North Coast Journal


Slugs, snails, slimy trails

by Terry Kramer

I'm normally a peaceful, meek individual, but when I find a slug devouring a succulent flat of basil starts that took weeks to nurture, I whip out the Swiss Army knife and slice the devil in half. In fact, from now until midsummer I will go hunting every morning, knife in hand.

Slugs and snails bring out a killer instinct in many gardeners because of the vast damage the gastropods can do in such a short time. The word slug basically means slow. Supposedly it takes a slug or snail 115 days to travel a mile. I find this difficult to believe, since they sure can rapidly move through a greenhouse, leaving havoc and destruction in their wake.

Entire seedlings can be devoured overnight; a cellophane trail is all that remains. Slugs can tear pansy flowers ragged and demolish the foliage of a beautiful hosta, ruining its appearance for the rest of the season. Slugs and snails eat bulbs, roots and the most toxic plants known to humans, including poison oak and poisonous mushrooms.

Slugs even eat each other, in addition to animal droppings and other foul, smelly things. I have seen a slug eat an earthworm alive!

In spite of the damage and frustration slugs and snails cause, they are amazing creatures with fascinating habits, some perhaps worthy of a category on the game show "Jeopardy."

Although slugs and snails are terrible garden pests, they are not insects or bugs. They are mollusks, kin to oysters, clams and other shellfish. Snails differ from slugs in that they have a shell in which to hide. A clever device to have, since snails can, when faced with unfavorable circumstances, go dormant in their shell for up to four years. A slug is a snail without a shell.

When a slug (or snail) is alert and on the move, you will notice two pairs of tentacles protruding from its slimy head. The largest pair have the eyes at the tip. The smaller pair below are used for inhaling your fresh turned soil and newly planted vegetable starts.

All tentacles move independently, allowing slugs to look and smell in several directions at one time. While vision may not be 20/20, the sense of smell is keen. Basil is one of their favorite scents, apparently.

Once a slug finds a succulent plant to feed upon, it sucks the leaf material into its round, puckered mouth and begins rasping away at it with a finely toothed tongue, called a radula.

While it is true that slugs eat a wide variety of materials, they also have several foes who prey upon them. Aside from the French (who eat more than 45,000 tons of snails every year), salamanders, garter snakes, foxes, porcupines, beetles, millipedes, crows, ducks, shrews, shrew moles and moles consume slugs and snails. Mosquitoes will also feed on slugs.

Considering all variety of creatures that prey on slugs and snails, you would think there wouldn't be so many feeding in your garden. These hermaphrodites (they have both male and female reproductive organs) lay clusters of 15 to 30 eggs anywhere it is moist, cool and dark. Hence, two slugs mating have the potential of producing 60 offspring after one session. Since this is a family column, we won't go into their habit of premating biting and a few of the other horrifying things they do.

Their slime is not only vital for reproduction, it is also necessary for movement, defense and water retention. Slime protects a slug from being eaten. It shields the body from potential injury by sharp materials such as rough rocks, thorns and even broken glass.

This is one reason a snail can climb up a prickly cactus and nibble away at it. Having a slimy body enables slugs to slip easily into tiny crevices. Slugs are even known to eat their own slime, provided it is debris free. On the other hand, gardeners who have a fear of slime may suffer from blennophobia.

Some slugs have the fascinating ability to produce a slime cord, which allows them to descend from high places much like a spider dangling from a web. Banana slugs like to use the slime cord trick when descending a redwood tree that took days to climb. Some European slugs use their slime cords to mate in midair.

Imported European slugs and snails seem to run rampant in American gardens. The pudgy, ugly red slug that consumes everything in sight and ignores slug baits, is called Arion ater. It was first reported in Oregon in 1942. Since then it has become a serious garden pest throughout the Pacific Northwest.

The brown garden snail, Helix aspersa, made its presence known throughout California in the 1850s. It is thought to have been intentionally cultivated for human consumption, the breeding stock imported from France. The spotted grey slug, Limax maximus, is common in local gardens as well as the tiny slug, Agriolimax agrestis.

Not all slugs and snails are bad guys, however. The Florida citrus tree snail, Drymaeus dormani, has been reported to attack enemies of beneficial insects in Florida citrus groves, as well as clean up citrus trees covered with sooty mold and algae.

North Coast banana slugs, Ariolimax species, are a vital part of forest ecology, cleaning up debris and dispersing mushroom spores and native plant seeds. They are a valuable food source for the Pacific giant salamander.

It would be far less time-consuming and atrocious if one could depend on an army of salamanders instead of a knife to control the slug population in the garden. I discovered recently that you can trap numerous slugs and snails with plates of chopped tomato. They love the smell and taste.

Other garden traps include plates of beer or wine (they like yeasty smells), pieces of potato, lettuce or cabbage leaves.

Unfortunately you must then dispose of your catch by committing some sort of atrocity. Gardeners who lack knives sprinkle salt or baking soda on the slimy beasts. One old timer told me he uses Spic-N-Span, a radical solution to be sure.

Creating barriers to prevent slugs and snails from getting to susceptible plants can be helpful. Try sprinkling rings of diatomaceous earth or ashes around vulnerable plants. Copper tape is useful because it emits a small electrical charge that irritates a slug's belly.

It seems the slugs generally ignore poisonous baits, while snails are more vulnerable. Cheap generic baits work just as well as name-brand ones. My favorite is Corry's Slug and Snail Death. I think it is the name that is so alluring.


April Garden Checklist


Terry Kramer is a Bayside free-lance writer and the owner of Jacoby Creek Nursery.

Comments on this story? E-mail the Journal:

The North Coast Journal Table of Contents

North Coast Journal weekly banner