A new DNA test developed by researchers at Te Herenga Waka—Victoria University of Wellington provides a faster and cheaper way to measure Phytophthora agathidicida (PA), the pathogen that causes kauri dieback.
Kauri are among Aotearoa New Zealand's most treasured native trees. Associate Professor Monica Gerth, who led the development of the new test, said one of the biggest threats to the trees is the soil-dwelling PA pathogen, which infects kauri through their roots and causes dieback disease.
“With no cure currently available, protecting kauri depends on finding the pathogen early and taking action to stop its spread. Our new test makes monitoring kauri health easier than ever, offering a simple, rapid, and affordable testing option,” said Associate Professor Gerth.
The test was developed by a research team at Te Herenga Waka, with Jade Palmer developing the first versions as part of her PhD, and fellow lab member Emily Hocking leading the in-house refinement and compiling the blinded samples used to validate the new test.
How the new test works
“As kauri roots die back from infection, the pathogen releases oospores into the soil—tough, long-lived survival spores that can persist for years and spread the disease further,” said Associate Professor Gerth.
“Because oospores are central to how PA spreads, they're also an ideal target for detection.
“The new test, known as the oDNA (oospore DNA) assay, isolates these oospores directly from soil samples, rather than requiring the pathogen to be grown in a laboratory first, as current methods do.”
Jade Palmer says extracting DNA from the spores takes about a day, after which the pathogen can be detected—and its levels quantified—within a few hours, delivering faster results than existing tests.
"In its simplest form, our test provides a quick and reliable yes-or-no answer on whether PA is present in the soil. With an additional step in the lab, it also gives us quantitative data on how much of the pathogen is there, allowing us to track disease progression and monitor whether management actions are working. That’s something that hasn't been available before,” said Jade.
Validation of the test
To ensure confidence in the test’s performance and use across the kauri protection programme, Tiakina Kauri commissioned an independent review, involving international experts and testing across multiple laboratories using blinded soil samples. The independent testing confirmed the test has exceptionally high specificity and reproducibility, correctly identifying known samples of soil with PA present, with no false positives.
Alongside this formal review, the test was also stress-tested in the field. Earlier versions of the test were prototyped and refined by the university team in partnership with Northland iwi Te Roroa. Their Kauri Ora (kauri health) team tested these prototypes, with the shared goal of having a version robust enough for the Te Roroa team to run themselves, in their own lab, putting advanced diagnostic capability into the hands of mana whenua.
“One of the biggest challenges in managing this soil pathogen is having access to accurate, reliable diagnostic testing,” said Taoho Patuawa, the Te Roroa Kauri Ora science and innovation lead.
“This assay provides a rapid and highly specific tool for detecting Phytophthora agathidicida in soil, helping identify new incursions while also giving us greater confidence in monitoring the effectiveness of management interventions designed to protect kauri.”
For the Victoria University team, the test approval marks a major milestone in a research effort that began in 2021. More than anything, the team is looking forward to seeing the research put to real-world use.
“Our test is now available directly from the university, and the team is supporting the establishment of community-based labs across the country, including with Te Roroa iwi,” said Associate Professor Gerth.
"Mana whenua, councils, and community groups have been asking for a test that's faster and more affordable, without compromising on reliability.
"We're proud to deliver a rigorously validated, highly sensitive test that does exactly that. We're excited to now put it into action to help protect kauri health."
The test approval aligns with the National PA Pest Management Plan (NPMP), which established Tiakina Kauri as a management agency within Biosecurity New Zealand. It prioritises partnership with mana whenua, investment in science and mātauranga Māori, and practical measures such as track upgrades and fencing to protect kauri ecosystems.
For Tiakina Kauri, approving the test expands the national biosecurity toolkit and helps to achieve the objectives of the NPMP, including reducing the spread and impact of PA and maintaining areas free of PA.
Mike Hogg, Tiakina Kauri manager said the test approval reflects Tiakina Kauri’s commitment to fostering innovation and supporting the adoption of emerging, evidence-based diagnostic approaches while ensuring processes are robust and useful for wider management.
“Our surveillance work, including soil sampling and kauri health assessments, helps to inform management and legislation to protect kauri.
“To date, PA has not been detected in all kauri forests, and ensuring the survival of kauri depends on all of us taking action to stop it spreading. The new test will help us achieve that.”
For further information, please contact: monica.gerth@vuw.ac.nz or 021-163-4374.
Notes to editors
- About the Gerth Lab & Research Team: led by Associate Professor Monica Gerth at Te Herenga Waka—Victoria University of Wellington, the lab develops practical, science-based tools to detect, manage, and mitigate plant pathogens affecting kauri, horticultural and agricultural crops. The team works in partnership with mana whenua, regional councils, biosecurity agencies, and growers.
- Tiakina Kauri is a management agency within Biosecurity New Zealand which works in partnership with mana whenua and in collaboration with the Department of Conservation (DOC), Northland Regional Council, Auckland Council, Waikato Regional Council, and Bay of Plenty Regional Council to implement the National PA Pest Management Plan.
- The National PA Pest Management Plan established 10 rules to reduce risk for high-risk activities of PA spread. In cases of clear and substantial or continued non-compliance with the rules, prosecution or infringement fees could be applied.
- About PA: PA is spread by movement of PA-contaminated soil, including via footwear, clothing, equipment, vehicles, and animals. PA infects kauri trees through their roots and restricts their ability to transport water and nutrients between their roots and the leaves. This causes the condition known as kauri dieback disease, which eventually starves the kauri.
- About oospores and PA lifecycle: oospores are the durable, long-lived survival stage of Phytophthora agathidicida. They form in infected roots and are released into the surrounding soil as kauri roots die back. Unlike the pathogen's other life stages, oospores can persist in soil for years, allowing PA to remain viable and infectious long after visible symptoms subside. This persistence is a key reason soil movement—via footwear, vehicles, and equipment—poses such a high biosecurity risk, and why early, sensitive detection is critical to managing spread.
- For more information about kauri protection visit www.kauriprotection.co.nz
