The Ministry for Primary Industries says more than 2000 stink bugs were found on four bulk carriers of cars from Japan since February.

An MPI spokesman said 8300 vehicles were turned away at Auckland's port, leaving people waiting weeks to pick up their new vehicle.

Three of these vessels carrying the brown marmorated stink bug had since returned and discharged their cargo, subject to strict biosecurity conditions.

The fourth vessel was scheduled to return on Thursday and would undergo similar measures, including fogging with insecticide.

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MPI said 2218 individual stink bugs had been detected this season.

"The number of detections has been going down as the season draws to a close. The high-risk period is September to April, which is when stink bugs in the Northern Hemisphere are more likely to hibernate in cargo bound for New Zealand."

Auckland car dealer Unique Japan Ltd manager Adam Leece said the bug issue hadn't affected the company in a big way, but was starting to.

"We've sold a few vehicles where people are having to wait longer to get them. There's one buyer who's had to wait an extra three weeks because the car hasn't got here yet.

"We don't really have a timeframe of how much longer it will be."

Vehicle Importers Association chief executive David Vinsen said at this time of year the industry imported about 12,000 vehicles a month.

Vinsen said a disruption such as this could have big consequences.

The hard-to-see, hard-to-kill, fast-breeding scourge has spread around the world from East Asia and is one of New Zealand's "least wanted" pests.

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Their arrival here would be a nightmare for agricultural sectors, native plants and humans – the bugs could invade homes and sheds, especially over winter.