Confirmation of PA at Long Bay Kauri Walk

Soil testing has confirmed the presence of Phytophora agathidicida (PA), the pathogen that causes kauri dieback disease, at the site of the oldest kauri at Long Bay Kauri Walk, near Coromandel town.
 
Waikato Regional Council, Thames-Coromandel District Council (the landowner) and local iwi have been monitoring the 1200-year-old tree since 2023 after receiving several reports that the tree was visibly unwell.
 
Waikato Regional Council Biosecurity and Biodiversity Manager Patrick Whaley says confirmation of PA is incredibly disapppointing.
 
“The Coromandel Peninsula has relatively few recorded cases of kauri disease, and none as publicly accessible as Long Bay Kauri Walk,” says Mr Whaley.
 
“Southern kauri forests are vital to the future of kauri, as they have been largely free from disease compared to forests in the north.
 
“Preserving kauri on the Coromandel Peninsula really depends on everyone playing their part in stopping the spread of PA.”
 
Phytophthora agathidicida is microscopic and spread through the movement of contaminated soil, including on dirty footwear, equipment, vehicles and animals.
 
It infects kauri through their roots, preventing them from taking up water and nutrients which eventually starves the tree. 
 
Infected trees weaken over time and may eventually die. Symptoms include bleeding gum at the base of the trunk, yellowing leaves, thinning canopy and dead branches.
 
The council has been testing for PA in Long Bay Kauri Walk and other areas of the Coromandel Peninsula for many years. However, detecting the pathogen can be difficult.
 
“PA lives in the soil and can occur in very small, patchy pockets,” says Mr Whaley.
 
“That means you can miss it completely in a soil sample, even if it’s present nearby. 
 
“We had suspected this tree might have kauri disease based on its symptoms, but kauri can become unwell for a range of reasons. Unfortunately, we now have confirmed the diagnosis.”
 
Mr Whaley says the Long Bay kauri has received phosphite injections to help suppress the pathogen and boost the tree’s natural defences. Another round would be done later this year.
 
However, the tree may not survive, he says. 
 
“The health of the tree has declined significantly over the past 12 months. Phosphite is not a cure, but a treatment that can help with long-term survival if it’s done early enough. All we can do is try to prolong the tree’s life and stop further spread of PA.”
 
Phytophthora agathidicida can survive in soil for over eight years, and it can take years to decades for an infected tree to show visible symptoms. 
 
The pathogen was first discovered in Auckland and Northland in the early 2000s. It led to a significant biosecurity response, including the widespread closures of kauri forests in the infected areas while popular walking tracks were upgraded to manage the risk of spread.  
 
At Long Bay Kauri Walk, Waikato Regional Council and Thames-Coromandel District Council, with advice from local iwi, have worked together to mitigate risk. Over the years, this has included: 
•    upgrading the track by installing wooden boardwalks and rails, and using gravel substrate in other areas, to protect kauri roots and stop soil from sticking to shoes
•    fencing off neighbouring farmland to keep stock out 
•    installing a cleaning station at the site entrance and kauri hygiene signage (and educational signage)
•    funding a summer track ambassador programme, to educate visitors about protecting kauri.
 
Waikato Regional Council Chair Warren Maher says the most important thing people can do to help protect the remaining kauri in the reserve is stay on the tracks, respect the barriers, and arrive and leave with clean footwear.

“Protecting kauri is a major regional and national priority – and a responsibility we all share. 
 
“Waikato kauri are one of this region’s greatest natural treasures. These ancient trees are not only an iconic part of our landscape, but they help create and support the habitats that many of our native plants and animals rely on.” 
 
Further surveillance and soil sampling has been carried out in the reserve and additional signage is being planned to educate the public about what they can do to help protect kauri.