Threats To Survival
The biggest threat to the survival of young kauri is invasive weeds – exotic invaders such as pampas grass, gorse, blackberry & kikuyu, which is why we place so much importance on releasing our trees until they are tall enough to survive on their own.
Gorse forms pure associations temporarily in many habitats, inhibiting the establishment of native plant seedlings. Increased nitrogen in poor soil types (eg. gumland, sand dunes) may change the types of species present and nature of habitats to the detriment of specialised plants, eg herbs, orchids, low ferns. Can have positive impacts on bared ex-forest sites as it acts as a nursery crop for native species, adds nitrogen, humus, windbreak and shade, and opens up when older and disappears when overtopped. Succession to native species may be less likely on dry sites.
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 gum 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.
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.
For more information please see the Kauri Dieback website
Kauri dieback is the deadly kauri disease caused by Phytophthora agathidicida. Following DNA studies, this fungus-like disease was formally identified in 2008 as a distinct and previously undescribed species of Phytophthora. Kauri dieback is specific to New Zealand kauri and can kill trees of all ages.