Disabling Trigger

Hello All,

Does any one know how disable a specific trigger i know the following way to 
disable trigger but it disables system generated default triggers too.

UPDATE pg_catalog.pg_class SET reltriggers = 0 WHERE oid 
='table_name'::pg_catalog.regclass;

I also tried the following

UPDATE pg_trigger SET tgenabled = FALSE where tgname='trigger_name';

But this too doesnt work.

Any help appreciated.

Cheers
Prasad.