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Elm Bark Beetle trap line moves south

The discovery of infected Elm Bark Beetles in the Mercer, Te Kauwhata and Huntly areas has forced a change to the trapping programme initiated in the north Waikato in November.

Weekly monitoring of a trap line stretching from Waitakaruru to Port Waikato revealed two  locations where infected beetles were present. A spot check of a site in the Huntly area also revealed a suspected case of Dutch Elm Disease in two trees.

Elm Bark Beetles spread Dutch Elm Disease, a fungal disease, by carrying fungus from diseased trees to other elms when they feed. Eggs are then laid in the bark and the beetles that hatch emerge and fly to the next elm tree and can also infect it with the disease.

Following expert advice from specialist biosecurity contractors, part of the trap line has now been moved further south to the Waiterimu, Tahuna, Ohinewai and Huntly areas.

The initial trap line set up in November contained about 50 traps, at 1.5km intervals, placed in an approximate east-west line from Waitakaruru to Port Waikato.

As infected beetles were discovered east of State Highway 1 on that line, and due to the western side of State Highway 1 being more rural and there being no evidence of infected beetles, the traps to the west of State Highway 1 have been moved down to the Waiterimu, Tahuna, Ohinewai and Huntly areas.

The initial trapping line on the eastern side of State Highway 1 has been retained.

This is all part of Waikato District Council’s efforts to try and help prevent Dutch Elm Disease spreading further south.

Dutch Elm Disease has been present in the Auckland region for about 30 years and last year Auckland Council’s  trapping programme detected the disease on the Auckland-Waikato border, in the Pokeno and Miranda areas.

The traps are placed on fence posts or utility poles, and remain active at least until May 2023. They are checked on a weekly basis.

If beetles are found in the traps, the contractors look for the potential source (infected trees) in the immediate area – which could be up to 5km around the source trap.

This response involves collaboration with neighbouring property owners in the form of door-knocking and letter drops in that immediate area.

If an infected tree is found and is confirmed to have Dutch Elm Disease, property-owners will be notified and given an additional letter to inform them of the presence of the disease on their property.

Waikato District Council will liaise with these property owners about the removal of infected trees, which has to be done by following the prescribed protocol and method of dealing with the tree debris in the appropriate manner to prevent the spread of the disease.

Wilting foliage, dead or dying branches, and dead elm trees are all typical signs of Dutch elm disease. The disease only affects elm trees.

If you suspect an elm tree in your area may be diseased, please call 0800 492 452.

What is Dutch elm disease (DED)?

  • It is caused by the fungus Ophiostoma novo-ulmi
  • The disease is commonly spread by the Elm bark beetle (Scolytus multistriatus) carrying fungal spores from tree to tree but can also be spread through root grafting.
  • DED is a destructive fungal disease and is almost always fatal once a tree is infected.
  • Infected trees must always be removed to prevent the disease spreading further

How do I identify an infected tree?

  • Elm trees are easily distinguished by their large leaves, which feature serrated edges, symmetrical veins, and an asymmetrical base.
  • Watch for signs of wilting, curling, or yellowing leaves or dying or dead branches and trees.