An outbreak of the highly invasive and noxious parthenium weed, Parthenium hysterophorus, has been detected for the first time on the New South Wales North Coast.
The infestation, covering an estimated two to three hectares, was found on a certified organic egg farm situated in the Nambucca and Bellingen shires.
The NSW Department of Primary Industries (NSW DPI) said it believed that a wholegrain organic chicken feed from Queensland was the source of the parthenium weed.
NSW DPI's State Priority Weeds coordinator Charles Mifsud said there could be more infestations and chicken owners who might have used such a feed should be on alert.
"They should have a look on their properties, where they've been feeding, and just see whether there's any unusual plants there that could be parthenium weed," he said.
"A lot of produce stores had stocked this organic chicken feed, and even pet shops, so potentially there could be a lot more backyard infestations but also some commercial chicken places as well."
The egg farmer, who has not used the feed for two years, is working with local council weed officers to remove the plants, either by hand or fenced off and sprayed, before the infestation spreads further.
Parthenium weed toxic to livestock
Regarded as a significant biosecurity threat in NSW, parthenium weed can be toxic to livestock, reduce crop and land value and can cause serious allergic reactions — dermatitis, hay and asthma — in humans.
Mr Mifsud said that while the weed is generally unpalatable to stock, it could cause a taint in the meat or in the milk if ingested.
"In this case with chickens we're unsure because this is an egg laying enterprise; we're unsure whether it could taint the eggs or not," he said.
"It can also be quite invasive so as it spreads that can lower the stocking density of livestock on the property quite significantly just through that reduced pasture production."
Mr Mifsud said that two other parthenium outbreaks in NSW this year, Engadine in Sydney and Ravensdale on the Central Coast, have been traced to the same contaminated feed.
"Wherever they've harvested the organic grain from it's been contaminated with some parthenium weed, and that would make sense because it's organic grain and they've not sprayed those properties," he said.
Vehicles and machinery that have travelled through Queensland, where the weed is endemic covering 18 million hectares of land, are thought to be the cause of other infestations in NSW this year.
There has now been 21 infestations in NSW since the start of April, the highest number of outbreaks in the state since 1999.
