Tackling the slimy snail trail

When you write about gardening in the Pacific Northwest, you come to love slugs and snails.

Not that anyone can actually get pleasure from the sight of one of these slimy interlopers, but because they provide endless fodder for comment at dinner parties and in question-and-answer columns.

Back in 1999, I wrote about this question from a reader: "Snails have invaded my garden; why do I have snails instead of slugs?" Conversations with gardeners today indicate that snail populations seem somewhat variable; one gardener noted that when she lived in Magnolia, she had slugs but no snails, and now sees snails in her garden in West Seattle.

I can testify from experience that they have certainly colonized the Capitol Hill area.

Most gardeners will see both slugs and snails. Introduced European garden slugs have been joined by their relatives, mollusks with attitude as well as shells.

One common type here is the brown garden snail (Helix aspera), now rummaging through Northwest gardens for breakfast, lunch, dinner and snacks. Some sort of definite irony is at work, because these snails were brought to California in the 1850s as delicacies — potential escargot. We're now feeding them the tender parts of our garden plants.

Cold winter weather, especially with temperatures below freezing, will reduce slug and snail activity but doesn't necessarily kill the critters. Snails aren't very active when temperatures drop below 50 degrees F, but they do remain alive.

Starting this month, gardeners need to patrol where tender bulb shoots emerge to be sure they aren't being scooped hollow by marauding snails and slugs.

Slug-management techniques also apply to snails. Snails seek damp, protected places. They often tuck themselves against walls or stones, or hide under rock-garden plants like candytuft. Handpicking snails is easier than hand-hunting slugs, because the shell serves as a handle. I toss the snails into the middle of the street and hope the crows will find them. (This would, I suppose, provide a snack called Es-car-crow.)

Snails multiply and grow fast and, like slugs, can be damaging at very young ages, and they mature between about 4 months and 2 years old, eating all the while. A baby snail has the shell complete and looks like a miniature of its parents. Snails, by the way, are generally hermaphroditic, as are slugs, meaning that they have both male and female sex organs.

Here are a few ways to tackle snails and slugs:

Go on an egg hunt. If you see a concentration of tiny snails, this will help you locate where the eggs are being laid. Snail eggs look like slug eggs, white and round small pearls, in heaps. Remove all eggs.

Find out which plants in the garden attract snails. In my garden, the Gladwin iris (Iris foetidissima) fills up with snails regularly. I comb them out of the plant, hoping for a complete rout, and come back in a week to search for more of the pests.

Trap 'em. Snails, like slugs, will come to beer traps. Copper strip barriers around raised beds and containers also repel snails. Ducks eat snails, and I've heard reports that some dogs do, too.

Bait debate. Do newer baits work? A survey of gardeners in 2002 indicated little if any difference in effectiveness between the newer baits containing iron (ferric) phosphate (sold as Worry Free and Sluggo brands) and the older, more toxic metaldehyde baits. The success rate of the newer baits is good news because the metaldehyde baits attract dogs and cats with often lethal results.

The survey was conducted by the Green Gardening program, a coalition drawn from Washington State University/King County Cooperative Extension, Seattle Tilth and the Washington Toxics Coalition. It's funded by the Local Hazardous Waste Management Team in King County.

Whatever method you use, remember to read and follow all label instructions.

Ideally you should not rely on just one method of control; combine handpicking, trapping and other methods. You can manage, though never eliminate, snails and slugs. Besides, think of the long silences in gardener conversations if they were gone.

Mary Robson is area horticulture agent for Washington State University/King County Cooperative Extension. She shares gardening tips every Wednesday. Her e-mail is gardeningtips@seattletimes.com.