Check if Website is hidden from Search Engines?

Any idea how to check if the website is hidden from search engines? The reason is I want to show a big red banner at the top of the homepage when this option is checked because I always forget that this option is checked.

The setting is stored in the option blog_public.

if( 0 == get_option( 'blog_public' ) ){
    echo 'search engines discouraged';
}