If slippery slugs and slimy snails are stealing your seedlings, let’s think like a slug and get one step ahead of the slime trail! Find out which control methods work to get rid of slugs and snails—and which don’t! Plus, see a helpful video.
We will help you bring your slug woes under control, as naturally as possible. Spoiler alert: That means there’s no room for slug pellets
What Are Slugs and Snails?
Did you know that the average garden contains upwards of 15,000 slugs?! No wonder our plants get nibbled or even destroyed.
Slugs and snails are not insects; they are soft-bodied mollusks. Unlike seagoing mollusks, these landlubbers are equipped with a single lung. The main difference between slugs and snails is that the latter have an obvious shell, which is primarily made up of calcium carbonate.
Slugs and snails are hermaphroditic, with each individual having both male and female reproductive organs. As you would expect, their love life is complex. The common gray garden slug dances an elaborate, hour-long nuptial waltz before mating, while other species perform acrobatic movements while hanging suspended from threads of slime.
But while slugs try the patience of us gardeners, they’re not all bad. For example, the slugs found in compost heaps help with decomposition, speeding this along. There are also lots of slugs that have no interest in your vegetables and prefer to eat things like algae instead. And then there’s their value as a food source for all manner of wildlife, from beetles to birds to frogs and toads. Like weeds, it’s not that slugs are intrinsically ‘bad;’ we just don’t want them in certain places, such as around susceptible plants.
Identifying Slug and Snail Damage
Most garden slugs and snails are gray, dull-orange, or dark brown and 1 to 3 inches long. They will hide in dark, damp places during the day.
Many people are prompted to ask, “Where do slugs come from?” This is because they are hard to spot in the soil due to their dark color, but also because they only feed at night and hide throughout the day. If you realize you have slug and snail damage but can’t find the culprits, you’re not alone.
Slugs and snails will leave a slimy secretion where they have been, so even if you can’t spot them, you’ll know they are there. Look for slime both on plants and surrounding soil. It is easiest to see the trails of slime first thing in the morning.
You can monitor slug and snail activity in your garden by digging holes that are four inches wide and six inches deep. Cover these holes with a board, and then check for slugs after three days. If you see many of them, these might be the sneaky pests that are eating your plants!
Slugs and snails lay their eggs in moist soil or compost. Their populations can grow rapidly in cool and moist conditions.
What Do Slugs Eat?
Slugs will feed on almost anything in the garden—look for holes and ragged edges on leaves and stems. The holes should have irregular shapes due to their file-like mouthparts. Small seedlings can be consumed entirely. Slugs can digest tissues from most plants, but you might find them especially liking your beans, lettuce, cabbage, and tomatoes.
Control and Prevention
Remove Hiding Places
The first step towards a more manageable slug population is to remove hiding places from within and around your main growing areas.
Cut down long grass right around vegetable gardens. Through regular mowing, you’re removing these opportunities for slugs to lay low.
Remove debris lying about. Upturned pots, bits of wood, old sacks – they are all potential hiding places for our slippery slimesters.
Work within beds to remove any dead or dying leaves as well as, of course, any weeds. Removing all this excess vegetation to the compost heap keep things more open in our growing areas, improving airflow and discouraging the damp, shaded conditions slugs love.
Trap and Remove Slugs
Create the perfect slug and snail trap by laying boards or pieces of cardboard on the bare soil around your plantings. Start by watering the ground if it’s dry, then place a plank of wood or similar over the surface. Check back the next morning and you’re very likely to find slugs lurking beneath. Pick them off and return the plank to collect the next batch.
Citrus halves like grapefruit skin are very effective slug collectors because they create a cool, shady recess for our slugs to hang out in. Again, lay shells down at strategic locations—close to susceptible crops like salads or tender seedlings. For something longer-lasting, you can use half a coconut shell at each corner of your raised bed (after you’ve enjoyed the coconut flesh of course) which they like to crawl into.
And then there are beer traps. Any cheap beer will do. Sink the container into the ground to leave a bit of a lip, which should reduce the risk of non-target species like beetles falling in and drowning.
Go On a Slug Hunt
If you really want to make an impact – fast – go out on the hunt for slugs when they’re most likely to be out and gorging on your plants: at night, particularly in warm, damp weather. You’ll need a bucket and a flashlight for this. Head out soon after dusk to begin your hunt. Relocate slugs to a less susceptible area, add them to your compost heap or, to be sure, take them out to a nearby wooded area or similar. Go on further slug hunts over the coming nights and you’ll pick up the stragglers and should make an appreciable dent on the slug population.
If you want to dispatch of your slugs, you have numerous gruesome ways to do this—from drowning them in a bucket of water, to squashing them, to cutting in half. I guess it depends on how squeamish you are! A less direct alternative might be to drop the slugs into a container, cover and place in freezer for three hours; when frozen stiff, dump them on your compost pile. Or, simply relocate them!
Slug Pellet Alternatives
We’ve moved from commercial slug pellets because of their impact on other animals and the environment; many are laden with chemicals that do a good job of killing slugs but that can also harm animals higher up the food chain too. In our enlightened times we should look at alternatives.
One option is to apply microscopic nematodes onto slug-affected ground. The nematodes are first suspended in water then simply watered over soil that has warmed up enough following the winter months. The nematodes find their way into the slugs where they infect them with a deadly bacteria. Sounds grim, but these nematodes have absolutely come with zero collateral damage, making them a very safe form of slug control.
What Does Not Work
Many solutions that have been tested simply are not very effective, including copper tape, bark mulch, wood ash, coffee grounds, coarse sand, pine needles, eggshells, sharp grit, and wool pellets. Every study has found them to be useless.
There have been some studies showing that a barrier of diatomaceous earth (DE) can help. This is a naturally occurring silica-based rock that can be crumbled into a fine powder. Slugs really don’t like crossing the moisture-sapping powder. Just make sure you buy “food grade” DE.
More Slug Control Tips
Some plants have been shown to do well despite being around slugs and snails. If you tend to see these pests and are having trouble getting rid of them, try planting astilbe, phlox, or mint to reduce damage.
Water in the morning if possible. This will give the soil surface time to dry out a bit before nightfall when the slugs come out.
Vulnerable crops like leafy greens and salads can be started off in pots or plug trays away from the growing areas. By the time they are planted, the plants will be that much bigger, more robust, and better positioned to withstand attacks.
You can protect recent transplants with cloches or any barrier that physically keeps slugs out, such as a bottomless plastic bottles popped over individual plants.
If you grow potatoes, dig them up as soon as they are ready because slugs love these tubers. Some varieties are also more tolerant of slugs than others.
Slugs and snails have many natural predators. If you have chickens or ducks, they will help by eating these pests and their eggs. Amphibians such as frogs and toads love to feast on slugs.
Companion planting is a great way to prevent pests. In order to keep slugs and snails away from more valuable plants, place plants that they love near your more-valuable plants as a trap, and then destroy the infested plants. Good traps for slugs include chervil, marigold, and thyme.
Ready to think like a slug? Ben shows us how to make many of the control methods listed above!