Kauri fungus found near forest giant

Kauri dieback (L) could affect ancient trees like Waipoua's Tane Mahuta. Photo / Northern Advocate

There are fears for New Zealand's most famous kauri, Northland's Tane Mahuta, after a deadly and infectious tree disease was found less than 500m from it.

DNA tests on a sick tree in the popular Waipoua Forest have revealed it is infected with Phytophthora taxon Agathis, or kauri dieback - a fungus-like infection that has been creeping through the remnants of ancient kauri forests.

Even more worrying to scientists is that the disease has also been found in a 600-year-old kauri in the nearby Trounson Kauri Park, a surprise finding that proves trees up to 1000 years old, with trunks 2m in diameter, could be at risk.

"It really does recalibrate our fears," said Landcare research scientist Stan Bellgard, who was part of the team that confirmed dieback in the Waipoua, Trounson and Raetea Forest in Northland.

"Up to this point we had seen it on ricker trees up to about 80cm [diameter] in the Waitakeres."

Dr Bellgard and Stephen King, of the Waipoua Forest Trust and Te Roroa iwi, want Government agencies to step up efforts to protect the home of Tane Mahuta before it is too late.

Te Roroa manages the Waipoua Forest with the Department of Conservation.

Until this week, councils and Government departments fighting the spread of kauri dieback had hoped to keep the disease out of Waipoua, where many of the country's tallest and oldest kauri live.

The area is in line to become New Zealand's next national park, and the only national park north of Taupo.

Mr King said Te Roroa kaumatua had long seen trees showing symptoms of kauri dieback but scientists have only just developed the necessary DNA tests to confirm it.

He was frustrated the department had been slow to replace walking tracks with boardwalks to prevent people walking over tree roots, and said it was doing little to kill off wild pigs that were trampling infected soil through the forest.

"It has meetings after meetings of talking about it but actually does very little," he said.

DoC spokeswoman Hilary Aikman said the pigs were an important resource to locals and it was not yet known how big a role they played in spreading the disease. "That is something we'll be looking at."

She said work was well under way to pull up the forest's network of gravel tracks and replace them with boardworks. "Clearly we are worried about Tane Mahuta and we'll do anything we can to protect that tree," she said.

The results are the first trial of a system Landcare Research is developing to confirm the presence of dieback.

The next stage is to survey the most iconic and at-risk forests to find out how many trees are infected.

Scientists do not yet know how to treat kauri dieback.

Ms Aikman said traditional fungicides such as those used on avocados and other commercial crops were not appropriate for kauri forests on conservation land because of the potential effects on other plants and animals.

Dr Bellgard said ancient kauri trees were "part and parcel of New Zealand's culture".

Run-down trees that were stressed by drought, water-logging or trampled roots were more likely to become sick, he said.

As well as being carried in soil, scientists believed dieback could be passed root-to-root from infected to healthy trees.