Expanding the Toolbox – Hornet Response Turns to Vespex and AI

Auckland’s fight with yellow-legged hornets continues, with nests still being discovered as winter approaches. Despite ongoing eradication efforts and a strong public reporting effort, experts warn that even a single surviving queen could see the problem re-emerge next spring, making vigilance, now, more important than ever.

By Eloise Martyn

“What I would prefer is that we were not finding so many nests still,” says Phil Lester, Professor of Biology at the School of Biological Sciences, Victoria University of Wellington. Lester’s research programme focuses on social insects – including honey bees, wasps, and ants – with a particular focus on protecting honey bee populations and managing invasive wasps.

Phil Lester, Professor of Biology at Victoria University of Wellington, has concerns at the number of yellow-legged hornets still being found in Auckland, with the potential for exponential growth in hornet colonies next spring.

Lester’s comment comes in the context of the ongoing eradication programme for yellow-legged hornets, whose nests continue to appear on the North Shore in Auckland. The operation is being strengthened in the lead-up to winter in an attempt to get ahead of the hornets before next season.

 “Right now, I was hoping people would be searching for hornets’ nests and not finding anything, unfortunately we are still finding things,” he says.

Lester does say, however, that it is encouraging to find no evidence of reproduction in new queens at this stage. But adds what is clear is that there are far more nests than were predicted or imagined, which is “not good”.

Biosecurity New Zealand’s Commissioner North, Mike Inglis says since the response started in November last year, 77 queens and 132 nests have been found and destroyed as of March 31 – “much of this thanks to an incredible effort from the public reporting sightings to us. We’ve had over 15,610 public notifications to date.”

Hornets have a life cycle that involves creating different types of nests. Early in the season, a hornet colony establishes a primary nest, usually small and on or near the ground. As the season progresses, the colony may move, building a larger secondary nest, often higher up in a tree.

The nests found thus far are a combination of both types. Up until December most of the nests found were primary nests. After December, both primary and secondary nests have been detected.

DNA testing confirms all hornets destroyed so far are from a single mother queen. With nests still being found as winter approaches, even one surviving queen could restart the problem next spring — and multiple survivors would make it grow exponentially.

“This is the critical bit,” Lester states. “Trying to stop queens reproducing this year, if one queen survives, we could be back to the exact same situation next year.” 

Hornet trap locations and detection area.

He adds that the hornets thrive in Auckland’s mild climate, adding to the difficulty of eradication.

Lester is part of a Technical Advisory Group (TAG) that meets regularly with the Ministry for Primary Industries (MPI).

“We meet every few weeks, and they (MPI) frequently have questions they want to ask us. Some of the recent questions have been around Vespex – specifically, when and where it should be deployed.”

TAG is made up of experts with experience in wasp and hornet management from New Zealand as well as overseas, including Switzerland, the UK, and France.

“It’s a diverse group and it’s been hugely beneficial having them here,” Lester says, reflecting on the international insights.

He notes that some members of the group have recently made their second trip to New Zealand.

“Their visit has helped shape what, and how, our ground teams do. As a result of their input, the teams have become a lot more productive,” Lester says.

He calls Vespex, a fipronil-laced protein bait currently being used, “another tool in the toolbox”. Having been effective against German and common wasps in New Zealand and overseas, we don’t yet know for sure how effective it will be for hornets. However, “there’s a good amount of evidence supporting its use,” Lester points out.

Vespex is currently being used in two outer surveillance zones from 1km to 11km from known hornet hot-spots, as autumn moves closer to winter the poisonous bait is expected to be deployed into “Zone A” within 1km of hornet finds.

In the meantime the focus is on finding as many nests as possible to destroy them and Inglis adds that the response toolkit will soon be boosted with AI-enabled cameras to help monitor hornets. These cameras from the University of Exeter Vespa AI Team in Britain have arrived in the country and in April teams will be testing their effectiveness at locating areas of interest for hornets and their nests.

“The cameras have been used experimentally in the UK, and we are supporting this research by deploying them at live-capture feeding traps here in Auckland. They’ll monitor hornet movements and help us pinpoint areas with high hornet activity.” Inglis explains.

“Because we’ve now found and destroyed a substantial number of hornets and nests, our teams are spending longer observing feed stations. Using these cameras means we can closely monitor activity online, freeing up our field workers for other tasks.”

Lester adds “It’s another tool, and I’m really pleased to see MPI utilizing tools that have been effective overseas.”

A Vespex bait station. The fipronil-laced protein bait has proven effective against common and German wasps species in New Zealand and now it is hoped it will kill off any hornet nests which are yet to be discovered in Auckland.

When asked what he thought the hornet situation might look like six months down the track, Lester replies, “I’m hopeful”.

For now, the focus is on putting into action the tools and strategies learned from overseas. All beekeepers are encouraged to keep a watchful eye for any unwanted hornet visitors. Every report helps, and public vigilance remains a critical part of protecting New Zealand’s honey bee populations. One thing is for certain: this is not where the yellow-legged hornets’ New Zealand story ends just yet.