There are several kinds of native wasps in New Zealand which have evolved here and have never become a nuisance. In contrast there are now four social species which have been accidentally introduced in recent years and which are classed as pests.
Social wasps live as colonies in nests of honeycomb-like cells.
The Asian paper wasp and the Australian paper wasp build small nests, about the size of a pear. The Asian paper wasp has been found in the North Island and top of the South Island but the Australian paper wasp remains confined to the north of the North Island.
German and common wasps
The more widespread German and common wasps live in large colonies, about the size of a soccer ball, but which can become huge if they manage to survive over winter.
The German wasp was introduced with United States aeroplane parts in the 1940s and the common wasp arrived relatively recently but is now widespread. These two are very similar in appearance, and both have the characteristic black and yellow colouration.
German wasp nests are grey. Common wasp nests are brown.
The threat of wasps
Beech seedlings sprouting from a fallen tree. Wasps present a particular ecological problem in beech forest
New Zealand has some of the highest densities of German and common wasps in the world. They have no natural predators here, our winters are mild and there is plenty of food for them.
Wasps present a particular ecological problem in beech forest where they are voracious consumers of honeydew. In beech forests there is an estimated average density of 12 nests, or about 10,000 worker wasps, per hectare. This makes the biomass of wasps in these areas higher than that of all native birds, plus stoats and rodents, put together. Honeydew is produced by a native scale insect and is an important food for native birds, bats, insects and lizards.
Wasps also prey on insects and have even been seen killing newly hatched birds.
Wasps are a nuisance to forestry gangs, and a worry to tourist operators. They are unwelcome guests at summer picnics and barbecues. No-one finds a wasp sting a fun experience and some people have an allergic reaction.
DOC aims to:
- reduce the removal of valuable food sources for native animals from our forests by wasps;
- reduce predation by wasps on native invertebrates and bird nestlings so that the impacts of wasps are insignificant alongside other mortality factors affecting these groups; and
- improve the public’s experience when visiting public conservation land.
The Rotoiti Nature Recovery Project contains large amounts of beech forest, full of honeydew. Common wasps build up to high densities here in summer. This project is a good example of DOC's work with wasps.
You can help
The best way to reduce a local wasp population is to find and destroy all the nests in the area. Usually wasps fly no further than 200 metres, so you should aim to kill all the nests within this range.
How to find nests
If you search on sunny days, near dawn or dusk, the low light angles will highlight the flight path as wasps enter and leave the nest. You can put out a bait of cat food sprinkled with flour which will make the wasps easier to see.
How to poison the nest
Place a dessertspoonful of insecticide at the nest entrance after dark when the wasps have stopped flying. You can use a puffer bottle for this job. Worker wasps flying in and out will spread the powder into the nest and the colony usually dies within a day. If activity continues repeat the treatment until wasp activity ceases.
Don't shine your torch into the nest or wasps will fly up the beam.
What poisons to use
There is a range of insecticides available from hardware and garden stores. These include Wasp Killer Dust and Permex Insect Dust, which have permethrin as the active ingredient, and Rentokil Wasp Killer and No Wasps Insecticidal Dust, which both use carbaryl. Follow the safety instructions supplied with the insecticide.