Ash dieback has spread rapidly since it was first discovered in Ireland over a decade ago and can now be found in every county.
The disease, which is also called Hymenoscyphus fraxineus, was first found in the state in October 2012, probably introduced on planting material.
However, ash dieback is likely to have been present for a number of years prior to that, the Department of Agriculture, Food and the Marine (DAFM) said.
Ash dieback
By the end of 2022 there had been findings in ash in all 26 counties in over 695 locations in various settings, according to the Forest Statistics Ireland 2023 report.
The disease was found in forests, nurseries and garden centres, on farm planting, roadside planting, hedgerows and private gardens.
With increasing presence, the DAFM switched to mapping findings on the basis of whether the disease has been found in 10km grid squares rather than recording individual findings.
The presence of ash dieback in Ireland suggests a rapid spread of the disease by way of aerial dispersal of spores, the report states.
Trees get infected when the spores of the fungus, which are carried in the air, land on healthy leaves and germinate and the fungus then grows into the leaves and down into the leaf petiole.
The progression into twigs, branches, and the stem causes the tree to lose a part of its crown and, in some cases, to collapse, according to Teagasc.
The wide range of symptoms associated with ash dieback, according to Teagasc, includes:
- Foliage wilt and discolouration;
- Brown/orange discolouration of bark with diamond shape;
- Dieback of shoots, twigs or main stem resulting in crown dieback;
- Necrotic lesions and cankers along the bark of branches or main stem;
- Epicormic branching or excessive side shoots along the main stem.
“Where the disease is already present in a locality, further local spread is likely to be caused by spores borne on the wind, each year travelling many kilometres from the original source.
“There is also a risk of introducing the disease into a locality where it is not yet present by bringing already diseased ash seeds or plants into that area for the first time,” Teagasc said.
On trees aged 30 years or under, symptoms include dieback in the crown, diamond shaped lesions on the stem, coppice regrowth both on the stem and in the crown and basal lesions.
On older trees the main symptom of the disease will be crown dieback. Older trees, although infected, tend to be more resilient and they should be closely monitored, Teagasc said.