm