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Two insects to be introduced from Europe to help tackle invasive wasp problem

For decades New Zealand's invasive wasps have had the run of the place, with no natural enemy to control the growing numbers. But that's about to change, with the green light given today to introduce two insects from Europe to take on the pest.

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A beetle and hoverfly will battle the wasps, which are damaging the environment. Source: 1 NEWS

The Tasman District Council, which has a big wasp problem, applied for the bio control agents, a hover fly and wasp-nest beetle.

The regulator, the Environmental Protection Authority assessed their safety.

"The reason why it's safe is because these two insects only attack wasps and that's been established both where they come from in Europe but also elsewhere," said Chris Hill, general manager of hazardous substances and new organisms.

Invasive German and common wasps, have overrun biodiversity in native forests and inflicted financial pain on farmers and beekeepers, costing them about $70 million a year.

Beekeepers' hives are often decimated by wasps.

"They'll sit on the outside of the hive and work their way in, they will kill the larvae because they're protein feeders and they'll kill the bees, but then they also steal the nectar as well," said Wendy Lane a beekeeper near Nelson.

The German wasp came here in the 1940s, stowed away on aircraft parts, while the common wasp arrived in the 1970s.

"When the wasps arrived here, they found a wasp utopia, as it were they had no real natural enemies here. They left all their parasites behind, and they also found an abundance of honey dew," said insect ecologist Richard Toft.

But "wasp utopia" is in for a shock.

The hoverfly and beetle will both target wasp nests.

"The hoverfly manages to get in there and lay eggs in the nest and their larvae eats the wasps larvae, so if you get enough of these parasites in the wasp nest, they can have an impact on the population of wasps," said Toft.

The Tasman District, with its honey dew covered beech trees, has the highest density of wasps nests in the world, with between 30 and 40 per hectare.

The wasps have monopolised the honey dew, depriving other insects and animals of a food source, disrupting the ecosystem.

Wasp expert with Landcare Research, Bob Brown called the introduction of the new insects "monumental" for conservation.

In the 1980s and 1990s, an attempt was made to suppress wasps numbers with the introduction of smaller wasps from Israel and North America but it didn't work.

The new beetle and hoverfly are expected to be effective, but the question is just how much?

"It's not a silver bullet, but it's one tool in the tool box," said Paul Sheldon, the Tasman District Council's biosecurity and biodiversity co-ordinator.