Author Archive

Fighting crop pathogens with viruses

Wednesday, November 30th, 2022

Nils Birkholz presenting his research at a Bioprotection Aotearoa hui, at Ōnuku Marae, Canterbury


This year has been a big one for molecular microbiologist and Postdoctoral Fellow at Bioprotection Aotearoa, Nils Birkholz. Highlights include publishing four papers in high-impact journals and presenting at two domestic and international conferences. His research, with supervisor Peter Fineran in Pou 2, aims to characterise the interactions between bacteria and the viruses that infect them, named bacteriophages (or phages for short).

Phages are extremely abundant in every environment and outnumber the bacteria that they prey on, says Nils. In nature, the relationship between bacteria and phages is ecologically important “because they impact bacterial populations everywhere, basically keeping bacteria ‘in check’”.

In April, Nils, Peter, and Bioprotection Aotearoa colleagues Simon Jackson and Robert Fagerlund published a paper in Nucleic Acids Research that analysed a certain type of defence system in Pectobacterium, a bacterium that causes diseases such as soft rot in potatoes and other crops.

This defence system provided strong protection against phage infection but also shut off another defence system in the same strain of the bacteria. This surprising interplay between different defences is under-researched but important as it impacts how the bacteria can be infected by bacteriophages. In this case, the kind of phage the bacterium is susceptible to depends on which defence system is active, which is why this research is valuable.

Their research also suggests that closely related or co-existing strains may differ with regards to the defence systems that are active or inactivated, which also changes the overall population’s susceptibility to phages.

This finding has implications for potential applications such as using phages to get rid of harmful bacteria or pests. In addition, the research could be applicable to other bacteria in the future. The team are using Pectobacterium as a model system because the system and genome sequences are well understood. However, they know that similar defence systems occur in other bacteria.

This point that specific findings may sometimes apply more widely is highlighted by another paper with contributions from Nils and Peter. Nils says that this second paper, primarily authored by Chris Brown’s group at the Department of Biochemistry at Otago, “shows that a type of regulation that we and others have found in particular model systems actually applies across many unrelated bacteria”.

Nils and Peter are also collaborating with a group in Korea to study the anti-defence mechanisms of phages. Together, they have published two papers on this subject, showing how phages control the production of anti-defence proteins that allow them to thrive on bacterial strains which they could not otherwise infect. Nils’ ongoing research attempts to further unravel the unexpected complexity of this regulation.

Nils says their research has important implications for agriculture and pests, since many of our economically important plants are impacted by bacterial and viral pathogens. While this research is not aimed at finding immediate solutions, discovering more about the bacteria-phage interactions and defence systems is critical to finding long-term bioprotection strategies.

Nils has reported on their research at two conferences this year. The Viruses of Microbes conference, held in July in Portugal, had over 600 delegates, all working on aspects of the interaction between viruses and microorganisms.

Nils says, “It was very interesting to see what others are working on and draw some inspiration. I knew many of these people by name only, so meeting them in real life was a nice experience.”

Nils also presented and won a speaker prize in August at the Queenstown Research Week CRISPR satellite meeting, which was a smaller but highly collaborative event.

Nils says he is enjoying the connections with other Early Career Researchers in Bioprotection Aotearoa.  “It’s a great opportunity being able to talk to them, listening to what they are working on and how they are experiencing their PhDs and postdocs”.

A recent noho (stay) at Ōnuku Marae was particularly valuable for Nils who originally comes from Germany.

“From my perspective as a “foreigner” I didn’t know much about Māori culture before I came to New Zealand. The event gave me a much greater appreciation of Māori culture due to the setting at the Marae and all the background that was provided by the team at Bioprotection Aotearoa.”

Nils says this was an awesome experience that he will remember for a very long time.

How do human disturbances impact soil microbes?

Tuesday, November 29th, 2022

Research team scoping Great Barrier Island. From left, Maui Duley, Alexa Byers, Prof. Amanda Black, and Dr. Nick Waipara


Soil microbes are central to life on Earth. They recycle nutrients, regulate water quality, support plant productivity, and sequester carbon. However, the microbes in soil change in response to disturbances, affecting the way they behave and in turn the many systems that rely on them.

Alexa Byers, a postdoctoral researcher at Bioprotection Aotearoa, is investigating the soil health of natural and productive ecosystems to understand the response of soil microbes to threats such as pathogen invasion, human disturbance and climate change.

Alexa is involved in two projects at Bioprotection Aotearoa. The first project on kauri dieback disease (Phytophthora agathidicida) involves screening kauri forest soils for the production of bio-active compounds that have the potential to suppress kauri dieback. This project has involved a large amount of fieldwork on the North Island, including trips to the remote Great Barrier Island, Northland and Auckland.

The work is critical, in part, because kauri forests are so important to Māori communities. Alexa and her supervisor, Professor Amanda Black (Tuhoe, Whakatōhea, Te Whānau ā Apanui), have done a lot of engagement work with multiple iwi in Northland to explain the research and involve them.

Alexa says, “It’s important to just be open about what we’re doing, asking them questions about how we can help and listening to their contributions.”

This engagement has taken time. Alexa says, “Science sometimes moves at a fast pace and when you engage with communities you can’t rush things. You need to give people time to think. That has been a learning curve, that it’s not fair on them to be rushed.”

But Alexa says, “It is definitely worth it. You want your research to mean something more than just publishing papers. If you know you’re finding ways to benefit communities, that’s very rewarding.”

For the second project, Alexa is studying how land-use change is impacting soil microbial function and soil carbon cycling for project 3.1. She is taking soil from each land-use type and inducing drought to see how the microbes respond. The results will show how land-use change impacts microbes’ ability to cope with climate change. This project is focused on productive landscapes such as pasture in Banks Peninsula, Canterbury.

Alexa is enjoying meeting the different communities, working in beautiful parts of New Zealand, and interacting with other Early Career Researchers in Bioprotection Aotearoa. She says, “Bioprotection Aotearoa is really good because of their focus on early career scientists. There are lots of us and we have regular meetings and chances to get together and talk about our research. A lot of time is invested in us.”

Positioning rangatahi to create impact for tomorrow’s future

Monday, October 3rd, 2022

Play Video | Outreach: Identifying kauri using paper, molecules, and computers


Te manu e kai ana i te miro, nōna te ngahere;

te manu e kai ana i te mātauranga nōna te ao. 

Bioprotection Aotearoa is committed to establishing opportunities that further promote science education and experiences for communities and their learners.

With aligned aspirations, Tiakina Kauri approached Bioprotection Aotearoa to help design and deliver an outreach programme to a group of visiting students from Ngāpuhi.

Lauren Waller, a Science Lead for Tiakina Kauri, has been working with communities in Northland, to protect kauri from the Phytophthora agathidicida (PA), which causes disease in kauri.

As a treaty partner, communication and co-design are key elements at every step of the relationship.  So when Tania Pene, from Te Rūnanga-Ā-Iwi O Ngāpuhi asked Lauren how to get the community involved with the scientific research that is taking place, Lauren saw an opportunity to get rangatahi involved.

Lauren picked up the phone and gave Professor Amanda Black a call, the director of Bioprotection Aotearoa.  Together they assembled a team to begin planning an outreach programme hosted at Lincoln University.

The programme centred around the theme “Identifying kauri using paper, molecules, and computers”.  It’s purpose was to take students through a journey that introduces scientific tools across various scales, that are used in the kauri protection space.

“Working with students is a good way to start, because they are the future,” says Lauren. “They can come down to Lincoln, be a part of this work, understand the context, and why we are doing it.”

Students were blown away by the university environment.  For many, this was their first time in the South Island, and the first time on a plane.  The experience sparked rich conversations around their own learning aspirations after they completed highschool.

Watch the video >

Māori kiwifruit growers determining their own pathway of success.

Monday, October 3rd, 2022

Joyann Te Moana, who upskilled and is now an Assistant Manager for Te Kaha 67


Te Kaha is a quiet coastal town located in the Eastern Bay of Plenty and is one of three focus regions of scientific research for Bioprotection Aotearoa. Te Kaha 15b Ahuwhenua Trust is an 11.5-hectare Māori freehold land block that sits within the rohe (boundary) of Te Whānau-ā-Apanui.

Māori agribusiness, Te Kaha Group, a collective of six ahuwhenua trusts, working together to oversee the management of the six blocks by the contracted pack-houses, where they predominantly farm the gold variety of kiwifruit.

It has been 20 years since the collective planted its first kiwifruit seedling, and in that time, the community has been adopting innovative management practices that benefit its whenua. It has also set up its own vertically integrated commercial enterprises to service operational needs as it manages its productive landscapes.

“We have our own spraying company, we do our own mowing and mulching, and have our own pruners. We are going to buy a couple of new capital items to enhance things even further,” says the Chairman of Te Kaha 15B. Ahuwhenua Trust, Norm Carter (Ngāti Awa, Te Arawa, Te Whānau-ā-Apanui). “We are trying to make sure the work stays within the coast, if we can.”

With this strong entrepreneurial spirit, not only has Te Kaha 15B helped to create jobs and generated economic well-being for its community, but it also offers educational pathways by sponsoring members of their community to gain tertiary qualifications in horticulture.

“Some whanau used to be just pickers and pruners on a block, earning minimum wage, and now they are taking $80- 120k into their family homes as supervisors,” boasts Norm. “They are making a difference to their own families. Plus the money is coming back into our own community.”

Upskilling their workers has also influenced the way in which workers perceive themselves. “You can see it in their faces, you can see it in their āhua,” Norm says, “just the way they are around other workers and how they supervise them, it filters out into the community.”

In addition to growing kiwifruit, the Te Kaha rohe also grow maize, but they are finding that growing maize brings its own set of challenges. “We are trying to get rid of maize, because it is terrible on the environment. It attracts vermin and rats and is hard on the soil. Plus, the things that live in there often go out into the kiwifruit blocks,” Norm says.

Te Kaha Group, of which Te Kaha 15B is one contributing block, are looking to diversify its crop production, and it has recently erected a state-of-the-art nursery to support this vision. Due to the location of Te Kaha it has a unique micro-climate, which offers an advantage over other regions.

“Our bubble is a bit different from everywhere else. We can grow stuff, usually three weeks before anybody else. That is our biggest point of difference,” says Norm.  They have also set up a Limited Liability Partnership, and members can choose to invest in any new developments, or not.

“A new exciting development is the planting of a new 15ha block in the green variety, in which 3 blocks, Te Kaha 15B, Te Kaha 2B and Te Kaha 67, have set up a joint venture with Seeka to establish a new orchard on the Coast.”

The philosophy of Te Kaha 15B has always been to give something back to the soil, plants, and people within their rohe.  This is why they value the relationship with Bioprotection Aotearoa.

“We are trying to get the best for the block from the people we are partnering with. If there is something there that needs fixing or addressing, we want to know what it is so we can do something about it,” says Norm.

Director of Bioprotection Aotearoa, Professor Amanda Black (Tuhoe, Whakatōhea, Te Whānau ā Apanui), says Te Kaha is a scientifically valuable site due to the variety of land use across the landscape. There are so many opportunities for learning about resilient landscapes due to the diversification and fragmentation of the land.

“This community is really enthusiastic to be partnering with Bioprotection Aotearoa, as they are currently diversifying their productive land blocks. This makes it the perfect time to address some of the needs for these Māori growers.”

Bioprotection Aotearoa has four research streams, with many projects within these four streams using Te Kaha as the field site for their research. The purpose is to understand the risk of pathogens being transferred around the landscape, and then identify any mechanisms that confer resistance and resilience against potential pathogen sources in the landscape.

Strategic Advisory Board member James Ataria (Rongomaiwahine, Ngāti Kahungunu, Raukawa) says the strength of Bioprotection Aotearoa is the “collection of scientists from diverse backgrounds who have a common focus on bioprotection and a passion for connecting their science with people and their community’s aspirations.”

James says the collaborative effort between multiple disciplines within Bioprotection Aotearoa not only provides more holistic research outcomes but also brings real value to the collaboration with communities.

Amanda says putting community well-being at the forefront of the research underpins the collective focus on ecosystem restoration in Te Kaha, “so when we go out to field sites with the growers, nursery managers, and iwi, everyone is included in discussions and planning.

“We truly are here to help the communities that we are partnering with and support our early career researchers to think about where and how their research might lead to impacts,” Amanda says.

National Policy Statement for Highly Productive Land (NPS-HPL)

Wednesday, September 28th, 2022

The new National Policy Statement for Highly Productive Land (NPS-HPL), was released by the Ministry for the Environment (MfE) in September 2022.  The intent of this policy is to ensure the availability of Aotearoa New Zealand’s most favourable soils for food and fibre production, now and for the future.

The policy is to provide direction to improve the way highly production land is managed under the Resource Management Act 1991 (RMA).

Director, Amanda Black released the following statement in response to the release of this policy.

“The protection of highly productive land has been a concern for food producers and scientists for more than two decades. The release of a NPS on highly productive land, at least, is an acknowledgement of the national importance that this issue has, and the impact that continued loss has on our own food security, the wider Pacific food security and of course income from export.

My concern is that it will take at least 3.5 years to really implement and relies heavily on coordination between authorities. While it comes into effect on the 17th October 2022, any land already marked for subdivision will still go ahead. There are also a number of exceptions to protecting highly productive land that begs the questions – will the NPS be able to adequately protect our future food supply, and is  this it too little too late?”

Today FM approached Amanda for further comment.

Listen to the full interview with Tova O’Brian.  Their korero features from 57.50 mins into the Full Show: 19/9/2022  >

Also published on Today FM, is an article that features a comment from Amanda.  Read article here >

Managing our wetlands in the coastal marine area

Wednesday, September 28th, 2022

In August 2022 The Ministry for the Environment opened up a consultation process seeking feedback to retain or amend the application of the Resources Management (National Environmental Standards) for Freshwater (NES-F) to the coastal marine area.

Wetlands in the coastal marine area are the interface of freshwater and marine ecosystems.  The (NES-F) was an original policy with the intent to restrict activities likely to cause the loss of degradation of all natural wetlands including those in the coastal marine area.

However, many councils and stakeholders initially interpreted the NES-F as applying only to natural inland wetlands (which are natural wetlands not in the coastal marine area).

In November 2021, the High Court held in Minister of Conservation v Mangawhai Harbour Restoration Society Incorporated (the High Court decision) that the NES-F wetland provisions do apply to natural wetlands in the coastal marine area.

Following the High Court decision, some concerns have been raised, prompting the Ministry for the Environment to open up a consultation process with the release of the discussion document, Managing wetlands in the coastal marine area.

The full discussion document on Managing wetlands in the coastal marine area, can be read here.

Our network of early career researchers from Bioprotection Aotearoa came together to review the options outlined in the discussion document, and decided to submit feedback for consultation.

Director of Bioprotection Aotearoa, Amanda Black says this is a valuable exercise for our early career researchers. “It helps to extend their critical thinking skills to National Policy Plans that relate to our environment, and teaches our early career researchers on how to have a say.”

Fellow early career researcher, Maui Duley has prepared this submission on behalf of Bioprotection Aotearoa.

Read the submission >

Strangers or co-conspirators? The co-occurring pathogens that occupy the soil below diseased kauri trees

Sunday, September 25th, 2022

Master’s student Taylah Dagg


Kauri dieback is the common term for the disease that is killing kauri trees here in Aotearoa New Zealand. The scientific name for the pathogen that causes the disease is Phytophthora agathidicida. It is present in the soil and enters the root system of kauri trees to cause the devastating disease, kauri dieback.

Over the past decade, this pathogen has been the focus of much scientific research in an effort to find tools and strategies that prevent kauri from falling victim to this disease.

But is this kauri-killing pathogen the sole mastermind behind the rapidly declining numbers of kauri trees? Or does it conspire with other pathogens to cause this devastating disease?

A previous study showed that, in the soil below infected kauri trees, P. agathidicida can co-occur with other Phytophthora species, including Phytophthora multivora and Phytophthora cinnamomiThough both of these co-occurring pathogens have been shown to cause disease lesions on kauri in glasshouse trials, it is not known if this is the case in a forest setting, or whether they have the ability to interact with P. agathidicida to cause kauri dieback.

As part of a project for Bioprotection Aotearoa, Taylah Dagg, a master’s student at Massey University, is conducting research that aims to understand to what extent a relationship exists between these three pathogens, and whether they interact and cause disease. “We are focusing on the proteins they are secreting into their environment, and how these influence their interactions,” says Taylah.

The first stage of Taylah’s project involved growing the three Phytophthora species on agar plates, inoculated in a triangular arrangement. The three Phytophthora species were grown in different combinations, separately (three colonies from one species), in pairs (one colony from one species and two colonies from a second species), and all together (one colony from all three species), to test whether they actively repelled each other.

The results of this simple test were not what Taylah and Carl were expecting. “We were expecting that if they were the same [Phytophthora species], they would grow into each other and cover the whole plate. If they were different, they might have a gap between them, indicating that they possibly actively repel each other,” Taylah says.

Carl adds that “normally, an individual Phytophthora colony would cover the plate in two or three days,” however, Taylah’s results showed something quite different.

“So far, even colonies from the same Phytophthora species are avoiding each other and staying apart,” Taylah explains, “I have a plate with three P. agathidicida colonies growing, and they still have a gap after 10 days of culturing.”

A secretome is an entire set of proteins secreted from an organism. The study of the secretome from each of the three Phytophthora species may reveal the reason behind the separation seen on the agar plates. Taylah suggests the three pathogens could be secreting some proteins that are actively preventing the three species from interacting, or that there could be some aspect of cooperation that is not currently being seen on the agar plates because it is happening at the protein level.

Stage 1 involved solid media, and for stage 2 Taylah is growing the different combinations of Phytophthora species in static liquid culture. On days 3 and 7 post-inoculation, Taylah will harvest the proteins that have been secreted into the liquid media they are growing in.

“With the liquid, I am then freeze-drying it, and then we are running it through something called LC-MS.”

LC-MS is an acronym for, liquid chromatography-mass spectrometry, a technique that will analyse Taylah’s samples to provide a list of all secreted proteins that are present.

This second stage will form the biggest component of Taylah’s thesis. It is currently unknown what proteins are secreted from the three pathogens in the presence of another Phytophthora species,

“The thought of having my name on a publication is so cool. Like even if it is just a tiny snippet of a massive project, I’m like wow, I contributed to something that is new and really meaningful, especially for kauri.”

The third stage will involve a model plant in place of kauri, called Nicotiana benthamiana.  This plant species will be inoculated with the three Phytophthora species, to see if disease lesions will form. Currently, the plants are being grown in a lightroom under controlled conditions. If growth is observed, it may then be possible to determine whether the growth of one species positively or negatively impacts the growth of another species, providing further insight into whether the three Phytophthora pathogens work together to cause disease.

Taylah says the new knowledge gained from the results of this research has the potential to protect a significant cultural icon of Aotearoa New Zealand, especially important to the cultural identity of Iwi.

“Being able to tell what we know in science to Iwi and working together to create change in that space is pretty cool,” says Taylah.

How does the microbiome mediate insect biocontrol?

Tuesday, September 20th, 2022

Parasitoid wasp bursting out of an Argentine stem weevil © Dr. Sarah Inwood


Dr. Sarah Inwood, is a postdoctoral researcher at Bioprotection Aotearoa based at the University of Otago.  She has always been interested in applied research that would improve outcomes for Aotearoa and its people.

Sarah says, “Growing up on a farm, I’ve always been interested in research aiming to make agriculture more sustainable, and the ways it can be improved to benefit everyone.”

Sarah’s current research, part of project 2.1: The mechanisms of microbiota-mediated protection, certainly falls in this category. Even though her research is largely lab-based at this stage, it has huge potential economic benefits for farmers and all of Aotearoa New Zealand.

Farmers lose hundreds of millions of dollars every year through damage by invasive insect pests. Sarah’s research is investigating how biological control can reduce this damage by considering both the pest and host organisms’ microbiomes. In particular, Sarah is interested in the viruses and bacteria that live within the host species and the parasite, and how these organisms influence their relationships.

Sarah is studying two examples of such insect host-parasite systems that are economically significant to Aotearoa New Zealand.

Argentine stem weevil and parasitoid wasp

The Argentine stem weevil (Listronotus bonariensis) is one of Aotearoa’s top three worst insect pests, costing pastoral farmers over $280 million dollars in lost production every year.

The weevil is native to South America and was introduced accidentally to Aotearoa New Zealand in the 1930s. Soon afterward, as the pest spread to rye grass across the country, farmers began to notice brown and wilted paddocks.

Pesticides were ineffective at controlling the weevil, and so in the late 1980s, scientists began to search for the weevil’s native enemies back in South America. They found a parasitoid wasp (Microctonus hyperodae), which they released into Aotearoa New Zealand in 1991 as a biological control. The tiny wasp, just one-third the size of your pinky fingernail, injects its eggs into the wasp, and the larvae eat the prey from the inside out, eventually bursting alien-like from the weevil’s body.

Once it was introduced to Aotearoa New Zealand, the wasp quickly took off. In many areas of the country, up to 90% of weevil hosts were parasitised. It was one of the most successful examples of biocontrol worldwide. Unfortunately, the system also turned out to be the first example in the world of a pest that evolved resistance to biocontrol. Within just seven years, national parasitism rates had declined by 44%.

Scientists were baffled. It was generally expected that, unlike chemical controls, biocontrol would evolve alongside their hosts, keeping resistance at bay. What had led to the weevil’s increased resistance to the wasp? Had the weevil changed its behaviour, or had it evolved genetic changes that helped it resist the wasp?

Sarah’s previous PhD research focused on this question by looking at the genome of the weevil to see if she could identify genetic changes that had increased the weevil’s resistance. Meanwhile, other researchers at the Bioprotection Research Centre (Bioprotection Aotearoa’s predecessor), focused on behavioural changes that might have affected the weevil’s response. Both projects also looked at differences in the weevil across its range, to see what might explain the geographic differences in parasitism rates from very high in the north to lower in the south.

The behavioural research found some changes in the ways weevils learned to avoid wasps, possibly contributing to its resistance. But the genetic work never found “a smoking gun” that conclusively showed an underlying genetic source of the resistance to parasitism.

However, Sarah’s research did uncover an intriguing finding. The parasitoid wasp carries a strange virus that it transmits to weevils when it infects them. Was this virus affecting how the weevil reacts to parasite infection?

This discovery was the beginning of an expansion of Sarah’s research to look at how viruses – and other organisms in the microbiomes of the host and parasitoid – might affect the host-parasite relationship and the species’ relative fitness. Sarah’s research now hopes to discover what impact the virus has on the wasp and what role it plays when injected into the weevil.

Sarah is also looking at bacteria in the microbiome of the weevil to determine if these bacteria play a role in the weevil’s resistance to the wasp.

Either scenario could help scientists pinpoint what has caused resistance and help make biocontrol effective again, or perhaps help create a new form of biocontrol using a virus or bacteria. This is significant because while laws about genetic modification prevent researchers in Aotearoa New Zealand from releasing genetically modified biocontrol agents, using a virus or bacteria for control is still possible.

Honeybees and varroa mite

The second insect host-parasite system that Sarah is studying is honeybees infected by the varroa mite. Unlike the Argentine stem weevil, honeybees (while not native to Aotearoa) are an economically important species, and the varroa mite transfers a virus that kills them and causes catastrophic hive collapse.

Sarah’s research is investigating whether bacteria might protect honeybees against either the mite or virus, and how viruses and bacteria all interact to affect the relationship between honeybees and mites. Although lots of research is being done elsewhere on the varroa mite given its economic importance globally, Sarah’s overall approach in studying the microbiome as an important aspect of the relationship between host and parasite is novel.

Recent advancements in genetic technology and tools are making this work possible.

Sarah says, “Part of the reason for my interest in genetics is that my mum studied this before she had kids. When she saw me take an interest in this, she was able to really foster that interest.

She’s fascinated in everything I do. Things have advanced so much, she’s always interested in how quickly we can do things that she slaved over for days.”

How can wetlands be more resilient to global change?

Tuesday, September 20th, 2022

Dr. Stephanie Tomscha


Wetlands are critical ecosystems, providing rich biodiversity, water purification, carbon sequestration, flood abatement, mahinga kai and whatu, and recreation and wellbeing. Aotearoa New Zealand has lost over 90% of its wetlands, and the restoration of some of these wetlands is needed to return these benefits to many parts of the country.

Based from Victoria University of Wellington, Dr. Stephanie Tomscha is part of a team at Bioprotection Aotearoa studying how wetlands might be restored to create resilience to global changes. They have been studying wetlands for more than four years in Wairarapa, a region where wetlands are scarce (only 2% remain), fragmented, small and largely on private property.

Stephanie, a Landscape Ecologist, is using GIS to model where new wetlands should be created in Wairarapa to maximise outcomes for native biodiversity and for local people through better water quality, more access to cultural resources, and better carbon storage.

More specifically, Stephanie’s models are also investigating where wetlands could be restored to protect the critically threatened endemic tree species, swamp maire (Syzygium maire). The species only grows in wetlands and it is culturally important to Māori as kai (it has 18 times the concentration of antioxidants as blueberries) and a natural dye for harakeke.

Like many wetland species, swamp maire declined in range because of the draining and conversion of wetlands to farmland since colonisation. However, prior May 2017 – when the fungal disease myrtle rust (Austropuccinia psidii) arrived in Aotearoa – its conservation status was ‘Not Threatened’. By 2018, its status had changed to ‘Threatened – Nationally Critical’.

Myrtle rust attacks all species in the Myrtaceae family, which is the second most prevalent family of plant species in Aotearoa. Swamp maire is particularly at risk from myrtle rust because of its fine and thin leaves.

Stephanie’s modelling includes climatic conditions such as wind, temperature and humidity, as well as features such as soil moisture and soil type, to identify where refugia for swamp maire should be located to protect it from the incursion of myrtle rust. Research in Australia suggests that valley bottoms that are protected from strong winds may be good refugia from myrtle rust, because the disease is spread by wind. Also, swamp maire only grows on the wettest soils, so it’s important that refugia are located on these soil types.

Landcare Research did similar modelling on swamp maire at a national scale several years ago and found very limited opportunities to protect the species from myrtle rust. However, more recent work suggests that there may be more potential for refugia than this work suggested. In addition, local modelling is needed to ensure the species survives in Wairarapa, as iwi want to be able to access the taonga locally, not just nationwide.

The work that Stephanie is doing for Bioprotection Aotearoa, is part of Project 1.3: Understanding the spatial dynamics of emerging threats to ecosystem health, led by Dr. Julie Deslippe. The group is more generally studying the relationship between plants and microbes, and how they affect the stability of ecosystems in the wake of global change.

The team is highly focused on myrtle species, because their prevalence in Aotearoa means that they are likely to be a large driver of ecosystem change in wetlands here. They will also study how the composition of myrtle species in a wetland affects the ecosystem’s resilience and how wetland species composition will change if myrtle species decline or disappear in the future.

Stephanie and the wider group are involving the community, especially local farmers and iwi, in their research to understand why wetlands are important to them and how this might affect their restoration. They recently published a paper showing that many local farmers are restoring wetlands on private land, because they are well aware of the benefits of wetlands, including water filtration, easier land management, and more.

Stephanie says, “I have been working on wetlands in Wairarapa since 2017, and so I have long-standing relationships with people there. Wetlands are so at risk and do so much for us. We need to look at them holistically to see the benefits and resources they provide. When we have healthy wetlands, what does that provide people and how can that help us protect them?”

Research uncovers what helps weeds invade mānuka and kānuka shrublands

Monday, September 19th, 2022

The edge of kānuka shrubland that has been invaded by weeds


Mānuka and kānuka shrublands are spread across Aotearoa New Zealand and provide important economic, environmental, and cultural benefits. They are a source of high-value honey and traditional medicines, and they provide a refuge for native birds and a nursing ground for native plant regeneration.

Unfortunately, mānuka and kānuka shrublands are also under threat from many factors, including incursions by weeds. To better protect shrublands across the country, postgraduate fellow Dr. Laureline Rossignaud is conducting research that will help us understand what factors help mānuka and kānuka shrublands resist weed invasion, and to better understand the dynamics of weed invasions through time.

This research is part of Nuku-a-rangi, Pou 3 for Bioprotection Aotearoa.  Laureline’s project 3.2 is led by Dist. Prof. Philip Hulme which aims to determine the role of landscape attributes, ecosystem characteristics, and species traits on weed incursion in mānuka and kānuka shrublands. Laureline is using large datasets to investigate the drivers for weed invasions at the landscape scale.

The main database, hosted by Manaaki Whenua Landcare Research, is part of the national vegetation survey databank which provides plant information from permanent plots in mānuka and kānuka shrublands.

The drivers that Laureline is investigating include:

  • the proportion of exotic lands surrounding the plots, which can host weeds and facilitate their incursion in the shrublands
  • the distance to the nearest roads and rivers
  • The climatic conditions at the plot (mean annual rainfall and temperature)
  • the plant community already in the plot, including the structure of the vegetation with native species richness and native plant cover across different heights.

Laureline’s research so far has found that native tree species richness is very important in helping shrublands resist weed invasions because exotic species must compete with native trees for resources. In addition, most exotic weed species are adapted to open habitats, so tall native trees also make the ecosystem resilient against invasion by limiting access to light and space.

On the other hand, Laureline’s research also confirms that factors that help weeds invade shrublands include the proximity of exotic grasslands and the fragmentation of habitats.

Laureline is now creating maps to investigate the relationship between climate and weed invasions. These maps show that shrublands on the West Coast and in the southern South Island have fewer weed invasions than shrublands in other parts of the country. This is probably because these areas are largely in national parks and they are wetter and colder than other parts of the country. Climate is significantly correlated with weed invasion in the models, and warmer climates generally help exotic species establish.

Laureline says, “I have really enjoyed making maps and looking at the distribution of exotic species. When I was building the maps, I discovered some exotic species are spreading and others aren’t, which is quite interesting. I’m now having a more detailed look at why this is happening.”

Laureline’s research over the next year and a half will work to identify which weed species are extending their ranges and invading more plots, what factors are driving this spread, and what threats the weeds pose to mānuka and kānuka shrublands.

Laureline is enjoying being part of Bioprotection Aotearoa and says, “It’s a great opportunity because such a large number of scientists are working in this space. It’s a huge network and I’m going to learn a lot from all of the other cool projects. I feel excited and lucky.”