Record outbreak of Dutch elm disease in 200 trees at the former Kingseat Hospital isn't the only case of the deadly fungus in South Auckland.
Eleven elm trees at the Manukau Memorial Gardens are also in line for the chop after the disease was discovered there over summer.
The Manukau trees are all dead or dying, apart from one American elm which has so far escaped infection.
All are thought to be at least 35 years old and were found during an annual survey of the 16,000 elms on Auckland Council's database, council arboriculture adviser Simon Cook says.
The felled elms will be mulched and the material used in the memorial gardens.
The 200 trees at Kingseat have already been felled. The infection at the Spookers haunted attraction theme park is the largest outbreak since the disease was discovered in New Zealand in 1989.
It is spread by a bark beetle carrying fungal spores or through the transfer of diseased material.
So far it has been contained within the Auckland region but there has been a resurgence since a government-funded control programme was cut in 2006, Mr Cook says.
The "devastating" Kingseat outbreak heightens the risk the disease will soon be found in the Waikato, where elms are common in both urban and rural zones.
An arborist made the find while assessing the trees as part of the rezoning of the Kingseat property for housing, Mr Cook says.
The infection appears to have set in two to three years ago, allowing a "huge" number of beetles to reproduce and posing a major infection threat, although it's hoped the stand of trees was big enough for the beetles to stay put, he says.
Council staff helped the owner ensure the elms were cleared safely.
"Kingseat is a historic character site with elms initially planted in the 1930s. It's a shame that they will be losing such a significant number of trees," Mr Cook says.
"However this demonstrates just how devastating the disease really is."
Infected trees have also recently been found at parks in Bucklands Beach and Pakuranga and on private property in Drury.
"We've had so many diseased trees this year that we haven't been able to cope."
The council is removing affected trees on public land. Private property owners are legally required to remove infected trees themselves but the council is happy to help, he says.
Material should be mulched, buried or burnt immediately.
New cases will become evident in spring with elms either not coming into leaf or wilting rapidly after bud burst, Mr Cook says.
"Given the speed at which Dutch elm disease can spread, and the fact that it's nearly always fatal for affected trees, we're taking every precaution to ensure we remove the trees safely and contain the threat."
DUTCH ELM DISEASE - WHAT TO LOOK FOR
- Dutch elm disease can infect any species of elm.
- It is usually spread by the bark beetle Scolytus multistriatus carrying fungal spores from tree to tree or through the transfer of diseased material.
- It can also spread between neighbouring trees when their roots fuse together.
- Once infected, the tree essentially kills itself as it plugs up channels to stop the fungus spreading. In the process, the tree blocks its uptake of water and nutrients. Wilting and death soon follow.
- Residents are asked to watch for dying or dead branches and trees as well as signs of wilting, curling or yellowing leaves especially during spring or summer.
- It is illegal to move elm material in and out of the Auckland area between the Bombay Hills and Albany or to sell elms at Auckland nurseries.
- Storage of elm wood - including for firewood - is forbidden under the Biosecurity Act 1993.
- Property owners are required by law to get rid of diseased trees and bury, mulch or burn the wood.
- To report an outbreak visit aucklandcouncil.govt.nz or call 301 0101.
- © Fairfax NZ News
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