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April 2018 Issue
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Vulgar wasps

Dr Phil Lester hopes New Zealand will one day be free of wasps. Photo: Grant Maiden
Entomologist Phil Lester has written a book about one of the tramper’s least favourite animals – wasps. He says these clever and skilful predators must ultimately be controlled.

Why a book about wasps? 

As I’m sure any hiker would be aware, we have massive densities of wasps in New Zealand – they are hyper-abundant, some of the highest densities known in the world occur here. They are a massive problem, both for biodiversity and people.

Why are wasps so abundant here?

A wonderful climate, believe it or not. In Nelson Lakes, we’ve got about one million hectares of honeydew beech forest and that really fuels the wasp population. Lots of sugar for them. New Zealand is an area where we didn’t have social wasps or bees until they were introduced, so there’s also an element of a lack of competition. But they really like the climate here. We can have perennial nest development – nests that don’t die off over winter – and they can become massive.

What does it mean to be hyper-abundant?

In Nelson Lakes we’ve sampled up to 40 nests a hectare. That’s an amazing number of wasps. If you can imagine each of those has between 5000 and 10,000 workers in them, that’s a lot of wasps.

What impact have wasps had on native birds?

They pester them and sting them, but wasps are also very much able to beat them to the resources. When you get a high abundance of wasps, the instant a resource becomes available, rather than a bird finding it, a wasp will find it.

Will your book change trampers’ attitude towards wasps?

I hope so in some ways. Even though they’re an invasive species, a big part of the book was trying to figure out if they’re actually a pest and do they do harm to NZ. That’s something worthwhile thinking about. There are benefits to having wasps: they are a major predator and will go after pests in horticultural crops. So they have these costs and these benefits. What’s the ultimate harm and should we do anything about them?

You suggest a gene drive is the best way to control wasps. Why?

We’re not going to be spraying a million hectares of our native forests with pesticides. What we’re going to need is something that is self-sustaining and able to control populations over a really large area. The best options are either biological controls – introducing a predator or a parasitoid that will kill the wasp – or a gene drive. Those have been theorised to be able to eradicate a pest species from a country. If we could get rid of wasps safely and effectively with minimal cost, the benefits would be huge.

What are your feelings towards wasps?

I have a certain admiration for them. They are really smart – they’re able to recognise human faces, they can follow a pheromone trail left by an insect in order to attack and eat it. They sting certainly and they will defend their nest vigorously, but they’ve evolved to do that because in Europe, where they come from, badgers and bears that will try to eat their nests. It’s not their fault they’re here.

But certainly if I finish my career and there are no more wasps in New Zealand, I’d be quite happy.

What’s the best way to flee wasps if you stumble on a nest?

The best thing is to be the person in the lead so that if you stand on a nest then the wasps will come out and attack the person behind you. If you can always take somebody tramping who runs slower than you, that also works pretty well. You have to watch where you put your feet and should you stand on a nest you have to remove yourself. Blue clothing seems to be attractive to them. Green clothes – drab green – is great.

– Lester’s book, The Vulgar Wasp, is published by Victoria University Press this month.