cron logging under RHEL 4

Tue May 23 19:50:04 UTC 2006

Does anyone know how to turn off the logging messages from cron under 
redhat RHEL 4 ? I am refering to the messages in /var/log/messages that 
indicate a user has logged in/out every time a user crontab is called.. 
these tend to fill up the log files when a user has a number of cron 
entries that are called every minute.

example..

May 23 14:49:01 wibble crond(pam_unix)[13740]: session opened for user 
bot by (uid=0)
May 23 14:49:01 wibble crond(pam_unix)[13740]: session closed for user bot

-- 
Steve.