The weed Madagascar ragwort has the potential to become a significant problem for pastoral farmers in New Zealand, following its discovery in the Wairarapa region.
Madagascar ragwort is an invasive and highly toxic pasture weed.
Greater Wellington
Previously thought to be confined to Northland, early detection is critical to preventing the toxic plant from spreading and establishing in the lower North Island.
The poisonous weed can cause serious illness. and in some cases even death in cattle and horses. Its seeds are easily dispersed by wind, making the plant particularly hard to manage.
It has been identified near Ngawi, where it took some time to distinguish it from other pasture weeds with similar bright yellow flowers.
The discovery follows an initial detection in Northland more than two decades ago. The weed may have entered New Zealand on farm machinery.
The Greater Wellington Regional Council said because it was so difficult to identify it was important farmers became familiar with the plant.
A spokesperson in the Pests and Plants team said it may have been growing undetected for the past five years around the latest site.
“Madagascar ragwort is a serious biosecurity threat with the potential to impact farms, animals and rural livelihoods across our region,” the council’s environment and climate committee chair Quentin Duthie said.
“Unlike common ragwort which is widespread, Madagascar ragwort is confined to an isolated area, giving us the opportunity to act before it becomes rife.
Barbie Barton, Wairarapa landowner and chair of Greater Wellington’s Farming Reference Group, said community vigilance was vital.
“We’re asking farmers, contractors, rural workers and coastal landowners to familiarise themselves with what this plant looks like and to report any suspected sightings,” Barton said.
“The eyes and ears of our rural communities are one of the most effective biosecurity tools we have.
Greater Wellington can collect samples for testing and provide advice to landowners on controlling this dangerous weed.”
Madagascar ragwort produces bright yellow daisy-like flowers about 1 to 2 centimetres in diameter and can germinate throughout the year. A single mature plant can produce more than 10,000 seeds that are dispersed by wind, allowing infestations to establish and spread rapidly if left unmanaged.
The weed has bright yellow daisy-like flowers.
Greater Wellington
“Experience in Northland and overseas shows this plant can be extremely difficult and expensive to control once it becomes established. It reduces the amount of productive pasture available, stock avoid grazing around it, and it remains toxic even when incorporated into hay or silage,” pest plants team leader Mark McAlpine said.
“At this stage our priority is understanding whether there are other sites in the Wellington region and supporting landowners with identification and management advice. Finding it early gives us the best chance of limiting its spread.”
Research commissioned by Northland Regional Council has identified Madagascar ragwort as a growing threat to New Zealand’s pastoral sector, with evidence of production losses on affected farms and concerns about its potential spread through wind, contaminated fodder, machinery, vehicles and livestock movements.
Greater Wellington is encouraging anyone who thinks they have found Madagascar ragwort to report it immediately. Reports should include, the location of the plant, the date it was found, photos if possible and contact details.
Cattle and horses usually won’t touch the thriving plants, however if a paddock has been recently sprayed, livestock may graze the weed while it is dying off.
Suspected sightings can be reported by emailing: Pest.Plants@gw.govt.nz or calling 0800 496 734.