The alligator weed is a dense mat-forming aquatic plant native to the Parana River basin in Brazil. It is not clear how this species established itself in Europe as it is not widely traded as an aquarium plant. It might have been introduced by mistake along with other similar ornamental specimens or as a contaminant of these. It is currently only established in France and Italy but there is a high risk that it could spread throughout the Mediterranean, as well as in countries with hot thermal springs. Once established the alligator weed rapidly chokes up riverine habitats, reducing both the quality and flow of water and preventing light and oxygen from entering the water column with drastic consequences for the ecosystem and its biodiversity. As the plant is still in an early stage of invasion, placing it now on the Union list will help prevent it from becoming a problem across the EU, by imposing a sales ban, by possibly taking measures on the pathways of unintentional introduction and spread, as well as by taking measures for the rapid eradication of any newly emerging populations and for the management of established populations. EU (EPPO) R.A.