The effects

Ash dieback has affected large numbers of trees since the mid-1990s, particularly in eastern and northern Europe (though the disease has been observed across much of its range) The disease has affected between 60 and 90 per cent of the ash trees in Denmark, and in Sweden more than 50 per cent of the trees have noticeable damage and 25 percent are severely injured. The disease was first discovered in the UK in 2012, initially only on imported nursery stock, but in October 2012 it was found on trees at two sites of established woodland in the East Anglia region.
Research into the genetics of the resistance of ash has shown that resistance does occur in European populations, but, at least for the samples tested, it is neither common nor strong.

From Wikipedia: Ash