Yellow-legged hornets in Kaipātiki: 5 month update

By now most of those in Kaipātiki will have heard about yellow-legged hornets. It has been five months since the first queens were found in Glenfield and the 'hornet hunt' commenced. As of the 26th of March, 75 queens and 127 nests have been found. While yellow-legged hornets (YLH) may no longer be in the news, time is still of essence, and work is ongoing behind the scenes.

On the 18th of April, Pest Free Kaipātiki (PFK) will be hosting an EcoFest biosecurity workshop that will have a section on the yellow-legged hornet. Click here to learn more.

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On the 18th of March PFK was able to visit the "Hornet HQ" in Glenfield, and talk to SPS Biota who are in charge of Biosecurity New Zealand's yellow-legged hornet response.

A learning curve

This is the first time that there has been a yellow-legged hornet incursion in New Zealand, so the response has shifted and developed as time has passed. Tracking has been informed by international experts from the Netherlands and the UK, but even then, Auckland's unique environment makes it tricky to understand just how the hornet will behave.

Tracking station set up with sugar-water lure and rocks. Source: Ministry for Primary Industries and licensed by MPI for re-use under the Creative Commons Attribution 4.0 International licence.

The latest update in the response has been the use of 'tracking stations' and Vespex bait stations and AI. Now that radio tracking has proved to be successful, tracking stations are a way to monitor hornets, while keeping them alive for tracking. As hornets fly back to their nests, their direct flight path can be noted to identify direction of nests. In addition to human observations, AI is being used to monitor and study hornet activity at the tracking stations.

Vespex is a special wasp bait, originally developed in New Zealand to control common (Vespula vulgaris) and German (Vespula germanica) wasps. It works by being transported to nests as a food source by worker wasps and poisons them from the inside out. Yellow-legged hornets are also attracted to the Vespex bait and are known to also take it into their nests. Unlike other countries that have native Vespula wasps, New Zealand does not. This means that our native wasps (and honey bees) are not be affected by the deployment of Vespex bait.

The bait stations are being placed within the 'Zone C' which is a radius of 11km around nest detections. They will be a last line of defence for the yellow-legged hornet, while also controlling surrounding invasive wasps.

Setting a Vespex bait station. Source: Ministry for Primary Industries and licensed by MPI for re-use under the Creative Commons Attribution 4.0 International licence.

Along with these new approaches, some patterns are arising in finding hornet nests. Hornet queens appear to share some preferences to the types of trees that they like building nests in, those that are very tall and straight, like our native tānekaha. If a hornet is tracked to an area but their exact location has not been found, trackers can now prioritise searches to these preferred tree types. This being said, yellow-legged hornet nests are very difficult to spot from the ground, so it may still take some time to identify their exact location in an area or on the tree.

Everyone has a role

The Hornet HQ was bustling with people, you could imagine it was like a hive itself. Hornet surveyors were arriving and leaving constantly, others were discussing, checking maps and traps, and every now and then phones would vibrate to signify a hornet being found.

There are a range of roles that hornet hunters do, and this includes members of the public.

Trap monitors

Trap monitors check traps that have been set up by MPI around Kaipātiki and further. Initially this role was mainly sorting through the catch and resetting the traps. But with the new tracking stations, trap monitors can watch as hornets fly in and out, which helps identify the direction of nests.

Nest trackers

Nest trackers use radio technology to follow hornets that have been equipped with a radio transmitter. If the nest is low to the ground, then nest trackers may be able to find it by themselves, if not, they may need some extra help.

Arborists

Arborists are skilled in tree climbing. Secondary YLH nests can be found high up within tree tops, therefore experts are needed to climb up trees safely and look for nests. Often these nests are hidden by foliage and branches, so cannot be seen from the ground. Arborists must wear specialized hornet protection suits while they climb, as YLH can sting through normal bee suits.

Control team

Once nests are found they can be destroyed. YLH are very aggressive, so destroying their nests is a very dangerous task, and cannot be done in the same way you would destroy a paper wasp nest. Now that Vespex bait is being used, nests may be controlled indirectly though the movement by worker hornets.

Hornet identifiers

Hornet identifiers are able to identify yellow-legged hornets from other wasps found in Aotearoa, they are the people who check the photos from public reports. They also identify hornets from traps and may do genetic analysis of samples.

Members of the public

Members of the public have made a great contribution to the hornet hunt through their reports to MPI. Public reports of hornets help identify areas where there may be a hornet nest. Furthermore, reports of nests can help SPS Biota quickly destroy it. Hornet nests have been found in a range of locations within private property and in reserves so it is important to stay vigilant of your surroundings. As of the 26th of March there have been 15,632 reports from the public.

Raising awareness

Since November 2025, PFK has been updating our Yellow-legged hornets in Kaipātiki blog post with the latest information. We have also been raising awareness through our social media and events, and creating resources (check out our 'spot the difference' below).

A special shout out also goes to our wonderful volunteers who are currently helping with different aspects of the hornet response. PFK volunteers often get involved in planting, surveying and predator trapping, so this experience lends well to hornet hunting. If you are interested in volunteering with PFK, feel free to contact volunteers@pfk.org.nz.

(Can guess which pattern, legs and colour belongs to each wasp? Answers on the last slide).

A promising future

The yellow-legged hornet has been eradicated before, and while it was from a small Mediterranean island, it still holds hope for Aotearoa. Visiting expert, Pete Davies from the UK, is impressed by our effort to eradicate the hornet and has been helping us to do so.

Though it is unknown just exactly where we will be in the next five months, in comparison to other countries, having Vespex is another good positive factor.

Finally, the number of nests found so far is approaching the 100 mark, this is promising because a single mated queen can create approximately 100 new queens, this means that we may be approaching all nests for this season (if the invasion started from a single queen). These nest finds couldn't have been done without reports from the public, especially in the early stages of the operation, so once again, good work Kaipātiki!

Display tracking station outside the 'Hornet HQ' photo by Shanti T.G.

For more yellow-legged hornet updates in the future, visit MPI's yellow-legged hornet page, or our main blog post.

Article by Shanti T.G

Header image credit: Ministry for Primary Industries and licensed by MPI for re-use under the Creative Commons Attribution 4.0 International licence.