Weed Alert: Eurasian water milfoil

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Eurasian water milfoil declarations

 

Contacts and Further Information

If you find this weed contact your local Council Weeds Officer or the nearest NSW Department of Primary Industries office immediately for positive identification and further assistance.

Alternatively call the NSW NSW Invasive Plants and Animals Enquiry Line on
1800 680 244 or send an email to weeds@dpi.nsw.gov.au









NSW No Space 4 Weeds

Eurasian water milfoil (Myriophyllum spicatum)

World Status | Spread | Identification | Control | Legislation

Eurasian water milfoil is a highly aggressive and invasive submerged aquatic weed that can spread rapidly. It forms a dense stand that shades out and replaces all other aquatic plants, seriously impacting on native plant and animal life. Dense mats also interfere with other uses of water bodies such as recreation and irrigation.

Eurasian water milfoil prefers lakes, ponds, shallow reservoirs and slow moving water, but will also grow in fast moving water.

It can tolerate and thrive in a range of temperatures and water conditions, including low levels of salinity.

This species has not been recorded as present in New South Wales (NSW) or elsewhere in Australia. If introduced, it has the potential to become a major weed of dams, lakes and reservoirs.

World Status

Eurasian water milfoil is native to Europe, Asia and northern Africa. It is now naturalised and a major weed of lakes and reservoirs in Canada and the USA. It is also considered to be an invasive weed in its native range.

Spread

Eurasian water milfoil spreads mostly via plant fragments. During the growing season plants automatically fragment, often developing roots before they separate from the parent plant. Water movement and human activities may also cause fragmentation.

Fragments are spread over long distances by water currents and are mainly dispersed between water bodies by boating and fishing activities.

Eurasian water milfoil plants can die back to their base during winter, reshooting in spring.

Identification

Eurasian water milfoil is a submerged perennial plant. Stems are rooted at the base and grow towards the surface. It can grow in water from 0.5 to 10 m deep, but most commonly at depths up to 3 m deep.

Key identification features

  • Stems are hairless and slender (5 mm) growing up to 7 m long. They are reddish-brown to whitish-pink in colour and branch profusely near the surface to form a dense canopy.
  • Leaves are usually submerged, olive-green in colour, less than 4 cm long and feather-like. They are arranged around the stem in whorls of four and have 5–24 pairs of divisions (usually more than 12).
  • Flowers are small and pinkish with four petals, occurring in whorls of four around the stem. They are held above the water in an erect spike up to 8 cm tall but then lie parallel to the water surface once fruit are set.

Control

Contact your local council weeds officer if you suspect you have found Eurasian water milfoil. Control of Eurasian water milfoil is difficult. Mechanical harvesting can lead to rapid reinfestation due to the plant being fragmented.

Legislation

Eurasian water milfoil is a Class 1 State Prohibited Weed across NSW under the Noxious Weeds Act 1993. It must be eradicated and land must be kept free of the plant. As a notifiable weed, all outbreaks must be reported to the local council within 24 hours, and the plant is prohibited from sale in NSW.

Acknowledgments

2006 Edition prepared by Rachele Osmond; 2013 Edition prepared by Elissa van Oosterhout; Reviewed by Rod Ensbey

References

  • Aiken SG, Newroth PR and Wile I (1979) The biology of Canadian weeds, 34. Myriophyllum spicatum L., Canadian Journal of Plant Science, 59: 201–215
  • Hosking JR, Sainty G, Jacobs S and Dellow J (in prep.), The Australian WEEDbook.
Last updated: June 2013.