Environmental issues

Pests and weeds

New and emerging weeds

OEH adopts a strategic approach to weed management that includes:

  • eradicating or containing high priority new and emerging weed species
  • reducing the impact of widespread weeds by protecting important assets.

This approach has been well-developed through threat abatement strategies such as the Bitou Bush and Boneseed Threat Abatement Plan and the Biodiversity Priorities for Widespread Weeds (BPWW). Priorities for new and emerging weed management are available for Weeds of National Significance (WoNS) and weeds listed under the Noxious Weeds Act 1993, but these do not encompass the entire range of new and emerging environmental weed species in NSW.

To counteract this, a joint OEH and Department of Primary Industries (DPI) project commenced in 2012 to determine the highest priority new and emerging environmental weeds on publicly- and privately-owned conservation lands in NSW.

Assessing emerging weeds for weed risk

An initial list of 439 weed species which were thought to be new or emerging threats in environmental areas was compiled. The list was culled to 218 species, to remove weed species that were already widespread in NSW as well as species not yet recorded in NSW.

Using the NSW Weed Risk Management System, assessments of individual weed species were completed at the statewide level for conservation areas, including aquatic areas. Sufficient information was available to complete weed risk management assessments for 146 of the 218 species. Weed risk assessments determined the management category for each of the 146 species. Outlined below are the six management categories relevant to this project.

Management categories under the NSW Weed Risk Management System

Management priority category

EradicationTo remove the weed species from NSW
Destroy infestationsTo significantly reduce the extent of the weed species in NSW
Contain spreadTo prevent the ongoing spread of the weed species in NSW
Protect priority sitesTo prevent the spread of the weed species to key sites/assets of high economic, environmental and/or social value
Manage weedTo reduce the overall economic, environmental and/or social impacts of the weed species through targeted management
Manage sites To maintain the overall economic, environmental and/or social value of key sites/assets through improved general weed management


Eighty-four species were in the eradication, destroy infestations and contain spread categories. Of these, thirty-six were in the eradication and destroy infestations categories, of which 24 are listed under the Noxious Weeds Act 1993. In addition, 12 species are listed nationally either as WoNS or under the National Alert List of Environmental Weeds.

Weeds listed in the 'eradication' management category

Scientific name

Common nameNoxious weed listing*National listing
Alternanthera philoxeroides  Alligator weed Class 2 & 3WoNS
 Chrysanthemoides monilifera subsp. monilifera BoneseedClass 2 & 4WoNS
Equisetum arvenseHorsetailsClass 1Alert
Gymnocoronis spilanthoides Senegal tea Class 1Alert
Hygrophila costata Hygrophila, glush weed Class 2 
 Leucaena leucocephala Coffee bush Not listed 
Mahonia (Berberis) lomariifolia Chinese holly grape Not listed  
Miconia calvescens MiconiaClass 1 
Nassella tenuissima Mexican feather grass Class 1 
Orbea variegata Carrion flowerNot listed  
Parkinsonia aculeata ParkinsoniaClass 2WoNS
Parthenium hysterophorus Parthenium weed Class 1WoNS
Pereskia aculeata Leaf cactusNot listedAlert
Pistia stratiotes Water lettuce Class 1 
Tamarix aphylla Athel pine Class 5WoNS

* As listed in Weed Control Order 28 under the Noxious Weeds Act 1993. ‘Class’ relates to the weed control class under the Weed Control Order.


Orange hawkweed (Hieracium aurantiacum) flowers

Orange hawkweed (Hieracium aurantiacum) flower and buds

The results of this project will assist with priority setting, ensuring that the highest-risk weeds and those that are most easily controlled are tackled first. For example, results have already helped determine the ‘critical – new and emerging’ weed programs in the NPWS Regional Pest Management Strategies.

The assessments were undertaken at a state level and additional regional assessments may be needed as statewide results will not always be the same as region-specific results.

There was insufficient information to complete assessments for 72 species. However, some information was obtained for these species and these assessments can be progressed as new information becomes available.

Boneseed (Chrysanthemoides monilifera ssp. monilifera)

Boneseed (Chrysanthemoides monilifera ssp. monilifera)

All completed and partially completed assessments will be included in an online database which is being developed by the Department of Primary Industries. The assessments will be made available to stakeholders in NSW, to assist them with their regional assessments. The assessments can also be considered when incorporating priority species in new or updated weed strategies or awareness-raising material.

Until the online database is complete, please email us if you require weed risk assessments completed under this project.

Page last updated: 14 February 2014