The discovery of a new weed on two properties in the Geraldton area has sparked a warning about the potential risks of weed seeds in imported pasture seed mixes. 

Amaranthus spinosus, commonly known as needle burr, was recently spotted by a vigilant grower in a paddock sown with a sub-tropical grass mix (2004 seed) and was reported to the Department of Agriculture, Western Australia.

This species was not previously known to be in Western Australia, but is common in the Eastern States and does not pose a threat to agriculture.  It is not a declared plant in Western Australia.

Department plant pests manager Damian Collopy said investigations had confirmed the weed on a second property and both cases were linked to an imported mix of sub-tropical perennial grass seeds. 

Mr Collopy said all seed mixes carried a risk of introducing new weeds at a low level and it was very difficult to ensure the seed was one hundred per cent clean despite rigorous testing procedures performed at international standards.

He said the Department was tracing all of the suspect seed and advising growers who had sown the seed to check for needle burr. Inspectors were conducting follow-up visits to each property.

“Needle burr is a summer-growing weed. Its tall habit and large paired spines make it very obvious and easy to identify,” Mr Collopy said.

“Growers who have already sown their pastures will need to monitor their paddocks to check for any emergence of unusual weeds. The plant is easily managed and does not pose a significant threat to agriculture.

“There are currently eight other Amaranth species established in Western Australia and none of these pose a threat.” 

A Farmnote with coloured pictures is available on the Department’s website to help with identification and printed copies will be sent to all affected landholders this month.