RHS slug study busts home remedy myths

Friday 28 September 2018

- Popular precautions prove ineffective in gastropod trial
- Slugs and snails undeterred by copper tape, egg shells and grit
- Charity recommends attracting garden predators and scientifically proven deterrents

Five home remedies traditionally used by gardeners to deter slugs and snails have proved entirely ineffective in the first scientific study of its kind by the Royal Horticultural Society (RHS).

Copper tape, horticultural grit, pine bark mulch, wool pellets and egg shells were shown to make no difference when applied to lettuce, with gastropods inflicting the same damage to those treated with the remedies as without. However, lettuces that benefitted from a layer of wool pellets or pine bark yielded a 50% bigger crop as the treatments acted as a fertiliser and mulch.

The RHS therefore recommends that gardeners encourage garden predators, employ other cultural controls such as physical removal or traps and, failing that, if damage cannot be tolerated, turn to scientifically proven deterrents such as nematodes and slug pellets. The latter used strictly according to the manufacturer’s instructions to minimise risk.

108 lettuces were sown in a series of pots and raised beds at the charity’s John MacLeod Field Research Facility in Wisley and treated with alternate control methods, including no control at all. The lettuces were grown for six weeks before being harvested and the leaves of each lettuce examined using a leaf area meter that calculated the proportional damage. The lettuces were then dried and weighed to establish yield.

Lettuces planted in the ground were found to be more susceptible to slugs, with 5.7% of each eaten on average. This compares to just 0.2% of those in pots, which, despite this advantage, still yielded less crop. The ready availability of lettuces at ground level is thought to have helped minimise damage to pots.

The RHS Lindley Library found that gardeners have turned to home remedies since the 1600s to counter slugs and snails. Those tested in the experiment were thought not to work because, although their rough and sharp textures look unattractive to soft-bodied animals, the thick mucus of slugs and snails acts as a protective shield, enabling them to glide over the barriers.

The two main gastropod culprits in the experiment were the grey field slug and common garden snail but gardeners are being reminded of the benefits of some varieties to gardens, including the green cellar slug which feeds on mould and algae and the leopard slug that prefers fungi and rotting material – making it a good garden recycler.

Dr Hayley Jones, Entomologist at the Royal Horticultural Society 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 egg shells, 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 to test slug and snail home remedies, investigating other factors, such as whether environmental conditions and local slug populations make a difference. The RHS also plans to test alternative control methods such as beer traps and is currently working to investigate ways to combine scientifically proven control methods into pest management strategies.

For more information about garden slugs and snails as well as other pests and diseases please visit www.rhs.org.uk


Notes to editors

About the RHS: The Royal Horticultural Society was founded in 1804 by Sir Joseph Banks and John Wedgwood to inspire passion and excellence in the science, art and practice of horticulture. Our vision is to enrich everyone’s life through plants, and make the UK a greener, healthier, happier and more beautiful place. We believe everyone in every village, town and city should benefit from growing plants to enhance lives, build stronger, healthier, happier communities and create better places to live.

We held our first flower shows in 1820, were granted a Royal Charter in 1861 and acquired RHS Garden Wisley, our flagship garden, in 1903. From our first meetings in a small room off London’s Piccadilly, we have grown to become the world’s largest gardening charity. At our gardens and shows and through our scientific research, publications, libraries and our education and community programmes we inspire a passion for gardening and growing plants, promote the value of gardens, demonstrate how gardening is good for us and explain the vital roles that plants undertake.

The RHS is committed to bring the joy of gardening to millions more people, inspire the next generation of gardeners and invest in the future to safeguard a £10.4 billion industry employing more than 300,000 people. We are entirely funded by our members, visitors and supporters. RHS membership is for anyone with an interest in gardening. Support the RHS and help us secure a healthy future for gardening. For more information call: 020 3176 5820, or visit www.rhs.org.uk/join

RHS Registered Charity No. 222879/SC038262

For more information please contact Laura Scruby in the RHS press office: laurascruby@rhs.org.uk / 0207 821 3060

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About the RHS

The RHS believes that gardening improves the quality of life and that everyone should have access to great garden experiences. As a charity we help to bring gardening into people's lives and support gardeners of all levels and abilities; whether they are expert horticulturists or children who are planting seeds for the very first time.

RHS membership is for anyone with an interest in gardening. Support the RHS and secure a healthy future for gardening. For more information call: 0845 130 4646, or visit www.rhs.org.uk

RHS Registered Charity No. 222879/SC038262