What little success I had in my organic garden last year was no thanks to the millions of slugs that inhabit my back yard. I’m one of those people that generally doesn’t kill bugs (except for silverfish… all bets are off with those creepy suckers), but the slug problem was of epic proportions last year so I have been trying to figure out a way to combat them using an effective organic method. I’ve heard that beer is a good slug bait that attracts slugs and drowns them, but that kills the poor little guys and beer in my household is a valuable commodity, especially in summer. Sorry slugs – I know you like it, but really, I’m doing you a favor.
So, as I’m mentally preparing for this year’s garden (I just bought seeds!), I have been thinking a lot about slugs. This of course led to some research on these pesky garden pests, which I will happily share with you now.
1. What are Slugs?
Slugs belong to the mollusc family, just like their tasty relatives oysters, squid, and clams. While those examples represent cephalopods or bivalves, snails and slugs belong to the gastropod phylum. In contrast to snails, which are very closely related, slugs do not have a shell (although in some cases they do have a small internal shell – don’t ask me how that works, I did not yet dive deeper, although I must admit that I’m intrigued!). I know that we also have a significant snail population on the island, but they seem to stick closer to the beach, perhaps feasting on the ample seaweed? There are countless types of slugs that live on land, in salt water, and in fresh water, but the type I’m most interested in is the grey garden slug.
2. What do Slugs Eat?
I can tell you from personal experience that slugs love lettuce. As do I, hence my battle cry. My research tells me that they also like calendula, beans, and peppers. My radishes and cucumbers seemed to be relatively slug-free, perhaps because the leaves are rougher and irritating to soft slug bodies. They’ll eat both foliage and ripened fruits and vegetables, both of which can be problematic. Slugs can eat foliage faster than the plant grows, effectively killing it or making it more susceptible to disease and environmental conditions. When they eat fruits and veggies they leave holes in them. While they are still perfectly edible, it does reduce shelf life and, frankly, doesn’t look very nice. They also like a lot of ornamental and flower species, and since the whole point of growing flowers is for them to look nice, slugs are obviously also a nuisance for flower gardeners.
3. How do Slugs Eat?
Okay, you maybe don’t need to know this, but I was curious… I’ve looked at slugs up close and didn’t really see a “mouth”. This is because a slug’s mouth is sort of under it’s head, just below the lower tentacles, which are used for smelling. They eat with a radula, which is a body part that all molluscs (except bivalves) have in common.
The radula is a chitinous ribbon (chitin is the same material shells are made of) that scrapes and cuts food before it’s digested. It has teeth (or denticles) that are constantly regenerated, sort of like shark teeth. When plant leaves look like they have holes torn out of them, this is the result of the radula doing it’s thing.
4. How do You Prevent Slugs?
One of the best ways to solve a slug problem is to avoid getting it in the first place. Slugs can’t live just anywhere. They will dry out and die if it’s too hot or dry, so they seek out dark, moist areas. You know, like where you just planted all those cute little seedlings you grew (and yes, slugs like seedlings too). So, if you can make your garden a less inviting place for slugs, you can stave off an invasion of the slimy little creatures. Watering earlier in the day will make the soil less moist at night, and underground drip irrigation systems reduce the amount of surface moisture that attracts slugs. Raised garden beds can also improve soil drainage and make it a less hospitable environment for slugs.
Slugs like to hide, so if you can eliminate or reduce potential hiding places, you can possibly reduce the slug population. While mulch is great for keeping weeds down, it also provides a lot of little nooks and crannies for slugs to hang out (and to be close to your mutual food source). If you do decide to mulch, use smaller wood chips to reduce the number of potential slug hangouts.
You can also create sacrificial plants around the ones you want to protect. Lettuce is a fast-growing plant that slugs really dig. Spread some lettuce seeds around other plant beds and hope they like it better than whatever else you’re trying to grow.
5. How do You Get Rid of Slugs?
Even your best attempts at slug prevention might fall short. When this happens, you have to decide whether to sacrifice some plants, kill the poor little guys with slug bait (organic or chemical), or repel them from your plants using organic methods. My weapon of choice is organic slug repellent. There are spray products that you can buy (and you know how much I love liquid lawn care), but in the case of a slug repellent, I think there is a better solution. Copper is a natural deterrent that slugs really hate because 1.) copper is toxic to slugs, and 2.) slugs receive a small electric shock when the come into contact with copper. It doesn’t kill them, just gives them a little zap. When you use copper as a barrier at the base of plants, slugs can climb up them to eat all those tasty leaves. Organic gardeners – 1, Slugs – 0.
Bonus Fact – Because It’s Interesting
Slugs are hermaphrodites, having both female and male reproductive organs.
Once a slug has located a mate, they encircle each other and sperm is exchanged through their protruded genitalia. A few days later the slugs lay around 30 eggs in a hole in the ground, or beneath the cover of an object such as a fallen log.
Apophallation is a commonly seen practice among many slugs. In apophallating species, the penis curls like a corkscrew and during mating often becomes entangled in the mate’s genitalia. Apophallation allows the slugs to separate themselves by one or both of the slugs chewing off the other’s penis. Once its penis has been removed, the slug is still able to mate using only the female parts of its reproductive system.
“Apophallation” – I’m adding that one to my vocabulary. Who can use it in a non-snail-related sentence for me?