personalmente no usaría plugin para el robots.txt
similar a este uso yo
Insertar CODE, HTML o PHP:
Sitemap: http://www.TUSITIO.com/sitemap.xml
# Google Image
User-agent: Googlebot-Image
Disallow:
Allow: /*
# digg mirror
User-agent: duggmirror
Disallow: /
# global
User-agent: *
Disallow: /cgi-bin/
Disallow: /wp-admin/
Disallow: /wp-includes/
Disallow: /wp-content/plugins/
Disallow: /wp-content/cache/
Disallow: /wp-content/themes/
Disallow: /trackback/
Disallow: /feed/
Disallow: /comments/
Disallow: */trackback/
Disallow: */feed/
Disallow: */comments/
Disallow: /*?
Disallow: /wp-login.php
Allow: /wp-content/uploads/
Disallow: /*.js$
Disallow: /*.inc$
Disallow: /*.css$
Disallow: /*.php$
Disallow: /author/
Disallow: /wp-
Disallow: /?s=
Disallow: /search
Disallow: /*/feed/$
Disallow: /*/feed/rss/$
Disallow: /*/trackback/$
Disallow: /*/*/feed/$
Disallow: /*/*/feed/rss/$
Disallow: /*/*/trackback/$
Disallow: /*/*/*/feed/$
Disallow: /*/*/*/feed/rss/$
Disallow: /*/*/*/trackback/$
User-agent: MSIECrawler
Disallow: /
User-agent: WebCopier
Disallow: /
User-agent: HTTrack
Disallow: /
User-agent: Microsoft.URL.Control
Disallow: /
User-agent: libwww
Disallow: /
User-agent: noxtrumbot
Crawl-delay: 150
User-agent: msnbot
Crawl-delay: 130
User-agent: Slurp
Crawl-delay: 110
User-agent: Mediapartners-Google
Allow: /*
se le cambia el sitio y se guarda como robots.txt y se sube al directorio principal donde están los folders wp-admin wp-content etc...