Police have been notified about the poisoning of more than 200 pine trees on council land in the small Southland town of Tuatapere.
Tuatapere Community Board chairperson Anne Horrell said she was shocked by the unusual act of vandalism that had left most of the 270 trees in the plantation yellowed and dying.
Poison had been administered through two to three drill holes in each tree, although it was unclear exactly what toxin had been used to kill the trees in the recreation reserve.
A nearby stand of macrocarpa on private land had also been targeted.
Southland District Council staff were called in after a member of the public noticed the evergreen trees had turned shades of Autumn.
Horrell said staff suspected the holes had been recently drilled into the trees because there was sawdust on the ground.
"It's certainly having the desired effect that the culprits wanted. The trees are dying very quickly," she said.
"It's very disappointing and quite shocking. I've never noticed any vandalism like this before. It's a real shame."
The pine trees were planted by the Tuatapere Domain Board more than 20 years ago and were next to a heritage orchard, Horrell said.
She said she had no idea why someone would want to poison the trees.
"It certainly defies belief that someone would go to this sort of trouble and why," she said.
"It's a bit of a worry if that sort of thing is happening in our little town."
The community board hoped the trees could be harvested, although it was unclear if they would be of any value.
Police confirmed they had received a report about the vandalism, which was being assessed.
A Southland District Council spokesman said it became aware of the poisoned trees last month.
"Council and the Tuatapere Te Waewae Community Board are in the early stages of determining the next steps. Discussions are being held with a local contractor who will provide information about the best path forward," they said.
"The cost of any actions relating to the poisoned trees is not yet known."