health & science

Transgenic wasps could bring down their own kind

Would we accept transgenic insects if it meant we could get rid of wasps? A national research effort is dedicated to putting some new wasp-busting options on the table, reports Eloise Gibson.

If ever there was a creature that might persuade New Zealanders to consider releasing transgenic insects, wasps may be it.

South Island beech forests are thrumming with the invasive pests, which eat honeydew before birds can get it and kill native insects that would otherwise supply food to other wildlife.

A 2015 study for the Ministry for Primary Industries and the Department of Conservation estimated wasps directly cost New Zealand $78 million a year, mostly by hurting the beekeeping industry.

Wasps attack beehives, kill the bees and eat their honey and larvae, sometimes destroying a third of a beekeeper’s insects in a single year, says Phil Lester, the Victoria University insect ecologist leading a nationwide team developing wasp-busting technologies.

Combined with their nasty stings, wasps’ predatory habits have made them the focus of a 10-year project under the government’s biological heritage National Science Challenge.

The wasp-fighting methods go right to the divisive cutting edge of genetic technology, with new research aimed at designing transgenic wasps that return to their hives and inadvertently destroy their own communities.

The ultimate goal is not just quashing wasps, but using them as models to devise pest-culling measures that could work on possums, rats and other warm-blooded invaders. “We can use them as a model and a test species for a bunch of different technologies that we can then try on other species,” says Lester.

“It is much easier to make a transgenic insect than a (transgenic) possum,” says Peter Dearden, a University of Otago biochemist who has joined the wasp-fighting effort.

One of the options being explored is using a virus to switch off genes associated with effective foraging, or genes linked to harmonious social relations, so wasp communities would no longer function properly. While that technique wouldn’t change wasps’ underlying DNA, another option would: gene-editing the pests so they produce more male or female offspring. Another, non-GM, possibility is recruiting wild, forest-dwelling wasps that scientists believe carry naturally-occurring mitochondrial gene mutations that lower the males’ sperm counts or sperm-mobility. Researchers could then breed the infertile males in captivity and release them en masse to try to collapse the population.

A similar trend in wild tuatara – caused by warming temperatures – is skewing the sex ratio in favour of males and is predicted to one day make some tuatara groups functionally extinct. The same idea could be harnessed against wasps, only using genetic manipulation, says Dearden. “We think by manipulating genes to do with sex determination we might be able to change the proportion of males and females, and the modelling people suggest that might be a really good way to control the population,” he says. “We are currently doing experiments in containment in other insects to try and work out how we might do that in wasps before we go anywhere near a wasp.”

Males don’t sting, so releasing lots of males wouldn’t hurt people, says Lester. Yet other pest-control options being worked on are more traditional; like devising insecticides that kill wasps but spare honeybees and other insects.

The goal of the more novel experiments is finding techniques that the wasps will spread themselves, and only to themselves, so wasps get wiped out more effectively than by pesticides and other insects aren’t affected. “The vast majority of New Zealanders really despise these animals,” says Lester. “A big part of the work is to find ways of controlling pests that don’t interfere with other things. What we’ve done historically is rely an awful lot on pesticides and typically broad-spectrum pesticides, and using those in any environment you are going to have effects on whatever other organisms are around.”

Researchers are about to complete the sequencing of the common wasp genome, the first step towards being able to try switching off genes they think are linked to wasp behaviour, says Dearden. But there are risks – for example the researchers must ensure the wasps can’t pass any damaging effects to bees or other species. While they are a long way from making GM wasps, let alone asking for permission to release them in nature, both researchers say if there is ever a chance New Zealanders will consider okay-ing genetically modified creatures, wasps might be the pests to persuade them.

Wasps are smart as well as social: Lester has footage of them carefully plucking ants off their food and dropping them a short distance away, gently enough so they don’t get sprayed by acid, the ant’s defence mechanism. They are super-successful and ravenous hunters – which is why other insects in the forest don’t last long when there are a lot of wasps around, says Lester.

Dearden says researchers know from studying honeybees that they should be able to change wasp behaviour using a double-stranded RNA virus that the insects’ bodies see as an invader and shut down, switching off the gene in question. It would be possible to design a tailored version that didn’t affect bees or other creatures, says Dearden. Once the affected wasps were out there, their social natures might mean they would have wide effects on their kindred. “Because wasps have this complex social structure you can target an individual and still have these wider social effects,” says Dearden. “We are hoping you have a wasp that takes it back to the hive and causes some kind of collapse in the social structure of that community,” he says. 

“We need to develop a lot of solutions to work out which one is going to work best and also which ones are socially acceptable. [But] We would be foolish to think that the technical barriers are only ones to developing gene technology.”

The first four years of the national project will be spent coming up with a range of options for eradicating wasps better, with fewer harmful effects on other species. Then the researchers plan to pursue the best ideas for the remainder of the research period. Concerns about gene editing may mean people find it more acceptable to use options that don’t require releasing transgenic wasps, for example breeding the naturally-occurring males with low sperm counts. 

Ultimately, what people support might depend on the potential trade-offs and benefits, says Dearden. That’s what he hopes to be able to tell people more about after the next round of research. “We need information about what the risks and benefits are and how effective they are, because at the moment we are arguing in a vacuum. If I said to you ‘I’m going to release 20,000 GM wasps and it’s going to halve the wasp population in New Zealand you might not be enthusiastic, but if I said I am going to release three wasps and there will be no wasps left at the end of 20 years, you might view it better,” he says.

“Everyone hates wasps. It may mean people are willing to accept the risk of genetic modification to eradicate wasps. But we still have a long way to go. We have no method at this point for making a transgenic wasp.”

Phil Lester and Peter Dearden are speaking about their work on April 21 at Victoria University’s free wasp management symposium in Wellington. 

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