Page 16 - ALG Issue 1 2019

General
RHS Slug Study
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).
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
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 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”.
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.
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 should be 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.
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
"the likes of egg shells, barks and mulch so far proving no discernible deterrent to slugs and snails"
How to make a Beer Trap
The above RHS press release about home remedies to deter slugs, inspired a fair bit of comment when posted on the Society’s Facebook page. Some people insisted that the disproved remedies worked for them but the majority of comments concerned the efficacy of Beer Traps; something the RHS are yet to test.
There are beer traps available to buy online; these
have the advantage of having a lid that stops the rain diluting the beer but homemade traps can be made with old tins or plastic bowls. There are numerous tutorials
on the internet but I liked the one that used a large size old water bottle. 2 x 10cm deep by 8cm wide doors are cut either side of the bottle, 7cm above the base, leaving the plastic attached at the bottom so that the door can be cramped and bent down to form a ramp for the slugs to slide up and enter the bottle. Dig in to a shallow hole in your soil. Fill the base with about 5cm of cheap beer; the top of the bottle (lid left on) keeps rain out of the beer. The drowned slugs can be added to the compost heap.
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