SOME SLUG DETERRENTS WASTE OF TIME, SAYS RHS
A scientific study by the Royal Horticultural Society (RHS) has found that some of the traditional remedies thought to deter slugs and snails are totally ineffective. Lettuce that was protected with copper tape, horticultural grit, pine bark mulch, wool pellets and egg shells incurred the same damage as lettuce where there was no deterrent in place at all.