are manual edits to crontab reflected immediately?

Our remote support guy made a change to a server that we are bringing online.
I need to change one directory in an existing /etc/crontab entry. If I make this change, will it be reflected immediatly, or do I need to poke something to get the change picked up?

The crontab is scanned every time cron fires, so as soon as you save your updates, cron should pick them up.