Something is killing the trees

19:55, Jan 31 2013
kauri stand
Jeanie McInnes from the Waikato Regional Council, Lee Hill and Nick Waipara from the Auckland Council inspect Ted Burrows' garden for signs of disease.

Kauri trees in New Plymouth's Pukekura Park will today undergo a health check for a disease killing thousands of the much-admired native in the north.

Scientists will inspect a stand of kauri trees off Brooklands Rd in Pukekura Park for phytophthora taxon agathis disease (PTA), a microscopic fungus-like pathogen also known as kauri dieback or kauri rot.

Auckland Council biosecurity principal adviser Dr Nick Waipara said they were only monitoring the trees and did not suspect they were infected.

In 2009 some of the Brooklands trees were found with suppurating lesions at the base of their trunks and were tested for PTA, but it was found they were blighted with Armillaria sp, or honey fungus, which also rots wood.

The trees were treated with by drilling holes into the trunks and dosing them with phosphorus-based pills.

But there is no cure for PTA and nearly all trees infected with the disease die.


Dr Waipara said testing techniques for PTA had become more reliable since the trees were tested last.

Over the last decade PTA has killed thousands of kauri in New Zealand.

The disease prevents nutrients from being absorbed and can kill saplings in a matter of weeks.

The Waitakere Ranges are most affected by kauri dieback, with 11 per cent of the kauri population infected.

It has also been found in several forests in Northland, and Auckland and was first discovered in the 1970s on Great Barrier Island.

Dr Waipara came to Taranaki with kauri dieback research and operations specialist Lee Hill and Waikato Regional Council biosecurity officer Jeanie McInnes.

The trio yesterday visited the Fitzroy home of Ted Burrows, who was concerned his prized and beloved kauri tree could have the disease.

"About three years ago I noticed the top of the tree was dying and it's lost about 2 metres from it now."

Leaves on the tree were also turning brown and yellow, another symptom of kauri dieback.

Growing steadily more concerned, last year Mr Burrows got in touch with the Taranaki Regional Council who couldn't help him, but put him on to the Department of Conservation who came to take photos to send to kauri dieback experts and put him in touch with Ms McInnes.

After an initial inspection of Mr Burrow's tree yesterday, Dr Waipara said it was unlikely to have PTA as it did not have lesions weeping a phlegm-like substance around the base.

"I'm 95 per cent sure it's not, but to be 100 per cent sure we're taking soil samples."

They would know the results of the test in 6-8 weeks, Mr Hill said.

Dr Waipara said the disease mostly infected kauri plantations, but could also affect individual trees, especially ornamental trees that have come from nurseries.

He said knowing where infected trees had come from could help them trace the spread.

"We're trying to keep track of the points of origin."

Kauri dieback is spread mostly through soil, so in infected areas like Waitakere, people walking on kauri roots are encouraged to disinfect their shoes to prevent transporting the disease elsewhere.

"It's not going to blow down to Taranaki on the wind."

Mr Burrows said he had watched the tree grow since he bought it as a 7-year-old seedling from a nursery in Rotorua around 40 years ago.

"I'm quite attached to my little kauri tree."

Taranaki Daily News gardening columnist Glyn Church said kauri trees were not native to Taranaki and did not expect the death of those here would bother people much.

"I'd be surprised if anyone noticed."

Taranaki Daily News