Pests
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Dutch elm disease (DED)
General information
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| Signs of Dutch elm disease |
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Elms are a significant part of the urban landscape in many New Zealand towns. In many parts of Auckland, one in 10 properties have elms. Elm
trees are easily distinguished by their large leaves, which feature serrated edges, symmetrical veins, and an asymmetrical base.
What is Dutch elm disease?
Dutch elm disease (Ophiostoma novo-ulmi) is a destructive and fast spreading disease. It is spread by bark beetles (Scolytus multistriatus)
carrying fungal spores from tree to tree, but can also spread directly through root grafting between neighbouring trees. The fungus clogs
water-conducting tissues in infected trees. The tree responds by forming gum within its tissues, causing it to wilt and then die.
The disease is nearly always fatal - it often kills trees it infects in just a few months and can sometimes kill in as little as two weeks.
Infected trees always have to be removed to prevent the disease spreading further and to prevent dying trees becoming a hazard.
This disease is present in New Zealand (first discovered in Auckland in 1989) but subject to a response programme. MAF Biosecurity New Zealand
(MAFBNZ) no longer contributes funds or manages the programme to control the spread of DED
from Auckland. Auckland City Council has managed the DED control programme
during the 2007/2008 season and is presently planning future programmes.
Identifying infected elms
Identifying infected elms is critical to the success of the programme. People can help fight the disease by looking out for:
- signs of wilting, curling, or yellowing leaves
- dying or dead branches and trees.
If you think you've found an infected tree, contain it and contact us immediately. You should not move or
destroy elm or zelkova material in the greater Auckland area. Elm wood is an ideal breeding site for the bark beetles that spread the disease.
Vegetation control zones
A vegetation control zone is an area where the movement of vegetation is controlled, in order to prevent the spread of a disease. The
vegetation control zone established by the Dutch elm disease programme restricts the movement of elm produce in the Auckland region. The vegetation
control zone is established under the authority of section 131(2) of the Biosecurity Act 1993 and there are severe penalties for violating it.
Areas covered by the control zone?
The vegetation control zone covers Waitakere, North Shore, Auckland and Manukau cities, and Papakura
District.
What can't be done in the vegetation control zone
You need permission to plant, transport, or destroy elm produce (trees, cuttings, seeds, firewood, timber and seedlings) in the vegetation control
zone. Contact us before taking part in any of
these activities.
Penalties for violating the vegetation control zone
Violating the vegetation control zone is an offence under the Biosecurity Act 1993 (see sections 154 and 157). It carries a penalty of up to
five years imprisonment or a fine of up to $100,000 for individuals or $200,000 for companies, or both.
Monitoring and fighting the disease
Auckland City Council is taking a lead role managing the monitoring and fighting of the disease in Auckland. The Dutch elm disease programme
has so far stopped the disease from becoming the national disaster it has been in many other countries around the world.
The programme is focused on identifying and removing infected elm material that the bark beetles, which spread the disease,
can breed in - and preventing the spread of the disease by restricting the movement of elm produce in Auckland.
Auckland City Council manages work carried out by:
- SPS Biosecurity - who carry out tree surveys and the pheromone trapping of beetles throughout the Auckland region
- Scion - who provide technical expertise, diagnostics and update database information.
The continued success of the battle against Dutch elm disease also depends on the public's support. You can help fight this disease by helping us
identify elm trees infected with the disease, and prevent the spread of the disease by observing the vegetation control zone.
Garden centres and nurseries
Garden centres and nurseries have an important role to play in protecting New Zealand's fragile environment from Dutch elm disease.
You can help by raising public awareness of the disease and how to fight it by ensuring customers are aware of:
- the vegetation control zone restrictions on planting or moving elm trees and produce in the Auckland region
- what infected trees look like
- the need to contact us if they want to cut down an elm tree, want to move elm produce, or
find a tree they suspect is infected.
Buying and selling elms trees
Garden centres and nurseries in the vegetation control zone cannot sell elms. Elms can be sold outside the vegetation control zone, however, care
should be taken to ensure customers are aware it is illegal to take elms into or through the vegetation control zone without permission.
This is particularly important if customers are from the Auckland region or are likely to be taking the elms into or through the region. Responsible
garden centres and nurseries in neighbouring regions should discuss this with every customer buying an elm tree.
Outside the Auckland region
Garden centres and nurseries in or near the Auckland region will play the greatest role in the fight against Dutch elm disease.
However, those outside the Auckland region, especially those in neighbouring regions, still have an important role by being on the lookout for
customers who might take elm produce (trees, cuttings, seeds, firewood, timber and seedlings) to or through the Auckland region.
Tree removal contractors
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| Removal of infected tree |
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Tree removal contractors have an important role to play in protecting New Zealand's fragile environment from Dutch elm disease. You can help by
preventing the spread of the disease and by keeping Auckland City Council informed of what's happening on the ground.
In particular, you should:
- look out for signs of infected trees and notify Auckland City Council if you think you've found an infected tree
- see General information for information about what they look like and what to do if you find one
- observe the vegetation control zone restrictions on removing, transporting, and disposing elm produce
- contact us if you are not sure what to do.
The council keeps a database of every known elm tree in the region and may need to inspect the elm tree before permission is granted for the above.
Hygiene requirements
Removal and pruning
- all material must be chipped. Logs can either be cut up and chipped, or
chipped and buried in landfill
- chip to be buried in landfill or kept at storage site is to compost for a minimum of three months. Chip should be sprayed with insecticide
(eg Deltamethrin) to prevent Borer (vector) spread
- clean all equipment (chainsaw, pruning saw) after use with methylated
spirits. Note - the fungus was spread to Napier via earthmoving equipment
- the tree stump must be stump ground or debarked.
Published May 2008
