rust on leeks

Mine have had a bit of rust on the older, lower leaves so I pull them off and bin them - it's never occurred to me to pull leaves off and use them in soups before the leeks are ready, but if it had I don't think I'd fancy rusty ones much anyway.   

Ah - thought it might be some sort of canny Scottish practice I'd never heard of! 

Same answer really - best to take off affected leaves so they don't spread it around any further, then hope that the plants continue to grow well enough to give you plenty of stems to eat.