Cross-Cultural Leadership Enables Collaborative Approaches to Management of Kauri Dieback in Aotearoa New Zealand

Abstract

In Aotearoa/New Zealand, the soilborne pathogen Phytophthora agathidicida threatens the survival of the iconic kauri, and the ecosystem it supports. In 2011, a surveillance project to identify areas of kauri dieback caused by Phytophthora agathidicida within the Waitākere Ranges Regional Park (WRRP) highlighted the potential impact of the pathogen. A repeat of the surveillance in 2015/16 identified that approximately a quarter of the kauri area within the Regional Park was infected or possibly infected, an increase from previous surveys. The surveillance program mapped 344 distinct kauri areas and showed that 33.4% of the total kauri areas were affected or potentially affected by kauri dieback and over half (58.3%) of the substantial kauri areas (above 5 ha in size) were showing symptoms of kauri dieback. Proximity analysis showed 71% of kauri dieback zones to be within 50 m of the track network. Spatial analysis showed significantly higher proportions of disease presence along the track network compared to randomly generated theoretical track networks. Results suggest that human interaction is assisting the transfer of Phytophthora agathidicida within the area. The surveillance helped trigger the declaration of a cultural ban (rāhui) on recreational access. Te Kawerau ā Maki, the iwi of the area, placed a rāhui over the kauri forest eco-system of the Waitākere Forest (Te Wao Nui o Tiriwa) in December 2017. The purpose of the rāhui was to help prevent the anthropogenic spread of kauri dieback, to provide time for investment to be made into a degraded forest infrastructure and for research to be undertaken, and to help protect and support forest health (a concept encapsulated by the term mauri). Managing the spread and impact of the pathogen remains an urgent priority for this foundation species in the face of increasing pressures for recreational access. Complimentary quantitative and qualitative research programs into track utilization and ecologically sensitive design, collection of whakapapa seed from healthy and dying trees, and remedial phosphite treatments are part of the cross-cultural and community-enabled biosecurity initiatives to Kia Toitu He Kauri “Keep Kauri Standing”.

Evaluating scent detection dogs as a tool to detect pathogenic Phytophthora species

“…The number of target samples was selected using a power analysis, where 211 samples returned an estimated 90% probability that the lower confidence interval estimate would have ≥60% sensitivity (see Section 2.3.1, below, for complete details). The number of non‐target samples was scaled to include five non‐target samples for every one target sample (i.e., 20% prevalence) because P. agathidicida was thought to have a similar prevalence in Aotearoa‐New Zealand's most heavily affected areas at the time of this study (Hill et al, 2017; although see Froud et al, 2022 for updated estimates).…”

Exploring Phytophthora agathidicida Oospore Viability and Germination

“…After initial reports of kauri dieback on Aotea in the 1970s, the disease was reported in several other areas including Waitākere Ranges Regional Park and Waipoua Kauri Forest (Figure 2) Beachman, 2017;Beever et al, 2009;Gadgil, 1974;Waipara et al, 2013). The Waitākere forest is now the most heavily infected area, with 10.6% of kauri trees infected (or potentially infected) in 2011 and 23.6% reported as infected in 2016 (Hill et al, 2021;Hill et al, 2017;Jamieson et al, 2014). Hill et al (2021) also showed that 33.4% of kauri stands nationwide were affected by kauri dieback, and infection was particularly prevalent in large stands (above 5 ha in size), with 58.3% of these kauri stands showing symptoms of kauri dieback disease.…”

“…The Waitākere forest is now the most heavily infected area, with 10.6% of kauri trees infected (or potentially infected) in 2011 and 23.6% reported as infected in 2016 (Hill et al, 2021;Hill et al, 2017;Jamieson et al, 2014). Hill et al (2021) also showed that 33.4% of kauri stands nationwide were affected by kauri dieback, and infection was particularly prevalent in large stands (above 5 ha in size), with 58.3% of these kauri stands showing symptoms of kauri dieback disease. They also revealed that 71% of kauri dieback zones were within 50 m of a walking track, suggesting that kauri dieback is predominantly spread by humans.…”

“…Wash stations containing TriGene are placed at entrances to forests to remove and inactivate potential sources of kauri dieback from shoes, and boardwalks keep people from coming into contact with kauri and the soils around them. Forest closures prevent tracking infected material within and from high-risk areas, such as the Waitākere rāhui (ban) and the Coromandel track closures (Bradshaw et al, 2020;Hill et al, 2021). Feral pigs are also thought to be a minor vector for spreading kauri dieback, so control of these animals is also carried out (Bassett et al, 2017;Bradshaw et al, 2020;Krull et al, 2013).…”

“…The kauri tree is an iconic and ecologically important part of Aotearoa, and we must protect these rākau rangatira. Unfortunately, Kauri dieback is now in 33.4% of kauri stands and is spreading despite the measures taken to prevent it (Hill et al, 2021). Furthermore, we know that Trigene, the chemical agent used in wash stations at the entrance to kauri forests, is ineffective against the oospores of P. agathidicida and phosphite, the current treatment of active kauri dieback infections, reduces disease symptoms but does not cure the tree.…”