Slugs are gross, pesky part of Northwest gardening

Published on Thu, Apr 2, 2009 by Jack Kintner

Read More News

A story I tell that always gets a groan is about when I was a camp counselor on Lopez Island and was putting on my shoes for the weekly dance. The shoes sat under my bed for six days, and on the seventh I slid one on and felt something soft and moist with my toes.

A banana slug had taken up residence in the far end, and came out reluctantly.

Slug. Rhymes with Ugh. Probably no other animal gets such a negative reputation, and all because they’re so yucky to deal with.

And yet they’re sometimes beneficial and, like mosquitoes and other dismal irritating critters, they’re a part of the great chain of life which is reason enough to at least try to understand them.

But first, what are they and why are they here?

Slugs are snails without shells. Because of this they can live in places without the calcium in their diets necessary for building shells. But it means they can dry out, which relegates them to the dark and the moist.
That means that we’re perfect slug country. There are over 25 species on the Olympic Peninsula, a bit less here. All are members of the class Gastropoda, which means “stomach foot,” because that’s about all they are, a stomach on a large slime-covered foot rolling through the garden like a Sherman tank.

Slugs love lettuce, tomatoes, peppers, squash and melons. For dessert, slugs hope you also have marigolds, dahlias, hostas and canna. Leopard slugs eat other slugs.

A mature slug can eat 40 times its weight in a day, equal to a normal person eating over three tons of food. No wonder they leave a garden of early spring shoots full of holes.

That’s part of their benefit, though, because like worms they process a tremendous amount of organic material, turning it into beneficial plant food. They can even be composted themselves when dead, although if you do that don’t go downwind.

As for the slime, it’s a handy field remedy for nettle and insect stings, providing instant relief. No one believes that, of course. Talk about the cure being worse than the disease. But you can always try that on a companion, and after they stop screaming at what you just did to them they’ll thank you I’m sure.

The slime is produced in the foot by the pedal glands – yes, really – and comes in various mixtures. Some of the slime actually increases traction, and since it absorbs water it can’t be easily washed off. Better to wipe it off and then wash.

How do you get rid of them? Poison is tempting but not a good idea because of what the active ingredient, metaldehyde, can do to a horse or a dog that’s attracted to the molasses used to draw the slugs. According to Oregon State University, metaldehyde can affect horses and kill dogs in a few hours, and dogs that survive, and horses, can develop liver failure. The stuff also is very slow to dissipate, staying around in your yard for a long time. And it’s indiscriminate, killing both the common bad guys (black) as well as the good guys (yellow-greenish banana slugs).

Slug bait that uses iron phosphate, according to the EPA, is safe for humans and non-targeted animals such as birds, fish and insects. Caffeine (coffee grounds) works as a repellent. Traps also work well. All you need is a buried chamber with a little beer in the bottom. Empty cottage cheese containers work well for this.

Since they move so slowly – about the same speed as the line-up in a grocery store – patrolling is also a good idea. It’s done at night with a flashlight (or better, for your neighbor’s entertainment, a headlamp).

To kill them, one needs to puncture their skin, and if they’re in the wrong place just toss them somewhere or put them in the garbage. They feed a lot of species themselves, like frogs, toads, birds and snakes, so a “clean kill” can be a nice surprise for one of these.

Slugs are trans-sexually hermaphroditic; that is, they have both male and female sexual organs, starting out as male and developing female organs at maturity.

When they mate, sometimes in mid-air, it goes slowly. You’ll see the advantage that comes with being able to make your own slime in such prodigious quantities. Both entwine like stripes on a candy cane, then entwine their male organs that poof out into a large bubble. Each fertilizes the other, and when it’s over after several hours they fall apart.
How does the leopard slug procreate in mid-air? It finds an overhang and then shinnies down on a rope made of its own slime.