Macquarie Valley Weeds Committee & Lachlan Valley Weeds Advisory Committee


Parthenium Weed

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Botanical Name: Parthenium hysterophorus
Other Common Names:


Class Regions
Class 1All Of N.S.W.
Landholder Responsibilities: The plant must be eradicated from the land and the land must be kept free of the plant
Why Is It Bad?: Parthenium is regarded as one of NSW most serious weed threat. It is a vigorous coloniser of bare ground, degraded pastures and disturbed sites. It is a fast growing annual plant with prolific seed production. Once established, parthenium weed very quickly builds a huge seed bank in the soil that makes erradication difficult and expensive. The weed contains powerful allergens that cause a range of human health problems, including asthma and sever contact dermatitis. The plant is a threat to agriculture because it is unpalatable to livestock and competes with pastures and crops.


Habit: Herb
Leaves: The upper half of the main stem becomes highly branched at flowering. The deeply-lobed leaves are alternately branched on the stems, pale green and covered with soft, fine hair. After flowering most leaves die. Stems become woody with age.
Flowers: Creamy white flowers occur at the tips of the stems. Clusters of male and female florets are grouped as five-lobed flowers on the terminal branches of the flower stem and measure 4-6mm in diameter.
Fruit: Seeds are small 1-2mm across, flattened, triangular and dark brown-black with two thin, white ,spoon shaped appendages.

Control Methods

Manual Removal: Anyone in NSW who suspect they have found Parthenium weed should not attempt to control it themselves. All suspected infestations should be reported to the local council Weeds Officer or NSW DPI to confirm indentification.NDW DPI and Weeds Officers will coordinate and carry out the control work. the intial control costs of notified parthenium weed infestations is covered by a contingency fund allocated by the Minister for Primary Industries. The location of all parthenium weed outbreaks on private property is kept strictly confidential.
Chemical Use:
Slashing & Cutting:
Biological Control: Researchers in QLD have located and tested numerous biological control agents against parthenium weed. These have included a gall forming moth, leaf miner, weevil, beetles and two rust fungi. Five of these agents have established since their first release in the 1980's but have not effectively controlled the weed.
Cultivation & Scalping:


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Image Credit: Biosecurity QLD Dept. of Employment, Economic Development and Innovation

Image Credit: Biosecurity QLD Dept. of Employment, EconomicDevelopment and Innovation

Image Credit: Biosecurity QLD Department of Employment, Economic Development and Innovation

Image Credit: Biosecurity QLD Dept. of Employment, Economic Development and Innovation

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