Sagittaria (Sagittaria platyphylla) (also known as Sagittaria graminea var. platyphylla) is a serious problem in the waterways of Northern Victoria and southern New South Wales.  There are a number of species and varieties and morphological forms of Sagittaria.  Here we use the term Sagittaria to represent Sagittaria platyphylla.

In Victoria Sagittaria is commonly known as arrowhead. In NSW, arrowhead (Sagittaria montevidensis) is an introduced perennial to 1m tall, primarily found in the rice-growing areas where it occasionally is a problem, obstructing drainage channels, or competing with growing rice.

Sagittaria is a serious problem for Water Authorities and irrigators (land and water managers) in these areas with channels and drains becoming more infested each year with this very aggressive and invasive weed.  In shallow waterways and wetlands Sagittaria dominates the emergent aquatic plant ecosystems.  Its vigorous choking habit restricts flow of water and threatens native aquatic flora and fauna by reducing plant biodiversity.  The degree of infestation can substantially alter the flow regime of many tributary streams, dramatically threatening biodiversity and stream health of creeks that are already stressed.

The continued spread of Sagittaria threatens the biodiversity of aquatic ecosystems throughout the Murray Darling Basin and rivers that run to the east coast of Australia, from Victoria to north Queensland, where water depths are at times less than approximately 50 cm.

Sagittaria spreads rapidly, being able to reproduce by seed, rhizomes and corms.  It has been estimated that, in the channel system administered by Goulburn Murray Water, up to 85% of the 14 000 km of creeks, drains and channels have minor infestations of the weed which have the potential to significantly reduce the efficiency of the channel delivery system. 

Click here to view Map of Sagittaria infestation on the River Murray.

Relevant Reports

Sagittaria Strategic Plan

Protecting River Murray icon sites from invasive species - Arrowhead (Sagittaria graminea).

This report represents the project deliverable for the eWater CRC Initial Project 88 “Protecting River Murray Icon sites from Invasive Species”. The project aimed to apply a metapopulation modelling approach developed in CRC for Freshwater Ecology Project C260 to the invasive aquatic weed Arrowhead (Sagittaria graminea).

Using monthly time steps an understanding and conceptualtisation of Arrowhead biology was developed (Fig ES1). Variability in population dynamics was included through multiple iterations per simulation, with the range including representation of feasible variation in each relevant parameter. In a number of cases data on model parameters were missing and assumptions have been made on these. Sixteen river reaches between Hume Dam and Mildura are represented in the model, with Barmah Forest (an Icon Site) representedspecifically.

A large number of potential management scenarios were identified, but due to time constraints and computational capacity only 12 were actually run. The model suggests:

• Arrowhead is a robust organism that is difficult to control
• there are opportunities to control Arrowhead even with floods
• timing of control is important as seed production may have strong consequences for future population size and spread. The model suggests it is optimal to start control as early in the season as possible
• seed management might be a useful management activity – more important than
• controlling vegetative spread
• control of upstream sites is important to prevent downstream spread and population
• growth.

The model can be used to explore costs and benefits of different control scenarios relative to each other, thus contributing to targeted management decisions on eradication or control scenarios.

The Biology and Control of Arrowhead (Giles Flower)

This G-MW funded research project was established in response to the variability of success with arrowhead management and concern about the spread of arrowhead into previously un-infested irrigation systems and natural waterways, in particular its proliferation in the River Murray. A lack of understanding of the plant's responses to and interaction with the environment and control methods was identified as one of the key shortcomings of the established management program. Investigations were conducted into aspects of arrowhead biology and control.

The social aspects associated with the continual spread of Sagittaria platyphylla (Lauren Forrest)

This Applied Science Honours thesis aimed to identify the social aspects associated with the continual spread of sagittaria. An exploratory qualitative methodology was considered most appropriate for this study. The major findings from this research project relate to the diversity amongst stakeholders in terms of awareness of sagittaria, involvement in control efforts, factors impacting on involvement, attitude and commitment to the Taskforce and participation in cooperative approaches.

NSW information sheet

Murray River Arrowhead Management Plan (link for download)

Describes distribution of Sagittaria, a spraying program , potential environmental impacts of control and their mitigation and a program to ensure validation of the spraying program.

Annual Report for the Control of Sagittaria on the River Murray From The Hume Weir downstream to Barham (07-08 control season) (Available for download)

This annual report provides a full and firm report satisfying all reporting requirements of NSW

Department of Environment and Climate Change for the continuation of the Sagittaria (Sagittaria graminea spp. platyphylla) control program on the River Murray from the Hume Weir downstream to Barham.

Tri State Sagittaria Taskforce

The tri-state Sagittaria Taskforce, that includes organisations from Victoria, South Australia and New South Wales

In 2002, a tri-state taskforce (henceforth Taskforce) involving representatives from New South Wales, Victoria and South Australia was established after collaboration between New South Wales Department of Primary Industries, Eastern and Western Riverina Noxious Weeds Advisory Groups (ERNWAG and WRNWAG respectively), the Interstate Liaison Committee and Goulburn-Murray Water (Victoria) to encourage cross-agency involvement in weed management.

While the initial intent of the Taskforce was weed control and management in general, the realisation that Sagittaria was an issue common to all three States narrowed the focus of the Taskforce to Sagittaria specifically.

Contact for further information

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Declaration status

Sagittaria platyphylla and S. montevidensis are declared species under State noxious weed legislation in Western Australia, Tasmania, South Australia and New South Wales (www.weeds.org.au).  In South Australia, both species are listed as Class 1 weeds and generally require notification and destruction throughout the State. In Western Australia, both species are P1/2 weeds which are subject to eradication and prevented from trade, sale or movement. In Tasmania, both species are declared weeds and restriction measures are in place to prevent introduction and establishment. In New South Wales, S. platyphylla and S. montevidensis are Class 5 State-wide restricted species and require notification on detection. Sagittaria platyphylla is also a Class 4 locally controlled weed. No Sagittaria species are declared in Victoria, Australian Capital Territory, Queensland and the Northern Territory, but in some cases (Vic., QLD) are under review

Summary of Strategy

The Arrowhead Strategic Plan comprised a series of linked recommendations:

1.  RECOMMENDATION:  That the Tri-state Sagittaria Taskforce appoint one agency for 5 years to be responsible for mapping plant distributions, and commit to supplying data to that agency in a suitable format, that encompasses the core attributes listed in Table 6.2.1. 

2.  RECOMMENDATION:  That data on the annual estimated cost of control be obtained from all agencies involved in waterway management in South Australia, NSW and Victoria.

3.  RECOMMENDATION:  That organisations involved in herbicide programs renew their APVMA permits, taking into account the possibility of needing to control Sagittaria over larger areas.

4.  RECOMMENDATION:  That the tri-state Sagittaria Taskforce establishes a detailed research program to a)  further explore chemical/physical control options, and b) proceed to the next stage of investigating biological control agents.

5.  RECOMMENDATION:  That a survey of the socioeconomic impacts of Sagittaria infestation be undertaken, focussing on the effects on waterway users, the community and businesses associated with agriculture and tourism.

6.  RECOMMENDATION:  That the tri-state Sagittaria Taskforce makes a submission to the Noxious Weeds Review recommending that Sagittaria graminea be classified as a Regionally Prohibited weed in all areas of Victoria. 

7.  RECOMMENDATION:  That the tri-state Sagittaria taskforce makes a submission to the Australian National Weeds Committee to heighten the awareness and significance of this weed species.

8.  RECOMMENDATION:  That one organisation provides for a dedicated full-time Secretariat, for a 5-year period, with other members of the tri-state Sagittaria taskforce contributing to the costs.

9.  RECOMMENDATION:  That the tri-state Taskforce formally establishes milestones for a five-year period based on six-monthly time steps.

10.  RECOMMENDATION:  That the tri-state Taskforce meets annually and formally reviews the agreed milestones for the period, and any changes that may be required to future milestones.

11.  RECOMMENDATION:  That the tri-state Taskforce undertake a 5-year formal review of the strategy based upon the success in meeting the proposed outcomes.

12.  RECOMMENDATION:  That the Secretariat be charged with maintaining monitoring records required for the evaluation and provides an annual update to the tri-state Taskforce based on the performance indicators and any submissions to vary milestones.

Progress on implementation of recommendations varies.

It is proposed to undertake a brief review of rthe Strategy in early 2010.

Sagittaria control

The most efficient and effective method of controlling arrowhead is with the use of glyphosate with an aquatic registration. Ideally applications will be conducted at appropriate intervals during the summer period (3 intervals from December to May). Mechanical removal, hand pulling or other forms of control for this weed species have proven to be ineffective or not appropriate for the aquatic environment. Biological control of arrowhead is being investigated by Department of Primary Industries Victoria (Keith Turnbull Research Institute (KTRI)) however it can take up to seven years for approval of control agents to be released and a further twenty to thirty years to establish numbers of the control agent to have a significant impact on the weed species.

Biocontrol

The Department of Primary Industries is preparing a a biocontrol program for arrowhead. This program involves five stages:

1 Declaration of the weed a Target for Biological Control

2 Selection of potential biocontrol agents

3 Host-specificity testing and release approval

4 Mass rearing and release

5 Monitoring, evaluation and integrated management

Work has commenced on Stages 1 and 2.

Sagittaria Symposium 1

A workshop/symposium involving stakeholders from across the Murray Darling Basin was held in May 2005 at Barooga on the River Murray. The Symposium presented an opportunity to inspect the issue first hand and then determine roles in dealing with arrowhead and set the path for its successful management into the future. Invitations were sent to a widespread group of scientists and stakeholders and a broad representation attended.

The symposium was organised in two parts with a tour in the morning followed by a workshop in the afternoon.

Tour

A tour of key locations to highlight the impacts/ramifications and magnitude of arrowhead in the Broken Creek, River Murray, GMW & Murray Irrigation channels and drainage system was organised.

Some of the reactions, or first thoughts, following the tour:

• The tour highlighted the actual extent of the infestations
• The extent of the infestation in the Broken Creek and Murray Rivers surprised and shocked many participants
• Surprised that so many of the feeder channels were so restricted as a result of arrowhead
• Rapid increase over the last few years has been incredible
• Once the natural waterways are infested it creates a completely different environment.
• Concerned for the impact on Barmah Forest wetlands and waterways. 

Workshop

Nigel McGuckian from RMCG facilitated the afternoon workshop to:

• define the issues and what needs to be understood more
• determine the goals in a 5 year plan,
• define a path for meeting goals
• assign rolls and responsibilities to various stakeholders
• gain a commitment from those in attendance.

A key outcome of the Symposium was the development of the Sagittaria Strategic Plan.

other resources/links