What is kauri dieback?
Kauri dieback is caused by Phytophthora agathidicida (PA), a soil-borne pathogen (a disease-causing organism) that infects kauri through their roots. It can kill kauri of all ages, and DOC says there's no known cure.
PA moves in soil: on dirty footwear, animals, equipment and vehicles. So every piece of advice comes back to soil. Spread is reduced by not moving soil around kauri roots.
It matters because kauri are already under pressure. Kauri's national conservation status was At Risk, Declining in the 2023 assessment, and DOC says a kauri can live for over 2,000 years.
Signs of kauri dieback
- Bleeding gum lesions at the base of the trunk
- Yellowing leaves
- A thinning canopy (the leafy top of the tree)
- Dead branches
None of these proves it on its own. Not every infected kauri shows a lesion, and not every lesion is caused by PA, which is why the rules ask you to report a sick tree rather than diagnose it.
The kauri rules
On 2 August 2022, a National Plan introduced 10 rules to manage the risk of PA, under the Biosecurity Act 1993. Tiakina Kauri, part of Biosecurity New Zealand at the Ministry for Primary Industries, explains the rules, and the plan involves councils in Waikato, Bay of Plenty, Auckland and Northland, where kauri naturally grow.
Around a home, three rules do most of the work. If your kauri look unhealthy, you must let Tiakina Kauri or your regional council know. A kauri hygiene zone is 3 times the radius of the dripline (the outer edge of the canopy). And since 2 August 2023, earthworks within a kauri hygiene zone need an earthworks risk management plan.
That plan has to set out how vehicles, machinery, equipment, footwear and clothing are cleaned so there's no dirt on them. In Tauranga, the council has to approve it before the work begins. Breaking the kauri rules can bring a fine under the Biosecurity Act 1993.
Tree work near kauri: what to expect
Work out the hygiene zone
Measure from the trunk to the dripline, then go three times that distance out. Anything planned inside that circle gets the hygiene treatment.
Arrive clean
Tiakina Kauri's message for contractors is arrive clean, stay clean, leave clean. Boots, gear, the truck and the chipper should turn up clear of soil.
Keep the soil where it is
Ask how the crew will keep vehicles and machinery from moving soil around the roots, and where the branches and chip will go.
Settle the earthworks question first
Whether stump grinding, digging or other root work counts as earthworks under the rules isn't something we could confirm. Ask the arborist and Tiakina Kauri before the job is booked, and if it does count, get the earthworks risk management plan in place first.
Check the district plan too
Kauri can be protected by the council as well. Auckland's Schedule 10 includes kauri, so see notable trees before any pruning or removal.
Leave clean
Before the crew goes, gear and footwear get cleaned again, so soil from your section doesn't travel to the next job.
What is myrtle rust?
Myrtle rust is a wind-borne disease caused by the fungus Austropuccinia psidii. It attacks the myrtle family: pōhutukawa, mānuka, rātā, swamp maire and ramarama, plus garden plants such as bottlebrush, lilly pilly and eucalyptus.
New infections show as bright yellow-orange powdery eruptions on leaves, often on the underside. The spores are microscopic and travel long distances on the wind, and also on contaminated clothing, insects, rain splash and equipment.
DOC says myrtle rust can't be eradicated from Aotearoa. Native members of the family were raised to Threatened conservation status in 2018 after it arrived, DOC lists pōhutukawa as under potential threat from it, and in Auckland pōhutukawa is already rated Regionally Declining.
If you spot myrtle rust
- Don't touch the infected plant, and keep others off it
- Don't collect samples or pick off affected leaves
- Photograph the rust close up, and the whole plant
- Report it on iNaturalist
- Spores ride on clothing, so change before you go near other myrtle-family plants
Who do I tell?
A sick kauri on private or council land: Tiakina Kauri's Report a Kauri page, or your regional council. On public conservation land: DOC. Myrtle rust: photos and a report on iNaturalist.
If an arborist is coming to look at a kauri or a pōhutukawa anyway, mention what you've seen when you book, so the crew turns up ready to work clean.
Dead branches on a sick tree
A kauri or pōhutukawa in decline can drop dead branches without warning. Keep people, cars and play areas out from under them, and don't climb the tree or prop a ladder on it to reach them. Taking dead wood out of a big tree is arborist work.
What you can do, and what's an arborist's job
You can
- Clean soil off boots, tools and tyres before and after you're near kauri
- In kauri forest, clean off visible soil going in and coming out, and use every hygiene station
- Keep cars, diggers and new garden beds away from kauri roots
- Photograph and report a sick kauri or a case of myrtle rust
- Leave infected leaves and branches where they are
Leave to an arborist
- Pruning or removal inside a kauri hygiene zone
- Stump or root work near kauri, once the earthworks question is answered
- Dead branches over a house, path or drive
- Work on a kauri or pōhutukawa listed in the district plan
Kauri dieback and myrtle rust: what to do next
If a kauri looked unwell, we'd report it to Tiakina Kauri before anything else, then talk to an arborist about any dead wood over the house. We'd want the hygiene plan sorted before the crew arrives: clean gear, soil staying on site, and a straight answer on whether any stump or root work counts as earthworks. For myrtle rust, a photo and an iNaturalist report does more good than a pair of secateurs.
Want an arborist to look at it?
Tell us the job and your postcode, and a local arborist calls you to talk it through.