3 Words: Shock and Awe. Personally, I'd make it a point to out-fart him. I'd load up on chili, doritors (cool ranch coes wonders), drink a little five-alive. Cabbage always works here. Then I'd just sit and wait with answer-backs. The moment he lets out the first one immediately stand up, yell "return fire" and let one loose in his direction. I've also noticed using the post-flatus scoop works wonders to quell opposition. I admit its rather unladylike, but it'll get him to stop. That or you might all need to relocate to the outdoors.
But in all seriousness (is anybody even still reading my response at this point?) after the first couple of times, a hearty "DUDE!" should've alerted your fragrant fellow to your displeasure. You can only rect(must fight urge to write "um")ify by talking to the other player. You can do it several ways: directly, comically, hostile. The latter likely won't get you anywhere. Personally, I'd use comedy and call him out in front of the group first and if that didn't fix it talk to him aside from the other players.
