Hornet Incursion – What’s the Risk and How to Help?

Last month three yellow-legged hornet queens were dectected and removed in Auckland, following on from the discovery of two male hornets in different suburbs of the city in June and July. The presence of both male and female of the species is a “considerable concern” says invasive species expert Prof. Phil Lester.

The public of Auckland are asked to be on the lookout for yellow-legged hornet and report sightings. 

Prior to this year the yellow-legged hornet (Vespa velutina) had not been detected in New Zealand, but is found widely across Southeast Asia and has been introduced to Europe and the USA.

Finding invasive insect species early is critical to elimination and while Lester, a Victoria University of Wellington Professor of Biology, stresses at this stage very little is known about the incursion, what is known is “worrying”.

Biosecurity New Zealand received two separate notifications of male hornet sightings from members of the public – one in late June from Grafton and the second in early July, 16km away in Albany. More recently in Glenfield, a suburb between the two where the male hornets were located, a queen was found in the early stages of nest building and was removed on October 17, then within 2km two more queens were discovered in the last week of October.

The male hornets may have come from a shipping container and dispersed themselves around Auckland, but given the distance between their locations a greater risk could exist.

“It’s hard to believe it is just an incursion from a shipping container when there are separate times and multiple locations, some distance apart, which seems to indicate there is a nest, or multiple nests in the area,” Lester says.

“The presence of the males, if they haven’t come off a container, suggests there was a reproductive event. A viable nest that has survived and reproduced. If that was the case, there is likely to be multiple queens produced as well as the males, which could have flown off and established."

Just hours after Lester made these comments, news of the two further queen hornets being found in Auckland broke.

Biosecurity New Zealand is appealing to the public to be vigilant and report any sightings of yellow-legged hornets, which are not classified as a notifiable or unwanted organism under the Biosecurity Act 1993, but are considered a biosecurity concern due to their potential impact on honeybee and wild bee populations.

"It is a highly adaptable predator with a broad diet, primarily feeding on bees, wasps and flies, but also ripe fruit and flower nectar, posing a risk to growers. It may compete with native insects and birds for food, and it has a painful sting,” explains Mike Inglis, Biosecurity New Zealand’s commissioner north.

Lester says the yellow-legged hornet has a wide climate tolerance, meaning there is potential for it to establish in many parts of New Zealand, and it is “a serious concern for beekeepers”.

"One of the things it'll do is hover outside honey bee hives and wait for returning workers and pounce on them, kill them and take them back to their nests. The workers are substantially affected by that,” Lester says.

This limits honey bee foraging behaviour and contributes to colony loss.

How to Help & What to Look For

“We don’t know at this stage whether there is a local population, which is why we are asking Aucklanders to keep an eye out and call us if they suspect they have seen this hornet or its nest,” Inglis says, noting “the most effective method for surveillance is through public involvement”.

Early embryo nests can be as small as a tennis ball and may appear within just a couple of days. Eves of buildings and trees are common locations. Biosecurity New Zealand advises not to disturb the nest, but to take a photo, and report it to them.

The yellow-legged hornet is large, 2-3 cm long, with a black head and a yellow face, black thorax and legs with black femur and tibia and yellow tarsis. The wings are a smoky brown colour and not transparent like other common wasps.

If a possible nest has been found, or if a specimen or photo of the yellow-legged hornet is taken, Biosecurity NZ’s pest and disease line should be phoned, 0800 80 99 66, or it reported online at https://report.mpi.govt.nz/pest/