Parthenium weed (Parthenium hysterophorus)

WEED ALERT: STATE PROHIBITED WEED
If you see this plant contact your council weeds officer, the NSW Invasive Plants & Animals Enquiry Line 1800 680 244 or email weeds@dpi.nsw.gov.au

Profile

Impact

Parthenium weed is a fast growing, annual plant that colonises bare ground in situations such as degraded pastures, establishing crops and disturbed sites. It is a threat to agricultural production, significantly reducing crop establishment and livestock carrying capacities by competing with crop seedlings and pastures (it is unpalatable to livestock). Its ability to rapidly build a large seed bank in the soil makes eradication difficult.

Parthenium has a vigorous growth habit and prolific seed production rate. It is one of the state’s most serious weed threats, with ideal growing conditions over most of NSW except in very dry or wet areas. Once established, plants will survive droughts and frosts.

Parthenium weed also contains allergens that can cause a range of health problems in humans, including asthma and severe contact dermatitis. Allergic reactions may not be experienced initially but can develop after repeated exposure. Landowners are advised not to touch the plant with bare hands and to always use a dust mask if working near the weed for extended periods.

Distribution

Parthenium weed is native to the Caribbean region. It is thought to have been introduced to Australia from the USA on machinery during World War II and as a contaminant of imported pasture seed during the 1950s.

It is endemic to central Queensland and is spreading into southern Queensland. Although there are no established populations in New South Wales (NSW), outbreaks do occur on roadsides (particularly the Newell Highway) and on private property.

Distribution Maps

Spread

Parthenium weed is spread by seed and easily establishes in disturbed, degraded or bare soil sites. Seed is carried on harvesting machinery and vehicles, and in hay and grain. Spread into NSW from infested areas of Queensland has occurred through these vectors. Compulsory border inspections of harvesting machinery entering NSW from Queensland by the NSW DPI have minimised spread, and good hygiene practices will further reduce the risk of parthenium weed spreading onto farms. Anyone in NSW who suspects they have found parthenium weed should report it to their local council weeds officer and should not attempt to control it themselves.

Description

Parthenium weed is spread by seed and easily establishes in disturbed, degraded or bare soil sites. Seed is carried on harvesting machinery and vehicles, and in hay and grain. Spread into NSW from infested areas of Queensland has occurred through these vectors. Compulsory border inspections of harvesting machinery entering NSW from Queensland by the NSW DPI have minimised spread, and good hygiene practices will further reduce the risk of parthenium weed spreading onto farms. Anyone in NSW who suspects they have found parthenium weed should report it to their local council weeds officer and should not attempt to control it themselves.

Acknowledgements

Prepared by: Kirrily Condon; Reviewed by Philip Blackmore; Edited by Elissa van Oosterhout, Birgitte Verbeek

References

NSW Department of Primary Industries Parthenium Primefact 707

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Control

Correct identification and quick action to prevent spread is important, however if you suspect you have found parthenium weed you SHOULD NOT attempt to control it yourself. Contact you local council weeds officer for assistance with identification, eradication and ongoing monitoring of infestations.

Biological control

Researchers in Queensland 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 releases in the 1980s but have not effectively controlled the weed. This work is now limited to the natural spread of these established agents or by landholders and community projects.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


2,4-D 300 g/L + Picloram 75 g/L (Tordon® 75-D)
Rate: 125 mL per 100 L of water
Comments: Spot spray. Rosette stage when plants are actively growing.
Withholding period: 1-8 weeks (see label).
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


2,4-D 300 g/L + Picloram 75 g/L (Tordon® 75-D)
Rate: 3.0 L/ha
Comments: Boom application.
Withholding period: 1-8 weeks (see label).
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Atrazine 900 g/kg (Various products)
Rate: 3.3 L/ha
Comments: Protects against emerging seedlings.
Withholding period: 28 days.
Herbicide group: C, Inhibitors of photosynthesis at photosystem II (PS II inhibitors)
Resistance risk: Moderate


Dicamba 500 g/L (Kamba® 500)
Rate: 40 mL per 100 L of water
Comments: Spot spray.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Dicamba 500 g/L (Kamba® 500)
Rate: 600 mL/ha
Comments: Boom spray. Apply to young, actively growing plants.
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Hexazinone 250 g/L (Velpar® L)
Rate: 70 mL per 100 L of water
Comments: Apply uniformly over the area. When spraying single plants treat soil for 1 m around. Do not use near desirable trees.
Withholding period: No stated withholding period.
Herbicide group: C, Inhibitors of photosynthesis at photosystem II (PS II inhibitors)
Resistance risk: Moderate


Metsulfuron-methyl 300 g/kg + Aminopyralid 375 g/kg (Stingerâ„¢)
Rate: 10 g per 100 L of water
Comments: Hand gun application.
Withholding period: 3 - 56 days (see label)
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors) + I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: High/Moderate


Metsulfuron-methyl 600 g/kg (Brush-off®)
Rate: 5 g per 100 L of water
Comments: Thoroughly wet all foliage to the point of run-off.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors)
Resistance risk: High


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Legal requirements

The content provided here is for information purposes only and is taken from the Noxious Weeds (Weed Control) Order 2014 published in the NSW Government Gazette, detailing weeds declared noxious in New South Wales, Australia, under the Noxious Weeds Act 1993. The Order lists the weed names, the control class and the control requirements for each species declared in a Local Control Authority area.

Area Class Legal requirements
All of NSW 1 State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant

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Parthenium weed
Parthenium weed (Photo: Bob Trounce)

Parthenium weed foliage
Parthenium weed foliage (Photo: J Gasparotto)

Parthenium weed at 6 leaf stage.
Parthenium weed at 6 leaf stage. (Photo: J.J. Dellow)

Parthenium weed seedling
Parthenium weed seedling (Photo: NSW DPI)

Parthenium weed infestation
Parthenium weed infestation (Photo: NSW DPI)

Parthenium weed flowers.
Parthenium weed flowers. (Photo: P. Blackmore)

Parthenium weed plant
Parthenium weed plant (Photo: Auld and Medd)