The Auckland and Waikato councils are asking farmers to be on the lookout for Noogoora burr as they attempt to eradicate the invasive species for good.
Sighting of the plant have dwindled over the years since it was discovered over a decade ago.
Auckland Council senior biosecurity advisor Lydia Starr said they suspect numbers of the plant are at a level where eradication is achievable.
However, they do not have the eyes to find the weed and are reliant on rural landowners to report it if they think it is on their property.
“What we are trying to do is find out if this weed is on any other properties within rural areas and get to it and eradicate it.”
The plant has been found in Kingseat and Glenbrook near the Auckland-Waikato boundary.
It was accidentally introduced to New Zealand as a contaminant in seed and is a serious threat to crops and pasture. It grows rapidly over late spring and summer, germinating quickly after rain.
Noogoora burr is an erect, fast-growing summer annual herb with a thick tap root and dense lateral root system that can reach heights of 1-2.5m.
It is the plant’s oval fruit, or burrs, that are a problem for livestock, causing discomfort and injury.
Burrs caught in cattle hooves can result in irritation and infection, and damage sheep’s wool, lowering its value.
The plant’s seeds and seedlings are poisonous to all livestock and cause contact dermatitis in humans and animals.
If landowners suspect the plant is on their property, Starr urged them to contact their local council so it can be eradicated.
There are 13 sites in Waikato where Noogoora burr is known. Of these, six are active, six are categorised as monitoring and there is a single historic site.
These sites are in Pōkeno and Waihou Piako areas.
Waikato Regional Council’s biosecurity pest plants team leader, Darion Embling, said they are working closely with farmers and contractors to control its spread.
He said they have not made any new finds of the plant outside those 13.
Within the known sites, there is a reduction in plant numbers and it is getting better.
“As a whole, we are seeing a reduction. There are good control tools for it. We worked with AgResearch and they came up with a good strategy for being able to crop the land and still manage to control Noogoora burr at the same time. As long as farmers stick with the plan, it goes really well.”
Noogoora burr’s rapid growth means it can outcompete pasture and crop species. It also produces chemicals that prevent desirable species from establishing near it and can carry fungal diseases capable of infecting horticultural plants.
One single, vigorous Noogoora burr plant can produce as many 11,000 burrs with the seeds able to stay in the soil for at least six years.
It is spread by seed contaminating agricultural machinery and crops and becoming attached to livestock or clothing.
Generally, Noogoora burr occurs in cropping paddocks or paddocks that have been cultivated, but it could establish anywhere in disturbed areas or along waterways and roadsides.
In Focus Podcast: Full Show | 26 April
Senior reporter Neal Wallace has been looking at the sheep sector and reporting on how farmers, processors, marketers and lawmakers are facing the challenges.
AgriHQ senior analyst Suz Bremner also joins the conversation. Not many people know more about what’s going on around the sale yards than Suz and as a sheep and beef farmer herself she’s got a first-hand perspective on how things are faring in the high country.
As usual we’ll check in with Federated Farmers – this week sharefarmer chair Sam Ebbett has some advice on how to avoid contract disputes over pasture covers.
