Eurasian water milfoil (Myriophyllum spicatum)
PROHIBITED MATTER: If you see this plant report it. Call the NSW DPI Biosecurity Helpline 1800 680 244
Eurasian water milfoil is an underwater weed with olive-green feathery leaves. It can quickly take over waterways.
Profile
How does this weed affect you?
Eurasian water milfoil grows quickly and:
- shades out and displaces native water plants
- reduces food and habitat for native fish and other aquatic animals
- interferes with irrigation water flows
- impedes fishing and boating.
What does it look like?
Eurasian water milfoil is a perennial aquatic weed that is mostly submerged except when flowering.
Leaves are:
- olive-green
- less than 4 cm long
- feather-like
- usually submerged
- in whorls of four around the stem
Each leaf is divided into 5–25 pairs (usually more than 12) of leaflets.
Flowers are:
- held above the water in an upright spike 5–20 cm long
- in whorls of 4 around the spike.
Male flowers are:
- in whorls above the female flowers
- 3 mm long with pink petals.
Female flowers:
- are 2–3 mm long
- don’t have petals.
Fruit are:
- 2–3 mm long
- red
- round with 4 smooth sections, divided by wrinkled ridges, each section contains one seed
- on spikes that are above the water surface but lie parallel to the water.
Stems are:
- red-brown to white-pink
- up to 7 m long and about 5 mm in diameter
- hairless
- branched near the surface to form a dense canopy.
Similar looking plants
- Hornwort (Ceratophyllum demersum), a native plant with free floating whorled leaves.
- Ambulia (Limnophila spp.) which has whorled leaves that are feather like when submerged and when emergent are dark green and broad.
- Parrots feather and other Myriophyllum spp., which has whorled leaves with toothed margins.
- Cabomba (Cabomba caroliniana) which has fanlike, opposite leaves.
Where is it found?
Eurasian water milfoil does not currently grow in Australia. If introduced, it could become a major weed of dams, lakes and reservoirs.
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.
What type of environment does it grow in?
Eurasian water milfoil:
- can grow from a depth of 10 m but usually grows in water up to 3 m deep
- thrives in a range of temperatures and water conditions including low salinity
- prefers slow or still water in lakes, ponds and shallow reservoirs
- will also grow in fast-moving water.
Maps and records
-
Recorded presence of Eurasian water milfoil during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
How does it spread?
By plant parts
This weed is mostly spread by plant fragments. During the growing season plants automatically break into fragments, often developing roots before they separate from the parent plant. Water movement and human activities may also cause the plants to break. Fragments are spread over long distances by water currents. They are mainly dispersed between different water bodies by boating and fishing activities.
Eurasian water milfoil may die back to the base during winter and reshoots in spring.
By Seed
Eurasian water milfoil produces up to 112 seeds per stalk and seeds may stay dormant for many years. Seeds usually need at least 15°C for germination. Overseas germination has not been observed often. Seeds are spread by moving water and by water birds.
References
Aiken S.G., Newroth P.R. and Wile I. (1979) The biology of Canadian weeds, 34. Myriophyllum spicatum L., Canadian Journal of Plant Science, 59: 201–215.
Grace, J. B., & Wetzel, R. G. (1978). The production biology of Eurasian watermilfoil (Myriophyllum spicatum L.): a review. J. Aquat. Plant Manage, 16(1), 1-11.
Hartleb, C. F., Madsen, J. D., & Boylen, C. W. (1993). Environmental factors affecting seed germination in Myriophyllum spicatum L. Aquatic Botany, 45(1), 15-25.
Hosking J.R., Sainty G., Jacobs S., and Dellow J (in prep.), The Australian WEEDbook.
More information
Control
Please do not attempt to treat or dispose of this weed yourself. Report this plant if you see it anywhere in NSW by calling the helpline listed at the top of this page immediately.
NSW DPI will lead an initial response for the treatment and disposal of the plant to stop it from spreading
Control of Eurasian water milfoil is difficult. Mechanical harvesting can lead to rapid reinfestation due to the plant being fragmented.
Herbicide options
WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
See Using herbicides for more information.
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 2.9 to 3.9 kg per 100 m2
Comments: Spread the granules over exposed soil. For best results apply to moist soils as close as is practicable to when the area will be flooded. Use higher rate for heavier infestations. DO NOT apply to water which will be used for crop irrigation, livestock watering, or human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 287 to 388 kg per ha or 2.87 to 3.88 kg per 100m2
Comments: Water less than 1m deep. Apply to standing (i.e. not moving) water and toward the end of the plant's dormant period, preferably July – August. Use higher rate for heavier infestations DO NOT apply to water which will be used for crop irrigation, livestock watering, or human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 388 to 574 kg per ha or 3.88 to 5.74 kg per 100m2
Comments: Water more than 1 m deep. Apply to standing (i.e. not moving) water and toward the end of the plant's dormant period, preferably July – August. Use higher rate for heavier weed infestations DO NOT apply to water which will be used for crop irrigation, for livestock watering, or for human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
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 pest 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 |
For technical advice and assistance with identification please contact your local council weeds officer.
Reviewed 2024
