Kauri Dieback – The facts on PTA

The facts on Phytophthora Taxon Agathis (PTA)

1. What is Phytophthora taxon Agathis?

Commonly known as PTA, Phytophthora taxon Agathis is a microscopic fungus-like plant pathogen (a disease-causing agent) that only affects kauri. Recent research has identified PTA as a distinct and previously undescribed species of Phytophthora.

2. What does it do to kauri trees?

Symptoms include yellowing of foliage, loss of leaves, canopy thinning and dead branches. Affected trees can also develop lesions that bleed resin, extending to the major roots and sometimes girdling the trunk as a “collar rot”. PTA can kill trees and seedlings of all ages.

3. How is it spread?

PTA is believed to be a soil-borne species spread by soil and soil water movement, plant to plant transmission through underground root-to-root contact, and human and animal vectors.

4. Where did it come from?

Formally identified in April 2008, its closest known relative is a chestnut pathogen from Korea (Phytophthora katsurae). The assumption is that it is an exotic pathogen. However, nothing is known about this particular species overseas.

5. Where is it?

PTA has been found at Huia and Maungaroa Ridge in the Waitakere Ranges Regional Park and at Department of Conservation reserves at Great Barrier and Trounson Kauri Park in Northland.

Symptoms of kauri dieback have also been observed at Cascade Kauri in the Waitakeres and other sites in Rodney, Franklin, Waitakere and the North Shore, as well as Pakiri, Albany, Okura and the Waipoua Forest.

6. What can we do to stop it spreading?

Make sure shoes, tyres and equipment are clean of dirt before and after visiting kauri forest.

Clean shoes and any other equipment that comes into contact with soil after every visit, especially if moving between bush areas.

Keep to defined park tracks at all times. Any movement of soil around the roots of a tree has the potential to spread the disease.

Keep your dog on a leash at all times. Dogs can inadvertently spread the disease if they disturb the soil around the trees.

7. What should I do if I have kauri on my land?

  • Minimise movement around kauri tree roots.
  • Keep dogs and animals away from kauri trees.
  • Download a warning sign and put it up to alert visitors to the dangers of spreading the disease. This can be laminated to make it more durable.
  • If you think your trees have PTA symptoms contact the Kauri Dieback Management Team on 0800 NZ KAURI (695 2874).

8. Will parks or reserves be closed?

At this stage there are no plans to close parks or reserves, but it is something we may have to consider in the future.