The following eight methods can help you cut down on the number of destructive snails and slugs in your balcony container garden. To learn more about snails and slugs, read “Pests: Garden Snails and Slugs.”
1. Gritty substances. The first method for garden snail and slug control is to use a gritty substance. Snails do not travel over gritty substances, such as crushed eggshells or sharp sand, that have been spread around your container plants. Put a layer of grit in your plant containers, and snails will avoid these plants. If they do crawl there, the grit will clog their slime glands and it will kill them. Spread sharp and angular gravel (not smooth rocks) over soil so the snails can’t climb. All of these gritty substances will irritate the snail and slug’s delicate undersides.
2. Beer traps. The second method for garden snail and slug control is to make a beer trap. First fill a shallow pan with stale beer and leave it out overnight. The snails will be attracted to the beer and climb into the pan. Make sure the pan filled with beer is deep enough so the snails will drown in it and not be able to climb out. Slugs will especially need a deeper container, such as a yogurt container. Replace the beer in the pan every couple of days. These trap must be buried so the top of the pan is at ground level, so balcony container gardeners (who cannot bury them in the ground) should provide easy access for the slugs and snails by creating some sort of ramp.
3. Other traps. Other traps will attract snails to a certain spot in the container garden where you can find them later and kill them. Put a pie pan upside-down on the ground (with a hole cut in the side so snails can climb in), and put some citrus peels or other snail food inside. The snails will climb underneath the pan for the food and for the cool, dark protection from the morning sun. Check every morning, and replace the food often.
4. WD-40. To deter snails in your container garden, you can set up barriers around your plants or their containers. For example, you can spray a band of waterproof WD-40 around your containers, and the snails and slugs will be unable to climb up it. WD-40 is waterproof, so it will be effective in the garden even after rain or watering. When spraying the WD-40 around the containers, make sure there are no gaps, as the snails and slugs will climb through any spots you’ve missed. Also protect any plants from the spray by covering them with newspaper or a sheet of plastic. The WD-40 should last an entire season. Vaseline can also be used in this same way, but it gets messy and needs replacing often.
5. Copper wire. Another snail barrier is copper wire. Attach copper wire around your plant containers or around a thick plant stem. Because snails have acidic slime, they will get a shock if they touch copper wire. It won’t kill them, but it will keep them from climbing up your plant containers or onto your plants, and they will go elsewhere. It isn’t always practical to put copper wiring or “tape” around all of your containers.
6. Salt. Salt is an other effective (but disgusting) method to control garden snails and slugs. Do not use salt as a prophylactic in the garden – only use it after you’ve found and want to kill a snail. Salt should not be included in potting soil, as it is detrimental to the health of your container plants.
7. Crushing. An unpleasant way to kill a snail once you’ve found one in the garden is to crush it. Hopefully there is someone in your household who is not squeamish about voluntarily crushing snails. It is recommended that you not crush them directly on your balcony floor, as it will leave a mess for days. Crush them on a tray that you will be able to throw away, or carry the snails outside, say, into a parking area, and crush them there.
8. Commercial snail and slug killers. You may find organic snail and slug traps and killers at your local garden shop. Purchase these chemicals only if you are losing the battle against these pests. Even organic chemicals can have unwanted side effects in the container garden. Learn more about organic pest control for the garden>>