Kauri dieback refers to the deadly kauri disease caused by
Phytophthora taxon Agathis (or PTA).
Following DNA studies, this fungus-like disease was formally
identified in 2008 as a distinct and previously undescribed species
Kauri dieback is specific to New Zealand kauri and can kill
trees of all ages.
Kauri dieback is not responsible for other dieseases commonly
seen on native plants in New Zealand. The cabbage tree disease
caused by phytoplasma (a specialised type of plant bacterium) is
spread by sap sucking insects that feed on the tree. Kauri dieback
is potentially a much greater threat than the cabbage tree decline
due to the long period required for kauri growth and the fact that
the soil is contaminated for years.
What does it do to kauri trees?
Microscopic spores in the soil infect kauri roots and damage the
tissues that carry nutrients within the tree. Infected trees show a
range of symptoms including yellowing of foliage, loss of leaves,
canopy thinning, dead branches and lesions that bleed resin at the
base of the trunk.
Some infected trees can show canopy dieback and even be killed
without any gum showing on the trunks as kauri dieback also acts as
a severe root rot below ground.
Kauri dieback can kill seedlings and trees of all ages. Nearly
all infected kauri die. In the past 10 years, kauri dieback has
killed thousands of kauri in New Zealand.
Scientists are currently working to find control tools for this
disease but there is no known treatment at this time.