A study by the RHS has sadly found five popular remedies to be entirely ineffective in deterring slugs and snails. Copper tape, horticultural grit, pine bark mulch, wool pellets and eggshells were found to make no difference when applied around lettuces, with slugs and snails inflicting the same damage as they did on untreated crops. The lettuces treated with wool pellets and pine bark did, however, yield a 50% bigger crop, as these treatments proved effective as a fertiliser and mulch.
One hundred and eight lettuces were sown in pots and raised beds at the John MacLeod Field Research Facility at RHS Wisley, and treated with the various control methods, or no control at all. After six weeks, each lettuce was examined using a leaf area meter that calculated the proportional damage, and the lettuces were weighed to establish yield.
The RHS suggests that, although the rough and sharp textures of the remedies on trial might seem unattractive to soft-bodied animals, the thick mucus of slugs and snails actually acts as a protective shield, enabling them to glide over barriers.
Dr Hayley Jones, RHS entomologist and lead researcher in the trial, who took these pictures at RHS Wisley, said: “Our study reveals that many gardeners could be wasting time and money by turning to home remedies in a bid to protect their prized plants. With the likes of eggshells, barks and mulch so far proving no discernable deterrent to slugs and snails, we would recommend using proven formulas like nematode biological control if the damage is just too much to bear.”
The RHS will continue its trials, investigating other factors such as whether environmental conditions and local slug populations make a difference. It also plans to test alternative control methods such as beer traps.
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