Time to wipe out wasps

In December, Stuff’s Marlborough newsroom teamed up with colleagues over the hill in Nelson to help launch the next chapter of Wasp Wipeout, a community-led conservation project that aims to significantly reduce German and common wasp populations in the Marlborough Sounds, Nelson Lakes, NelsonTasman and other areas this summer. To help explain why, Jonathan Carson reports on the devastating impact of vespula wasps on our environment, people and economy.

Here, in New Zealand’s native beech forest, war is being waged.

In the height of summer, you can hear it— the drone of vespula wasps ransacking the forest. It drowns out the songs of native birds— tui, bellbirds, kaka.

It puts fear into families trying to picnic on the stony shore of Lake Rotoiti, trampers venturing into the bush, and mountain bikers hitting the trails.

The wasps’ hum, the white noise of the forest, is a constant reminder that they— the foreign invaders— are winning.

They are having a devastating impact on our native birds, bats, lizards and insects, exploiting the most valuable food sources of the forest and entirely altering New Zealand’s natural biodiversity.

These wasps are also a serious threat to people, delivering painful stings that can cause lifethreatening allergic reactions and — in extreme cases— death.

A VILLAIN OF THE FOREST

The German wasp ( vespula Germanica) and common wasp ( vespula vulgaris) have been described as New Zealand’s most abundant and devastating invertebrate pests. To appreciate their impact on the environment, and our native species, we first have to understand how many wasps there are.

Studies have found that, at their peak, there can be up to 40 nests per hectare of beech forest. A nest can produce thousands of queens and thousands of workers, and there are about a million hectares of beech forest in the South Island.

Based on these figures, there could be up to 40 billion wasp queens in the beech forest at the height of summer, and many more workers.

Insect ecologist Richard Toft says the impact of that amount of wasps on the ecosystem has ‘‘got to be catastrophic’’.

‘‘We have a lot of talk about rats and stoats and mice and their impact on systems.

‘‘But put wasps in those same forests, the biomass of wasps exceeds the combined biomass of all the rats, all the mice, all the stoats and all the birds.

‘‘You simply can’t add that amount of biomass into an ecosystem and expect it to have no impact.’’

THE INVASION

The German wasp arrived in New Zealand soon after World War II, most likely on a ship carrying aircraft parts from Europe. It was first sighted near Hamilton in 1945.

A newspaper article at the time reported that ‘‘it appeared that the pest was now established in New Zealand and could not be eradicated’’.

The common wasp arrived in the 1970s, but Toft says genetic testing suggests there were up to 10 separate introductions.

Despite arriving later, the common wasp has largely displaced the German wasp in beech forests.

PHOTO: MARION VAN DIJK A container of Wasp bait used at the start Department of Conservation and Project Janszoon wasp control at Abel Tasman, partly funded by the Wasp Wipeout campaign.