I noticed this white stuff on the trunk of my Rowan tree this morning. Is it anything to worry about and how do I treat it (if needed)
Scariff, County Clare, Ireland
Looking at my 3 rowan trees confirms that this is perfectly normal - they just have patterned bark when mature.
Make sure the green ties for your lights aren't cutting into the bark though. They look a bit tight...
"The one who plants trees, knowing that he will never sit in their shade, has at least started to understand the meaning of life." Rabindranath Tagore
I may be 'well off the mark' here , but to me (can't magnify enough) , those growths resemble Barnacle Lichen .