Economic Importance Eurasian watermilfoil adversely impacts aquatic ecosystems by forming dense canopies that often shade out native vegetation. Monospecific stands of Eurasian watermilfoil provide poor habitat for waterfowl, fish, and other wildlife. Significant rates of plant sloughing and leaf turnover, as well as the decomposition of high biomass at the end of the growing season, increase the internal loading of phosphorus and nitrogen to the water column. Dense Eurasian watermilfoil mats alter water quality by raising pH, decreasing oxygen under the mats, and increasing temperature. Eurasian watermilfoil impacts power generation and irrigation by clogging dam trash racks and intake pipes.
Stagnant water created by Eurasian watermilfoil mats provides good breeding grounds for mosquitoes.
Eurasian watermilfoil interferes with recreational activities such as swimming, boating, fishing and water skiing. Geographic Distribution Eurasian watermilfoil is native to Europe, Asia, northern Africa and also occurs in Greenland. Eurasian watermilfoil is mainly a problem plant in North America, but it has been reported from Australia. In North America, Eurasian watermilfoil is found from Florida to Quebec in the east, and California to British Columbia in the west. It appears to be primarily spread from waterbody to waterbody through boating activity, although anglers have been known to deliberately plant this species in lakes.