If you have ever felt the squish of a slug between your toes as you ventured to the refrigerator for a midnight snack, you know what a nuisance indoor slugs and snails can be. Slugs and snails ooze their way over your kitchen floors and counter tops and onto your furniture. House slugs huddle together to conserve moisture and their slime rails signal other slugs where to find a tasty meal. In places like Hawaii and Florida, they can carry serious diseases than infect humans. In other parts of the world, they transmit parasites that infect cats. But you don’t have to break out the bug bomb or get the exterminator to tent your house to get rid of these slimy pests.
Even experts in slugs and snails can suffer home invasions of the slimy pests. British biologist and slug and snail specialist Robert Cameron tells the story of how he had a slug problem in his own house. He would find black slugs feeding on cat food, but he was sure that they were not strong enough to slide up his back door and open the cat flap. With a little detective work he eventually found a crack about 4 mm (1/6 of an inch) wide around the pipe through which his kitchen sink drained outside. Sealing the crack locked out the slugs.
Slugs don’t have bones. They don’t have shells. Their slime is like Super Glue, enabling them to climb walls and even to travel upside down across the ceiling. And because they are so flexible, they can enter your house through incredibly tiny cracks. Slugs are enticed by a variety of delicious smells and aromas – cat food is among their favorites – and finds your house to be a haven of warmth and moisture. They will find their way inside if you don’t block their entry.
You don’t have to do a lot of searching to find the slug highway that is bringing them into your house. They will identify it for you. Just follow the slime trail back to the outside wall and you will usually find the crack that is letting slugs into your house. The easiest way to follow the slime trail is to turn off the lights, waiting until night if there is lots of natural light, and use a flashlight to see the trail more clearly. Look for holes in the wall, loose fittings around electrical conduits and gas and water pipes, and gaps around doors and windows.
It is best to seal smaller cracks with silicone. For larger cracks, use expanding polyurethane foam – but beware using too much. Polyurethane sticks to everything it touches, including hair, clothes, pets, and passing children. Lay down newspapers or plastic sheeting. Be sure to carry a rag to catch any foam oozing out of the nozzle. Plan to use the entire can in one session, because leftover foam will harden in the nozzle. But for filling cracks, there is no longer-lasting or more effective homeowner’s tool than expanding polyurethane foam.
Poisoning indoor slugs usually isn’t practical. The places you will find them in your house are almost always frequented by pets or children who might also be exposed to the toxin. You simply can’t put out enough poison indoors to stop a slug invasion without endangering your health. Barriers to entry are best.
Indoor snails don’t usually come in from your lawn or garden. Indoor snails most often hitch a ride on potted plants or in potting soil. They can also arrive in “empty” snail shells collected as a hobby or for decoration. Drenching potting soil with metaldehyde (Meta) will kill them. In you prefer an organic approach, a caffeine spray or a strong, caffeinated beverage will kill the snails that might otherwise kill your plant.
Metaldhyde comes in sprays, dusts, and pellets. Metaldehyde does not evaporate, so it does not move through the air when it is used as pellets, but metaldehyde dust can. In your home, you would want to use it in pellet form. The pellets are a mixture of snail and slug poison and a cereal bait. They eat the bait and die, usually not too far from where they find the pellet. Just be sure that your children and pets don’t play with the pellets. Metaldehyde won’t kill pets or people in the doses used for pest control, but eating it would be a very unpleasant experience.
If your indoor plants are in a sensitive location, or if you simply don’t use pesticides indoors, consider a caffeine spray or a copper barrier. Commercial caffeine sprays are about 10 times as concentrated as a cup of strong coffee. They make snails “hyper” so they can’t extend their front foot and they freeze in place. You can pick them and relocate them, or simply throw them in the trash.