In the Pacific NW, spring means slug season. When my family first came out west when I was little, I had never even seen a slug before. The first time I discovered one, I was pretty intrigued with the unusual little beast I had found. And of course, I soon learned the strange and horrible things that kids knew to do with slugs - like pouring salt on them (horrible!), or licking a banana slug to see if your tongue really went numb (strange!). I also have clear memories of my mom out in her flower beds, struggling with slugs and the damage they would do. Slugs are a big deal here, especially if you are trying to grow things.
All that said, slugs are interesting creatures. They are hermaphroditic, meaning they each contain both sexual organs. If necessary, a slug can mate with itself and produce offspring, making reproduction easy. They breathe with a single lung, through a respiration hole near the top of their head (the anus and sex organs are located at the bottom of this hole), and they can also breathe through their skin. They have 2 sets of tentacles. The upper set senses light, and the lower set senses smell. And their tenacious slime has a number of purposes - luring mates, protecting themselves from dryness and harsh surfaces, and allowing them to move along all kinds of slopes without falling. Slugs have teeth - like, 27,000 of them, with which they consume decaying matter, fungi, plants, animal droppings, and some are even predatorial and will eat worms and even other slugs (for the visually squeamish, this is a warning...).
Here in the NW there are what I consider to be 2 main categories of slugs that I encounter. The Banana slug, a native species here; and the the very common European red and black slugs which are considered invasive.
|Native Banana Slug|
|note the 2 sets of feelers|
While banana slugs are native to the NW, it is fairly rare that I will find one in the garden. Even at their impressively large size (said to be the 2nd largest terrestrial slug species in the world), I don't mind finding them around our place. They prefer to be on the forest floor, processing leaves, animal droppings, fungi, and dead plant material. They are an important part of the ecosystem here, recycling decaying matter into rich humus. And it is true, if you lick one, your tongue will go numb. Their slime contains an anesthetic, which works as a defense mechanism against predators (if you picked something up with your mouth, and it went numb, you would probably drop it!).
|note the reddish edge along it's belly. I think this is a red slug variant.|
The European red slug, the European black slug, and their variants, are considered invasive to our region and as such, tend to do excessive damage and reproduce rapidly. As my experience tells me, they are truly problematic. And their damage is not confined to the vegetable garden.
I have spent a lot of time in our garden hunting countless slugs and replanting losses to them. During wetter seasons, they have taken whole beds of small seedlings, chewed the stalks of well established sunflowers right off, wasted beds of daffodils and chewed the giant leaves of rhubarb patches until they are all completely riddled with holes. It's kind of impressive, and can be really frustrating! I even once saw a slug eating an earthworm (sorry?). It was a first, for sure. It's a predator universe out there...
Ha, but with that said, with a pretty solid no-kill motto here, even if something is considered a pest (not to say that I have never killed a slug, though I have more than kindheartedly relocated hundreds of them), we went searching for options. We have tried many (non poison) options without real success. For the curious, this included crushed egg shells, crushed nut shells, coffee grounds, cedar shavings... they didn't seem to mind any of it at all.
Enter copper tape. This particular option is still a work in progress, but it feels like we have found an option worthy of pursuing. The reason we have been rearranging the layout of our garden, as I mentioned earlier, is to create a path around the perimeter. This, in part, will create a gap between outer vegetation and the interior of the garden, so there will be less places for slugs to hide and live, but it will also provide a place to apply copper tape. The vegetable garden is surrounded by 2x lumber - example above - making for a relatively easy application of the tape, if the wood is kept clear. Last year I installed copper tape to one side of the garden, and then spent embarrassing amounts of time out there quietly watching to observe it's effectiveness at repelling slugs. In short, it does repel them and they do not care to cross it. But there will be those occasional larger, more adventurous slugs that will work up the courage, and the thickest slime barrier, to arch over the tape. It was truly pretty arduous though, and took quite a long time. I would say the thickness of this particular copper tape (about 1 1/4") is a little on the narrow side.
|a section installed last year (stuck down and then stapled in place)|
Another longer term preventive that interests me, is to create habitat for some of their natural predators, particularly frogs, snakes and certain birds. Their natural predators include frogs, toads, snakes, moles, mice and some birds such as ducks, thrushes and robins.
Do you have slugs in your zone? If you have come up with an organic solution for keeping them under control in your garden, I'd love to know how, and what you have learned. Thanks for reading with me! I enjoyed researching this, and I enjoy finding solutions that work.