‘Spring queening’ time will be crucial for finding any surviving yellow-legged hornets

The next few months will help determine whether New Zealand has successfully eradicated the yellow-legged hornet, one of the world’s most damaging invasive pests.

The government invested more than NZ$12 million in the effort to find and destroy every last hornet.

Encouragingly, the last known nest was detected in late March and extensive winter surveillance, including trapping, and the monitoring of beehives failed to find any evidence that hornets remain.

There is cautious optimism at the Ministry of Primary Industries (MPI) and members of the technical advisory group that eradication was successful.

But the real test of success is about to begin, and it depends on ensuring no queens that may have survived the winter escape detection.

As our research shows, honey bees were a major component of the yellow-legged hornets’ diet and even a single surviving queen could set off a new incursion, with potentially devastating consequences for beekeepers.

Any surviving queens will be emerging now

If any queens survived the winter undetected, they are likely to start waking from hibernation now.

This is a critical stage in the hornet’s life cycle. Each autumn, a nest produces new queens that mate, store sperm and spend winter hidden away in sheltered locations. In spring, those queens emerge alone and begin the task of building a new nest.

At first, the nest is surprisingly small. Often hidden under house eaves, in hedges or among shrubs, an embryo nest may be no larger than a tennis ball. The queen must do everything herself – collecting food, building the nest and raising the first generation of young.

For a brief window, the future of an entire colony depends on this single insect.

If the queen succeeds, her first workers take over foraging duties and the colony begins to grow rapidly. The nest may reach the size of a coconut before the hornets relocate to a much larger nest, often high in the canopy of a tree. By late summer, a mature colony can contain thousands of hornets.

This is why spring is such an important time for surveillance. A single survivor could allow hornets to establish and become widespread in New Zealand.

Hornets eat a lot of honey bees

We’ve recently completed a preliminary analysis of what yellow-legged hornets were eating in Auckland, and the results highlight why eradication is so important.

Each and every hornet larva we analysed was fed honey bees. The adult hornets that feed the larvae were not occasional bee predators – they were regular bee hunters. Overall, almost one-third (31%) of the hornet diet appeared to consist of honey bees.

If these hornets had established across New Zealand, beekeepers would have faced a very different future. That future would not only affect beekeepers but have consequences for pollination of crops such as kiwifruit, avocados and many other horticultural and agricultural products.

To understand what the hornets were eating, we analysed DNA found in hornet larval faeces. The larvae deposit their waste in the base of the nest cells, creating a biological record of what the adult hornets had been hunting and feeding to their young.

The results revealed a remarkably broad diet. In total, we detected evidence of 77 different animal taxa. Alongside honey bees, the hornets regularly preyed on flies, cicadas and even common and German wasps.

We also found DNA from blackbirds, mice and sheep. These species were unlikely to have been hunted and were probably scavenged from carcasses.

The hornets also made extensive use of New Zealand plants. We found evidence they collected nectar from a wide range of species, including mānuka and camellia.

DNA recovered from nest material suggests they were constructing nests using fibres from plants such as kānuka, tōtara and poplar, among many others.

77 queens captured

The early discovery and quick action to destroy the yellow-legged hornet nests in Auckland may have prevented a widespread population explosion that would have been extremely difficult to reverse.

Between October 2025 and March 2026, a total of 77 queens were captured. We believe those queens were likely the offspring of a single nest that had survived from the previous season.

At first glance, 77 queens may not sound like many. But if those 77 queens had survived, established nests and each produced 77 more queens, by now there could be almost 6,000 new queens waking from hibernation. Eradication would have been near impossible.

If they had established throughout New Zealand, I have no doubt honey bees and beekeepers would have suffered significant impacts. Since honey bees are important pollinators, protecting them means protecting the infrastructure that underpins New Zealand’s food production.

One of the most important lessons from hornet incursions elsewhere is that the public can play a crucial role in finding and eliminating invasive pests.
Overseas eradication programmes sometimes encourage ” spring queening ” to catch queens before they can establish a colony.

If any queens survived the winter, finding them now could prevent a new generation of hornet nests from becoming established and spreading across New Zealand.

Over the past year, MPI received more than 18,200 suspected hornet reports from members of the public. That extraordinary response helped define the boundaries of the infestation, supported surveillance efforts and contributed to the search for nests.

MPI is asking people who sees anything that looks even remotely like a yellow-legged hornet to report it immediately to 0800 809 966 or via the online reporting form . Beekeepers and members of the public can find more information and guidance on hornet surveillance and trapping on the MPI website .