Weeds and diseases

Weeds

Invasive weeds are a serious threat to biodiversity in Victoria both on land and in aquatic environments.

Weeds compete with native plants for space, nutrients and sunlight. They change the natural diversity and balance of ecological communities. Weeds also affect the function native species have in providing nutrients and habitat for other species.

Weeds that have been introduced into the Australian environment have no natural controls from insects, grazing animals or fungi that feed on them to limit their spread.

There are over 1000 species of weeds occurring on public land in Victoria.

  • Weeds often reproduce in a way that allows them to spread over large distances. For example, willows have winged seeds that are carried on the wind tens of kilometers from their source
  • Woody weeds, such as blackberry and gorse, shade out native plants and create impenetrable thickets
  • Scrambling weeds such as Bridal Creeper, smother native plants and create dense root mats that prevent other plants from accessing adequate moisture and nutrients
  • Some exotic grasses out-compete native grasses and can create high fuel loads that can cause greater bushfire intensity
  • Some weeds, like the Hawkweed, can produce biochemicals that inhibit the growth of other plants around them
  • Marine weeds can release large amounts of spores allowing them to reproduce quickly.

 

Management

Parks Victoria works with the Department of Environment and Primary Industries, other land managers, land owners and community groups to manage weeds in parks.

The four objectives for weed management are to:

  • Prevent their spread by making sure equipment and vehicles are clean of seeds and spores
  • Eradicate small infestations that are unlikely to have spread beyond a definable boundary
  • Contain infestations where they can be prevented from expanding beyond a defined containment line
  • Protect assets (e.g. native plants and animals, neighbouring agricultural land) from the impacts of invasive weeds by reducing population densities.

 

Weed infestations are controlled mainly through the use of chemical sprays. However, in fragile environments such as the alpine peatlands and marine environments, weeds may be pulled manually by hand.

Biological control is another way weeds are controlled. This is when one living species (such as a plant, fungi or insect) is introduced to control an unwanted species. Biological control may be used when weeds are too widespread for chemicals to be used.

 

Cinnamon fungus

Cinnamon Fungus (Phytophthora cinnamomi) is a microscopic, soil-borne disease-causing organism that attacks and destroys plant root systems causing plants to die through lack of water and nutrients. Patches of dead or dying vegetation can indicate the presence of this silent killer and grass trees are particularly susceptible. It is spread through infected plants and the movement of contaminated soil and gravel, and there is no known cure.

Help stop the rot

Parks Victoria is working in conjunction with other State and Federal Government agencies to control Cinnamon Fungus and you can help too. Taking the following measures will help to minimise the spread of this pathogen (and noxious weed species) through both private land and our precious parks and reserves.

  • Be clean on entry and exit. Vehicles, tyres, machinery, footwear and camping gear should be free of soil, gravel and mud prior to entering or leaving any park, reserve or campsite (particularly in high risk areas). Don’t bring soil or gravel in – and don’t take any home!
  • Use boot cleaning stations and vehicle wash down bays where available – they are there for a reason.
  • Keep to formed roads, tracks and pathways at all times. Moving from infected to uninfected areas can spread the pathogen - particularly during wet weather when soils are wet and sticky.
  • Obey all track and road closure signs. Do not enter areas of vegetation that have been quarantined.
  • Avoid travelling through areas infected with Phytophthora. If in doubt – ask! Call Parks Victoria on 13 1963.
  • Do not remove plants or plant material from parks and reserves – they are protected by law.

Plant killer

Known variously as die back, root rot and Jarrah dieback, PC and Phytophthora, Cinnamon Fungus derives its name from the bark of Cinnamon trees where it was initially isolated in Sumatra in 1922. Phytophthora literally means plant killer and this pathogen has lived up to its name, destroying vast tracts of vegetation around the world.
It is listed in the top 100 of the world’s most invasive species and is Victoria’s most significant plant pathogen affecting both native ecosystems and the horticultural industry.
Phytophthora cinnamomi is a soil borne water mould closely related to brown algae.

On the move

Cinnamon fungus was first detected in Australia in 1935 and has since spread across the country infecting hundreds of thousands of hectares of native vegetation in Victoria, Tasmania, South Australia, Western Australia and Queensland. Heathlands, coastal woodlands and dry Eucalypt forests are most at risk.
Within Victoria, the pathogen has had serious impacts in the Brisbane Ranges, Grampians, Great Otway, Lower Glenelg, Point Nepean, Kinglake, Croajingalong and Wilsons Promontory National Parks in addition to Lerderderg State Park, Lake Tyers, Anglesea Heathlands and the coastal forests of east and south Gippsland.

Detection

Without proper soil testing, this microscopic pathogen is difficult to detect. It is more actively spread in moist soils during warm weather and can survive drought. It can be present even if vegetation appears healthy as not all plants are susceptible. Infected plants appear drought affected and develop signs of ‘dieback’. Infected plants are rarely in the same stage of decline at any one time.

Easily spread

While the pathogen can spread locally through soil or water via tiny swimming spores, it is more commonly spread through the movement of contaminated soil and gravel carried by vehicle or foot traffic. It can also be spread through infected plant material and potting mix.

Long-term impact

The presence of Cinnamon Fungus threatens not only vegetation communities – it can alter the ecology of entire ecosystems. As susceptible plant species like shrubs and colourful wildflowers gradually die out, they are replaced by resistant species like grasses and sedges.

Birds, insects, reptiles and mammals that depend on the original plant species for their survival also decline in numbers as shelter and food sources disappear.

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