25 Feb 2019

Computer technology measures forces behind kauri dieback

6:45 pm on 25 February 2019

Computer technology is helping scientists to better understand the diseases that are threatening our native flora.

A rāhui has been in place by local iwi Te Kawerau ā Maki at Waitākere Ranges from earlier this year.

A rāhui was put in place by local iwi Te Kawerau ā Maki at Waitākere Ranges last year. Photo: RNZ / Dan Cook

Researchers working in the laboratory are measuring how kauri dieback and myrtle rust penetrate the plants and have found these organisms pack a punch.

It has been a decade since the discovery of kauri dieback, which kills almost 100 percent of the trees it infects - but there is still no cure.

Biosecurity New Zealand's recovery and pest manager John Sanson said comprehensive surveillance revealed the extent of its spread.

"Where we've seen the greatest of detections of the disease to date have been areas such as the Waitakere Ranges Regional Park in Auckland, small number of sites in the Coromandel and a number of sites throughout various parts of Northland," he said.

The disease can be spread by just a pinhead of soil, which is why kauri forest visitors are being told to scrub and disinfect their shoes and stay on the paths.

John Sanson said science was playing a fundamental role in the search for new tools.

"We need the science to come up with some answers, we've seen some promising results to date from research into the use of phosphite injections as a measure to protect individual trees, but we need to sustain the search for other tools," he said.

An example chip on a microscope slide.

An example chip on a microscope slide. Photo: Supplied

University of Canterbury's senior lecturer in electrical and computer engineering, Volker Nock has been part of a project that focuses on how the spore drills into the trees.

He's been working closely with associate professor Ashley Garrill, a fungal biologist, to figure out if scientists could interrupt that process, which could stop the disease getting a foothold.

"We're interested in how to generate that force and can we actually influence the force that it generates, using some form of bio-control agent for example," he said.

In order to do this, Dr Nock has used a special computer chip to measure those forces - and has now worked out how the spore penetrates.

"It involves structures that look like translucent tentacles that grow out of this single very small ball that lands on the leaf.

"These structures then physically push, by growing or extending themselves, push through the skin of the plant, whether that's on the leaf or on the root to get into the individual cells that make up the plant and suck the nutrients out of them," he said.

He added for such a tiny organism, the force created is quite significant.

What it looks like when the fungi starts growing lots of these drill bits (hyphae) on the chip.

What it looks like when the fungi starts growing lots of these drill bits (hyphae) on the chip. Photo: Supplied

The next step will be to investigate other plants that have resistance to these spores.

"There's a pepper bush that has been known to have anti-fungal properties that Māori people have known for a long time and it has been studied in the New Zealand science context, but no one has looked at it in terms of force generation for example."

This technology could help create new treatments for both kauri dieback and myrtle rust.

One of Dr Nock's students was also looking for funding to investigate the electric fields of a tree's roots, which could be attracting spores.

"Something we want to do is characterise what electric fields, voltages or strength of electric field will attract these spores, how these spores identify certain trees from others and then swim towards them to infect them," he said.

The project will take a couple of years, but could in the future lead to electrodes being planted as decoys, to protect the trees from incoming spores.

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