College students key to stopping Kauri dieback in Warkworth

From left, board of trustees chair Dean Iversen, environment group leader Natalie Caldwell, Kauri dieback advisor Zacc Forbes-Smith and forest restoration coordinator Colin Binsted.

Kauri trees exchange nutrients with each other through roots which can, unfortunately, also spread dieback.

Mahurangi College has been working with Auckland Council this month to establish a kauri dieback management plan for the bush surrounding the Mahurangi River on the school’s edge.

The bush, along with a “living classroom” located inside, had to be closed off last year when one of the kauri trees was found to be infected with dieback.

Details are still being worked out, but the management plan will tentatively provide students with first-hand experience of being caretakers of a bush with dieback and preventing spread.

All kauri in the bush will be fenced off, preventing access to the trees, but there will still be work to be done, including pest trapping to prevent animals from spreading the disease.

The students will have to adhere to strict protocols, including removing footwear before entering the bush.

Dedicated footwear and tools will be stored in the living classroom and will not be removed. This is to prevent any possibility of dieback spores leaving the area.

Even within the bush, gardening tools used in one area will have to be washed with chemicals before being used in another area of the bush to prevent spreading the disease.

Auckland Council kauri dieback advisor Zacc Forbes-Smith gave a presentation to Mahurangi College staff and students to prepare them for their new roles as caretakers.

The main cause of the spread of kauri dieback is human interference, with 71 per cent of cases being within 50 metres of a walking track.

Dieback is spread by a spore that lives in the soil and can remain dormant for at least a decade.

“Ten thousand kauri dieback spores could fit on the head of a pin, and a speck of dirt on a boot could contain 100,000 spores,” Zacc said.

“It only takes a single spore to infect an entire forest and a spore could sit dormant on a boot in a cupboard for more than ten years.”

Kauri trees have feeder roots which spread along the surface of the soil and are extremely delicate and easily damaged.

The roots extend from the trunk and reach three times the length of the tree’s leaf canopy.

If they are broken by humans or pests, they release a pheromone which triggers dormant dieback spores to become swimming spores, which migrate to the tree.

“When the spores sense pheromones they morph and grow a proboscis which then injects enzymes into a tree, which sucks it all up like a milkshake,” Zacc says.

There is no cure for kauri dieback, although some programmes exist where kauri are treated with an injection of phosphite which slows the spread of the pathogen.

A common identifying symptom of kauri dieback is a yellow-red excretion, which usually starts close to the base of the tree where infection first occurs.

The tree senses the pathogen and attempts to flush it out by bleeding, but it is unable to because the dieback pathogen is in the soil.

Dieback is a Phytophthora (fungal disease), similar to the Irish potato blight, which caused famines in the 1800s.

The exact origins of kauri dieback are unknown but in the 1960s agathis plants, related to kauri, were brought from around the world and planted in New Zealand.

A pathogen similar to dieback was first found on Great Barrier Island in 1973 and it is believed then evolved into dieback.

Mahurangi College principal David McLeod said it was important to get students involved and interested in taking care of kauri to ensure their survival.

“We don’t want kids raised in a concrete jungle stuck on devices. We want them exposed to the natural environment,” he said.