I have a young self-seeded ash tree which I have pollarded. This year swellings have appeared on the trunk and the tree does not look as healthy as previous years, which I put down to wood pigeon damage. I don't think it is ash die back. Any ideas?
Certified GKH Gardening Expert
I am not sure what these swellings are, but they look like some sort of burls (abnormal growth usually caused by stress, which can include injuries).
Alternatively, this article states that the lilac borer insect can cause swellings on ash trunks. I'm not personally familiar with the damage that insect causes though.