Kauri dieback is a microscopic ‘fungus-like' plant disease that only affects kauri and can lead to their death. Its botanical name is Phytophthora taxon Agathis (PTA). It can affect kauri of any age and causes yellowing foliage, leaf loss, canopy thinning, dead branches and in severe cases, death. Affected trees can also develop lesions that bleed resin, extending to the major roots and sometimes girdling the trunk as collar rot.
Photo: Tāne Mahuta, a national treasure under threat
To date, the disease has been found in the Rodney District and North Shore City and has also been identified in the Waitakere Ranges and on Great Barrier Island. The disease has been isolated from soil in Northland and DOC is currently carrying out more soil testing to confirm the spread of the disease.
PTA is soil-borne and spreads by the movement of soil or water. The disease can also be spread by root-to-root contact between infected individuals and neighbouring trees and by human and animal vectors.
In response to this new threat, MAF Biosecurity New Zealand, the Department of Conservation and four regional councils, including NRC, have established a joint response team to identify and manage the risks to kauri. The Kauri dieback team is currently:
· Assessing the risks posed by the organism to individual trees and their ecosystem;
· Determining methods for limiting the spread of the pathogen and assessing the effectiveness of these methods;
· Collecting further information on the distribution of the disease to inform a response decision.
In the interim, landowners with kauri on their land and the general public can help prevent the spread of PTA by taking the following steps:
· Minimise movement of vehicles, livestock or people around kauri roots;
· Make sure shoes, and other equipment, are clean of dirt before visiting kauri forest;
· Clean shoes and any equipment that come into contact with the soil after each use;
· Keep to defined tracks in parks and reserves at all times;
· Keep dogs on a leash at all times;
· If they have kauri on their land, erect warning signs to alert visitors to the dangers of spreading the disease; and
· If they think a kauri on their land has symptoms of PTA, contact the Kauri dieback response team on 0800 NZKAURI (69 52874).