Early-stage research at Teagasc has shown “promising” outcomes that young ash trees are developing a tolerance to ash dieback.

AshforFuture, launched in 2024, is an all-island project that builds on earlier work by bringing targeted resources to support the long-term recovery of ash.

Dr Dheeraj Rathore, Teagasc tree improvement research officer, said initial observations are positive but the dieback disease is complex.

“This new study is about fast evolution within the ash tree population which we don’t generally expect, this is why the study received significant attention in the scientific and non-scientific world. Using DNA comparisons, the study reported that within one generation, evolution towards resistance or higher tolerance in ash trees has been evident.

“But evolution can happen on both sides: in the host (ash tree) and in the pathogen (dieback).

“The results are promising but it’s quite early to say that this is going to continue towards the desired resilience levels until we do the required testing ourselves.

“The environment can have a big influence on either encouraging the pest/pathogen to be more virulent or making the trees more resilient.”

Tolerance

For more than a decade, ash dieback has been observed in Ireland, caused by the invasive fungal species Hymenoscyphus fraxineus.

Approximately 1% to 3% of ash trees exhibit a higher level of natural tolerance to dieback. In this project, researchers are taking cuttings from trees showing tolerance to graft onto other trees and seeds from such trees to grow young ash saplings in “high disease pressure” plantations.

Dr Rathore said it is hoped that there will be results from these progeny trials by 2028.

“It’s only been a bit more than a decade since the disease was first noted in Ireland and we haven’t reached the peak of the disease’s establishment yet,” he added.

“We will see a bit more of the trees’ susceptibility and mortality but then we will reach a stage where the small proportion of more tolerant trees, in natural woodlands or hedgerows will revive.

“What we are doing as researcher is just accelerating and facilitating this progression,” he maintained.