The guava moth, which ruins feijoas, is getting worse and spreading south from Northland, growers say.
The pest, which came from Australia 20 years ago, is typically found in the subtropical climates of Auckland and Northland, but Northland grower Peter Jack said it was now in Waikato and could survive as far south as Nelson.
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.
Mr Jack said, because it was spreading to many private orchards and gardens, it was hard to say how far it had gone.
"There's not enough research done on it that if it does become a really big issue, to combat it.
"That's why we are getting a bit of publicity, to see if we can actually get some funding to see if we can find something out there we can control it with - whether it is a predator, an insecticide, or a lure and kill pheromone."
It was becoming a "bit of a nightmare" for his orchard, and he'd lost half his crop this season, he said.
"With this wet season, I think they've bred maybe two or three times. Unlike the fruit fly, this thing will handle cold weather, so it has the capability of being just as much a problem."
The Feijoa Growers Association is applying for funding to research solutions.