THE Agriculture Department warned city residets to be on the look out for skeleton weed after a huge infestation was found in a northern suburb.
More than 1000 mature plants spread across 1.5ha were discovered at a disused market garden in Wanneroo.
Last summer, 30 infestations of skeleton weed were detected and reported to the department and it is the time to be on the lookout.
Department project officer David Atkins said the weed was found predominantly in Landsdale and Duncraig in the northern suburbs and Eden Hill, Kewdale, Jandakot and Murdoch in the southern suburbs.
He said all detections of the weed were treated with herbicide to kill the plants and prevent them setting seed.
"This season the department is undertaking surveillance in Perth to quantify the extent of skeleton weed in the metropolitan area," Mr Atkins said.
"We'll be working with metropolitan shires and the Main Roads Department to provide information to skeleton weed, to aid in identification.
"Skeleton weed has a similar appearance to wild radish, a common garden weed.
³The easiest way to distinguish the plants is that the skeleton weed stems are hairless and do not have seed pods attached.
"We're also employing a person to undertake surveillance in and around last year's sites and any new infestations."
Mr Atkins said the department was keen for assistance from the public but that relied on them knowing what to look for.
Skeleton weed grows from rosette into a sparsely-leafed erect plant up to 1m and has bright yellow, daisy-like flowers.
The stems are generally erect with little or no foliage. The stems ooze sticky white sap when broken.
It is a perennial plant with a deep taproot that is spread by seed and regeneration by root fragments disturbed by cultivation.
Root fragments as small as 1cm and from depths as great as 1.2m can produce new plants.
³Skeleton weed is a member of the daisy family and must be eradicated when found in WA," Mr Atkins said.
"If it is not controlled, skeleton weed can drastically reduce cereal yields by up to one tonne per hectare by competing for water and nutrients, mainly nitrogen, and its tough wiry stems impede harvesting.
"The cost of managing the weed in WA is around $4-5 million per annum, while the potential for lost income through reduced yields is even greater."
Rural travellers who may be in Perth during the December to March period, are also being asked to keep a look out for skeleton weed and report anything suspicious to local department offices or contact David Atkins at the Merredin office on 9081 3152.