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Noxious weeds

Aquatic weeds and treatment

Declared noxious aquatic weeds include Ludwigia longifolia (Longleaf Willow Primrose), Hygrophila costata (Hygrophila), Salvinia molesta (Salvinia), Eichhornia crassipes (Water Hyacinth), Sagittaria species (Arrowhead), Pistia stratiotes (Water Lettuce), Alternanthera philoxeroides (Alligator Weed), Cabomba species and Gymnocoronis spilanthoides (Senegal Tea Plant).

The sale of water plants that have been declared noxious is prohibited.

Aquatic weeds are usually described as submerged, floating or emergent, although some plants can combine these features. Submerged weeds are the hardest to treat and have the greatest potential for damage to natural and human use of waterways.

The file below contains images of common noxious aquatic weeds. For additional information on aquatic weeds or native look alike plants contact the weeds office at Council.

Please report possible occurrences of aquatic weeds to Council.

Aquatic Weed Treatment – please see Environmental Works

The NSW Department of Primary Industries (DPI) are responsible for declaring weeds noxious in NSW. The noxious weed list for Port Stephens was changed in early 2010. To view a current list of noxious weeds please visit the NSW Department of Primary Industries website.

The changes DPI made include declaring Lippia canescens and Sagittaria montevidensis as class 4 noxious weeds across NSW, both of these species are known to be present in Port Stephens.

Alligator Weed

A national Alligator Weed control manual is available - free!

The 90 page publication brings together for the first time detailed information on the eradication and suppression of Alligator Weed (Alternanthera philoxeroides) in Australia.

Containing hundreds of colour images and information from over 30 years of research and experience in Alligator Weed control; the manual includes chapters on control, containment and herbicide, biological and mechanical control methods.

Copies of the manual are available free to people who live or work in Alligator Weed affected areas and can be obtained from the administration building at Raymond Terrace or by phoning (02) 4980 0255. The manual can also be downloaded from the NSW Department of Primary Industries.

Alligator Weed identification and control

Alligator Weed is a summer growing perennial herb (non woody plant). It has small white flowers that appear mainly between November and March. The plant has hollow stems with shiny, spear-shaped, opposite paired leaves. Of the total Alligator Weed recorded in Australia about three quarters (3500 Ha) are located in Port Stephens.

Alligator Weed does not produce seeds in Australia and spreads only from plant fragments. These fragments can be very small and are able to survive extreme conditions. Alligator Weed spreads naturally when fragments float downstream; this is exacerbated during flooding when mat sections are deposited on the floodplains.

Spread assisted by human activity is responsible for moving Alligator Weed between catchments and into new areas. Examples of human assisted spread include movement on contaminated machinery and in soil supplies, resulting in new outbreaks throughout Port Stephens and as far afield as Griffith. The Protocols for Working in Alligator Weed Affected Areas provide guidance on how to prevent the spread of fragments during excavation and other activities.

Alligator Weed disrupts the aquatic environment by blanketing the surface and reducing light penetration. It competes with native flora, contaminates grazing pastures, threatens our drinking water supplies and renders valuable land unfit for cropping. The weed mat impedes stream flow promoting sedimentation and flooding problems as well as providing a habitat for mosquitoes.

It is illegal to sell turf from land affected by Alligator Weed.

The control requirement for Alligator weed throughout Port Stephens is "the plant must be fully and continuously suppressed and destroyed".

The four broad methods of controlling weeds are chemical, biological, cultural and physical.

Control using herbicides is effective if the correct herbicide is used. Trials have demonstrated over 98% kill rates on old established plants and 100% kill of young plants. Contact the Weed Officers for advice before commencing a chemical treatment.

The Flea Beetle (Agasicles hygrophila) was introduced as a biological control in 1976 and provides good control for aquatic infestations, although it has little impact on the terrestrial Alligator Weed.

The Flea Beetle is widespread and has been found at all known aquatic infestations. New insects are being evaluated for release in Australia, and work is also underway researching the potential to use native fungi to control Alligator Weed. Flea Beetles are suited to areas that cannot or will not be otherwise treated, and should be integrated with other methods. When using herbicides to control aquatic infestations, consider leaving a small patch untreated as a refuge for the Flea Beetles to breed in and spread out to eat the regrowth. Try to time herbicides so that the peak of Flea Beetle activity (usually just after Christmas) coincides with the regrowth phase of Alligator Weed.

A permit is required before moving Alligator Weed plant material, even if it is included in excavated soil. Any machinery and equipment used to dig Alligator Weed must be cleaned of all soil and plant material before leaving the site. Anyone intending to conduct excavations in Alligator Weed affected areas should contact the council for advice before commencing.

The value of excavation is usually limited to small and isolated infestations. The deep roots must be carefully removed and follow up digging maintained until no new shoots emerge. Disposal of fragments and excavated soil must be done carefully to avoid spreading the weed. Follow up work involving spraying and hand picking fragments is also required.

Cultural control involves manipulating the site to favour plants other than Alligator weed, for example a dense cover of Kikuyu has been demonstrated to inhibit Alligator Weed in pastures. At no stage should ploughing or cultivation be used in Alligator Weed affected areas.

It is vital to combat the spread of alligator weed by reporting sightings to Council's Weeds Officer to assist in mapping, recording and managing this problem. All property owners/occupiers should conduct regular monitoring to control infestations.

Suspect plants can be identified by Council Weed Officers, who can also show you the confusing species and explain how to identify Alligator Weed. It is best to leave plants where they are found and simply mark the spot with a semi permanent marker such as a timber stake rather than collect some to bring in.

If Alligator Weed is confirmed, a thorough search of the site is required to determine the source and extent of the infestation. The key to controlling Alligator weed is to stop the spread of it through human activity and to keep infestations suppressed at all times.

For further information on Alligator Weed visit NSW Department of Primary Industries.

Bitou Bush

Bitou Bush affects mostly coastal areas, but is slowly moving inland.

Council and various other agencies undertake control programs on land under their control and expect owners and occupiers of private land to also control the weed.

Spread by birds eating the fruits, control programs should attempt to prevent seeding of large plants and establishment of new plants.

Control using herbicides, physical methods and biological agents are most effective if combined. Council staff can advise on the best methods for particular situations.

Remember to look out for native plants and animals before undertaking control measures.

The NSW Department of Environment, Climate Change and Water has a large amount of information available from their website.

Chinese Violet

Chinese Violet (Asystasia gangetica subspecies micrantha)

Chinese Violet is a national priority weed that is the subject of an eradication project being conducted by Council.

Of the recorded infestations in Australia, almost all occur within the Port Stephens area with three known from nearby sites.

Already a major weed overseas, Chinese Violet is a pretty garden plant that the commonwealth Bureau of Rural Sciences has recommended be eradicated from Australia before it can spread further into agricultural and environmental areas.

The rapidly growing plant has a smothering habit and can outcompete most crops for water and nutrients. It is mostly spread by seed but can also send down roots from the sprawling stems, smothering native and other desirable plants.

Chinese Violet is a class 1 notifiable noxious plant throughout New South Wales which makes spreading it through the movement of soil, machinery and plant material etc.an offence.

People undertaking activities on land affected by this weed should contact the weed officers for advice before commencing works.

Occupiers of affected land have obligations to control the plant and should contact council officers for advice on how to proceed. The Noxious Weeds Act control requirement is "The plant must be eradicated from the land and the land must be kept free of the plant".

Please report any suspected occurances of Chinese Violet to Council's Weeds and Pest Management Officers (02) 4980 0392.

The following files contain information on how to identify and control Chinese Violet.

Groundsel Bush

Groundsel Bush is spreading in Port Stephens.

Groundsel Bush (Baccharis halimifolia) is a poisonous and invasive shrub or tree. It can tolerate waterlogging, drought, acid sulphate and saline soils. Plants seed prolifically and the light seeds spread over long distances through human activity or by wind.

Groundsel Bush belongs to the daisy family (Asteraceae) and is native to North America.

Plants are considered poisonous to stock and can form dense thickets that prevent vehicular and animal passage. It can also block drains and transform open wetlands into densely wooded bogs.


Plants are upright, dense with dark bark and leaf edges toothed similar to holly. Leaves are light and bright green. Male and female plants separate. Female plants covered with persistent fluffy white seeds. Each seed weighs about 0.1 gram and is designed to fly on the wind or stick to animals, earth and equipment.


Advise Council of plants or to request confirmation of suspect plants. Carefully remove seeds heads and bag, ask Council what to do with them. Kill plants by using an overall spray for small plants or by cutting at the base and poisoning the stump for larger plants.

Ludwigia longifolia (Long Leaf Willow Primrose)

Ludwigia longifolia in Port Stephens most infestations are in the Salamander Bay area.

Ludwigia flowers and (right) a shoot damaged by Altica beetles.

A relatively new weed with an obvious ability to invade and dominate shallow wetlands Ludwigia longifolia has been declared a class 4 and 5 noxious plant. This means that the sale of plants is banned and existing plants must be controlled.

Research has found it can produce 25 million seeds per square metre under two year old plants. Seeds are easily spread by water, wind, human activity and animals, resulting in rapid spread. Control of plants with herbicide or by physical means is effective but constrained by the nature of the wetland habitats and the prolific seedling growth.

A native beetle Altica sp. has been observed feeding on plants. Research into the effectiveness of these beetles for ludwigia control indicated they are not going to provide adequate control except in situations where access is very limited for other methods.

Please report suspected infestations of Ludwigia longifolia.

Mother of Millions

Resurrection Plant (Bryophyllum pinnatum) grows easily from leaf fragments

All species and hybrids of the Bryophyllum genus are declared noxious weeds. This includes B. daigremontianum (Mother of Millions), B. delagoense (Mother of Millions) and B. pinnatum (Resurrection Plant).

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