Dutch Elm Disease: Waikato trees to be vaccinated

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

Waikato trees are rolling up their leaves to be vaccinated against Dutch elm disease.

The fatal and fast-spreading tree disease was discovered in the Waipā district in February. It is caused by a species of fungus and almost always deadly.

While there were only three reported cases in the district, Waipā District Council said it would take a proactive approach and vaccinate elm trees on local parks, reserves, and streets.

Arborist planner James Richardson said the vaccination would not harm the trees and was a form of biological control.

“A solution containing a Verticillium fungus is injected into the active sapwood of the tree at 10cm intervals around the circumference of the trunk,” Richardson said.

“The injection of the fungus initiates a defence response from the tree that allows it to fight off Dutch elm disease infection and greatly reduces the chances of them dying if they get the disease.

“The injection is conducted in spring, at a time before the tree can be infected with Dutch elm disease, but when it is active enough for proper uptake of the vaccine.”

The tool for the injection resembles a large syringe and needle.

The vaccination programme will start in November and is estimated to cost Waipā District Council $25,000.

In vaccinating the trees, Waipā is following in the footsteps of Auckland Council which has seen a decrease in trees dying from the disease over the past three years since the vaccine was introduced to New Zealand.

The vaccine, called DutchTrig, is manufactured in the Netherlands and has been used there since the 1990s.

The tool to administer the vaccine against Dutch elm disease resembles a syringe and needle.

It is currently not available to the public.

Richardson said Dutch elm disease was considered to be one of the most devastating tree diseases in the world.

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

Infected trees must be removed to prevent the disease from spreading further.

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

However, it can also be spread via the trees’ connected root systems, by movement of firewood, or by contaminated pruning tools.

Symptoms develop quickly within a four to five-week period, and signs of the disease include wilting, curling, yellowing of leaves and dead branches.

The disease was first discovered in Europe in 1910. It was first found in New Zealand in 1989 in Napier and Auckland.

It does not affect trees unrelated to the elm species.