Know your molluscs

Collecting slugs and snails by hand is the best control method, but there's that yuck factor. So here are some alternatives, writes FIONNUALA FALLON

I HAVE WHAT Americans might call “a conflicted attitude” when it comes to garden slugs and snails. On the one hand, where plants are especially vulnerable, I’ll sprinkle slug pellets with only the mildest twinge of guilt (in my defence, only the organically acceptable, iron-based types). I also laughed out loud when I read The Little Book Of Slugs, and its account of the man who wrote, “Slugs! You Can End It All Here”, in foot-high salt letters outside his back door (apparently, 95 per cent of those that did so hurled themselves, lemming-like, at the word “here”).

On the other hand, while I appreciate that it’s the swiftest form of execution, I find it next to impossible to slice any slug in two with a sharp secateurs, or to squash snails underfoot. I’ve also been known to unceremoniously yank the salt cellar out of the hands of anyone planning to use it, executioner-style, on the grounds of unnecessary cruelty.

So when I spent a strangely enjoyable hour last week studying the elegant peregrinations of a large black slug (Arion ater), it was in the spirit of both quiet desperation and curiosity . Or as Sun Tzu, the Chinese general, renowned military strategist and author of that ancient but definitive tome, The Art of War, would have said, as a means of getting to “know thy enemy”.

Because the sad fact is that 2012 will not go down in the history books as the year of the roses, the year of the vegetable garden or the year of the butterfly (there are depressingly few of these to be seen anywhere), but as the year of the slug and the snail. Much of the reason for this is the weather. Between April and July, more than 15 inches of rain fell on our capital city, 80 per cent more than the mean average for that time of year. Cork, meanwhile, enjoyed a whopping 19-and-a-half inches of rain in the same period.

While humans may not like such vast quantities of morale-sapping, gloom-inducing rainfall, slugs and snails most emphatically do. The result is that they’ve spent the summer feasting and reproducing with such orgiastic abandon that they’ve become the molluscular equivalent of Hitchcock’s birds. In the last few weeks I’ve seen slugs so big that they’ve made grown men squeal (disturbingly, some can reach a length of 20cm). So what to do? To paraphrase General Sun Tzu, it’s a case of devising a plan of attack and then varying your tactics. Here, to help you on the way, are a few suggestions:

Know your molluscs

While the black slug may look intimidatingly large, it does relatively little damage to growing plants, other than in early spring. Smaller slugs such as the field slug (Deroceras reticulatum), the Budapest slug (Tandonia budapestensis) and the garden slug (Arion hortensis) are far greater pests. Damaging snails include the garden snail (Cornu aspersum), the strawberry snail (Trochulus striolatus) and the white and brown-lipped snails (Cepaea hortensis and C. nemoralis). See habitas.org.uk/molluscireland

Keep a tidyish garden

Slugs love cool, dark places where they can hide from bright sunlight, and are attracted by decaying vegetation. So keep beds as neat and weed-free as possible, and make a habit of regularly checking the bases of plant pots and trays. Hoeing in spring will also bring slug eggs to the surface where they’ll be eaten by birds and insects.

Encourage natural predators

Incorporating hedges, garden ponds, trees, nest boxes and bird-feeders into a garden will attract birds, hedgehogs, frogs, marsh flies and ground beetles, all of which will help to keep slug/snail populations down.

Grow plants ‘hard’

Seasoned gardeners know that tender seedlings/transplants raised indoors in a polytunnel or glasshouse are caviar to slugs and snails, so make sure to harden them off well before planting them out. Lush plants that have been overfed are also a target, while certain plants (hostas, delphiniums, dahlias) are simply irresistible.

Grow slug-resistant plants

Try astrantias, crocosmias, euphorbias, hellebores, Japanese anemones, perennial geraniums.

Drown them

Use shallow containers almost sunk into the soil and filled with milk or beer (leave a 1-inch lip to protect ground beetles from drowning).

Collect them by hand

This is by far the most effective method of control, but it comes with a big yuck factor (a few stiff drinks helps). Best done at night, by torchlight, wearing gloves. When it comes to slugs, mollusc expert Prof William Symondson suggests impaling them on a sharp hat-pin or similar needle-like item bound tightly to a stick with string, then dunking the bodies in boiling water.

Use pellets

Poisonous pellets kill slugs and snails and can be based on methiocarb, metaldehyde or iron phosphate – if at all possible try to use the latter, which is organically friendly but can be surprisingly difficult to get your hands on. Mail order firm Fruithill Farm sells large bags (0.75kg for €9.15, under the brand name Ferramol, fruithillfarm.com). Always scatter pellets rather than put them in little piles.

Try nematodes

The nematode control, “Nemaslug” or Phasmarhabditis hermaphrodita (available from most good garden centres) offers good control against slugs. However, it’s only slightly effective against snails, whose tough shells offer protection, while, given its relative cost, it’s best suited to smaller gardens.

Use physical barriers

Copper strips, soot, crushed eggshells, coffee grinds, sharp grit and plastic bottle cloches all offer some protection, although wet weather reduces their efficacy. Some gardeners swear by pellets made from sheep wool, which expand to form a barbed barrier (see sluggone.com).

This week in the garden

Cut raspberry canes that have finished fruiting back down to ground-level, continue feeding bedding plants.

Dates for your diary

South County Dublin Horticultural Society's Summer Flower Show 2012 takes place today

in the County Hall, Marine Road, Dún Laoghaire, 2pm to 5.30pm. Admission free.

Hunting Brook Garden's 10-year-anniversary celebrations take place tomorrow, 12pm-6pm and include music, food, plant/seeds for sale, a talk by owner Jimi Blake as well as a prize for best-dressed man/woman (think floral). Admission: Kids go free, adults €6, OAPs and students €4.

See huntingbrook.com for details