By the looks of those photos, something much larger than ants are chewing on the tree. Probably a 4-legged something. (If not that, perhaps 2-legged vandal.)

If ants are feeding at the wounds, they are secondary to whatever caused the wounds in the first place.

Bottom line: The ants aren't the problem.

I'll agree that the ants are probably just secondary to whatever is chewing this bark. But what could it be? What would chew the bark off of the shamel ash trees and leave the nearby citrus trees alone? Is there a pest that specifically likes the shamel ash?