If you were pressed to name the most unwelcome garden pest, it might be a slug. Perhaps it’s the combination of larger size (compared to a caterpillar or aphid) and slimy habits that makes them so maligned. Whatever the rationale, gardeners will go to extremes to keep out these common molluscs. But wait! If you want to eat tasty organic produce straight from the garden, the solution will have to be pesticide-free. So what are the alternatives?

There are lots of different slug species, depending on where you live. Not all of them are garden pests - so it is important to recognize your slimy little neighbours. In fact, many native species are harmless to garden plants and surprisingly beneficial to garden ecology. Slugs play a role in nutrient cycling, breaking down plants and creating detritus. Many animals, including birds, mammals, and snakes, eat slugs.

How do you know if slugs are causing problems? Leaves will have large, irregular holes, while some tender young plants may be eaten completely. Look for characteristic silvery trails left by mucus, although snails also produce these marks. On cool and rainy days, slugs can be found around favourite food plants.

So you've deduced that slugs are the culprits - now what? Don’t reach for the box of slug pellets. These chemicals often contain metaldehyde, a neurotoxin, along with more tasty ingredients like molasses. Dogs and other animals can suffer from poisoning and death after eating slug bait. Recent tests have found metaldehyde in drinking water. Adding to the debate, slugs and snails have been known to become resistant to chemical baits.

Beer traps are traditionally popular but have variable success. Some people swear by them, while others have no luck. Other, more beneficial, animals like ground beetles also come to a sticky end in these traps. Garlic is another alternative.

If you are looking for a longer term solution, copper may be a good deterrent. Whether in the form of wire, sheeting, or screens, copper is thought to react with slug mucus to create an unpleasant “shock” sensation. Slugs prefer not to cross these barriers - so vegetable beds can be surrounded with a thin wall of copper, and trees can be banded. Barriers seem to be most effective if the copper is bent down to form a lip. Be careful that you are keeping slugs out and not in!

Coffee grounds may also help. There is some evidence that slugs dislike caffeine, so using grounds as mulch might work. Spikier mulches – shredded bark, ashes, eggshells, and crushed rock –  are known to deter slugs.

Stayed tuned tomorrow for some more tips to help ease your summer slug wars.

Photo credit: Louise Joly