big server LOAD wpua_has_gravatar_cron_hook

Since a week ago my server was a big load. I put a display into cron and saw thousand of lines like this executing in my cron every 5 minutes:

(wp_unsheduled_event1419067822 hook=wpua_has_gravatar_cron_hook args=Array)
done(do_action hook=wpua_has_gravatar_cron_hook args=Array)

I try to remove wpua_has_gravatar_cron_hook using CRONTROL withh no success, I try to remove it from options table in database but it comes back any time I remove it. I uninstalled WP avatar but wpua_has_gravatar_cron_hook still there… How can I delete it from my cronjob?

Thanks!