Gardeners urged to go snail bowling
Gardeners struggling with snails chumping through their prized plants should develop a strong throwing arm to tackle the problem, research suggests.
Removing snails at least 20 metres (65 feet) - around the length of a cricket pitch - out of the garden is as beneficial as killing the molluscs, a new study says.
Gardeners employ a range of methods besides chemical pellets to tackle snails, including beer traps, egg shells and standing on them.
And a fifth admit to lobbing snails over the fence, although the research shows a "homing instinct" which means the pests frequently make their way back from next door.
However, they almost always failed to return from distances of 20 metres or more, t he study published in the journal Physica Scripta said.
The study found there was little advantage for gardeners in killing the snails they discovered in their flower beds, as they were part of a much larger, wider population coming in and out of the garden.
Even systematic search and kill missions would take months to bring down the total population significantly.
Reducing numbers temporarily to protect young plants is achieved just as well by removing the snails over a wall or five metres (16 feet) away, the researchers said.
And the near total-failure of snails to make it back from 20 metres away suggests gardeners could better control them with " a stronger throwing arm or mechanically-assisted lobbing".
But the researchers said it might be better for the local gardening community to take the snails to a nearby wasteland, rather than shifting the problem onto the neighbours.
Study co-author Professor David Dunstan, from Queen Mary University of London , said: "We showed that the number of snails regularly or irregularly visiting a garden is many times greater than the number actually present at any one time in the garden.
"As such, gardeners shouldn't be setting out to eliminate snails from their gardens. To achieve such a feat would require a gardener to rid the whole neighbourhood of snails, which would be a slow process.
"Gardeners should be setting out to minimise the damage done by snails, which our results showed could be quickly achieved by simply removing the snails over 20 metres away."
He added: "A recent poll by the Royal Horticultural Society showed that one in five gardeners in the UK have thrown snails into their neighbours' gardens.
"Whilst our study shows that this may be more beneficial than actually killing them, we believe the gardening community would benefit as a whole by removing the snails to a convenient wasteland rather than passing the burden onto their neighbours."
Co-author Dr Dave Hodgson, from the University of Exeter, discovered with amateur scientist Ruth Brooks in 2010 that snails have a homing instinct.
Prof Dunstan's research began with an experiment in 2001 in which snails found in a small suburban garden were marked and thrown five metres over a brick wall and into wasteland.
Every time they returned they were given another mark on their shell and lobbed into the wasteland again. A total of 416 snails were marked and thrown over the wall 1,385 times over six months.
Previously suffering plants such as hostas thrived under the regime, suggesting it was keeping the number of snails at a reduced level.
Dr Hodgson and Prof Dunstan have analysed the results through a computer model which simulated snail behaviour and found they could only replicate what happened in real life if they gave the snails a "homing instinct".
In the second year of the experiment, the snails were numbered and even-numbered snails were thrown over the wall, and odd-numbered snails taken four doors up the road to a garden around 20 metres away.
Virtually none of the snails that were taken further afield came back to the garden, the study found.