Oral Presentation Australasian Plant Pathology Society Conference 2025

Safeguarding giants: research and innovation in kauri protection and disease management (120060)

Nari Williams 1 2 , Ian Horner 1 , Matthew Arnet 1 , Shannon Hunter 3 , Nick Waipara 3 , Bruce Burns 2 , Peter Scott 4 , Jack Hosking 1 , Ellena Carroll 1 , Julia Sowarto 5 , Vicky Hodder 5 , Cate Macinnis-Ng 2 , Cecilia Latham 6 , Andrew McDonald 7 , Taoho Patuawa 8 , Juliane Chetham 9 , Steve Johnson 9 , Ari Carrington 9 , Waitangi Wood 10 , Dean Anderson 6
  1. Plant & Food Research, Hawkes Bay, New Zealand
  2. School of Biological Science, The University of Auckland, Auckland, New Zealand
  3. Plant And Food Research, Mt Albert, New Zealand
  4. ArborCarbon, Perth, Western Australia, Australia
  5. BioProtection, Scion, Rotorua, BOP, New Zealand
  6. Manaki Whenua - Landcare Research, Christchurch, HB, New Zealand
  7. BoSpatial, Whangarei, HB, New Zealand
  8. Te Roroa Iwi, Dargaville, HB, New Zealand
  9. Patuharakeke Iwi Trust, Whangarei, HB, New Zealand
  10. Wai Communications, Auckland, HB, New Zealand

Kauri (Agathis australis) is a cornerstone species of Aotearoa-New Zealand’s forests, holding immense ecological, cultural, and spiritual significance. These ancient trees shape entire ecosystems, supporting unique biodiversity, while also being deeply revered by Māori as taonga. However, the health of kauri forests is increasingly threatened by soil-borne Phytophthora species, particularly Phytophthora agathidicida, which has been linked to severe root infections and forest decline. Protecting kauri and maintaining forest health requires an integrated research approach to understand pathogen dynamics, identify alternative hosts, refine detection methods, and evaluate treatment strategies. Recent advances research have made substantial progress in understanding pathogen dynamics, improving disease detection, and enhancing strategies for kauri protection. This presentation synthesizes key findings from multiple studies, highlighting advancements in safeguarding these iconic trees and the forests in which they stand.


Investigations into pathogen ecology confirm that while P. agathidicida is the primary concern, other Phytophthora species coexist in kauri forests with less direct impact on kauri. Research into potential alternative hosts of P. agathidicida has refined our understanding of pathogen reservoirs, but low infection rates in a range of hosts suggest that stringent biosecurity measures remain the most effective means of protecting forest health.


Encouragingly, phosphite treatments have shown long-term efficacy in reducing P. agathidicida inoculum and improving tree vitality3,4,5. Emerging research into foliar phosphite applications presents a promising alternative to trunk injections, offering a less invasive and scalable treatment approach. Complementing these efforts, remote sensing technologies, including hyperspectral and thermal imaging, present options for scalable and early detection of tree decline, enabling proactive intervention before visible symptoms appear.
A risk-based surveillance model is also transforming monitoring efforts by prioritizing high-risk areas, optimizing resource allocation, and providing a scalable framework for demonstrating disease absence1. In the Waitākere Ranges, comprehensive pathogen profiling has reinforced the importance of continued containment strategies, including track upgrades, access restrictions, and enhanced public biosecurity compliance2.


Together, these advances mark a significant step forward in kauri protection. With improved disease suppression tools, smarter surveillance strategies, and enhanced early detection capabilities, we are better equipped than ever to preserve these ancient forests. By integrating research-driven solutions with strong community engagement, we can ensure a future where kauri thrive for generations to come.

 

  1. Latham, M.C., Lustig, A., Williams, N.M. et al. Design of risk-based surveillance to demonstrate absence of Phytophthora agathidicida in New Zealand kauri forests. Biol Invasions 27, 26 (2025). https://doi.org/10.1007/s10530-024-03501-4
  2. Hunter, S.; Horner, I.; Hosking, J.; Carroll, E.; Newland, J.; Arnet, M.; Waipara, N.; Burns, B.; Scott, P.; Williams, N. Phytophthora Communities Associated with Agathis australis (kauri) in Te Wao Nui o Tiriwa/Waitākere Ranges, New Zealand. Forests 2024, 15, 735. https://doi.org/10.3390/f15050735
  3. Hunter, S., McDougal, R., Williams, N. et al. Variability in phosphite sensitivity observed within and between seven Phytophthora species. Australasian Plant Pathol. 51, 273–279 (2022). https://doi.org/10.1007/s13313-021-00846-5
  4. Hunter, S, Waipara, N, Burns, B, Scott, P, and Williams, N 2024 Impacts of phosphite treatment on Phytophthora community assemblages and inoculum abundances in Phytophthora-infected forest soil. Trees, Forests and People. https://doi.org/10.1016/j.tfp.2024.100687
  5. Horner, I., Hough, E. and Horner, M. 2015. Forest efficacy trials on phosphite for control of kauri dieback. New Zealand Plant Protection. 68, (Jan. 2015), 7–12. DOI:https://doi.org/10.30843/nzpp.2015.68.5791.