Species
Kauri Dieback
Phytophthora agathidicidaPhytophthora agathidicida is a soil-borne water mould specialized in attacking New Zealand kauri trees. Its motile microscopic zoospores swim through waterlogged soil toward chemical signals emitted by kauri roots, penetrating root tissues and cutting off water and nutrient transport. The pathogen forms resilient thick-walled oospores that survive in dry dirt for years, turning human boot treads, hiking poles, and feral pigs into prime vectors across vulnerable forests.
PathogenMicroscopicSoil-dwelling
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Diet & preyKauri tree roots, Kauri tree cambium
ThreatsTrack hygiene stations, forest closures, biosecurity containment
HabitatsKauri forest soils and root systems across northern New Zealand
Life spanDecades (resting oospores remain viable in soil for years)
Classification
- FamilyPeronosporaceae
- SpeciesPhytophthora agathidicida
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Safe to observe at a normal distance, but poses an extreme biosecurity threat to trees.
- What to notice
- Recognized in the field by symptoms on host trees, including basal resin bleeding, yellowed leaf crowns, and canopy defoliation.
- Support conservation
- Strictly follow forest hygiene protocols, wash all hiking gear at trailhead stations, and never step onto native forest soil off-trail.
Responsible observation
- Cleaning stations: Always thoroughly scrub and disinfect footwear before and after entering kauri forests.
- Stay on tracks: Remain strictly on designated boardwalks to avoid spreading microscopic spores to uninfected tree roots.
- Report symptoms: Photograph bleeding resin and canopy thinning from marked trails and report sightings to local biosecurity teams.
Host Plant (c) Jacqui Geux, some rights reserved (CC BY), uploaded by Jacqui Geux · cc-by
Vector Valentin Panzirsch / CC BY-SA 3.0 at · cc-by-sa
Close Relative (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda · cc-by
Close Relative (c) Rasbak, some rights reserved (CC BY-SA) · cc-by-sa
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