Long-leaf willow primrose (Ludwigia longifolia)

Long-leaf willow primrose is an invasive aquatic weed. It can form dense colonies in slow moving or static waterways.

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How does this weed affect you?

An invasive aquatic weed threatening NSW waterways and wetlands Ludwigia longifolia can form dense colonies in slow moving and static waterways. If no control action is taken it will dominate temperate and tropical wetland and riparian systems throughout Australia.

Where is it found?

Long-leaf willow primrose is a native of South America, recorded from Brazil to Argentina and is considered a major weed in its native range.

This species was introduced to Australia as an aquatic ornamental plant and was first recorded as naturalised near Sydney in 1991. It has also been recorded from the Port Stephens and Gosford areas on the Central Coast of NSW and near Brisbane in Queensland.

How does it spread?

Spread of long-leaf willow primrose is by either seeds or stem fragments. Seeds are extremely small, less than 1 mm long and can be dispersed by water, wind, or human activity. Vegetative propagation occurs via rooting of stem sections.

What does it look like?

Long-leaf willow primrose is an erect annual shrub up to 3 m high which has a shallow fibrous root systems.

Leaves and stems

Alternate linear leaves up to 35 cm long and 2.5 cm wide, reducing in size up the stem. The stems are red, narrow, winged, 4-angled and winged, usually branching  towards the apex.

Flowers

Flowers are solitary and found in the junction of upper leaves. The petals are yellow and 2–2.5 cm long. Flowering occurs from summer to winter.

Fruit

Fruit is oblong to narrow-oblong, 4-angled, 1–3.5 cm long, 0.4–0.8 cm wide with numerous minute seeds in each chamber that are brown to yellow in colour.

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Control

Control of long-leaf willow primrose is very difficult. Mechanical/hand removal may be the most desirable method for small isolated infestations. However care must be taken to dispose of the material appropriately; care should be taken to avoid fragmenting the plant and leaving behind pieces that could start new infestations. Correct disposal is essential to prevent further spread. All plants should be removed before seed set and destroyed by burning or deep burial to stop plant regrowth from stem sections.

Preventative measures such as planting riparian vegetation to out-compete L. longifolia, reducing any nutrient inflow into the system and preventing animal and machinery access to the site will prevent further spread and disturbance of the site.

For any activities concerning control of long-leaf willow primrose, it is recommended that you contact your local weeds officer to seek advice on identification, disposal and best practice control methods before you start.

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 14731 Expires 30/06/2019
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: 1.0 L per 100 L of water
Comments: Spot spray application.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


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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.
Hunter
Land Area 1: Core infestation area of Newcastle, Lake Macquarie, Port Stephens and Mid Coast. Land Area 2: Rest of region
Regional Recommended Measure*
Land Area 1: Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land where feasible. Land Area 2: 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.
North Coast
Exclusion zone: All lands in the region except the core infestation area of Nambucca Shire Council, Bellingen Shire Council, Coffs Harbour City Council, Clarence Valley Council, 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