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New Zealand Plant Protection 69 (2016): 320

What is the host range of Phytophthora agathidicida in New Zealand?

J.M. Ryder, N.W. Waipara and B.R. Burns


Phytophthora agathidicida is a virulent oomycete plant pathogen, which is currently known to only infect Agathis australis in New Zealand. Phytophthora species rarely have a single plant host, so other hosts for P. agathidicida are likely but unknown. Phytophthora species are also often cryptic and sometimes asymptomatic on their host plants, making it a challenge to identify their true host range. Once an exotic Phytophthora species is introduced to an area, it becomes virtually impossible to eliminate. A sound understanding of a Phytophthora's epidemiology is needed to prevent its spread onto uninfected hosts. This study determined whether P. agathidicida has a wider host range than currently recognised. Plant community composition was compared between healthy and infected kauri forest to detect possible susceptible species, and detached leaf assays were utilised as a further screen of possible hosts. Results showed a significant difference in species abundances between sites infected with P. agathidicida and sites without P. agathidicida that was unrelated to other potential variables. Leaf assays also indicated several other native plant species other than A. australis as possible carriers or hosts, including Knightia excelsa and Leucopogon fasciculatus. Identifying the host range of P. agathidicida is important for optimising the design of future control strategies for this pathogen.

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