“Cautiously Optimistic” at Hornet Eradication, but Only Time Will Tell

While the leadership at the Ministry for Primary Industries' (MPI) Biosecurity New Zealand are encouraged by a recent lack of yellow-legged hornet sightings, there is agreement that the incursion response must continue apace for at least another month before taking a new tact over winter.

There were no yellow-legged hornet sightings in New Zealand in April, but it will take years of that to confirm eradication and thus the incursion response continues at strength.

Zero hornets in all of April. Following 132 nest finds in Auckland between October last year and March 25 2026, it’s an impressive and encouraging result, leaving both Biosecurity NZ commissioner north Mike Inglis and technical lead of the vespa velutina response Scott Sinclair “cautiously optimistic”.

Eradication of the invasive pest, first detected in the form of two male hornets in June and July 2025 in Auckland, has always been MPI’s goal. Any chance of proving that will be several years down the track, requiring two seasons of no sightings.

To this point hornet activity has been largely inline with expectations: nests building up through spring and then moving to “secondary” nests, often high in trees, as temperatures rise. That has seen MPI’s response employ a range of tactics to identify hornets and their nests, and destroy both. Ground searches, feeding stations, traps, radio-tracking technology, field observations – including around beehives – and poison bait have all be utilised in the six-month long response.

As temperatures cool and autumn moves to winter yellow-legged hornet nests typically die-off, each leaving behind potentially hundreds of mated queen hornets, known as gyne, to attempt to survive winter and start nest-building again in spring. That natural reproductive cycle begs the question, is the reason no hornets or nests have been located since late-March simply because only hard-to-find, gyne queens now remain?

“Mapping the phenology from the northern hemisphere onto New Zealand’s seasons, we would expect a lot of hornet activity at this time of year, as it would be too early for nests to die off,” Inglis says, explaining their optimism.

“We have not seen a hornet for about a month now, when we would expect at this time to have peak activity.”

They will continue to look closely over at least the next month though says response technical lead, Sinclair.

“We are looking to destroy all the nests we can before they enter the reproductive phase. While we have detected some male hornets in the environment, we have had no detections of any gynes, the next generation future queens, yet,” he says.

Vespex’s Value

Autumn sees the hornets seek protein to meet dietary needs, and so protein-based, fipronil poisoned bait Vespex has been used and it is believed to have been attractive to the wasps, providing an encouraging tool.

“We have done a small trial that demonstrated the presence of fipronil in nests around which we had deployed Vespex. This indicates that hornets do take Vespex back to their nests, in a similar manner to Vespula wasps,” Inglis says.

Sinclair says Vespex has been used around the three Zones of the response in Auckland “to cover off areas which are difficult for the field team to reach and to provide a level of confidence that any hornets not coming to our feeding stations, traps or observed by members of the public are eradicated”.

What Now for Winter?

Hibernating queens become a “very difficult part of the hornet lifecycle to impact,” Sinclair says.

“They could be anywhere and we have no real tools to impact the hornet at this time, other than strong awareness and messaging around the types of places they might hide, such as firewood stacks or goods which may be attractive for a hornet to hide in.”

Therefore the response will soon move to just such education, while also taking the opportunity over winter months to better research how the hornet may have arrived into New Zealand, and how it has responded here.

“We are unsure how long the hornet season will last in New Zealand, but it is important for us to analyse the data we have gathered over the season and start planning for next season,” Sinclair says.

As for how the pest – native to several parts of Asia but which has migrated to Europe – may have entered New Zealand, that’s “difficult to know exactly”.

“It may be through the shipping of personal effects, golf clubs or jackets coming back from overseas, it may be through shipping containers. What we do know, based off genetic analysis, is we are fairly confident this hornet has originated from the invaded population in Europe, rather than its native range in Asia,” Sinclair says.

Continued Public and Beekeeper Help Needed

MPI has received in excess of 17,000 notifications suggesting potential hornet sightings “from Invercargill to Cape Reinga” and, while relatively few have been “positive”, Sinclair says it is important public vigilance continues and beekeepers can play an important role in that.

“There may be hornet activity around your hives, but it is unlikely this time of year. So, we are asking the highly engaged apiarists to really be advocates and keep awareness up out there. One of the best tools we have is public awareness and people calling in sightings,” Sinclair says.

To assist that area of the response, MPI is being encouraged by New Zealand Beekeeping Inc advisor Ian Fletcher – who along with Apiculture New Zealand, has been meeting with MPI to represent beekeepers – to establish a smartphone app to simplify identification and reporting of hornets.

A map highlighting where notifications regarding yellow-legged hornet have come from. Few are “positive” MPI say, but regardless public vigilance is still highly important.

Questioned on whether such a piece of technology was in the pipeline MPI was noncommittal, Inglis saying only they are “exploring more novel tools”.

There’s a chance what tools they have used this season have worked, but it is all still an unknown and thus Sinclair reinforces their position.

 “It is positive, but no one is getting ahead of themselves just yet. There could still be small, difficult to detect nests out there. We certainly are not diminishing our operations. We are looking to maintain a high level of activity for another month or so before we start to think there is not much out there for us to find this season.”

MPI’s yellow-legged hornet response page has a range of resources and regular updates.