Weed Spotter newsletter
Issue number 11 – Summer 2010/11
A State prohibited weed found floating in Eltham
Julia Vanderoord – Weed Spotter
While collecting water bugs for Waterwatch at the Alistair Knox park wetland in Eltham, I discovered a plant which looked very much like water hyacinth (Eichhornia crassipes), a State prohibited weed. Water hyacinth is a free floating perennial plant which is characterised by its leaves, which have swollen air-filled bladders at the base, and by its attractive purple flowers which have six petals and a distinctive yellow spot on the upper petal.
Fortunately, I had recently completed the Department of Primary Industries (DPI) aquatic Weed Spotter training where we looked at pictures and live specimens of water hyacinth as well as other State prohibited aquatic weeds - such as salvinia (Salvinia molesta), alligator weed (Alternanthera philoxeroides) and lagarosiphon (Lagarosiphon major). All of these aquatic weeds are likely to be found in wetlands and creeks in the Melbourne area.
At the time of discovery, I took photos of the three or four clumps of floating suspect plants. When I got back to my office, I completed a Weed Spotter report online and checked my WEEDeck (weed identification guide) to make sure the plants were actually water hyacinth. They were.
Within a week, DPI Weed Alert Contact Officer Lana Russell followed up on my report. Lana was excited because I had discovered a new infestation and, because it was still small, it should be relatively easy to get rid of. The DPI team removed 15 clumps of water hyacinth from the wetland and checked the nearby Diamond Creek to ensure the water hyacinth hadn’t spread.
Water hyacinth originates from southern Brazil and Paraguay and has the potential to choke and cover wetlands and lakes, removing oxygen from the water. This can have a terrible impact on the local aquatic fauna, such as fish and frogs, which rely on oxygen rich waterways.
In nutrient rich, warm waters (above 20 degrees) water hyacinth is capable of doubling the area it covers every two weeks. Fortunately I found it while the weather was still cold.
It is important people in the Eltham area check their ponds and dams for water hyacinth. According to DPI officer Kylie Woods, it is not known where the plants came from. Water hyacinth has been banned from sale since it was declared a noxious weed. However its attractive appearance means it is still sometimes found for sale at markets, garage sales, pet stores and even on internet auction sites.
While these plants may look attractive in the garden, and seem harmless in a home pond or dam, new infestations of State prohibited weeds can often be traced back to gardens where they have either escaped or have been deliberately pulled out and dumped. It is therefore essential that sightings of State prohibited weeds are reported to DPI immediately so they can be removed and treated properly.
Anyone who thinks they might have water hyacinth in their pond or dam, or believes they may have seen it being traded is urged to contact DPI on 136 186. Please do not attempt to control or dispose of this weed in any way yourself.
Floods highlight the potential for aquatic weed movement
Kim Gowers - West Gippsland Weed Alert Contact Officer
With the recent heavy rainfall and flooding, it is easy to comprehend how aquatic weeds can rapidly move and establish across potentially vast areas of the landscape. Unfortunately, a plant that is pretty in a pond or dam can quickly become dominant and may infest downstream water ways in a single flood. The environmental, social and economic impacts of this can be significant.
Only one small fragment is needed to invade and infest a previously clean waterway or water body. Free floating aquatic weeds can disperse over vast distances in a short period of time using water movement to spread and, in ideal conditions, can double in size within three days.
The highly invasive nature of aquatic State prohibited weeds can be demonstrated by salvinia, a pretty aquatic fern. An infestation of salvinia was recently discovered at Dawson in Gippsland. The plant had successfully moved to other properties during a relatively low rainfall event.
During flood salvinia can spread to dams that would normally be isolated. The plants can also settle in billabongs and lagoons along waterways, ready to spread further downstream during the next flood.
Floods and subsequent aquatic plant movement mean Weed Spotters and DPI need to remain vigilant in the search for invasive water weeds. The potential for these plants to spread means ongoing monitoring of surrounding waterways is extremely important. The risk of not maintaining a close watch is too great.
Mesquitelook-alikes … your quick guide!
Lucy Ivey – Weed Alert Contact Officer
Mesquite(Prosopis spp.), a thorny State prohibited weed, is being targeted by DPI in the Wimmera, Mallee, North Central and North East catchments.
Mesquite’s fern-like leaflets and thorns can make identifying it from some look-alike species tricky. Some common garden and street trees, such as peppercorn trees, robinia and honey locust, have similar leaf structures to mesquite. Robinia and honey locust trees can also have thorns.
Mesquiteis a threat because of its impact on agriculture and the environment. It is an aggressive competitor which invades grazing land and, due to its suckering ability and thorny branches, can inhibit stock movement, particularly access to water holes. Once established, plants can survive severe water stress, they are long-lived and produce a large number of seeds.
Take time to examine the pictures of mesquite and its look-alikes, and use the table to make comparisons between the species.
Next time you are visiting a friend’s property or your favourite old farmhouse, it may be worthwhile to look closely at the trees. Mesquite has been found in these types of locations and you may just be able to help DPI stop an aggressive competitor from taking hold.
| Mesquite (Prosopis spp.) |
Robinia (Robinia pseudoacacia) |
Honey Locust (Gleditsia triacanthos) |
Peppercorn (Schinus molle) | |
| 2 photos for each species showing distinguishing characteristics |  |
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| Life form | Shrub or tree (deciduous), 1-15 m. Branches zig-zag shaped. | Tree (deciduous), to 17 m. | Tree (deciduous) to 10 m. | Tree (evergreen) to 12 m. |
| Leaflets | Linear to oblong. 12-18 pairs. | Oblong to oval, well-spaced. | Oblong, margins finely toothed. | Sticky when crushed and smell like pepper. |
| Thorns | Sharp and long (to 75 mm). Usually present in pairs above each leaf stalk. | Short spiny appendages (stipules) on stems. | Sharp and large. Where present, occur singly or branched/cross-shaped. | No thorns. |
| Flowers | Summer. Yellow-green ‘lambs tail’. |
Spring. Pink, purple or white. Fragrant, pea-like. |
Spring. Green-yellow. Inconspicuous. |
Year round. Small, white drooping sprays. |
| Fruit | Seed pods (straw-coloured to purple). Smooth, resemble a string of beads. | Seed pods (reddish brown). Flat, smooth, pods 3-8 cm. |
Seed pods (black).Twisted, very large. | Berries (red) with hard inner stone on female plants. Aromatic. |
*Main distinguishing features of each species appear as shaded squares in the table.
Weed Spotter Survey and Quiz 2010
Ashley Hall – Weed Alert Project Officer
Thank you to all Weed Spotters who completed our annual Weed Spotter survey and quiz. We had a great response with 245 Weed Spotters taking the time to complete the questions. We appreciate your feedback and hope you enjoyed the opportunity to test out your Weed Spotter knowledge.
Congratulations to Judy Munro who answered all the quiz questions correctly. Judy has been awarded a copy of Weeds of the South-East for her efforts.
Use the answers below to see how your responses compare and look out in our next newsletter for a summary of the survey results.
If you found a State prohibited weed what would you do?
Report it to DPI immediately on 136 186 and leave it where it is
Image 1: Water Hyacinth |
Image 2: Orange Hawkweed |
Image 3: Alligator Weed |
Image 4: Salvinia |
Image 5: Horsetails |
You see what you think is a hawkweed plant in your friend's garden, do you:
Report it to DPI immediately on 136 186 or
Tell your friend it is a State prohibited weed and to report it to DPI
You see what you think is water hyacinth in a local wetland, do you:
Report it to DPI immediately on 136 186
Weed Spotter with an eye for Mexican feather grass
Catherine McInerney – Weed Spotter Coordinator
A keen Weed Spotter from the Geelong region successfully discovered four infestations of Mexican feather grass in the last 12 months. Peter Gibbs first learnt about Mexican feather grass when he attended Weed Spotter training at the City of Wyndham, where he works as an Environment Officer.
Although Peter’s work regularly takes him to places where he has the opportunity to look for State prohibited weeds, all of Peter’s discoveries have actually occurred out of hours - while on the road home or visiting friends.
Peter said he found the Mexican feather grass plants by spotting them from the window of his car. The characteristics that stood out to him were the distinctive bright green colouring, the upright tussock shape of the plants and their height. These characteristics were emphasised during Weed Spotter training. However it was the opportunity to see a real live plant specimen that ensured the species really stuck in his mind.
Peter found that seeing the plant in real life was not the same as a photograph.
Peter is also familiar with native grasses, which helped him distinguish Mexican feather grass.
The Mexican feather grass infestations that Peter discovered occurred some distance apart with two in the suburbs of Melbourne and two in the Geelong region.
Peter proudly holds the record for the most Mexican feather grass infestations spotted by a non DPI employee.
Great effort Peter and keep up the good work. We look forward to receiving your next report.
Snapping back at alligator … weed
Erin Cox – Weed Alert Incursion Controller
Spring and summer are the seasons for treating the highly invasive alligator weed (Alternanthera philoxeroides), which is considered one of the world’s worst weeds because of its damaging impact to both aquatic and terrestrial environments. All infestations will be subject to treatment and ongoing monitoring this season.
Alligator weed is declared as a State prohibited weed under the Catchment and Land Protection Act 1994. This is the highest declaration category under the Act, reflecting the very serious threat these plants pose to our environment.
Victoria has a significant number of alligator weed infestations, with the majority in metropolitan Melbourne. Alligator weed eradication is vital to the ongoing health of Victoria’s waterways as it can quickly cover them, causing harm to native wildlife as well as restricting irrigation use and recreational activities.
The success of DPI’s eradication program relies on a coordinated and strategic treatment approach. To minimise the risk of re-infestation, alligator weed treatments start at the highest upstream infestation, and work progressively downstream. For example, the uppermost infestations of the Merri Creek continue to be subjected to intense eradication efforts using mechanical excavation and hand removal. Although costly, these methods completely remove the plant, including the root mass, and have proven highly effective in eradicating these sites and preventing reinfestation downstream.
If you think you have seen this invasive plant or would like more information on alligator weed, contact your local Weed Alert Contact Officer.
