Down With Slugs!

Slugs have long been considered one of the most stubborn enemies of gardeners. These small mollusks, with eyes on tentacles, resemble snails without shells. They secrete a mucus from their feet that acts as a lubricant, allowing them to move across rough surfaces.

Some slugs are actually beneficial, feeding mainly on dead or yellowed leaves, but most attack our garden plants, especially vegetables, annuals, and perennials, piercing holes in the leaves. They can completely decimate fragile seedlings.

Unfortunately for us, slugs have a long life span and can live for several years. They can consume 40% of their body weight in vegetation in a single night.

And they are mainly nocturnal, preferring the humidity and coolness of the night to do their work. However, in rainy weather, they can be seen at work at any time of day. They dislike dry conditions. During the day and even at night when it is dry, they hide under the ground, stones, or boards in search of coolness and moisture. During these periods, they change tactics, eating the roots of our plants rather than their leaves!

How To Control Slugs

There are almost as many slug control methods as there are gardeners! Here are just a few of them:

• Collect them manually: crush them or throw them into soapy water.
• Place boards on the ground to serve as shelters and then crush them. Half a grapefruit placed on the ground would have the same effect.
• Pouring salt on them kills them quickly… but be careful! Salt is toxic to plants.
• Spraying with ammonia (1 part ammonia to 4 to 10 parts water) can kill slugs when applied directly to them. However, spraying the ground or plants has not been shown to be effective in repelling slugs or protecting crops, as ammonia evaporates quickly. This method also poses risks to plants and soil, and the available scientific data is limited.
• Sprinkling diatomaceous earth (fossilized algae) on the ground is effective… until it rains. Diatomaceous earth only works when dry. It quickly loses its effectiveness when wet and requires frequent applications.
• Release chickens or ducks in your yard… but this may not be allowed in urban areas.
• Surrounding plants with copper wire or tape can sometimes deter slugs, but its effectiveness varies.
• Covering the ground with mulch will eventually eliminate almost all slugs in the area.

This seems counter-intuitive, because isn’t it true that mulch keeps the soil cooler and moister? Which should encourage slugs? Yes, but the slug’s enemies (beetles, shrews, nematodes, toads, etc.) increase just as much in a mulched bed and end up winning the battle.

Unfortunately, the popular belief that eggshells repel slugs has proved unfounded. As for wood ash, some – notably oak, beech and spruce – have demonstrated real effectiveness as a physical barrier or in direct contact, in dry conditions. However, like diatomaceous earth, the protective effect of ash disappears as soon as it becomes damp, which limits its practical use in rainy or dewy conditions.

The Beer Trap

The beer bowl trick is popular. Slugs are attracted by the smell of malt and can drown in it. However, this method has limited effectiveness: it does not usually reduce the slug population significantly and requires regular maintenance. It is best to place the bowl some distance away from your plants to avoid attracting more slugs to the garden… perhaps to your neighbors?

Commercial Products

Metaldehyde baits are still sold, but are not recommended, as they are highly toxic to children and small animals. Iron phosphate baits are more effective and are considered organic. They are non-toxic to mammals.

The Laidback Solution to Slugs

Personally, I solved my slug problem very easily. I stopped growing slug-prone plants, that’s all! After much searching, I found slug-resistant varieties in almost every plant. Yes, even slug-resistant hostas! And romaine lettuce is never affected, whereas curly leaf lettuce is reduced to lint. If your land is free of the plants they like to eat, the slugs will go… to your neighbors!

---

Larry Hodgson published thousands of articles and 65 books over the course of his career, in both French and English. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil on June 19, 2010.