What is kauri dieback disease?
Kauri dieback can kill kauri of all ages. It’s a disease caused by a microscopic fungus-like organism, called Phytophthora agathidicida (PA). It lives in the soil and infects kauri roots, damaging the tissues that carry nutrients and water within the tree, effectively starving it to death.
There’s currently no proven cure or treatment and nearly all infected kauri die. The disease is easily spread through soil movements e.g. when soil is carried on dirty footwear, animals, equipment and vehicles. A pinhead size of soil is enough to spread the disease.
Even though a lot of infected kauri will show physical disease symptoms, a tree can still be infected and not show any symptoms of the disease at all.
Kauri dieback disease is threatening our kauri, our taonga. We can save our kauri forests with your help by containing the disease and stopping it spreading to other areas.
Kauri dieback disease infects new trees in seven steps:
1: Oospores (resting spores) are introduced into an area of kauri, typically by human activity, but also by animals such as pigs. It only takes a pinhead of soil to move enough oospores to spread the disease.
2. The oospores germinate to form sporangia (a structure which produces zoospores).
3. Zoospores are released during and immediately after rain.
4. The zoospores swim (propelled by their tails) through moisture in the soil towards a kauri’s roots, where they attach themselves to the outside. They then germinate to produce mycelia (branded tubular structure) which infects the root. The tree’s fate is now sealed.
5. The mycelia spreads through the root system to attack the tissues at the base of the kauri’s trunk (eventually stopping the transport of nutrients and water to the canopy).
6. More sporangia are formed from where there are areas of infected root. These sporangia release more zoospores during and after rain, ensuring that it is only a matter of time before any other kauri in the vicinity are infected.
7. More oospores form within the tree's infected tissue. These are released into the soil as that tissue decays.