1
Disable Settings/Discussion Settings “Allow link notifications from other blogs (pingbacks and trackbacks)”.

2,
Run this MySQL commands on your WP database to hide message of earlier posts:

UPDATE wp_posts SET ping_status='closed' WHERE post_status = 'publish' AND post_type = 'post';
UPDATE wp_posts SET ping_status='closed' WHERE post_status = 'publish' AND post_type = 'page';

source: http://www.wpbeginner.com/wp-tutorials/how-to-disable-trackbacks-and-pings-on-existing-wordpress-posts/