Top End landholders have been urged to be on the lookout for parthenium weed (Parthenium hysterophorous) after it was found at Victoria River Research Station (VRRS) recently.

Native to Central and South America, parthenium weed was first recorded in Australia in 1955 and has since spread through central Queensland and New South Wales where it is well established.

Parthenium is a major problem in rangelands and cropping areas of Queensland costing farmers and graziers more than $22 million a year in reduced production and increased management costs.

Department of Environment and Natural Resources (DENR) Weed Management Branch director Geri Lee said parthenium is a Class A (to be eradicated) and Class C (not to be introduced) weed in the Northern Territory, as well as being classified as a Weed of National Significance (WoNS).

“Parthenium is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread and economic, health and environmental impacts,” Ms Lee said.

“That’s why we are very thankful that the VRRS station manager contacted us as soon as he came across parthenium weed on a vehicle track near a creekline.

“This enabled DENR and the Department of Primary Industry and Resources to respond immediately and possibly avert an environmental disaster that could have cost millions of dollars to fix.

“The immediate response included surveying a six kilometre stretch of land around the discovery site.

“Vehicle movements have been investigated with surveys of other research stations currently underway.

 “The one parthenium plant found last week was very close to seeding, further emphasising the importance of early detection.”

Once introduced into an area, parthenium can establish and spread very quickly.

“Plants can reach maturity in 28 days with a single plant able to produce up to 15,000 (2mm long) seeds that can persist in the soil for up to six years,” Ms Lee said.

“The recent finding appears to indicate that germination occurred following early rains in the area.

“All parts of the parthenium plant, at any stage of growth, are toxic to humans and animals.”

Parthenium was first discovered in the Northern Territory along Elsey Creek in the Mataranka district in 1977.

The infestation was eradicated following an early intervention program that combined ground and aerial herbicide spraying as well as manual removal.

Smaller infestations have been reported and controlled in the Katherine, Borroloola and Tennant Creek areas.

An informal quarantine zone remains in place in the Tennant Creek stockyards following a parthenium infestation in 2010 with no seedlings found since 2011.

To the best of DENR’s knowledge, these are the only known successful eradication sites for the parthenium weed in Australia, and were largely successful because of the early detection, containment, control and monitoring activities undertaken.

The public is urged to report parthenium sightings by calling 89994567.

Go to www.nt.gov.au/environment/weeds for more information.

Media Note – Geri Lee is available for interview on 89994414