A yellow-legged hornet. Photo / Giles San Martin
While the unwanted yellow-legged hornet has not been seen in Bay of Plenty kiwifruit orchards, local and well-known pest wasps have been.
The hornets were not a pest of kiwifruit, but they feed on bees, which were regularly used for kiwifruit pollination.
After hornets were identified in Auckland late last year, Biosecurity New Zealand immediately began an intensive response aimed at eradication, supported by Kiwifruit Vine Health and other industry groups, to minimise risk to growers.
“We continue to urge vigilance for the yellow-legged hornet and any suspect nests,” KVH said. “There have been over 17,000 public notifications to date, reflecting significant community commitment to supporting the ongoing response.”
The pollination schedule usually sees beekeepers drop off hives at kiwifruit orchards in late October, with 8-10 hives per canopy hectare.
Hives were usually left at orchards for at least a week before collection.
KVH said kiwifruit was particularly reliant on insect pollinators as its male and female flowers are located on separate plants.
The yellow-legged hornet has distinctive dark legs with bright yellow tips and is much larger than honeybees and common wasp species seen in New Zealand.
In contrast, common wasp species, such as the German wasp, typically have uniformly yellow or yellow-striped legs.
While the hornets are unlikely to directly target kiwifruit, KVH said they pose a biosecurity risk because of their potential impact on honeybee and wild bee populations, and there may be indirect impacts through reduced numbers of pollinating insects.
KVH has also received several reports of possible hornet and nest sightings through the response period from sites close to and beyond the Auckland response zone, including Tauranga, Te Puke and Katikati.
“All have been negative for YLH and not of a biosecurity concern, including German and Asian paper wasps and their nests, and one Australian paper wasp find.”
The yellow-legged hornet and paper wasps look similar, with the sightings all coming from reports made to KVH by growers or others within the kiwifruit industry.
“We always encourage reports of new, unusual, or concerning pests or unusual symptoms on kiwifruit vines,” said KVH.
“These reports highlight the biosecurity awareness and vigilance of our industry.
“This reporting demonstrates industry engagement and raises awareness of threats to our honeybee and wild bee populations.”
KVH said identification of unusual wasp presence is valuable on growers’ sites, as wasps pose health and safety risks for orchard staff and contractors, and place additional pressure on honeybee pollinators.
When observed, growers were encouraged to contact their local beekeeper for advice.
Recent Manaaki Whenua - Landcare Research projects indicated that 8-9% of honeybee hives in New Zealand were destroyed or seriously damaged due to wasp attacks on foraging bees and hive robbing.
Regional councils could also guide wasp management options.
Bay of Plenty Regional Council said while less aggressive than German and common wasps, Asian and Australian paper wasps prey on insects and chew weatherboards.
They were classified as “advisory pests” by the council – “established within the region and are known to negatively impact on environmental, production and/or public values”.
These pests were not the subject of programmes and rules in the Regional Pest Management Programme, but the regional council does provide control advice.
“It is the landowner/occupier’s responsibility to manage these pests,” the council said.
Professional pest controllers are recommended.
The council said insecticide needs to be strategic and well-coordinated, or results would be limited.
Wasp nests were sprayed at dusk when the majority of wasps are back at the nest.
KVH said reporting of potential yellow-legged hornets or their nests remains important.
“If anyone sees any suspected hornets or large aerial or concealed nests, they should take photos and make a report.”
Call the Biosecurity New Zealand hotline on 0800 80 99 66 or email info@mpi.govt.nz
Tauranga Moana Biosecurity Capital, of which KVH was part of, has organised a free yellow-legged hornet response update next month.
As part of its Connect & Protect Series, TMBC will be hosting an online session on Thursday, May 21, at 1pm, with a speaker line-up including Mike Inglis, northern regional commissioner for Biosecurity New Zealand.
He oversees border clearance services, the national detector dog programme and major projects such as the new Auckland Processing Centre.
Also speaking will be Professor Amanda Black, director of Bioprotection Aotearoa, a national Centre of Research Excellence (CoRE) that leads innovative bioprotection research framed by Māori values.
The centre partners with seven organisations to develop scalable, science-based solutions for biosecurity and ecosystem protection, supporting both environmental sustainability and the Māori economy.
Black is a professor at Lincoln University, specialising in soil chemistry, biochemistry and microbiology with a focus on ecosystem resilience and indigenous knowledge.
Visit TMbiosecurity.co.nz to register.