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A weed is any plant out of place.

Environmental Weeds

Environmental weeds are plants that represent a threat to the conservation values of natural ecosystems. They invade native plant communities and out-compete them causing a reduction in plant diversity and resulting in a loss of habitat for native animals.

Some examples of environmental weeds are bridal creeper, bitou bush, boneseed, blackberry and lantana.

Environmental weeds can also be native Australian plants that are not local (indigenous) to the area they are growing in. They have the potential to displace and out-compete plants within the local plant community. Examples of native Australian plants that are doing this are sweet pittosporum and coast wattle.

Noxious Weeds

Some serious weeds are required by law to be controlled by all landholders in an area. These are known as noxious weeds and the law that controls these in NSW is the Noxious Weeds Act 1993.

Weeds that are declared noxious are those weeds that have the potential to cause harm to the community and individuals, can be controlled by reasonable means and most importantly, have the potential to spread within an area and to other areas.

A weed is declared noxious because its control will provide a benefit to the community over and above the cost of implementing control programs.

The Noxious Weeds Act 1993 classifies weeds into five control classes, each of which require a different level of control. For land within a local government area, Council is the Local Control Authority (LCA). For a full list of Declared Weeds in the Bayside Council LCA and the required control measures for each plant, please see NSW WeedWise.

Control Program

Alligator weed (Alternanthera philoxeroides) 

Originating from South America, Alligator weed (Alternanthera philoxeroides) is a weed of National Significance. Alligator weed is a potentially devastating weed that grows in water and on land, affecting both waterways and floodplain areas by blocking water flow. Floating mats of alligator weed crowd and out-compete native aquatic species, restrict light penetration and ultimately cause anoxic or anaerobic conditions. Prolific growth restricts flows and increases sedimentation, aggravating flooding by acting as a barrier and collecting debris. Floating mats can lodge against other structures and inhibit flow further, hindering access to, and use of, the waterway.

Council undertakes an annual treatment program to control this weed. This will involve three applications of metsulfuron-methyl 600g/kg at specific times during the growing season. Over six months, bush regeneration contractors will be spraying locations where alligator weed is present. You may see signs and some grassed areas not being mown. This is to reduce the spread of the weed while it is being treated. Accidental spread commonly occurs through human activities (eg. through the slashing and mowing of infested areas; in mulch, gravel extraction and turf).

The herbicide, Associate, will be used for the control of Alligator Weed within and along Bardwell Creek, Bardwell Valley; Bado Barong Creek, Sans Souci; Bicentennial Ponds, Rockdale; Scarborough Ponds, Rockdale; Tonbridge Creek, Ramsgate; Waradiel Creek, Sans Souci and Barton Park, Banksia. The herbicide will be used in line with the manufacturer's instructions and AGVET Off-label permit PER12789. This method of suppression and control is in line with the NSW Department of Primary Industries Alligator Weed Control Manual.

Ludwigia or Water Primrose (Ludwigia peruviana and Ludwigia longifolia) 

At the same time the Bush Regeneration contractors are controlling the Alligator weed, they will also be targeting Ludwigia or Water Primrose (Ludwigia peruviana and Ludwigia longifolia). Originating from Central and South America, Ludwigia was introduced to Australia in 1911. It is a fast growing terrestrial or partially submerged shrub to 4m tall, usually confined to freshwater creek lines, banks and wetlands. Ludwigia is deciduous in Sydney.

Ludwigia is spread by either seeds or stem fragments. Seeds are extremely small, (ie. less than 1mm long) and can be dispersed by water, wind, or human activity. Vegetative propagation occurs via rooting of stem sections.

Control of Ludwigia is very difficult and herbicide is the most effective means of control. The herbicide, Roundup Biactive, will be used for the control of Ludwigia within and along Bardwell Creek, Bardwell Valley; Bicentennial Ponds, Rockdale and Scarborough Ponds, Rockdale. The herbicide will be used in line with the manufacturer's instructions and AGVET Off-label permit RER11566.

Duckweed at Bicentennial Ponds

During the summer months duckweed does occur at Bicentennial Ponds. This plant floats on the water surface in a bright green layer.

This weed is a native plant and appears in waterways when there is the presence of excess nutrients.

Duckweed is non toxic and is a food source for many animals that live within the wetlands. Its main benefit, however, is its ability to remove excess nutrients from the water - a common problem for urban waterways.

Research has also found that duckweed prevents a number of noxious weeds from growing in our waterways, for example, blue green algae.

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Additional Resources

Below are some resources to assist you with identifying and controlling noxious weeds on your property.

The Department of Primary Industries have produced a comprehensive and useful weed identification online tool - Weedwise, a resource that identifies all the noxious weeds in our LGA as well as treatment and control methods which can also be downloaded as an app on your Apple or Android device.

The Sydney Weeds Committee have a number of useful fact sheets, as do the Department of Primary Industries

If you think you have seen a noxious weed for sale, you can report it by emailing Council's Noxious Weed Officer (available Fridays).

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