This story began in 2015 when Kew Gardens came to Allt Rhongyr to find healthy female ash trees. They selected 15 maternal trees and assessed their health.  This August they returned to reassess the trees.
Of the 14 trees they were able to locate all were in either a progressed state of decline or already dead.  

Owen Blake, UK Tree Seed Collecting Project Officer says; “Of the maternal trees we are returning to, we have visited roughly 250 trees where seed was collected previously, we have found maybe 2 that are potentially tolerant.”

Similar to our own Ash safety surveys the Kew Gardens team grade the health of the trees based on loss of the crown canopy, dead stems and the presences of epicormic growth on the branches.

On a plus note they did find a smaller tree by the Allt Rhongyr bridlepath that showed no signs of disease and so could be tolerant to ash dieback disease. They took a leaf tissue sample from this tree and another non-tolerant tree to act as a comparison.

Paradoxically now that the disease has now taken hold across the country, Owen and his team have a better chance of spotting resistant trees.
“Anecdotally different areas of the UK seem to be having contrasting years where the ash either look healthier or in decline.” 

The fungus does less well in hot dry weather, but ash trees also suffer in prolonged drought. This makes it even more difficult for the researchers to be able to define the genetic component of resistance from environmental factors.