Parthenium hysterophorus L.
Parthenium weed is declared under the Catchment and Land Protection Act (1994) as a State prohibited weed. It originates from parts of North and South America. It was first discovered in Queensland in 1955 and was thought to be introduced via contaminated machinery during World War II. It currently infests over eight million hectares of Queensland, New South Wales and the Northern Territory. It has not been found in Victoria but there is a high risk that it could be introduced.
Parthenium weed can germinate, grow and set seed within a four week period.
What are State prohibited weeds?
State prohibited weeds either do not occur in Victoria, or are present and can reasonably be expected to be eradicated. State prohibited weeds are the highest category of noxious weeds under the Catchment and Land Protection Act (1994). The Department of Economic Development, Jobs, Transport and Resources (DEDJTR) is responsible for the eradication of State prohibited weeds. The Victorian Government is committed to preventing the introduction of high-risk weeds into Victoria, to protect our environment, economy and social values.
Why is it a problem?
Parthenium weed costs the agricultural industry in Queensland over $22 million annually in lost production and control costs, and is a serious threat to Victoria's agriculture. Each plant can germinate, grow and set seed within four weeks, resulting in multiple germinations in one year. One plant can produce up to 20,000 seeds per year. It produces chemicals in its leaves which leach into the soil inhibiting the growth of other plants. Contact with, and pollen from, parthenium weed can cause dermatitis and in sensitised individuals it may cause severe allergic reactions. It is toxic to cattle.
How to identify parthenium weed
Parthenium weed is an annual or short-lived herb to 2 m tall. It invades disturbed land such as roadsides, stockyards and overgrazed pastures. It has the potential to infest the semi-arid regions of northern Victoria.
Leaves are grey-green, deeply divided, 5-20 cm in length and covered in fine hairs. The leaves are initially in a flat rosette. Mature stems have distinct grooves along them and are covered in fine hairs.
Flowers are creamy-white, star-shaped and 4 mm across. They are in open branched clusters above the foliage. Flowering can occur all year round in favourable conditions, but usually in summer.
What should you do if you find parthenium weed?
If you think you have seen a parthenium weed plant, please contact DEDJTR by telephoning 136 186 or use the online reporting tool.
Please do not attempt to control or dispose of this weed yourself.