An invasive pasture weed has been found in Southland and authorities are calling on farmers there to report any further sightings of it.
Giant buttercup is endemic in Taranaki and the Nelson Bays areas and is known to reduce edible dairy pastures in those regions by up to 50%.
Environment Southland says that while giant buttercup is not an official pest plant in Southland, it is extremely difficult to control once it gets established.
The plant is poisonous and unpalatable to dairy cattle, although sheep can graze on it.
Environment Southland biosecurity officer Randall Milne says farmers need to get in touch if they notice giant buttercup.
He says over the last couple of years there have been reports of giant buttercup in various locations in Southland.
Mr Milne suspects giant buttercup hitched a ride into the region with the dairy industry which has boomed in Southland in recent years.
The pastoral science body, AgResearch, estimates it costs the dairy industry $150 million in lost revenue each year.
It estimates the pest plant reduces a typical Golden Bay dairy farm's profit by more than a third.