Forest & Bird is urging the government to boost funding to control wilding pines - which it says pose a major threat to the country's ecosystems.
The environmental group has sent a letter to Cabinet ministers saying it is critical to act against the invasive tree species now.
An extra $100 million over four years was needed to contain the spread of pines, said Forest and Bird spokesperson Nicky Snoyink.
A previous budget pledged $21m for 2019 to 2020.
Snoyink said with the current funding, the spread of wilding pines would have dire consequences for the Central Plateau, the Marlborough high country, the Mackenzie Basin, and the upper Waimakariri.
Official figures show wilding pines pose a $4.6 billion threat to the national economy.
"For every year that the work cleaning up wilding pines is put off, the price goes up 30 percent... so we need to get ahead of the problem and really throw some money at it," Snoyink said.