‘All of island’s ash trees to have dieback in five years’

The disease, which is fatal to nearly all ash trees, was first detected in 2012, when it was found on imported saplings.

That was dealt with successfully.

But in 2018 the disease was detected in older trees and, following further investigations, it was found in seven locations across Guernsey and was therefore considered to be established.

A planning application was recently submitted to fell an infected tree on the protected register, which prompted Agriculture, Countryside & Land Management Services, which is part of the Committee for the Environment & Infrastructure, to set out the seriousness of the threat across the island.

‘Once infected, the tree is unlikely to survive, and the risk of infection is likely to be close to 100% over the next four to five years because spores, which spread the disease from one site to another, are windborne,’ it said.

Natural environment officer Emily Coule said the figure of 100% was based on estimated infection rates.

‘This can vary depending on genetic traits, tree health, the surrounding environment and the number of ash dieback spores in the atmosphere, but we expect to lose significant ash populations,’ she said.

‘Initial findings estimate that 1-5% of ash trees may show tolerance to ash dieback, but none have been found to be completely resistant yet.

‘Therefore, increasing the genetic diversity of our woodlands and planting a mix of native species will help to improve the resilience of our woods to future diseases.’

She did not know if the 2018 infections which have since taken hold came from being blown in or from imported trees.

‘As a Bailiwick we are able to introduce biosecurity and plant health check measures on imported goods which can help protect our biodiversity against disease,’ she said.

‘We can also source locally grown plants to lower the number of imports which can reduce the risk of the disease.’

In the UK, people who manage ash trees near roads, railways, buildings and other publicly accessible land are advised to consider the risks posed by infected ash.

Ms Coule said that Guernsey was not routinely removing ash trees because retaining healthy trees allows the survival of potentially tolerant ash trees.

‘Trees on public land are regularly inspected for damage and disease, particularly in relation to the health and safety of members of the public, which is our primary consideration,’ she said.

‘The ash trees at greatest risk are young trees grown near each other where humid conditions are favourable for the spread of spores and the infection of leaves. Large trees in isolation will be less susceptible.’