Use bird friendly ferris iron based slugs pellets. You must keep putting them down too, especially after very wet weather. Also try liquid Slugclear or Sluggit watered onto the plants after a heavy shower. Put pellets down in the autumn too when slugs are laying their eggs to overwinter. Organic alternatives are copper rings, coffee granules, egg shells, human hair, grit, beer traps, copper filings and cooking bran.