Kauri killer hits Rodney forests

SICKLY SYMPTOMS: This tree exhibits the weeping welts of a kauri with dieback disease.

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The kauri killing dieback disease has been found in Rodney.

It is on Conservation Department land and private property at Pakiri, in the Okura and Albany scenic reserves, on private property in Waimauku, and also on Great Barrier Island.

The plant pathogen, phytophthora taxon agathis, is found in the soil and attacks the kauri root system. It was originally identified as responsible for the death of kauri in the Waitakere Ranges, hits trees of all ages, and has no known treatment.

Spread appears to be by contaminated footwear and also by feral pigs, particularly with their natural rooting habit in the soil.

The pathogen is now known to have been in New Zealand 50 years, slowly causing deaths among kauri. Once the disease was identified in the Waitakere Ranges, the Auckland Regional Council immediately took action to reduce its spread and to identify how widespread it was. Signs, and disinfectant mats for shoes, have now been placed at all Waitakere Ranges entry points, and eight new hunters have been employed to blitz the wild pig population there.

"We really want people to cooperate with us so that we can limit where it is," says regional councillor Sandra Coney. "We have to do everything we can think of to stop the horror scenario of there no longer being a kauri forest."

The outbreak at Pakiri involves aboout 100 trees both on DoC land and private land. There had been reports of pig rooting activity in the area. The department has two blocks of bush and scrub land at Pakiri, each around 40ha.

Dr Nick Waipara of the Auckland Regional Council has visited the site and confirmed the pathogen. He briefed the Rodney District Council last week about the situation and possible actions by the region’s councils.

Symptoms of trees under attack from phytophthora taxon agathis include foliage yellowing, canopy thinning, appearance of dead branches, and tree death. Affected trees can also develop lesions that bleed resin.

A regional working party is likely to be formed to help raise awareness and introduce procedures to help prevent the disease’s spread.

Kauri is an ancient form of conifer that appeared between 190 million and 135 million years ago. While initially widespread during the Jurassic period, this genus is now found only in small areas of the Southern Hemisphere, including Borneo, Fiji, Australia and New Zealand.

New Zealand kauri only naturally grow from the Waikato northward and generally live to about 600 years, although many individual trees are thought to be up to 1000 years old.

Tips for trampers: Make sure you have clean shoes when you go into the Waitakeres; always wash your shoes and remove soil from the tread when you return; stay on the track, do not go into the bush or into streams because water can carry the pathogen to other parts of the forest; keep your dog on a leash at all times; report any suspicious signs on kauri to the Auckland Regional Council.

- © Fairfax NZ News