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Dutch elm disease hits Pukekohe elms

Contractors will remove plagued trees

Published: 17 February 2020

Four trees hit by Dutch elm disease in the Pukekohe Park Raceway are to be removed.

The trees are on the road reserve next to Gate 3 and Auckland Council arboriculture specialist Simon Cook says removing them is critical to stopping the disease spreading.

“We are trying to retain some fantastic elms in the grounds by removing the diseased trees as soon as we can.

“Diseased trees harbour beetle larvae that become infected with the fungus that causes the disease, and when they mature and fly, they carry it to nearby elms.”

Dutch elm disease reached Pukekohe in 2017, its furthest point south, and recently reached Orere Point, its furthest point east. Contractors felled the infected trees.

Before Orere Point, the closest previous incident was in Whitford, and because the beetle travels less than a kilometre, council staff think the disease was carried in on infected firewood or logs, even though it is illegal to transport elm - dead or alive - within Auckland under the Biosecurity Act.

The fungal disease is almost always fatal and infected trees must come down to stop the disease spreading.

Caused by a fungus, it is commonly spread by the elm bark beetle carrying spores to new trees but can also be spread by root grafting.

Cook says it’s critical elm is not taken out of Auckland as logs or firewood. With current fire restrictions, burning is not an option, and storing it is not permitted. Infected trees should be removed and mulched so dying trees can’t become a source of infection.

“The infestations are a reminder for residents to check elms on their properties. Signs include wilting, curling or yellowing of leaves, or dying or dead branches.”

The deciduous trees are distinguished by their large leaves with serrated edges, symmetrical veins, and an asymmetrical base.

While diseased trees must be removed by a property owner at their own cost, people should not attempt removals themselves because incorrect processing can spread the disease. Instead, call Auckland Council on 09 301 0101.

Auckland Council has a beetle pheromone trapping system set up on the southern border with Waikato. It alerts staff to infected sites within 500m-1km of the traps, and Cook says so far all the beetles caught have been negative to the fungus.

Read more: Environment Franklin

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