Mountain Ash (Rowan) problem.

Good afternoon everyone

Mr Kandy has been doing some work out in our front garden and has noticed a problem with the leaves on our Mountain Ash (Rowan).I have taken a couple of photos and wonder if anyone on here can identify what the problem is and whether we shall end up losing the tree which has been in the garden for fifteen years and this is he first time we have had this problem which we don't know how long the tree has had this particular problem.

Any advice would be appreciated as I have had a Google but can't seem to get an answer

Thanks for reading

 

Sorry Kandy, I can't help you with that, I've not come across it before.

 

Thanks @Sheal for taking the time to answer my post It is the first time we have ever had the problem and just can't find an answer by Googling so will have to hope that whatever it is doesn't kill the tree

 

Looks like Leaf Miner