Mystery fungus creeps near Northland kauri

Biosecurity authorities are investigating an alien fungus in Northland's kauri tree heartland, but do not yet know whether it is linked to dying kauri in West Auckland.

Biosecurity New Zealand has been testing kauri infected with a fungus at Maungaroa Ridge, near the popular west coast surf beach of Piha, since early this year.

So far 36 kauri have died and a further 90 are sick and expected to die.

A further 11 trees of varying species, including kanuka and northern rata, have died and around 40 are sick.

Yesterday the agency said it had found a new fungus in Northland at two sites, an orchard, and at Trounson Kauri Park, one of the North Island's most famous kauri stands, about 30 minutes drive north of Dargaville.

Biosecurity NZ spokesman George Gill said he did not know whether the detection of the fungus at Trounson was linked to infected trees in the Waitakeres.

"We have no evidence of that at the moment," he said. "We are aware of the infection out there [at Piha]."

He was not aware of any kauri at Trounson that had died from the fungus because so far it had only been found in soil at the 450ha forest reserve.

The fungus, Phytophthora kernoviae, was detected during routine testing and identified using new DNA techniques.

Mr Gill said it had so far been found on only one plant species, cherimoya or custard apple, in a Northland orchard.

It has been associated with stem die-back and "bleeding cankers" on a range of species, including oak, rhododendrons, beech, magnolia and other ornamental species in Britain.

Phytophthora kernoviae is a plant pathogen (a bacterium or virus or other micro-organism that causes disease) and an unwanted organism under New Zealand's Biosecurity Act.

The Auckland Regional Council principal ranger based at Arataki Visitor Centre in the Waitakere Ranges, Bruce Andrell, said MAF had taken further samples of fungus on kauri recently. "We're waiting to hear back."