Hygrophila (Hygrophila costata)

Profile

Impact

Hygrophila is a highly invasive aquatic weed. It grows up to 1.5 m high in shallow water, forming mats of dense growth around the margins of freshwater lakes, rivers and watercourses where it can dominate and out-compete other vegetation. It grows all year round but most rapidly during the warmer months.

Dense infestations are likely to displace native flora and fauna by destroying their natural habitat. Hygrophila can also interfere with recreational activities such as boating and access to the water’s edge.

Distribution

Hygrophila is native to the Americas from southern Mexico to Argentina, and has naturalised in many tropical and subtropical areas around the world.

In New South Wales (NSW), hygrophila has become invasive in the far north coast, central coast and greater Sydney regions. Infestations are also occurring in southeast Queensland.

Distribution map

Spread

Reproduction is by either seed or stem fragments. Spread occurs when seeds and plant fragments attach to animals, machinery or watercraft, or are dispersed by wind or water.

Spreading stems sprout new roots from their nodes when they come in contact with the soil, enabling a new plant to form.

Description

Hygrophila is an erect emergent herb which grows to 1.5 m in height.

Key identification features

  • Leaves are hairy, up to 18 cm long and 3 cm wide, in opposite pairs and tapering at their base. They have prominent veins and a distinct midrib.
  • Upper stems are 4-angled, erect and rarely branched; lower stems are prostrate and root at nodes; the stems may have a red to purplish colour.
  • Flowers have white petals and are about 10 mm long. They occur in whorls just above the junction between leaves and the stem.
  • Fruit capsules are about 7 mm long, spindle-shaped and inconspicuous. Seeds are pale brown, flattened, round, about 0.3 mm wide and become sticky when wet.

Acknowledgements

Authors: Peter Gorham, John Hosking; Reviewers: Melissa Freeman, Birgitte Verbeek; Editors: Annie Johnson, Elissa van Oosterhout.

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Control

Control of hygrophila is very difficult as new infestations can form from any remaining pieces of the plant. Contact your local council weeds officer for assistance if you suspect you have found hygrophila.

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

See Using herbicides for more information.


PERMIT 14729 Expires 30/06/2019
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: 1.0 L per 100 L of water
Comments: Spray when plants are actively growing, re-treatments may be necessary. Do not spray directly onto waters surface or non-target species.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


PERMIT 14729 Expires 30/06/2019
Metsulfuron-methyl 600 g/kg (Brush-off®)
Rate: 5–10g per 100 L of water
Comments: Minimise off target damage and water pollution by spraying towards the bank. Do not apply more than 3 times a year.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors)
Resistance risk: High


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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.
Central Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Central West Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Greater Sydney Regional Recommended Measure*
The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Hunter Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
North Coast
Exclusion zone: all waters in the region excluding the core infestation area of Richmond Valley Council, Ballina Shire Council, Lismore Council, Kyogle Council, Byron Shire Council and Tweed Shire Council
Regional Recommended Measure*
Whole region: The plant or parts of the plant should not be traded, carried, grown or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should reduce impacts from the plant on priority assets.
North West Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
South East Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed click here

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Reviewed 2017