Dutch elm disease in Waipā under close scrutiny to limit spread

A fatal tree disease that wiped out vast forests of elms in North America and killed off nearly all of Europe and Britain’s mature elms has been discovered in Te Awamutu.

Tests last week confirmed a tree on private property in Te Awamutu has Dutch elm disease.

It was caused by a species of fungus and almost always deadly. Infected trees must be removed to prevent the disease from spreading further.

Efforts in the UK and Europe to prevent the spread of the disease proved worthless.

It was first discovered in 1910, but a more virulent strain was detected in 1967 through shipments of logs from Canada for the shipping industry.

By 1990 very few elms were left in Britain.

The disease is believed to have come to North America in 1928 through a shipment of logs from the Netherlands.

Some European and American cities have saved thousands of trees, but at huge expense.

According to Wikipedia Winnipeg has 200,000 elms and spends $3 million per year controlling the disease.

Waipā District Council arborist planner James Richardson said Dutch elm disease was rightly considered to be one of the most devastating tree diseases in the world.

It is spread by elm bark beetles, which carry the fungus from an infected tree and bore into new trees nearby.

It can also be spread to other elms via the trees’ connected root systems, movement of firewood or contaminated pruning tools. It does not affect trees unrelated to the elm species.

He said the beetles were not very good at flying, so their movements, and therefore the spread of the disease, was quite slow.

Scolytus multistriatus or European elm bark beetle carries disease spores from tree to tree.

The threat from humans and human activity was more concerning.

Dutch elm disease was first found in New Zealand in 1989 in Napier and Auckland.

It was eradicated in Napier but has continued to spread from Auckland.

“It is very concerning to have confirmation the disease is now in Waipā,” Richardson said.

“We will be working closely with Waikato Regional Council, SPS Biosecurity and Environmental Services, the Ministry for Primary Industries (MPI), local arborists, Cambridge Tree Trust and the community to limit the spread of the disease.”

Waipā District Council arborist planner James Richardson in front of a row of Golden Elm at Te Awamutu's Centennial Park. Photo / Dean Taylor

An infected elm tree can die in as little as three weeks, or over two to three years.

Symptoms develop quickly within a four to five-week period, and signs of the disease include wilting, curling, yellowing of leaves and dying or dead branches. There is no known cure for infected trees.

“When removing the infected trees, all material should be immediately chipped, burned or buried on-site or at a landfill site. Incorrect processing can spread the disease further.

“People should contact MPI if they suspect their elm trees to be infected.”

Elms can be identified by their large leaves, which feature serrated edges, symmetrical veins, an asymmetrical leaf base and feel like sandpaper.

The next step for the council would be to collaborate with SPS Biosecurity and Environmental Services to monitor the spread of the disease.

The elm was once a popular tree for parks and reserves and Waipā District Council has over 250 mature elm trees it maintains.

Staff would be monitoring and assessing them regularly to identify any trees with the disease early and manage any actions required.

If residents suspect the disease is present on an elm tree, they can report it to MPI’s Exotic Pest and Disease Hotline on 0800 80 99 66.

For more information visit, waipadc. govt.nz/dutchelmdisease

Dean Taylor is a community journalist with more than 35 years of experience and is editor of the Te Awamutu Courier and Waikato Herald.

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