The Scarthin Slug-Moat

The Scarthin Slug-Moat (Slugmoat)

Is the moat leaking? Has the hot sun evaporated all the water? Has it subsided at one corner, leaving the opposite corner dry? Have wilting leaves bridged the barrier? Are there actually slugs and snails trapped inside the perimeter? Has a heron taken the goldfish? These are some of the worries of the carrot castellan.

A Snail’s Pace

Snail-racing is an old Scarthin tradition. As snails (and slugs) are difficult to direct, we race then outwards from the centre of a sort of Darts Board with successive circles at 10, 15, 25 cms. etc. The fit snail can easily manange 10cms. per minute from a slimey start, getting up to a maximum speed of some 15cms. per minute, though a certain randomness in direction finding reduces the average cross-country range to no more than 5 cms., or two inches, per minute. On warm, damp Spring nights, when slugs and snails do their worst damage to the horticulturalist’s newly-emerging tender shoots, these predators have at least six hours of bird-free darkness in which to make it to their munching grounds and back, giving them a range of some 180 X 5 cms. – about 9 metres or 30 feet. A farmer can, perhaps, afford to lose much of the productivity of such a belt around the margins of a 2-acre field, a hundred yards across, but unless a gardener’s plot is more than 60 ft. square, measuring from the nearest hedge, wall, shrubbery or uncultivated path, then the slugs and snails will meet in the middle. One muggy night in May or early June and every delicious infant carrot will have been nibbled to the ground.

When a problem is almost insoluble, there will be many solutions – think of the Doctor’s proven Cures for overweight, for arthritis, forgetfulness, cancer, melancholy or laziness – particularly when conventional medicinal magic bullets are distrusted. Even I, a classic pre-1968 square, scientific-optimist-Black’s-of-Greenock-Anorak eschew the magic bullet of the slug-pellet, having been told that birds will eat the victims and be poisoned in turn, but I refuse to turn to the alternative medicine of beer traps, milk traps (for those who don’t like wasting beer) or barriers of soot, sand, lime, crushed egg-shells or double-whammy combinations of the above. Nightly expeditions with torch and tin-can can be very effective in reducing the depredations of the wolfing-packs. In my hot youth, I used to hurl my catch over the roof of an adjoining bungalow, blissfully ignorant of their fate, or that of any passers by. Nowadays I self-righteously heave them into the woods or onto a neighbour’s wilderness. But can I keep it up over a wet Summer of rampant weed-cover like those of 2007 and 2008? Just one night missed, as with fox-and-hens or caterpillars-and-cabbage, can result in irretrievable loss. Sometimes I mark captured snails with white or fluorescent tippex (getting hard to find) before lobbing into the wild. This allows the statistician to make some estimate of the total snail population, as well as measuring their mobility.

In the absence of slug-pellets, old wives masquerading as gurus crowd in – beer traps, milk traps (for those who don’t like wasting beer) or barriers of soot, sand, lime, crushed egg-shells or double-whammy combinations of the above are advocated but are tedious to install, can vanish in a night’s heavy rain and are at best only partially effective. My preferred solution requires capital expenditure but is then almost maintenance-free and has a working lifetime of years, perhaps decades. It is the SCARTHIN SLUG-MOAT (or for Google’s Sake SLUGMOAT).

A four-metre length of four and a half inch (yes, the imperial measure survives in the width, but not in the length) half-round black or grey plastic guttering will cost you about �10. If you buy two of these, plus two two-metres lengths and four corner joining pieces, the total should be about �40 and, after a thumb-straining struggle to join them up you have the Slug Moat enclosing an area of eight square metres at a capital cost of �5 ($9 for international readers) per square metre. Of course, the cost arises from the linear scale of the boundary, while the area is proportional to the square of this. A hectare could be enclosed by four hundred metres of gutter and still only four corners at a cost of no more than a thousand pounds, a cost of 10p (18c) per square metre. In the Fenlands of Lincolnshire, Norfolk and Cambridgeshire, most fields are surrounded by water-filled dykes, so if draw-bridges and tractor-washes were installed it should be possible to render both the slug and snail extinct over large areas, thus restoring the state of affairs achieved, according to Bede, by the prayers of St. Guthlac of Crowland in the seventh century. Bede recounts the saint’s perigrinations around the settlement of Snaildyke but the site of this is now lost.

My aims are however more modest. Most gardens are not as flat as the fens, so the first need is to level the site, the partially-filled moat acting as its own spirit-level. Otherwise one end or corner may need to be raised on an earthen bank where erosion will produce gaps under the guttering through which the shape-changing slug can intrude itself. The second need, in hot dry weather, is for regular topping-up every couple of days, or a dry bridge may be formed. I have surprised the occasional particularly intrepid snail ducking its way through a shallow section, rather like a caver forcing a short sump! I have experimented by submerging snails on the inside of a bucket. The snail will leave its shell safely stuck to the side, but will emerge and questingly extend upwards. It will escape and survive so long as its extreme proboscis-end – and they are good at stretching themselves – can emerge above the water-line and reattach itself. The rest of the body and the shell (which cannot re-stick under the water-line) are then hauled up to safety. You can’t help but applaud. As a result of some natural occurrences of this experiment, there may be an evolutionary trend in our showery climate towards a ducking-ability in snails and slugs. At least they don’t yet swim. This hypothetical amphibious tendency does mean that the interior of the slugmoat should be swept for intruders regularly. You do not want to trap them INSIDE. In the warmth of even a wet Summer, insects will deposit eggs in the moat, which may become a seething soup of larvae and a significant source of midges. One solution is to introduce small goldfish to consume the eggs and larvae. Hence the final theoretical problem of defence against the HERON – a bizarre consequence of the defence against arthropods that I rather hope one day to encounter, and to which even I have not yet imagined the solution. DJM Sept.08