Every gardener with a moist, shady area knows slugs are pigs. With their rough, file-like tongues, these mollusks devour several times their own body weight in one night, leaving gaping holes in leaves, torn foliage, and-yuck!-slime trails in their wake. Hostas and lettuce are their most common targets, but corn, beans, strawberries, annual flowers, and many other garden favorites are susceptible to attacks. In our test gardens, we've battled the slimers and tried a many different strategies for controlling them. The following tactics work best for us.
Beer trap. This type of trap works because slugs are attracted to the fermented yeast in beer. In a study by Whitney Cranshaw, Ph.D., professor of entomology at Colorado State University, nonalcoholic Kingsbury Malt Beverage was found to attract the most slugs. Michelob and Budweiser placed second and third out of the 12 beverages tested. (We're still waiting for the results from the gardeners' taste test.) "Take a shallow container (such as a sour cream or yogurt cup) and bury it so that it is even with the soil level," explains gardening expert Willi Evans Galloway, who gardens in Seattle. "Then fill the container with beer to within an inch of the rim. The slugs crawl in and drown." For best results, change the beer every few days.
Diatomaceous earth (DE).
After testing all kinds of slug barriers, Jeff Gillman, author of The Truth about Garden Remedies and professor of horticulture at the University of Minnesota, concluded that DE is the most reliable. "DE is a white powder made from the fossilized remains of diatoms, one-celled algae that have a skeleton made of silicon," Gillman says. "To a slithering slug, this lethal powder is extremely sharp and cuts their undersides, causing dehydration." DE does have to be replenished each time it rains, making it a better choice for climates where it does not rain frequently. (Note: Buy only untreated diatomaceous earth formulated for garden use, and wear a dust mask when applying it. DE made for swimming pools is chemically altered and not suitable for use in any garden, much less an organic one.)
You can buy bags of Diatomaceous earth at Gardener's Supply or Planet Natural.