Four accidentally introduced species of social wasp are classified as invasive pests. Most often seen are the introduced German and common wasp, but the Chinese and Australian paper wasps are more recent arrivals.
The German and common wasp are very similar in appearance, and both have the characteristic black and yellow colouration. They live in large colonies, about the size of a soccer ball, but can become larger if they survive over winter. German wasp nests are grey. Common wasp nests are brown.
The Asian paper wasp and the Australian paper wasp build small nests, about the size of a pear.
Why are wasps pests?
Wasps are one of our worst pest creatures in New Zealand, making a huge impact on biodiversity - everything from birds to other insects. Sadly their impact is not well known to most people.
Wasps have no natural predators in New Zealand. With mild winters and warm springs around 10% of wasp colonies can survive and become even more plentiful each year, making heavier impacts on already vulnerable ecosystems.
In areas of honeydew beech forests the rate of predation of wasps on some species of invertebrates is so high that the probability of an individual invertebrate surviving through the wasp season is almost zero! Wasps probably reduce or even eradicate some populations of invertebrates.
Wasps eat a very wide range of invertebrates including spiders, caterpillars, ants, stick insects, weta, bees, and flies. It has also been suggested they prey on bird chicks. They have been known to eat meat and on carrion as well as sweet fruit and nectar, especially species in the weedy ivy family such as the commonly planted Japanese Aralia. Planting these in your garden will attract wasps during flowering season.
Wasp nests are built with wood fibre. Common wasps collect fibre from dead or rotten wood, while German wasps use sound wood. Often nests are built in darker, mostly dry places like attics, house roofs, eaves, walls and natural banks, but can be found on moist banks near water as well. It’s recommended to stay away from a wasp nest as mass attack can happen if the nest is disturbed. If you see a wasp nest in a public reserve or nearby either pass this information to us or Wellington City Council.
How to make a wasp trap
With free flying wasps a wasp trap is very easy to build and will make a huge difference. These can also be purchased at garden centres.
You will need:
- an empty two-litre plastic bottle with straight sides.
- a sharp knife.
- a steady hand.
Use your knife to cut off the top of the bottle, just below where the sides start to straighten. You’ll need both pieces so make the line neat.
Fill the bottom 2cm of the bottle with wasp bait: fruit juice and a piece of meat.
Remove the bottle cap and insert the top section, upside down, into the bottom section. The pieces should fit together snugly but use duct tape along the top edge to secure if needed. You now have a wasp trap!
Place the wasp trap upright where your pest wasps tend to be. Take precautions to secure it against that wonderful Wellington wind.
The wasps will fly into the trap to get at the bait but will have trouble finding their way out, eventually drowning in the liquid bait.