Trees removed from Mt Hobson after disease found

Dutch elm disease is spread by bark beetles The fungus clogs water-conducting tissues in infected trees. The tree responds by forming gum within its tissues, causing the tree to wilt and then die.

More than 20 trees on Ohinerau/Mt Hobson are being removed after they became infected with Dutch elm disease.

Contractors started removing the infected trees from the eastern slope of the Tupuna Maunga this week.

Auckland Council is carrying out this work in its role of providing the maintenance for the Tupuna Maunga, which are owned by Nga Mana Whenua o Tamaki Makaurau and governed by the Tupuna Maunga o Tamaki Makaurau Authority (Maunga Authority).

"The discovery of the disease on one of Auckland's treasured maunga is heart-breaking, but there is no choice but to remove them," says Councillor Christine Fletcher, chair of the council's Parks, Sport and Recreation Committee and Deputy Chair of the Maunga Authority.

"Doing nothing is not an option as it puts other elms on the maunga and in neighbouring suburbs at risk of the disease."

Dutch elm disease is an extremely virulent fungal disease that causes trees to wilt and die. It is transferred from tree to tree through root grafting or via the elm bark beetle.

An infected beetle was trapped on the maunga in early January and subsequent tests identified several trees showing signs of the disease. The council has an ongoing monitoring and trapping programme in place for the elm bark beetle.

Auckland Council Arboriculture and Landscape Advisor, Simon Cook, says staff are working under the direction of the Maunga Authority to ensure the careful removal of the trees.

"Dutch elm disease can spread quickly and it is nearly always fatal for the affected trees so we take every precaution to ensure we remove the trees carefully and contain the threat of the disease spreading any further afield."

It is also a timely reminder for all Aucklanders to check elm trees on their properties for signs of the disease.

The council is also monitoring trees in Gifford Road, Papatoetoe after three infected trees were removed earlier this week.

Elms are deciduous Northern Hemisphere trees distinguished by their large leaves, which feature serrated edges, symmetrical veins, and an asymmetrical base. Signs to look out for include wilting, curling or yellowing of leaves or dying or dead branches on elm trees.

Under the Biosecurity Act 1993, the fungus is an 'unwanted organism' so Auckland Council is obliged to undertake every reasonable effort to destroy the fungus once found.

"Do not be tempted to use the timber for firewood either," says Mr Cook. "Elm wood cannot be stored, elm material cannot be moved in or out of the Auckland area between the Bombay Hills and Albany, and cannot be brought into or sold at nurseries in the region," he says.