Bougainville's agriculture minister says ants that crossed the border from Solomon Islands into the Papaua New Guinea province are harmless to crops.
The ants are believed to have been brought in during the Bougainville crisis in the early 1990s, when there was no quarantine service.
Dominic Itta says the ants have spread and are now everywhere.
"It's not very serious. They've some sort of smelly [excretion] that can affect or burn some plants. But they don't destroy the plants."
But Dominic Itta says the ants are threatening the survival of the endemic ant species.