Comparison of methods used to detect the organism responsible for kauri dieback, Phytophthora agathidicida, from soil samples

Justin Singh, Fiona Curran-Cournane, Nick Waipara, Luitgard Schwendenmann, Gavin Lear
Auckland Council Research and Evaluation Unit, RIMU
Publication date:

Kauri dieback is known to be caused by the microbial pathogen Phytophthora agathidicida. Trees infected by the organism show symptoms of decline including yellowing of leaves, canopy thinning, root damage, copious gum exudation, and eventually death. Since first being identified as causing disease in kauri on Great Barrier Island in the 1970s, Kauri dieback has spread throughout many stands of New Zealand’s iconic kauri forest. For these reasons, kauri dieback disease has been declared an Unwanted Organism (UO) under the Biosecurity Act 1993 and is a strategic priority of the New Zealand Conservation Authority.

To study the distribution and spread of kauri dieback and the efficacy of various control strategies, it is essential to be able to accurately determine the presence and abundance of P. agathidicida in the environment. Methods for detecting P. agathidicida in soil largely centre on a culture-based approach known as baiting, but this approach is slow, taking up to 20 days to complete, and may be subject to biases in culturing and species identification that can lead to false positive or negative results. To overcome the inherent issues of baiting for Phytophthora, we test alternative molecular (DNA-based) methods for the detection of P. agathidicida in soil.

Auckland Council technical report, TR2017/019


14 September 2018

Unfortunately, the original 2017 version of this report contained an error. In the original document it is stated that ‘P. agathidicida is a soil-borne oomycete, which is aggressively pathogenic on kauri seeds, seedlings and trees of all ages (Horner & Hough, 2013)’ (Introduction page 1)

The article of Horner & Hough (2013) does not provide evidence that P. agathidicida is pathogenic on kauri seeds. The correct wording of this sentence should be ‘P. agathidicida is a soil-borne oomycete, which is aggressively pathogenic on kauri trees of all ages (Horner & Hough, 2013).’

Last updated: 2017-08-14