70 Boffa Miskell Ltd | Waihi North Project | Terrestrial Ecology Values and Effects of the WUG | 22 June 2022 6.5.3 Spread of Kauri Dieback Disease Phytophthora agathidicida (PA) is the pathogen regarded as a primary causal agent of dieback disease in otherwise healthy kauri, while other Phytophthora species may also have a role in the expression and severity of disease symptoms. Kauri dieback infects trees through their roots, and spreads primarily through the movement of contaminated soil and water, as well as by root-to-root contact between trees (Bradshaw et al., 2020). No PA has not been recorded in vicinity of the Wharekirauponga catchments to date. The magnitude of effect of introducing / spreading kauri dieback disease in the Wharekirauponga catchment would be Very High and the ecological value of kauri within the catchment is Very High. OGNZL has an established Kauri Dieback Management Plan for working within the Wharekirauponga catchments to minimise both the introduction of PA spores and to reduce potential spread from one site to another. In the absence of any PA detections, the primary focus of management is on strict inspection and hygiene procedures to ensure no soil is imported to the site on gear or machinery. All personnel and machinery is flown to and from the site While PA has not been recorded in vicinity, we note that survey effort to detect the disease within the Wharekirauponga catchments and surrounds is low, and there may be a significant lag between infection and trees showing symptoms. Therefore, the Coromandel Forest Park Kauri Dieback Management Plan (CFP KDP) developed for WUG also includes protocols for containment of PA infection that may be present and undetected. Mature kauri trees, seedlings and saplings may be present in the vicinity of the proposed footprint and along walking tracks between the shaft sites, helipad and camp site. The root systems of trees have the potential to harbour kauri dieback disease, and movement of machinery, equipment and people between sites during construction and drill site operation is a key pathway for the spread of kauri dieback. Recent surveillance work has found that PA can occur in soil away from the rhizosphere (root zone) of kauri (Biosense, 2020), though the frequency of detection is much higher near to kauri trees. This is likely to be because the pathogen primarily reproduces within the rhizosphere of kauri, and therefore concentrations of propagules are much greater there. The likelihood of Phytophthora invasion increases with the number of viable spores that are introduced into the habitat. Key factors are the total volume of contaminated material that is moved and the density of Phytophthora propagules in this material (Swiecki & Bernhardt, 2016). Phytophthora distribution in soil is typically non-uniform because these pathogens are normally associated with host roots (Swiecki & Bernhardt, 2016). Effects management Proposed management actions for vibration impacts includes: • Variable mining methods to minimise vibration related impacts on the surface and potential disturbance to fauna within the CFP. • Biodiversity Offset initiatives to benefit Archey’s frogs (and other fauna groups) where uncertain but potential residual risks have been identified (see Section 8.5.3).
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