A feijoa grower has found the crop-destroying guava moth breeding in the plant's flowers, which damages the fruit's development.
The pest, which came from Australia 20 years ago, is typically found in the subtropical climates of Auckland and Northland.
The moth attacks feijoa by making a pinprick hole as it burrows into the fruit, and then the fully-grown caterpillar chews its way out.
The fruit is ruined in the process.
But Feijoa Growers Association spokesperson Peter Jack lost half his crop last year and was now seeing the larvae in the small flowers, which he said was a first.
Very little is known about the pest and growers were calling on the government to help fund further research so it could be managed, he said.
He was trialling a treatment spray but said that option could be out of reach for home gardeners because it cost $400-$500 for three 180 gram packets.
The Ministry for Primary Industry said it was considering the association's application for funding under the government's Sustainable Farming Fund.
A decision was expected early next year.