Kauri killer now in Kaiwaka

A disease killing Northland's iconic kauri trees is spreading, a new infection being detected on private land in Kaiwaka.

Soil samples taken from a Kaiwaka farm have confirmed that kauri dieback is present in the soil and killing trees there.

Northland Regional Council biosecurity staff recently inspected the farm and collected the samples after the owner reported that kauri on his property appeared unhealthy and some were dying.

The NRC is part of a multi-agency government-funded response group working on a $4.7million kauri dieback management programme. The programme, which began in 2009, is charged with researching the detection and spread of kauri dieback and methods to control it, and developing a public awareness campaign.

Kauri dieback, or phytophthora taxon agathis (PTA), is a microscopic fungus-like plant pathogen of unknown origin, that affects only kauri. Symptoms include yellowing foliage, loss of leaves and canopy thinning. Trees can also develop lesions that bleed resin extending to the major roots and sometimes girdling the trunk as a "collar rot".

NRC acting chief executive Tony Phipps told the council's monthly meeting this week the owner of the Kaiwaka trees had been given information on controlling the risk of spread to other areas on his property. Biosecurity staff were also continuing to work in the Kaiwaka area to ascertain the extent of the disease.

He said the multi-agency response group (led by MAF, with Biosecurity NZ, DoC, NRC and the four regional councils covering the northern North Island area where kauri grow) had completed a major survey of 30 sites about three months ago. Soil analysis results were due shortly and the next stage would be an in-depth investigation of affected areas.

NRC chairman Craig Brown said the situation could be of grave concern to the North depending on the extent of the problem.

Councillor John Bain said the question in his mind was, could the disease be contained by felling the affected trees and taking out the roots? Don McKenzie, NRC biosecurity senior programme manager, said yesterday the focus of the response was to work out a strategy for containing the disease. The PTA pathogen had existed and killed kauri for millennia, and like other associated pathogens affecting other trees, seemed to be activated under certain conditions or combinations of conditions, and stressors on the trees. That could include human and animal disturbance. An associated pathogen also affected other species but was not always fatal. "It will be a very complicated set of circumstances and science is where the answers will be found," Mr McKenzie said.

Kauri dieback (phytophthora taxon agathis, PTA) How it spreads: By soil and water movement, plant-to-plant transmission through underground root-to-root contact, and human and animal contact.

Where: The disease has been isolated from soil in Northland including just 500m from the 2000-year-old famed forest giant Tane Mahuta of Waipoua Forest; in Rodney district and North Shore City; the Waitakere Ranges and Great Barrier Island.

What can I do to help stop PTA spreading? Make sure shoes and equipment are clean of dirt before visiting a kauri forest. Clean shoes and any other equipment that comes into contact with soil after every visit, especially if you intend to visit other bush areas. Keep to tracks at all times. Any movement of soil around the roots of a tree has the potential to spread the disease. Keep dogs on a leash at all times.

What should I do if I have kauri on my land? Minimise movement around kauri roots. Keep dogs and animals away from kauri as much as possible.

What should I do if I think kauri on my land have symptoms of PTA disease? Contact the Kauri Dieback Response Team on 0800 NZ KAURI (695 2874). Erect a warning sign to alert your visitors to the dangers of spreading the disease.

Will parks or reserves be closed? The Response Team says there are no plans to do so at this stage but it is something to be considered in the future.