Narrabri Shire Council

Parthenium Weed - The Fight Against It!

Parthenium Weed (Parthenium hysterophorus) is a very dangerous weed, which can have a devastating effect on agriculture, the environment and human health.

Parthenium Weed is an annual herb with a deep taproot and an erect main stem. The plant usually grows to a height of 1 to 1.5 metres. The leaves are pale green, deeply lobed and covered with fine hairs. Little creamy white flowers occur on the tips of the numerous stems. A single Parthenium plant can produce 15,000 seeds. Parthenium Weed mainly germinates in spring and early summer, however if conditions are suitable the weed can grow at any time of the year.

What makes this weed so aggressive is that Parthenium Weed can germinate, grow, mature and set seed all within 28 days if the plant is stressed. Therefore if the plant feels the need to it will put all its energy into producing seed before it dies.

Parthenium Weed is a problem in Queensland (especially Central Queensland) because it affects the viability of primary production, both with livestock and grain enterprises. As well as causing health problems for humans and animals. Parthenium Weed causes estimated losses of $16 million per year for Queensland pastoralists and has the potential of spreading extensively throughout Australia to cause expected losses of $109 - $129 million annually. Parthenium Weed has made its way down to NSW and was first found in 1982, here in Narrabri Shire. Both New South Wales and Southern Queensland authorities are fighting very hard to prevent Parthenium from entering and establishing in our regions, however despite this fight some infestations have occurred.

In cattle country the weed dominates pastures and has the potential to exclude useful forage plants, decreasing pasture productivity, carrying capacity and land values. Parthenium Weed has also spread to grain producing areas where it threatens exports by contaminating grain and other produce. The weed affects crop yields and is a burden to the landholder because paddocks often need to be reworked or sprayed before planting. Parthenium Weed is allelopathic, which means it can chemically inhibit pasture growth and seed germination of other plant species.

Parthenium Weed can cause serious health problems for humans. In severe cases people have been forced to sell their property and move away from Parthenium infested areas. Repeated contact with the weed and pollen can cause allergic reactions in some people. Reactions include: severe contact dermatitis, dermatitis that develops when in contact with Parthenium Weed and sunlight, respiratory problems such as hayfever or asthma and increased allergic reaction to other plant species (cross sensitivity). Typical symptoms include: skin rashes on face and hands (itchy, red, irritated and weepy skin), peeling skin, puffy eyes, swelling, fatigue and weight loss. Reactions to Parthenium Weed can occur on first contact or may take longer to develop after a number of exposures. The severity of a reaction may worsen over time.

The best way to prevent an allergic reaction to Parthenium Weed is to AVOID contact. If you find a suspected Parthenium Weed DO NOT remove the plant. Mark the area and request your Local Council Weeds Officer to come out and identify the plant.

Parthenium Weed is also toxic to animals. It can cause dermatitis, eye irritation, and loss of condition and death.

Parthenium Weed seed is spread by water, vehicles, machinery, stock, feral animals and humans. Contaminated feed and seeds can also spread Parthenium.

The easiest way to deal with Parthenium Weed is to prevent it from establishing in the first place. As with most weeds, prevention is much cheaper and easier than cure.

Simple prevention measures include:

Be Aware of Parthenium Weed.

  • Be Aware when purchasing stock feed (grain, hay etc) and crop or pasture seed
  • Always keep a close watch on areas where stock is fed, for the emergence of Parthenium plants.
  • Do not purchase seed that does not comply with the relevant seed Acts.
  • Do not purchase seed infected with Parthenium Weed.
  • Be Aware of the origin of stock
  • Dip and yard stock for 48 hours
  • Place new stock into an easy to monitor holding paddock
  • Bang-tail cattle, as the tail is a potential seed carrier
  • Avoid moving stock during wet periods as muddy cattle readily transport seed.
  • Be Aware of the origin of machinery and vehicles
  • Only allow clean machinery and vehicles onto your property
  • Always move machinery and vehicles over roadways and tracks that are easily monitored
  • Tarp down truckloads
  • Drive visitors around your property in your own vehicle.
  • Be Aware of pasture composition. Pastures maintained in good condition, with high levels of grass crown cover, will limit Parthenium Weed from colonising. Problem areas include: heavily grazed areas, watering points, roadsides, Holding paddocks.
  • Be Aware of procedures for cleaning vehicles

Good property hygiene is a very important factor in our fight against Parthenium Weed. Everyone needs to be aware of Parthenium and understand the importance of preventing this dangerous weed from establishing.

Parthenium Weed is a W1 declared noxious weed, therefore if a plant is found it must be reported to your local council or Department of Agriculture on 1800 680 244.

If you require any further information on Parthenium weed, please do not hesitate to contact the Parthenium Project Officer of the Namoi-Gwydir region on

Telephone: (02) 6799 6706