AgResearch's Map and Zap device is a glimpse of a future without herbicides

While we're concentrating on a predator-free New Zealand, rampant weeds are choking the life out of our native species - and we can't keep using chemicals on them.

The search for a way to deal with New Zealand's $1.7 billion weed problem - without relying on herbicides - has thrown up a solution straight out of the future.

If the AgResearch invention can be developed commercially, expect to see drones cruising paddocks and vineyards to swoop on weeds, blasting them with a laser bolt of intense heat to kill them instantly.

You can watch a video of it here:

https://www.youtube.com/watch?v=yiByGS-SiBU

AgResearch principal scientist Dr Graeme Bourdôt was involved in the 'Map and Zap' programme.

"It certainly is a novel way of killing weeds," he says.

"The idea is that you map a species from the air with a camera mounted on a drone... that same drone may also be carrying a laser which can fire a shot at the weed and kill it.

"I think the idea has potential in certain areas of weed management, particularly perhaps in natural environments where you've got very difficult-to-access sites, say down bluffs where currently we have people abseiling down to dig out some plants.

"I can imagine Map and Zap being potentially a much safer replacement for that method of weed control."

Whether it becomes mainstream for managing weeds in crops or pasture remains to be seen.

"In those cases we are talking about hundreds, if not thousands of weed plants per square metre," says Bourdôt.

Today on The Detail we look at why these unwanted plants pose such a danger to the economy, why we have to cease our national love affair with herbicides, and what other methods we could use to rid ourselves of weeds.

For example, Stu Loe is a farmer from the Scargill Valley in North Canterbury who is trialling the use of a leaf-eating tortoise beetle which kills Californian thistle.

It's been about 10 years since their introduction.

"We've still got them and they're chipping away," he says. "It's not going to happen overnight, but I am seeing reduced numbers where we've released them."

Loe hasn't used herbicides for thistles for about 15-20 years, saying the spray drift could damage the crops at nearby vineyards.

He's confident that the beetles won't spread beyond the thistle, because that's all they eat. …

Go to this episode on rnz.co.nz for more details