The invasion of Eichhornia crassipes in Italy
Although the exact date of the first introduction of Eichhornia crassipes (Pontederiaceae, EPPO A2 List) in Italy is unknown, records of its use as an ornamental plant date back to at least the first half of the 19th century, when it was cultivated in botanic gardens, e.g. in Padova and Naples. The first occurrence of the species in Italy was recorded in 1982 in Sicilia. Shortly after, the species was recorded as casual in several sites: Lazio in 1983, then Friuli-Venezia-Giulia, Toscana, and more recently in Veneto, Campania and Sardinia.
The outbreak in Sardinia became evident in 2010 when the river Mare ‘e Foghe (central-eastern Sardinia) was invaded by a dense mat of E. crassipes. This mat covered 8 km stretch of river with a total surface area of 560;000 m², mixed with Hydrocotyle ranunculoides (Apiaceae, Liste A2 de l’OEPP). The mechanical removal of the plant in 2010, which was not completed due to difficulty in accessing the site, resulted in the collection of about 6700 tonnes of phytomass at a cost of 175;000 EUR. In 2012, the presence of thick mats of these 2 alien aquatic plants prevented a national carp-fishing tournament from being organized at the site, resulting in an important loss for the local community.
In the Lazio, E. crassipes was recorded for the first time in the Pontine plains in 1983. Until 1995, the populations remained very small, limited to a few sites on the shore of the Rio Martino river near the Fogliano lake, sometimes even in brackish waters. In the following years, E. crassipes spread to other sites within the Pontine plains, covering a total surface of 5000 m² in 2004 and 2005. Since then, the surface occupied by the plant remained the same. Every autumn, the species is mechanically removed by the local authority.
E. crassipes is commonly traded in Italy, and entered the country as an ornamental plant. Another significant pathway for the introduction and use of E. crassipes in Italy is related to its use in phytoremediation. Despite warnings on its invasive behaviour, E. crassipes is promoted by local authorities for its ability to hyperaccumulate heavy metals.
Sources
Brundu G, Azzella MM, Blasi C, Camarda I, Iberite M ; Celesti-Grapow L (2013) The silent invasion of Eichhornia crassipes (Mart.) Solms. in Italy. Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology: Official Journal of the Societa Botanica Italiana, DOI: 10.1080/11263504.2013.861536.