Eurasian water milfoil (Myriophyllum spicatum)

PROHIBITED MATTER: If you see this plant report it to the NSW Invasive Plants & Animals Enquiry Line 1800 680 244

Eurasian water milfoil is a highly aggressive and invasive submerged aquatic weed that can spread rapidly.

Profile

Impact

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.

Distribution

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. 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.

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.

Description

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.

Habitat

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

Acknowledgements

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.

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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.

Herbicide options

Contact your local council weeds officer for control advice for Eurasian water milfoil (Myriophyllum spicatum).

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW Prohibited Matter
A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017