Kauri Dieback: Death in the Ngahere
This episode of Project Mātauranga looks at the steps being taken to address the spread of kauri dieback disease. Kauri dieback disease could decimate the iconic forests in the north of New Zealand and push kauri, the giant of the ngahere, to the brink of extinction.
Note that the pathogen Phytophthora agathidicida used to be known as Phytophthora taxon agathis (PTA) when it was first identified in 2008. This former name is used throughout this video.
Transcript
Dr Ocean Mercier
Māori have always been scientists, and we continue to be scientists. Our science has allowed us to live, work and thrive in the world for hundreds of years. My name is Dr Ocean Mercier, and I’m a lecturer in pūtaiao Māori at the Victoria University of Wellington. My job takes me all over the world to talk about Māori science and how traditional knowledge is being married with western science here in Aotearoa in order to find innovative solutions to universal global issues. In this programme, we’re going to show you how these worlds of science are intersecting and how the paths to our future are being formed.
Kauri are a tuakana species in Aotearoa, and our forests are among the oldest in the world.
These forests once covered over a million hectares from the Far North to Te Kauri, near Kawhia. Engari, ka matemate ngā ngahere nei i te kaha turakina e ngā Pākehā tuatahi ki tēnei whenua. (However, the population was decimated by intensive felling during the early period of colonisation.)
Today, only about 142 hectares remain, and though these days it’s a protected species, kei mua tonu i te kauri tētahi wero hōu wero nui hoki (the kauri faces a new and even greater threat).
Ko te kauri dieback, Phytophthora taxon agathis, PTA rānei, koia te tipu moroiti kei te patu i tēnei momo rākau taketake kia korehāhā haere (Commonly known as kauri dieback, Phytophthora taxon agathis, or PTA, is a microscopic plant pathogen that threatens to wipe out the species).
Nā tēnei whakaweti, kua kotahi mai te Manatū Ahu Matua, Te Papa Atawhai, Manaaki Whenua, ngā kaunihera e whā o te rohe me ngā iwi o te Ika-ā-Maui, ki te tohu i kauri i te ara o te moa. (It’s a threat that’s brought together the Ministry for Primary Industries, the Department of Conservation, Landcare Research and four regional councils, who are working alongside North Island iwi to save the kauri from extinction.)
Kei roto te uri o Ngā Puhi a Ian Mitchell i te ranga e noho takawaenga ana ki ngā roopu whai pānga ki te hōtaka. I te rā nei, kei te haere a Ian i tana kāinga i Hokianga ki Waitakere ki te tirotiro i te āhua o ngā ngahere kauri. (Ngā Puhi descendant Ian Mitchell has been part of that team, liaising between the many partners of the programme. Today, Ian is visiting Waitakere from his home in the Hokianga to check on the area’s kauri forests.)
Ian Mitchell
What scares us with this disease, it has the potential to wipe out the kauri. Te taha o mātauranga Māori, ko te kauri te rangatira, te kauri te whakaruru hou o ngā mea katoa. So the kauri is the shelter or protector of many other species, and all of these other species are sheltered by the kauri. Tēnei te ahua o te rangatira – this is how rangatira are, they protect and shelter the many other forms of life. You take out the kauri tree from that scenario, and potentially our whole bush changes as we know it.
Dr Ocean Mercier
Kauri dieback, also known as Phytophthora taxon agathis or PTA, is a microscopic plant disease spread through soil. The disease, which infects kauri through its roots, causes lesions on the trunk and yellowing of the foliage. Every kauri that contracts the disease is eventually killed.
Kei Maanaki Whenua i Tamaki Mākaurau, ngā kaipūtaiao e rangahau kaupapa ana e taea ai te mate nei te pēhi. Kei te rangahau a Tākuta Stanley Bellgard, me pēhea rā te rapu i te mate nei i roto i te one – nā te mea, kāore i te kitea i ētahi rākau, ahakoa kua roa pea e pāngia ana (At Landcare Research in Auckland, scientists are searching for ways to contain the disease. Dr Stanley Bellgard has been working on ways to detect the disease in the soil as the trees themselves may show no symptoms of the disease for years after infection.)
Dr Stanley Bellgard
The way we detect Phytophthora taxon agathis is via a bioassay where we use bait tissue – so these are plant, pieces of plant material to basically fish the Phytophthora out of the soil. And we take advantage of the ability of these spores to swim through water, and they swim through the free water that we provide in the bait box. In the bush, the Phytophthora parasitises the living tissue of the kauri. We use an artificial media to enable the Phytophthora to grow out. And we can see that the organism has colonised the bait tissue and has now grown out from that bait tissue. But the most challenging aspect of this organism is that it is microscopic and so it remains hidden in the soil.
But let’s go have a look at it under a compound light microscope. On that agar plate, there are close to 100,000 oospores. So the potential for Phytophthora is its ability to lay down many many resting residual structures, and this is how they perpetuate themselves in an infested site. And that is the challenge to us is how to control it, because as they sit in the soil, they have the potential to cause infection.
We’re working in the conservation estate, and so the particular types of chemicals we use, we can’t kill and cure here, we have to be aware of the other biota, the other living entities that are in the soil, because some of those entities are actually symbionts of kauri, live with kauri. So we have to be very selective about how we go about managing this disease.
Ian Mitchell
We can see hundreds of trees affected by kauri dieback disease and including this tree, which is probably a 500-year-old tree. The disease enters the tree through the fine feeding roots, which come right up to the surface of the soil, rots out the cells that are transporting the nutrient and the water from the roots up into the foliage. And in around the base of the tree, you’ll start to see the symptom of gum bleeding – that’s the tree’s reaction to the disease, it’s trying to push the disease out, but it doesn’t seem to be working. If the Phytophthora had been working, you know, had been living in conjunction with the kauri, they would have some sort of a relationship. We’re not seeing any of that sort of relationship. The kauri always dies, so is every kauri tree that we know of that’s contracted the disease dies.
For those of us that are working with this problem, with this challenge, it affects us actually at a spiritual level. From a Māori point of view, you know, these are our brothers, you know, we whakapapa to the same place. Just from a Kiwi point of view, this is a the Kiwi icon – this is up there with the All Blacks and Tāne-mahuta, the kauri, so you know, it’s affecting who we are as a people both from an indigenous point of view and from a contemporary point of view.
It’s really, really sad. I’ve taken many people to these trees and watched people cry, see people say prayers in English and in Māori for the health of the tree, to support the tree. When you see big old trees like this that die, that’s the one that really gets you, it’s the one that to imagine that this tree has been standing for 500 years before you and I were even a twinkle in anyone’s eye and to think that this disease wasted this tree very quickly. It’s a scary thought.
Dr Ocean Mercier
The potential for kauri dieback to annihilate the species has now been realised, and its impact on the forest environment could be catastrophic. A containment strategy seems to be the way forward, i ngā kaipūtaiao e rangahau ana me pēhea te aukati (while scientists search for ways to halt its spread).
Kauri dieback is a microscopic disease that threatens to destroy our country’s kauri forests.
With no known cure, containment has become the focus for saving kauri from the disease.
Kei Maanaki Whenua a Tākuta Stanley Bellgard e tumanako ana, kei roto i ngā rākau e ārai ana i te mate nei, te rongoā mo te kauri dieback. (At Landcare Research, Dr Stanley Bellgard hopes the answer to fighting kauri dieback can be found in other species that appear to be immune to the disease.)
Dr Stanley Bellgard
So our research not only focuses on New Zealand natives, but we’re also looking at other species of Agathis. And we have tested Phytophthora taxon agathis against Queensland kauri – Agathis robusta. And we have plants that were inoculated 3 years ago that are still living, so Queensland kauri is resistant to Phytophthora taxon agathis. Can we leverage or can we take advantage of these sorts of things that are occurring in other countries and transfer them across to New Zealand? That remains our challenge.
Ian Mitchell
If this disease is such that it stays in this country, that we can’t actually eliminate it from this land, then the real pressure will be on us trying to contain it within the areas that it is known and to try and stop it from spreading to areas where we know it’s free of the disease.
The long and the short is this disease will spread with soil movement. Anything that moves a lot of soil carries high risk of moving the disease. You know, it only takes – if each person takes out of here half a gram of soil and treks into Northland next weekend, we could have that disease spread very quickly throughout Northland, so we’re really concentrating on our ability to contain the disease right now – give our scientists a chance to come up with the cure or a way of halting the disease – and in the meantime, the onus is on us personally, individually and as communities to try and contain the disease, to try not to move soil from one place to another.
Dr Ocean Mercier
Kua uru te mate kauri dieback ki ngā ngahere maha o te raki o Tāmaki-makau-rau. Pēra i te Waipoua te tūrangawaewae o te kauri rongonui o te motu – o Tāne-mahuta. (Kauri dieback disease has infiltrated many forests north of Auckland including the Waipoua Forest in Northland, home to our most iconic kauri – Tāne Mahuta.)
Dr Stanley Bellgard
We were engaged to test the efficacy of TriGene. TriGene is a quaternary ammonium compound that has been used successfully to manage Phytophthora cinnamomi dieback in Western Australia. We tested a 2% solution of TriGene, and TriGene at 2% kills mycelium and kills zoospores. However, there is the other side to PTA and its ability to form long-lived, thick-walled oospores, and these are more resistant to TriGene, so then the challenge remains that the presence of the organism stays in the soil and so we have to look towards how we can help the tree fight this disease.
Hori Parata
We just got our whanaunga and are teaching them how to go and look at this disease, look at trees, because as you know that kauri trees, they’ll bleed. They’ll bleed because that’s what they do – they bleed gum out all the time. When you look at the disease of the Phytophthora, Phytophthora actually travels through the roots – travels through the roots of the tree – and it gets up to just above the ground, and then it’ll hit it there. It’ll hit it in what they call the cambium part of the tree, you know, and it’ll get in there. And of course, it’ll start bleeding, and it looks really severe, it looks really sore actually. And that’s what it’ll do, it’ll eventually eat all the way around that base of the tree and ring-bark the tree, and that’s how it kills the tree.
You know, and people are going into the forest 24/7, night-time and all, you know, you’ve got these walks and they’re wandering around in the forest, and we’re saying that, hey, you know, that’s not right. You know, our tūpuna were very careful about how you went into and came out of the forest. You made sure that you were clean when you went in, you made sure you were clean when you came out, and you did that not only physically but in terms of cleaning your wairua and all of those things as well.
Ian Mitchell
OK, so we’re coming up to a cleaning station. The best protection we have at the moment is to try and stop the spread of the disease. So what we have is brushes. The main thing is try and take as much soil off as you can before using this disinfectant – this is called TriGene – and just give your shoes a good coverage to disinfect the bottom of your shoes.
TriGene is a disinfectant designed to kill the zoospore. We’re still working on research as to whether it kills the long-term survival mechanism of this disease. It also has a penetrant, which gets right into the soil that may be left on your shoes. What concerns us about these cleaning stations where they’re situated – we’re asking people please, please use them. Currently, the compliance rate on these cleaning stations is between 20 and 50%. That means up to eight out of 10 people are not using this cleaning station. That really concerns us. The only thing we have to stop this disease at the moment, cause we have nothing to cure the disease – all we can do is to stop it from spreading. Please use the cleaning station.
Dr Ocean Mercier
Scientists like Dr Stanley Bellgard are still struggling to identify which forests have been affected and are looking for a cure that could be widely used in a forest environment. But Dr Ian Horner at Plant & Food believes he could have found a way to halt the disease in individual trees. Hei muri i ngā whakatairanga ka tūtaki tātou ki a Tākuta (After the break, we meet) Ian Horner and look into some mātauranga about the forest that could help save the kauri.
Kia ora tonu ai te kauri i tōna manawakioretanga (With the survival of kauri in the balance), scientists, councils and iwi have joined forces to try to save the iconic tree. After a visit to Waitakere, Ian Mitchell’s been confronted by a forest environment that’s reeling from kauri dieback disease, but things are far worse in Albany, where he’s visiting with Nick Waipara.
Kua tau te māramatanga kāore e taea ēnei rākau te whakaora. Hei taa Nick Waipara, Ko te raranga i ngā momo kete mātauranga katoa te huarahi whakamua. (The sobering reality is that these trees are beyond saving. Nick Waipara believes that combining knowledge systems is the way forward.)
Nick Waipara
Well this disease is really unusual because it’s also unknown. Like a lot of our pests that we’re fighting in Aotearoa – our possums, our weeds, kiwifruit vine disease – we know a lot about their basic biology, whereas this thing, kauri dieback, we have a lot of – we don’t have a lot of knowledge. So therefore, how do we manage it? How do we stop it? So that basic biology is really important. Fundamentally, what is it? We don’t know, so we need to know.
Dr Ocean Mercier
Ahakoa te korenga o tēnei momo mātauranga, kua wāhi angitū tonu te rautaki a Tākuta Ian Horner, e pōpōroa ai, e mutu ai rānei te horapa haere o te mate nei ki tēnā rākau, ki tēnā rākau. (Even without this knowledge, Dr Ian Horner from Plant & Food has had some success with a technique that seems to slow or even stop the spread of the disease with individual trees.)
Dr Ian Horner
Phosphite is a fairly simple chemical. It’s been used in the horticultural industry for many years, probably since probably about the 1980s. It’s been widely used in horticulture for treating plants, trees that have got Phytophthora diseases. The process we’re using within kauri is very similar what has been used in the avocado industry.
Right, so these are spring-loaded syringes, and we fill those with a phosphite solution, and then as you draw the liquid into them, you can then twist the handle and it locks, so it stays in there ready to go. We then drill a hole into the tree. First of all, we calculate the volume that the tree will need, and that is based entirely on the size of the tree. At this stage, we’re trying about one injector every 20 centimetres of circumference, which is a formula that we used in avocado trees and has worked well, but it’s certainly experimental at this stage with kauri.
It moves throughout the tree, right up into the leaves and then back down into the root system, and there it should do its job and fight the Phytophthora. The way it appears to work is that it’s first of all slightly fungicidal towards Phytophthora and related organisms, but it’s quite specific to that group. But it also helps the trees to actually fight the disease, and one theory as to how that might work is that it weakens the pathogen just enough so that the pathogen releases molecules, so instead of sneaking under the tree’s radar, it’s actually protected by the tree, so the tree is able to put up its own defences to it.
We started off with some glasshouse trials, just as – using small seedlings, 2 or 3-year-old kauri seedlings growing in the glasshouse. We inoculated them with the PTA pathogen, and some trees we treated with phosphite, and we injected using a hypodermic needle. The untreated trees all died, every single seedling died within a few weeks of inoculating the pathogen. The trees that we injected with phosphite, the vast majority of them survived. If you go into a kauri forest, then it’s a totally different system, you’ve got a huge scale to deal with, so I don’t see this technique being a particularly good technique for right across kauri forests.
Dr Ocean Mercier
Nō ngā rautau ki muri, te mātauranga mo te kauri i Te Tai Tokerau. Engari, kei tēnei mātauranga pea te rongoā kāore i te kitea e ngā kaipūtaiao. (In Northland, knowledge of the kauri spans back centuries, and some of the ideas are radical, but this knowledge may hold a key that’s eluded science.)
Will Ngakuru
Looking at the overall forest and then looking specifically at kauri dieback and the issues related to that, I think one of the things our people have been discussing is the tools we would have traditionally used to manage something of a similar nature – degradation to a certain resource – and quite often, that would be to give it a time to recover, to rest it. You know, rāhui has always been for Māori an effective tool. What’s been proven internationally is that, in responding to, you know, Phytophthora incursions and other incursions, that quite often placing a closure on an area – it’s become standard best practice internationally – closing off clean areas gives some … you know, it’s one way of protecting it and also closing off areas that are infected and then allowing them, like I said, time to observe the area and respond to the area has been really beneficial.
Rāhui gets misconceived by our point of view, especially in the media, we get, you know, front page headline that says Māori, you know, want to ban people from doing this, doing that, and it’s … people have taken it out of context. It’s important that people understand the context in which rāhui exists as different to closure that maybe a government agency might put in place. It’s complex, but it’s also simple.
Nick Waipara
A lot of what’s happening in the universities and CRIs is really important research, it’s really fundamental research. It’s taking it right back to what this organism is. But what we also are needing to know is how the whole ecology, how the whole forest, how the whole ngahere interacts, how it grows, and a lot of that holistic principle of the health of the forest is really important as well alongside, and in fact, I think a lot of the mātauranga and the knowledge around how our ngahere work, which is generations old, will also provide valuable answers to restore, to protect our kauri. So it’s equally important that that holistic and mātauranga Māori knowledge is incorporated into this programme, and there’s going to be a lot of answers come forth from that way as well.
Side by side, western science and mātauranga will I think give us some really exciting ways to protect our kauri.
Dr Ocean Mercier
Hei tā Ian, ko tēnei mātauranga te mere pounamu e patu ai tātou i tēnei mate. Mēnā ka titiro ki te mahi a te kauri dieback ki Okahukura, me kakama ka tika. (For Ian, this knowledge is a key component to overcome this devastating disease, and witnessing the effects of kauri dieback in Albany has been sobering.)
Ian Mitchell
We come into an area like this, a relatively small area, a lot of kauri, a lot of young what would normally be healthy regenerating youth of the kauri world, and instead we’re surrounded by death, and it’s disturbing to be – like being in an urupā, like being in a cemetery.
That makes it really imperative that we take whatever steps we can now to learn about the disease and to see what we can do to eliminate it altogether from this land in the meantime, so that we can give our scientists time in terms of learning about the fundamental biology of the disease – the stuff we don’t even understand yet because it’s all new to science. And at the same time, we have our mātauranga Māori, the whole world view of a healthy forest, healthy ecology, and giving our people time to also absorb what’s happening and to apply our traditional knowledge to this problem, to this very, very serious problem.
Dr Ocean Mercier
Kauri dieback has only recently been identified, and the fight to save this taonga of the ngahere is in its infancy. At this stage, identification and containment is key, hēoi, mā te kōmitimititanga o te mātauranga Māori me te pūtaiao Pākehā (but with the merging of mātauranga Māori and western science), it’s hoped that the kauri will survive.
Acknowledgements Video courtesy of Scottie Productions. © Scottie Productions, 2013.
