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Weed spotter newsletter
Spring newsletter 2021 – Issue number 32

Welcome to the latest Weed Spotter newsletter. In this issue we find out which State prohibited weed is an Olympic champion, how Weed Spotters have been working together with surveillance programs across Australia and New Zealand and about a group of Weed Spotters who spotted a high-risk species on their televisions.

If you have any feedback on this edition or suggestions for future articles, please email:

Reminder to Weed Spotters

Please remember that if you are moving to a new house or changing your employment, the contact details that Agriculture Victoria have recorded for you, including postal address and email address, may need updating. Please send an email to to avoid missing the latest newsletter.

New to the Weed Spotters?

Weed Spotters assist the Victorian Government by looking out for and reporting State prohibited weeds. These are a group of high risk invasive plants that are declared under the Victorian Invasive Plants Classifications. The Weed Spotters program is for those who work in an industry or who are part of a group where they are likely to spend time in places where State prohibited weeds could be found. To catch up what you’ve missed, have a look at the Agriculture Victoria website to find past issues of this newsletter.

1. Going for gold in the State prohibited weed Olympics

The Tokyo Olympic and Paralympic games were very entertaining viewing for many of us and have inspired Agriculture Victoria to discover which of the State prohibited weeds would be an Olympic champion of the State prohibited weed Olympics! To answer this question and to find out whether we have a clear winner, the High Risk Invasive Plants team did a comparison between species and results were surprising. It wasn’t a straightforward exercise to directly compare all the State prohibited weeds with each other, as the wide variation in the biology of each species meant that not all species met the criteria to enter every Olympic event.

The species that can withstand the lowest temperature
Plants that have competitive traits such as being able to withstand temperature extremes can become very successful weeds. This is why hawkweed is such a threat to the alpine region of Australia.

Table depicting the winners of the species that can withstand the lowest temperatures medals. Gold, hawkweed, silver, alligator weed, bronze mesquite.

Most seeds produced per plant annually
High seed production is a competitive trait that weedy species possess as it increases the chance of new plants growing and spreading.

Table depicting the winners of the most seeds produced per plant annually medals. Gold, parthenium and branched broomrape, silver, karoo thorn, bronze water hyacinth.

Longest roots
Deep roots offer a competitive edge to some of our State prohibited weeds, as it means these plants can reach further for water and nutrients than other plants around them. Root depth can also influence which method is used to treat these weeds.

Table depicting the winners of the longest roots medals. Gold, giraffe thorn, silver, knotweed, bronze mesquite.

Dormancy is the time that seeds or small pieces of a plant can remain ready and waiting in the soil to grow. It is an important aspect of plant biology for the management of high risk invasive plants as it can help determine how many years State prohibited weed sites need to be monitored for re-emergence.

Table depicting winners of the dormancy medals. Gold, water hyacinth and Silver, branched broomrape.

In the end, we don’t have a clear winner of the State prohibited weed Olympics. Many species have been lucky enough to finish up with a medal, but all State prohibited weeds have a variety of traits that make them a serious threat to Victorian agriculture and the environment. We hope that you have enjoyed reading about the species and have perhaps learnt a few new and interesting facts about these high risk invasive plants.

2. Mexican feather grass sites discovered

During the warmer months of 2020/2021, several new interesting infestations of Mexican feather grass (MFG) were found in Victoria.

The first was reported to Weed Spotters in mid-December 2020 after an Agriculture Victoria staff member spotted it in the front yard of a house he had recently moved into at Killara, near Wodonga. He took photos and sent these to Weed Spotters for identification. A local Biosecurity Officer visited the property and removed one mature plant and several seedlings that had spread across the nature strip.

Image right: The Mexican feather grass plant spotted in the yard of a property near Wodonga.

The Mexican feather grass plant spotted in the yard of a property near Wodonga.

To determine the source of this infestation, Biosecurity Officers reviewed a series of photos of the garden taken by the real estate agent managing the property. This revealed that the plant had been in the location over several years and that it had a nursery plant tag with the label Festuca glauca ‘blue grass’. An investigation followed, and it was concluded that the ‘blue grass’ may have been contaminated with MFG seed, the original plant had died and decomposed and the MFG had emerged from the soil medium.

The second infestation was spotted by a weeds officer from South Australia in mid-December 2020, in photos on social media. The reporter contacted Weed Spotters to report the plants and commented that they looked like either MFG or serrated tussock, a look-alike of MFG. Biosecurity Officers located the property in the photos, contacted the owner and completed an inspection. A total of 22 mature, flowering MFG plants were identified and removed from the front yard of the property in the outer southern suburbs of Melbourne. The site was visited again in March 2021 where a further 25 seedlings were removed. The owner shared that the plants were purchased two years earlier and were labelled as Stipa lessigiana. Unfortunately, further investigations did not reveal the source of these plants.

Biosecurity Officer removing the plants found at a property in Frankston South.

The third infestation was found in the garden of a private residence in Frankston South in March this year. A friend of the resident, who works for a Catchment Management Authority and was visiting, spotted the plants and suspected MFG immediately. The pair sent photos of the plants to Weed Spotters, who confirmed their suspicions.

Image left: Biosecurity Officer removing the plants found at a property in Frankston South.

Biosecurity Officers inspected the property shortly after the report was received and removed 46 mature plants and more than 250 seedlings! The owner has been at the property for several years and can vouch that the plants have been present throughout this period.

These three cases demonstrate how important it is to be on the lookout for Mexican feather grass, both in Melbourne and across Victoria, especially during the warmer months when the plant is flowering. To find out more about Mexican feather grass please visit the Agriculture Victoria Mexican feather grass page here. If you see a Mexican feather grass plant anywhere in Victoria, please report it to the Agriculture Victoria Customer Contact Centre on 136 186 or email

3. Masses of water hyacinth smother rural dam

You may remember reading in the last Weed Spotters newsletter about a large infestation of water hyacinth that was discovered in January 2021 after a diligent landholder reported finding it in their dam. It was detected after the landholder removed blackberry from the top of the dam, revealing water hyacinth underneath.

Image right: The water hyacinth plants growing thick across the dam prior to removal.

The water hyacinth plants growing thick across the dam prior to removal.

With abundant sun and space, the water hyacinth quickly smothered the dam in thick mats that blocked dam access.

Agriculture Victoria Biosecurity Officers inspected the site and confirmed the infestation came to a whopping 1400m2, one of the largest Victoria has ever seen. The plants ranged in age from seedlings to mature plants, suggesting it was an old infestation with a large seedbank. Agriculture Victoria engaged a contractor to treat the site, who used machinery to scoop out all the plants and scrape the seedbank from the dam floor. All contaminated material was deep-buried on site to prevent spread.

Timely and effective treatment was a top priority, however the large extent and potential off-target impacts of treatment could have slowed works down. Agriculture Victoria collaborated closely with Yarra Ranges Council, the contractor, landowners, and neighbouring properties to minimise impacts and comply with local legislation. This involved site visits with Yarra Ranges Planning Officers and Biodiversity Officers to discuss native vegetation, habitat and other environmental or planning values. The comprehensive collaboration ensured the infestation was treated effectively and promptly before rains could spread the water hyacinth or impede works. The discussions also resulted in protection of adjacent trees and other habitat values.

The removal works took roughly three weeks to complete, followed by a week of remediation works to prevent subsequent erosion and re-introduction of common weeds. Although treatment was completed to the highest standards, some seed germinated post-treatment but was detected and removed immediately. To find out more about water hyacinth visit the Agriculture Victoria website here. If you see water hyacinth anywhere in Victoria, please report it to the Agriculture Victoria Customer Contact Centre on 136 186 or email

Both mechanical and hand removal methods were utilised to eliminate the water hyacinth from the dam.


Image left: Both mechanical and hand removal methods were utilised to eliminate the water hyacinth from the dam.

Image below: Aerial image of the dam taken by a drone after removal of the water hyacinth was complete.

Aerial image of the dam taken by a drone after removal of the water hyacinth was complete.
4. ‘Making general surveillance work’

You may remember reading in the Spring 2020 newsletter that Weed Spotters were invited to participate in the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) project ‘Making general surveillance work’. ABARES is part of the Australian Department of Agriculture, Water and Environment. The Victorian Weed Spotters network is an example of a general surveillance program, where people from all walks of life participate in gathering and reporting information about the presence of pests, weeds, and diseases. This information makes an important contribution to supporting government and others dealing with biosecurity issues.

The aim of the research project was to develop guidelines for people involved in creating and running general surveillance programs to support the design, planning, and implementation of such programs. To develop the guidelines, the researchers drew on the practical experience of people involved in several case studies from across Australia and New Zealand, including Victorian Weed Spotters. It has been a valuable experience to be part of this research, as it has encouraged collaboration between Weed Spotters and other surveillance projects from across Australia and New Zealand.

A few examples of Weed Spotters collaborating with other general surveillance programs include:

  • The Queensland Weed Spotter network are excited to look at developing an online training module by mirroring the Victorian template.
  • The Pests and Diseases hotline in New Zealand have been interested to learn more about how new Weed Spotters are recruited in Victoria, to assist in the development of surveillance programs there.
  • Agriculture Victoria has been interested to hear about the role of voluntary coordinators who operate to support Weed Spotters in their local area across the Weed Spotter Queensland Network.

The project has also resulted in the production of an infographic which illustrates the project findings about Victorian Weed Spotters, how Weed Spotters functions and a timeline to show how the project developed. You can find this infographic and more information about the project on the ABARES website.

Image below: The infographic which illustrates the findings from the Making General Surveillance Work project.

The infographic which illustrates the findings from the Making General Surveillance Work project.
5. Keep a look out for parthenium weed

Parthenium weed (Parthenium hysterophorus) is a State prohibited weed that has not yet been recorded in Victoria. With infestations widespread in Queensland and spreading south in NSW, it is important for Weed Spotters to keep an eye out for this species in order to catch it early if it does enter Victoria, so we have the best chance of eradicating it.

Parthenium weed is an annual herb that has the potential to invade the semi-arid regions of northern Victoria. It is likely to invade roadsides and agricultural areas.

It is an extremely fast-growing plant, which can germinate, mature, flower and set seed all within four weeks. One plant can produce up to 20,000 seeds per year!

Aside from growing so fast, parthenium weed also produces chemicals which inhibit the growth of other plants. It is highly allergenic and can cause dermatitis and hay fever, and is also toxic to cattle. It costs Australia’s beef industry $16.5 million per year and cropping industries several million dollars per year.

Image right: Parthenium weed flowers.

Parthenium weed flowers
Parthenium weed plant in flower

Parthenium weed can grow up to 2m tall. It has deeply divided, grey-green leaves that begin as a rosette close to the ground. Mature stems have distinct grooves that make them look striped. The small (4mm), cream-white flowers can appear all year round, but are more common in summer and are in branched clusters above the foliage.

To find out more about parthenium weed please visit the Agriculture Victoria website here. If you see parthenium weed, please report it by emailing, or by calling 136 186.

Image left: Parthenium weed plant in flower.

6. Weed Spotter online training becomes invaluable during the pandemic

Did you know that Weed Spotter training is still available to Weed Spotters while face to face sessions are on hold? The online training module mirrors face to face training and was created from the face-to-face format and materials. It includes photos and videos of State prohibited weeds so that Weed Spotters can become more familiar with these plants while the potted plant specimens are locked away in Agriculture Victoria’s glasshouse. It also describes how to report a State prohibited weed and has interactive quizzes and exercises to help you learn.

The course takes about an hour to complete but could be shorter or longer depending on how much time you choose to spend reading the material provided. The course can be paused and recommenced at any time, without losing your place. All Weed Spotters who complete Weed Spotter training receive a set of State prohibited weed identification cards. One Weed Spotter who recently completed the training said, “it was a pleasure and very enlightening”. Another who had a group of their staff complete the training said “Thank you for providing access to the Weed Spotter training – I thought the course was terrific. It was clear, informative, and easy to follow”.

To access the training please go to and create a log in for the site by clicking ‘sign up’. When creating a new account, make sure you select ‘I am a Weed Spotter’ in the ‘Why are you here?’ drop down menu. Once you have created an account, you can select Weed Spotter training.

Image below: The online Weed Spotter training module.

The online Weed Spotter training module.
7. Water hyacinth spotted on television

During the airing of a gardening and landscaping program on the ABC, some eagle-eyed Weed Spotters spotted what they thought looked like water hyacinth. The suspicious plants were only onscreen during fleeting shots of a garden in Melbourne which was all it took for these savvy Weed Spotters to correctly identify the plants. This is a great example of how Weed Spotters can be really successful with four separate people reporting the plants to the Weed Spotter email address. The program is available online, so Biosecurity Officers were able to review the footage and identify the plants very quickly.

Once identified, the officers were able to locate the address and visit the property for an inspection. The owner was surprised to hear that the plants are a State prohibited weed as they had not planted the garden themselves and had purchased the property after the garden was established. Sixty-five plants were removed from the garden and carefully disposed of to ensure the risk of spread was eliminated. Agriculture Victoria will continue to work with gardening television programs and landscape gardeners to ensure that they are aware of the plants that are declared noxious under the Catchment and Land Protection Act 1994 in Victoria and that it is an offence to buy, sell, display, or transport a State prohibited weed in Victoria.

To find out more about water hyacinth please visit the Agriculture Victoria website here. If you see a water hyacinth plant anywhere in Victoria, please report it to the Agriculture Victoria Customer Contact Centre on 136 186 or email

Image right: Water hyacinth plants that were removed after being shown on television.

Water hyacinth plants that were removed after being shown on television.

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