Ash dieback, also known as Hymenoscyphus fraxineus, has rapidly spread throughout Ireland since its initial discovery over a decade ago. The disease was first identified in the country in October 2012, most likely introduced through planting material. However, the Department of Agriculture, Food and the Marine (DAFM) believes that ash dieback may have been present for several years prior to its official detection.
According to the Forest Statistics Ireland 2023 report, ash dieback has now been found in every county in Ireland, with over 695 locations affected. The disease has been observed in various settings, including forests, nurseries, garden centers, farm plantings, roadside plantings, hedgerows, and private gardens. Due to its increasing prevalence, the DAFM has shifted its approach to mapping findings based on 10km grid squares rather than individual occurrences.
The presence of ash dieback in Ireland indicates a rapid spread of the disease through the aerial dispersal of spores, as stated in the report. Trees become infected when the spores, carried by the wind, land on healthy leaves and germinate. The fungus then grows into the leaves, down into the leaf petiole, and further into the twigs, branches, and stem. This progression leads to the loss of a portion of the tree’s crown and, in severe cases, its collapse, according to Teagasc, the Agriculture and Food Development Authority.
Teagasc outlines various symptoms associated with ash dieback, including foliage wilt and discoloration, brown/orange discoloration of bark in a diamond shape, dieback of shoots, twigs, or the main stem resulting in crown dieback, necrotic lesions and cankers along the bark of branches or the main stem, and epicormic branching or excessive side shoots along the main stem.
The disease can spread locally through spores carried by the wind from an existing source. Each year, these spores can travel many kilometers, contributing to further spread within a locality. Additionally, there is a risk of introducing the disease to new areas by bringing already infected ash seeds or plants into those regions for the first time, warns Teagasc.
Symptoms on trees aged 30 years or younger include crown dieback, diamond-shaped lesions on the stem, coppice regrowth in both the stem and crown, and basal lesions. In older trees, crown dieback is the main symptom. Although older trees tend to be more resilient to the disease, they should still be closely monitored, advises Teagasc.
It is crucial to address the spread of ash dieback in Ireland to protect the country’s ash tree population. Efforts should include monitoring and surveillance, as well as raising awareness among the public and those involved in the forestry and horticulture sectors. Collaboration between government agencies, researchers, and stakeholders is essential to develop effective strategies for managing and mitigating the impact of this devastating disease.