What does it look like?
Common wasps are very similar in appearance to German wasps. In these species, members of the colony cooperate in the care of the young, and the building and protection of the nest. Females are easily identified by:
- a black mark behind the eye on the side of the head
- an anchor-shaped or dagger-shaped mark on the "face"
- yellow bands on the "shoulders" that are expanded centrally
- black dots and rings on the abdomen which are usually fused (this is very variable)
Why is it a problem?
New Zealand has some of the highest densities of social wasps in the world. Large densities have been observed in beech forests containing honey dew. Their natural enemies are not present here, winters are mild, and there is an abundance of food for which they can out-compete our native insects and birds.
There are a range of insecticides available from hardware and garden stores which have permethrin as the active ingredient. Follow the safety instructions supplied with the insecticide.
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. 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.
Once a nest has been located, place a dessert spoonful 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.
Alternatively, a targeted wasp bait is available from Nelson-based company Merchento. The bait, Vespex, was developed in conjunction with DOC, although we do not supply it. To purchase the bait contact Merchento. You will have to pass their online test before purchasing.
Note that Vespex may be used on public or private land, but members of the public wishing to carry out wasp control operations on public conservation land need to follow DOC's pesticide permission process.
- Biological control has been used to try and achieve widespread control of wasps. Since 1987, a parasitoid (called Sphecophaga vesparum vesparum) has been released at hundreds of sites throughout New Zealand. This parasitoid was brought from Europe where it attacks the same wasp species we have here. It lives in wasp nests, feeding on and thus destroying developing wasps. Other trials used include the use of pathogens.
Chemicals can be used against wasps in two ways - either finding and destroying all nests in the area, or using poison bait. The advantage of poison bait is that foraging wasps carry the poison back to the nest. This means you don't have to find and approach nests. Both methods will only alleviate the problem for the current season, and workers from further away are likely to turn up looking for food. In the next season, the area will almost certainly be reinvaded by queen wasps, which can fly from 30 to 70 kilometres before establishing a nest. The problem will therefore have to be dealt with each year.