This is a tricky issue, because EPiServer 4.61 don't fire any events when deleting a language branch of a page(other then the master language branch). I've tried to find a good solution to the problem myself, but without success. As far as I know, there ain't any plans for fixing this in 4.61 either.
If you wanna make a dirty hack you can parse the EPiServer log file for the log entry:1.6.13, which actually logs the page language deletion( INFO Page: {PageID} Language: {LanguageID} was deleted by user {User} )
-Geir Allan Hove