Popular traditional deterrents used by gardeners against slugs and snails will not protect prized plants, a study suggests.

A series of home remedies from copper tape to eggshells were tested in a study by the Royal Horticultural Society (RHS), and were found to make no difference in protecting lettuce from the pests.

In light of the results, the garden experts are recommending green-fingered householders encourage natural predators such as birds, or use traps or physically remove slugs and snails.

Gardeners can also use deterrents such as nematodes or slug pellets, making sure they use them strictly according to the manufacturer’s instructions to minimise any risks they pose to wildlife and pets.

The study saw 108 lettuces sown in a series of pots and raised beds at the RHS’s John MacLeod Field Research Facility in Wisley and treated with various methods for controlling slugs and snails, including nothing at all.

The five home remedies tried out in the study were copper tape, horticultural grit, pine bark mulch, wool pellets and eggshells.

The lettuces were grown for six weeks before being harvested and the leaves of each lettuce examined to work out the proportion of damage.

Results showed that the slugs and snails inflicted the same amount of damage on the lettuces treated with the remedies as those without.

Lettuces treated with wool pellets or pine bark did yield a bigger crop, however, as the treatments acted as a fertiliser and mulch, the RHS said.

Although the rough and sharp textures of the home remedies might look unattractive for soft-bodied creatures, the thick slime of slugs and snails is a protective shield, allowing them to glide over the barriers, the experts suggested.

Dr Hayley Jones, entomologist at the RHS and lead researcher, 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 discernible deterrent to slugs and snails we would recommend using proven formulas like nematode biological control if the damage is just too much to bear.”

RHS experts said they would continue to test home remedies for tackling slugs and snails, looking at whether other factors such as environmental conditions and local slug populations make a difference.

They will also be testing other classic methods for tackling the pesky pests, such as beer traps.