Indicator: Pest Plants

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Summary

Pest plants remain a significant problem throughout much of the ACT, impacting on biodiversity values (especially in lowland areas), and affecting rural productivity and plantation forestry. It is not possible to determine an overall trend but to note significant achievements, such as pest willow removal, woody weed control (including weeds of horticultural origin), and preventing establishment of pest water-plants. However, some species remain widespread pests (Blackberry, St John’s Wort), and continue to invade new areas (Chilean Needle Grass, African Love Grass).

Weed proliferation following the extensive bushfires of January 2003 is of major concern to land managers. There is a coordinated approach to weed control by government agencies in the ACT through the Weeds Working Group and major control programs have been undertaken in the reporting period. Over this period, expenditure on weed management in the ACT by federal and ACT government agencies has totalled $4.34 million.

What the results tell us about the ACT

Pest plants (weeds) are a major problem throughout much of the ACT and region reflecting an Australia-wide situation in which the condition, with regard to invasive species, is assessed as deteriorating (Australian State of the Environment Committee 2001).

Since the first ACT State of the Environment Report in 1994 discussed the problem, a wide range of weed control activity has been undertaken. Some species have been successfully targeted, while others have emerged as new threats.

Weeds spread after bushfires

The spread of weeds in the areas of the ACT burnt in the bushfires of 2001 (3411 hectares) and 2003 (164,914 hectares) is a major concern for land managers and community groups. Following the January 2003 fires, the ACT Weeds Working Group identified the need for extra funding and early control of weeds, such as Paterson’s Curse (Echium plantagineum) and Nodding Thistle (Carduus nutans), expected to flourish in the absence of competition in burned, graded and drought affected areas. Early intervention is expected to be the best way to reduce the weed control burden in the future. However, some species, such as Blackberry, that are showing widespread recovery can only be treated with herbicide when sufficient foliage has appeared. As this can take a year or more for many species, a post-fire weed control program is expected to be needed for a number of years.

Costs of weed control

In 2000–01, expenditure on weed management by ACT and federal government agencies in the ACT totalled $1.59 million, with willows ($0.42 million) and woody weeds ($0.42 million) being the main targets. In 2001–02, expenditure was $1.82 million, targeting willows ($0.47 million), woody weeds ($0.37 million) and ‘other weeds’ ($0.37 million). In 2002–03, drought conditions affected our ability to carry out herbicide-based weed control, and expenditure fell to $0.93 million, with ‘other weeds’ (including pine wildings) ($0.19 million) and Serrated Tussock ($0.17 million) being the main targets.

Community groups work with government

Community groups, including Urban and Rural Landcare, Park Care and Paddock Care, are continuing to make a significant contribution to weed control in the ACT. In 2002, the Friends of Mt Taylor recorded removal of the 40,000th weed from the reserve (Environment ACT 2002). In collaboration with the ACT Parks and Conservation Service, Park Care groups have been carrying out work in Canberra Nature Park, the Murrumbidgee River Corridor, Tidbinbilla Nature Reserve, Googong Foreshores, and Namadgi National Park (at Gudgenby).

The groups anticipate active involvement in weed control as part of the recovery following the 2003 bushfire. Within a few months of the fire, regrowth of weed species was evident – Paterson’s Curse on Cooleman Ridge and Urambi Hills and Blackberry, African Love Grass and Serrated Tussock in the Murrumbidgee River Corridor (Environment ACT 2003).

Weed control activities in the ACT are reported in the annual program reports and complete information can be found at .

Weed management plans ready

Ten year (2002–12) weed management plans for the ACT have been completed for both declared pest plants in the ACT and other weed species. They are:

  • Broom* (Cytisus spp. and Genista spp.) and Gorse* (Ulex europaeus)
  • Aquatic Weeds including Water Lettuce* (Pistia stratiotes), Water Hyacinth* (Eichornia crassipes), Parrots Feather (Myriophyllum aquaticum), Cabomba* (Cabomba caroliniana)
  • Serrated Tussock* (Nasella trichotoma)
  • Chilean Needle Grass* (Nasella neesiana)
  • Blackberry* (Rubus fruticosus)
  • Noogoora Burr* (Xanthium occidentale)
  • ACT Woody Weed species covering trees and woody shrubs of horticultural origin viz. Box Elder (Acer negundo), Service Tree (Sorbus aucuparia and S. domestica), Hawthorn (Crataegus monogyna), Nettle Tree (Celtis australis), Black Alder (Alnus glutinosa), False Acacia (Robinia pseudoacacia), White and Lombardy Popular (Populus alba and P. nigra ‘Italica’), Tree of Heaven (Ailanthus altissima), Sweet Briar (Rosa rubignosa), Cotoneaster* (Cotoneaster spp.), Firethorns* (Pyracantha spp.), Narrow and Glossy leaved Privet* (Ligustrum lucidum and L. sinense), Rhus tree*Rhus tree* (Toxicodendron succedanuem), African Boxthorn (Lycium ferocissimum).
    * = ACT declared pest plant

Other initiatives

Weed Swap days were organised in October 2001 and April 2002. On these days, members of the public swapped woody weeds removed from their gardens with non-invasive native species. This was repeated in October 2002 (1236 plants swapped) and April 2003 (1197 plants swapped). The events were organised by the Australian Native Plants Society in conjunction with Environment ACT, and were supported by funding from the Natural Heritage Trust.

Local nurseries now bush friendly

All local nurseries have agreed to be ‘bush friendly’ by not selling any of the plants shown in a colour brochure, Are Your Garden Plants Going Bush?, produced by the ACT Weeds Working Group. The decision by nurseries follows visits in 2001–02 by the Conservation Council weeds officer (supported by the ACT Government).

The ACT ‘Bush Friendly Nursery’ scheme aims to eliminate known and potential problem species from nurseries through education and awareness. Promotion of particular plants and sales by nurseries can contribute to existing and potential pest plants securing a greater foothold (Low 2001). While ACT legislation provides for declaration of pest plants and requires that a plan to control their propagation be prepared, there is no legislation to prohibit sale of declared pest plants. Many weed species in the ACT region originated from gardens, ponds and aquariums.

However, checks of nurseries show that problem species, such as various forms of Broom, are sometimes still stocked. Not all nurseries display the ‘Bush Friendly Nursery’ sign and greater publicity of the scheme and its commercial advantage may be needed to encourage increased compliance and willingness to display the sign.

Declared pest plants

Twenty-four species (or groups of species) have been declared as ‘pest plants’ since the Declaration of Pest Plants Instrument was made in June 1999 under the Land (Planning and Environment) Act 1991 (see Table 1).

Of these, Cotoneasters, Broom, African Love Grass, Privets, Serrated Tussock, Chilean Needle Grass, Firethorns, Blackberry, Willows, Gorse and Noogoora Burr occur in the ACT. For the other listings, seven are water-weeds most of which are widely used in aquaria and have potential to spread into the ACT, and six are terrestrial species which do not currently occur or have been found only occasionally in the ACT.

These listings reflect the serious problems these species have created elsewhere in Australia

and the need to be proactive in preventing their introduction into the ACT.
Table 1: Declared pest plants in the ACT during the reporting period 2000–03
Species Condition Pressure Response Status/outlook
Broad-kernel Espartillo (Achnatherum caudatum) A tussock forming perennial grass occurring in NSW and Victoria. Not present in ACT. N/A. Species invades native grasslands, open forest and woodland and riparian vegetation. Land management agencies alert to possible spread of species into the ACT. Potential pest plant in ACT. Ongoing monitoring necessary.
Alligator Weed (Alternanthera philoxeroides) Waterweed. Noxious weed Australia-wide. Potential to spread, and control extremely difficult. One small infestation in biological wastewater treatment facility (1999–2000), potentially urban lakes (found regularly in Lake Ginninderra), urban backyards where grown as vegetable Nil, as suitable habitats and urban backyards where previously grown are monitored annually and any outbreaks are eradicated. Continuing eradication program from Lake Ginninderra. Dept of Urban Services working with Sri Lankan community to eradicate from urban yards. Community awareness program 2001 and ongoing. Species controlled. Ongoing monitoring, eradication and education necessary.
Cabomba (Cabomba caroliniana) Waterweed. Not present in ACT. Widely sold throughout Australia for use in aquaria so likely to spread.
A weed of national significance
N/A Checks for, and provision of information on aquatic weeds at nurseries, aquarium suppliers, pet shops (Environment ACT). Included in 10-year Aquatic Weeds Management Plan in place from 1 July 2002. Potential pest plant in ACT. Ongoing monitoring and education necessary.
Spotted Knapweed (Centaurea maculosa) Noxious weed in NSW. Occasional occurrence in ACT. Minimal Only known site inspected Spring 2002 and Autumn 2003. Any seedlings present destroyed. Potential pest plant in ACT. Ongoing monitoring necessary.
Scotch Broom (all Cytisus spp.) and Montpellier Broom (all Genista spp.) Related to Spanish Broom (Spartium junceum) also environmental weed. Broom found throughout ACT. Seed may remain viable for up to 30 years. All known sites, including previous sites, have been recorded by Environment ACT. All invade dry forest and woodlands. Scotch Broom also river corridors. All known sites on public land mapped in 1999 and updated each year. All known infestations on ACT Public Land have been treated and are inspected annually. Mostly removed from Defence land and ongoing policy to remove completely. Ongoing Canberra Urban Parks and Places program to remove broom from urban nature strips. Biological control agents for broom released at two sites in Namadgi National Park 1999–2000. Ten-year Management Plan in place from 1 July 2002 Substantial progress made in eradication and control of broom. Longevity of seed means ongoing monitoring of former sites necessary. Education and nursery compliance are important.
Water Hyacinth (Eichornia crassipes) Waterweed. Noxious weed Australia-wide. A major weed of rivers, wetlands and irrigation channels, especially warmer areas. Not present in ACT N/A Checks for, and provision of information on aquatic weeds at nurseries, aquarium suppliers, pet shops (Environment ACT). Included in 10-year Aquatic Weeds Management Plan in place from 1 July 2002. Potential as major pest plant in ACT is not high.
Horsetail (Equisetum arvense) Naturalised only near Sydney but has been imported and sold by nurseries in other states. Invades wetlands, low-lying wet areas and grasslands.
Not present in ACT
N/A Species included in Are Your Garden Plants Going Bush? brochure. Species has potential for establishment in ACT and with extensive rhizome system and deeply buried tubers is difficult to control. Important to maintain education and nursery compliance.
Senegal Tea Plant (Gymnnocoronis spilanthoides) Waterweed. A very hardy, freshwater or marsh growing emergent perennial herb, introduced as an aquarium plant. Noxious plant in NSW.
Not present in ACT
N/A Checks for, and provision of information on aquatic weeds at nurseries, aquarium suppliers, pet shops (Environment ACT). Monitoring of urban lakes. Potential pest plant in ACT. Ongoing monitoring and education necessary.
Kochia (Kochia scoparia) Summer growing annual. Toxic to stock. Capable of widespread seed dispersal as ‘tumbleweed’ in wind. Not present in ACT. N/A Land management agencies alert to possible spread of species into the ACT. Potential pest plant in ACT. Ongoing monitoring necessary.
Lagarosiphon (Lagarosiphon major) Waterweed. Noxious weed Australia-wide. Recorded as naturalised at Shepparton and Melbourne and found in aquaria in Sydney. Not present in ACT N/A Checks for, and provision of information on aquatic weeds at nurseries, aquarium suppliers, pet shops (Environment ACT). Monitoring of urban lakes. Species is potentially serious weed of deep-water storages. Ongoing monitoring of ACT lakes and education necessary.
Lobed Needle Grass (Nassella charruana), Serrated Tussock (N. trichotoma) and Chilean Needle Grass (N. neesiana) Lobed Needle Grassis not present in ACT.
Serrated Tussock is theworst weed on the Southern Tablelands and Monaro, highly invasive with broad site tolerance. Widespread infestation but may have occupied only 20% of potential range (ACT Serrated Tussock Management Plan 2002). It is a weed of national significance.
Chilean Needle Grass is widely distributed in temperate SE Australia. In ACT, species has infested urban open space and private lawns and lesser extent in rural areas. Not well recognised. Occurs in or adjacent to natural temperate grassland sites in ACT (ACT Chilean Needle Grass Management Plan 2002). It is a weed of national significance.
Serrated Tussock: High conservation value natural temperate grassland and grassy woodland is vulnerable to ongoing invasion.
Chilean Needle Grass: Species surveyed late 2000 and 2002. Present in or adjacent to 85% of natural temperate grassland sites. More common and more abundant in urban area, but still present at 50% of peri-urban and rural sites. Threat to native grassland and grassy woodland.
Serrated Tussock: All government land managers have undertaken control programs based on herbicide application and follow up at known sites. Canberra Urban Parks and Places has treated infestations in urban parkland, ACTP&CS areas such as Gungahlin Grasslands and Paddys River catchment. Defence Infrastructure began an intense 5 year control program in 2001.
Chilean Needle Grass: As well as control based on herbicide application, attention given to identification and other control options in conservation areas, e.g. grazing in Crace grasslands. Ten-year ACT Management Plan for N.trichotoma and N.neesiana in place from 1 July 2002.
Both Serrated Tussock and Chilean Needle Grass will need ongoing programs to locate and treat infestations.
Parthenium Weed (Parthenium hysterophorus) Not present in ACT. Species is capable of major infestations. First recorded in Australia in 1955, it was a ‘sleeper’ until high rainfall years 1974–77. An aggressive coloniser of roadsides, wasteland and over-grazed pasture. Extending south from Qld especially on roadsides.
It is a weed of national significance
N/A Land management agencies alert to possible spread of species into the ACT. Ongoing monitoring required especially of roadsides. Species rarely invades well managed areas with existing groundcover.
Water Lettuce (Pistia stratiotes) Waterweed. Not present in ACT. Previously used as aquarium plant. Species is frost sensitive and does not readily establish in southern Australia. Noxious weed in NSW. N/A Checks for, and provision of information on aquatic weeds at nurseries, aquarium suppliers, pet shops (Environment ACT). Included in 10-year Aquatic Weeds Management Plan in place from 1 July 2002. Potential pest plant in ACT. Ongoing monitoring and education necessary.
Firethorns (Pyracantha angustifolia, P. coccinea, P. fortuneana) Woody weed. Formerly widely planted in gardens and as hedges on private leases and public land. Attractive berries, seed dispersed by birds. Common in urban Canberra especially older suburbs. Invades dry forest and woodland adjacent to urban areas mainly from bird-dispersed seeds. Firethorn removed as part of woody weed control programs by all agencies. Park Care and rural and urban Landcare groups undertook woody weed removal across the ACT. Defence Infrastructure aims to remove all Firethorn by June 2003. Firethorn control part of 10-year ACT Woody Weed Management Plan from 1 July 2002. Species no longer sold by ‘bush friendly nurseries’. Ongoing program to eradicate plants on ACT public land and Commonwealth land, to educate public, and remove from nursery trade. Potential to bring under control in long term.
Blackberry (Rubus fruticosus L. agg.) Highly invasive closely related group of species and hybrids. Readily invades native bushland as well as farmland and production forestry areas. Excludes most other vegetation. High fire risk, burns fiercely and re-shoots after fire. Seeds spread by birds and mammals. Estimated to affect 5 million hectares Australia-wide.
It is a weed of national significance.
In ACT, blackberry is major weed in Paddys River catchment, plantation forests, native forests and woodland. All government land managers have undertaken control activities. Areas include Tidbinbilla NR (severely burnt in January 2003), Murrumbidgee River Corridor, parts of Namadgi National Park, Defence land, small infestations throughout the ACT, public use areas in ACT Forests plantations. ACT Blackberry 10-year Management Plan in place from July 2002. Blackberry is likely to continue to be a significant pest plant in the ACT requiring a range of control measures. The opportunities created by the January 2003 fires for infestation of burnt and disturbed areas is of concern and specific action may be needed to treat blackberry outbreaks.
Salvinia (Salvinia molesta) Waterweed. Not present in ACT. Noxious plant Australia-wide. May form large dense infestations in stationary or slow-moving water especially where nutrient levels are high. In water features of retail pot store (2000–01). N/A Land management agencies alert to possible spread of species into the ACT. Potential as major pest plant in ACT is not high.

Other weeds of concern

The Weeds Working Group has identified a broad range of other weeds that need attention, even though they have not been declared as 'pest plants'. Some of these are the focus of specific eradication or control programs, or are included in more general programs on roadsides, in conservation reserves or urban open space (see Tables 2 and 3).

Table 2: Examples of other (non-declared) pest plants in the ACT and control work, 2000–2003
Species Control work
St Johns Wort (Hypericum perforatum) Googong Foreshores, urban and rural roadsides, urban parkland, Canberra Nature Park (Several Reserves)
Paterson’s Curse (Echium plantagineum) Cooleman Ridge, Urambi Hills and Mulligans Flat (Canberra Nature Park), urban and rural roadsides, Federal Highway verges
Radiata Pine (Pinus radiata) Mt Pleasant, Majura Field Firing Range, native forest areas adjoining pine plantations
African boxthorn (Lycium ferocissimum)
Former abattoir holding paddocks (Fyshwick) and ActewAGL Fyshwick sewage farm (target to control all Boxthorn by 2005)(Included in 10-year Woody Weeds Management Plan in place from 1 July 2002)
Hawthorn (Crataegus monogyna)
Naas and Honeysuckle valleys, Ginninderra Creek (Included in 10-year Woody Weeds Management Plan in place from 1 July 2002)
White Poplar (Populus alba)
Woolshed Creek (Duntroon), Ginninderra Drive, Athllon Drive (Included in 10-year Woody Weeds Management Plan in place from 1 July 2002)
Cootamundra Wattle (Acacia baileyana) Mt Pleasant
Saffron Thistle (Carthamus lanatus), Scotch Thistle (Onopordum acanthium); Spear Thistle (Cirsium vulgare), Variegated Thistle (Silybum marianum) National Land managed by the Dept of Defence in the ACT
Woody weeds (declared and non-declared)
All areas of Canberra Nature Park, agistment areas (e.g. adjacent to Mt Tennent), urban open space, National Land managed by the Dept of Defence, Gudgenby valley. Some of this work has been undertaken as part of fuel reduction programs in reserve areas. Parkcare and Landcare groups have been actively involved

Source: Environment ACT

Table 3: Environmental Weeds Monitoring List (Draft, May 2003)
Species Condition and response
Winged Everlasting
(Ammobium alatum)
Monitor and manage outbreak (2002) in Nicholls and Gungahlin
Spanish Heath (Erica lusitanica) Monitor and manage in creek near University of Canberra
Butterfly Bush (Gaura spp.) A relatively new introduction. Monitor in all sites
Rosemary Grevillea
(Grevillea rosmarinifolia)
This species (and many of the hybrid grevilleas with G. rosmarinifolia as one of the parent species) naturalise very readily. As it is a commonly sold and used species, it is establishing over wide areas in the region, from the rocky slopes of Molonglo Gorge to grassland areas close to planted specimens
Mares-tail (Hippuris vulgaris) Potential as a very serious weed of regional ecosystems. No evidence of spread at present, but very similar in appearance to native Myriophyllum spp. Some specimens have apparently been identified as native Myriophyllum. Monitor all waterways and target aquarium industry
Olives (Olea spp.) Of considerable concern because of high potential to spread in the future. Monitor near olive plantations
Pistacio (Pistacia chinensis) Spreading in some nature conservation areas. Monitor and manage in nature conservation areas. Only male plants should be propagated
Cherry Plums, Black Cherry (Prunus spp.) Monitor and manage in nature conservation areas
Onion Grass (Romulea rosea) Noticed spreading. Monitor and manage in nature conservation areas
WA Bluebell Creeper
(Sollya heterophylla)
Monitor and manage in nature conservation areas
Sweet Vernal Grass (Anthroxanthum odoratum) Distribution unclear. Concern about outbreaks in Namadgi National Park and Tidbinbilla Nature Reserve

Source: ACT Weeds Working Group

Sleeper weeds

As well as the established and known pest plants, many of the introduced plants already in Australia may become weeds given sufficient time or a favourable change in conditions (Low 2001; Williams et al. 2001). These are termed 'sleeper' weeds. Two ecological factors useful in predicting sleeper weeds are time from naturalisation and relocation to a more favourable site as may occur, for example, during floods (Groves 1999).

Berry and Mulvaney (1995) assessed the weed potential of a wide range of species found in the ACT, including those that had a restricted distribution but a moderate or high weed potential. They recommended that these species be a high priority for targeted control programs with a ‘hit team’ formed to locate and eradicate them. Such a team operated during 1998–2000 and focused its efforts on urban open space and areas adjoining conservation reserves.

Data sources and references

ACT Weeds Working Group, Are Your Garden Plants Going Bush?, .

Australian State of the Environment Committee 2001, Australia State of the Environment 2001, CSIRO publishing on behalf of the Department of Environment and Heritage, Canberra.

Berry, S & Mulvaney, M 1995, An Environmental Weed Survey of the Australian Capital Territory A report prepared for the Conservation Council of the South-East Region and Canberra, Conservation Council, Canberra.

Cremer, K 1999, ‘Willow management for Australian rivers’, Natural Resource Management, (Special Issue) December 1999, pp. 2–22.

Environment ACT 2002, The Scribbly Gum Park Care Annual Report 2001–2002, Environment ACT, Canberra.

Environment ACT 2003, The Scribbly Gum Autumn 2003, Environment ACT, Canberra.

Groves, R 1999. ‘Sleeper weeds’, in Proceedings of the 12th Australian Weeds conference, Tasmanian Weed Society, eds AC Bishop, M Boersma and CD Barnes Hobart, Tasmania, pp. 632–6.

Lang, S 1999, ACT Willow Survey, unpublished, Environment ACT, Canberra.

Low, T 2001, Feral Future: the untold story of Australia’s exotic invaders, Penguin, Ringwood, Victoria.

Parsons, WT & Cuthbertson, EG 1992, Noxious Weeds of Australia, Inkata Press, Melbourne.

Sainty, GR 7 Jacobs, SWL 1994, Waterplants in Australia 3rd Ed., Sainty & Assoc, Darlinghurst.

Williams, J, Read, C, Norton, A, Dovers, S, Burgman, M, Proctor, W & Anderson, H 2001, Biodiversity, Australia State of the Environment Report 2001 (Theme Report), CSIRO Publishing on behalf of the Department and Environment and Heritage, Canberra.

Note:

Some of these references are cited in Table 1

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