Dealing with slugs and snails

Slugs and snails are among the most despised and destructive garden pests, so what can you do to combat them? Alan Titchmarsh reveals a few tricks of the trade…

Tools for the job

 

After the wettest winter on record in many areas, gardeners up and down the country are bracing themselves for a plague of slugs and snails. With literally hundreds of control methods and techniques to choose from, it can be bewildering to know where to start. The very fact there are so many options available, is a sure sign that none provide the perfect solution. Most experienced gardeners have their favourites, but there is not a consensus, other than that slugs and snails are unpredictable and very difficult to control. I take the belt-and-braces approach and use a combination of methods to keep my plants safe.


Environmentally friendly slug-control methods

As with all garden pests, it pays to know your enemy when trying to thwart them. There are nearly 30 species of slugs in the UK, fortunately only a few are serious garden pests. The huge, lumbering so called ‘black’ slug (that is just as likely to be brown, grey, red or yellow), is often spotted slithering across a shady paths, but this does little harm in the garden – preferring to diet on decaying plant material. No, it’s the much smaller brown and grey garden and field slugs, which lurk unseen, which do the serious damage.

The one control method on which all gardeners can agree, is the use of natural predators. The more frogs, toads, ground beetles, centipedes and hedgehogs you have, as well as slug-eating birds, such as thrushes and blackbirds, the less slug damage you get. Installing a wildlife pond, providing strategically placed insect hideaways and setting up nesting sites, will encourage these natural predators to set up home in your garden and help keep slug numbers down to a tolerable level.

For complete control, however, you will need to take on the slugs and snails directly. The myriad of anti-slug measures include barriers, traps and cultural methods, as well as biological and chemical controls.

Barriers Some gardeners swear by rough barriers that slugs and snails don’t like to cross. You can buy ready-to-use products, such as recycled, ceramic shards that are can be scattered around vulnerable plants or you can try more traditional home-made remedies, such as baked, crushed egg shells, grit, ash or soot which are variable in their effectiveness. Barriers with a sharp edge, such as thorny leaves and plant collars, cut from plastic drinks bottles, are rated by some for protecting individual plants and seedlings. Or you can go hi-tech with loops of copper tape that generate tiny electric currents that slugs are said to find irritating and so avoid. Now available in various forms, these can be a convenient, long-term solution for protecting vulnerable plants in containers. You can also use copper barriers to protect raised beds, provided there aren’t any slugs already in residence. Cocoa shell mulches are also known to be an effective barrier to slugs when spread over the soil between vulnerable plants. Or you might like to try the pure wool slug pellets that act like a mulch and are said to keep slugs at bay.

Traps Many organic gardeners opt for traps and shelters that slugs and snails find irresistible. Their main drawback is that they have to be checked and emptied regularly for them to remain effective. Upturned skins of half grapefruit may not be aesthetically pleasing on beds and borders, but they make attractive refuges to slugs - as do decaying piles of vegetation and wet newspaper. A more aesthetically pleasing option is the beer trap – a boozy grave for foolhardy slugs that seem to have a weakness for the beer-filled grottos.

Cultural methods If your garden is particularly prone to slugs, you could adjust what and how you garden to minimise the risk of damage. The most effective thing to do is replace slug-prone plants, such as clematis, delphiniums, doronicums, hollyhocks, hostas, hyacinths, ligularia, lilies, lupins, pansies, primulas and tulips with slug-resistant plants including acanthus, achillea, alchemilla, agapanthus, astilbe, astrantia, crocosmia, digitalis, eryngium, nepeta, penstemon and sempervivum. If you still want to grow hostas, try ‘Sum and Substance’ which forms textured mounds of yellow-green leaves that have a reputation for being slug- and snail-proof. Other steps you can take include raising young plants in pots until they are robust enough to be untroubled by slugs. It’s also worth tidying beds and borders regularly to eliminate slug-friendly hiding places. If you have shady corners where slugs are known to congregate, check them periodically to evict the pests. During sunny spells it’s also worth roughing up piles of leaves and other hiding places to expose hidden slugs to predators and the desiccating effects of the sun. Some gardeners even go on nightly slug hunts to catch the little blighters in action – grabbing them with barbecue tongs and dropping them into jars of salty water – or beer!

Biological control You can now get a biological control for slugs that contains millions of microscopic worm-like nematodes that are completely harmless to other creatures. When applied as a soil drench, the nematodes infect lurking slugs with a bacterium which stops the slugs feeding within a week and kills them within two. Since the biological control remains active for up to six weeks in moist conditions, one application should be sufficient to protect plants while they are at their most vulnerable.

Chemical controls Traditional slug pellets have rightly fallen out of favour, mainly because they were based on noxious chemicals that harmed other wildlife and pets. But they also had to be reapplied regularly to remain effective, especially during persistently wet weather. An environmentally friendly alternative is ferrous phosphate slug pellets. These can be used just like the traditional pellets, but do not harm other creatures. Simply scatter them thinly, around vulnerable plants, on a warm evening when the soil is moist and there is no rain forecast.