Salvinia molesta

Salvinia molesta is commonly known as giant salvinia, or kariba weed, after it infested a large portion of Lake Kariba between Zimbabwe and Zambia. It is a free-floating aquatic fern, with fronds that are 0.5–4 centimetres (0.20–1.6 in) long and broad, with a bristly, waterproof surface caused by the hair-like strands that join at the end to form eggbeater shapes. The fronds are produced in pairs with a third modified root-like frond that hangs in the water. Though native to south-eastern Brazil, it has been accidentally introduced or escaped to countless lakes throughout the United States, including Caddo Lake in Texas, where the invasive species has caused eutrophication to occur.

Since 2019, S. molesta has been included in the European Union's List of invasive alien species of Union concern. The species cannot be imported, cultivated, transported, commercialized, planted, or intentionally released into the environment in the European Union.