Ash Dieback Question...

[Bee-Key-Pur]

I have a very old, massive ash tree on my land, but it's showing no signs of die back, in fact it's looking very healthy.
Does the problem effect old trees in a different way, showing different signs or is it a case that it may not have been affected yet?

 

[Erichalfbee]

I understood that old mature trees could cope with the fungus.
I'm sure I read that somewhere
I have three all about 30 meters tall.
I would hate to lose them. The beeches near the house....now that's a different story Grrrrrrrrrrrrr